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POTENTIAL FAILURE MODĘ AND EFFECTS ANALYSIS (FMEA) Reference Manuał Fourth Edition

Flrst Edition, February 1993 * Second Edition, February 1995 • Third Edition, Juty 2001, Fourth Edition, June 2008 Copyright © 1993. © 1995, © 2001, © 2008 Chrysler LLC, Ford Motor Company, Generał Motors Corporation ISBN: 978-1-60534-136-1

FOREWORD 4 ,h Edition The FMEA 4& Edition is a reference manuał to be used by supplieis to Chrysler IXC, Ford Motor Company, and Generał Motors Corporation as a guide to assist them in the development of both Design and Process FMEAs. The manuał does not define requirements; it is intended to clarify questions concerning the technical development of FMEAs This manuał is aligned with SAE 11739 Sum mary of Changes in the 4th edition FMEA Reference Manuał The DFMEA and PFMEA methods described in the 4* edition FMEA Reference Manuał include those associated with design at the system, subsystem, interface, and component level and the process at manufactuiing and assembly opeiations

Generał Changes •

• • • • •

•

The formatting used in the 4& edition is intended to provide easier reading o An index is included o icons are used to indicate key paiagraphs and visual cues aie used Additional examples and veibiage have been provided to improve the utility of the manuał and to provide a closer tie into the FMEA process as it develops Reinforcement of the need for management suppoit, inteiest, and ieview of the FMEA process and resuits Define and strengthen the understanding of the linkage between DFMEA and PFMEA as well as defining the linkages to othei tools Improvements to the Seveiity, Occunence, Detection ranking tables so that they aie moie meaningful to real woild analysis and usage Alternative methods are introduced that are currentiy being applied in industry o Additional appendices which have example foims and special case application of FMEA. o The focus on the "standard form" has been repiaced with seveial options that represent the current application of FMEA in industry The suggestion that RPN not be used as the primary means for assessing risk. The need for rmprovement has been revised including an additional method, and the use of thiesholds on RPN is ciaiified as a practice that is not recommended

Chapter I provides generał FMEA guidelines, the need for management suppoit and having a defined piocess fot developing and maintaining FMEAs, and the need fot continuous impiovement Chapter U describes the generał application of the FMEA methodology, which is common between DFMEA and PFMEA processes This includes the planning, stiategy, action plans, and the need for management suppoit and responsibility in FMEAs Chapter Ifl focuses on DFMEA (Design Failure Modę Effects and Analysis), establishing the scope of the analysis, use of błock diagrams, vaiious types of DFMEAs, formation of the teams, basie piocedure for analysis, action plans, and follow-up, aftematives to RPN, and connection to PFMEAs and validation plans

i

Chapter IV focuses on PFMEA (Piocess Failure Modę Effects and Anatysis), establishing the scope of the anatysis, use of flow diagtams, foimation of teams, basie procedurę foi analysis, action plans, the connection to DFMEAs and the development of contro! plans The Appendices have seveial examples of foims for DMFEA and PFMEA and addresses different applications and piocedures for addressing design and piocess tisk. The Suppliei Quality Requirements Task Foice would like to thank the fbllowing individuals, and theii companies, who have contiibuted their time and eftbits to the development of this edition of the FMEA Refeience Manuał: Michael Down, Generał Motois Coipoiation Lawrence Biozowski, Generał Motois Corporation Hisham Younis, Ford Motor Company David Benedict, Chrysler LLC

JohnFcghali, Chiyslei LLC Michael Schubert, Delphi Rhonda Brender, Delphi Gregory Giuska, Omnex Glen Vallance, Contiol Planning Initiatives Milena Krasich, Bose William Haughey, ReliaTiain This manuał is a copyiight of Chrysler LLC, Ford Motoi Company and Generał Motois Coiporation, with all nghts reserved. Additional copies may be obtained irom AIAG @ www.aiag.org Supply chain oiganizations of Chrysler LLC, Ford Motoi Company 01 Generał Motois Corporation have peimission to copy foims used in this manual.

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TABLE OF CONTENTS Generał Changes Chapterl Generał FMEA Guidelines Intioduction FMEA Process Puiposeof Manuał Scope of Manuał Impact on Organization and Management FMEA Explained Follow-up and Continuous Improvement Chapreill Ovetview of FMEA Sttategy, Planning and Implementation Intioduction Basic Stiucture Approach - ... Identify the I eam Define the Scope Define the Customer Indentify Functions, Requiiements, and Specifications Identify Potential Failure Modes Identify Potential Effects.... Identify Potential Causes Identify Contiols Identifying and Assessing Risk .... Recoramended Actions and Results Management Responsibility Chapterlll DFMEA Design Failure Modę and Effects Analysis ...... mnoduction Customei Defined . . . . IeamAppioach Manufactuiing, Assembly and Seiviceability Considerations Development of a Design FMEA Piereąuisites Błock (Boundaiy) Diagiams .. Parametei (P) Diagiams Functional Requiiements. . Other Tools and Infoimation Resouices Example DFMEA Header of the Design FMEA Foim (fields A-H) Body of the DFMEA Foim (fields a - n) MaintainingDFMEAs Leveraging DFMEAs Linkages Design Veiification Plan & Repoit (DVP&R) PFMEA Chaptei IV' .. . * • PF MEA Process Failure Modę and Effects Analysis . . Intioduction Customer Defined Ieam Approach . DesignConsideiations ........ Development of a Process FMEA

iii

Prerequisites — Process Flow Diagram and Iinkage to PFMEA Olher Tools and Infoimation Souices. ... Reseaich Infonnation , ExamplePFMEAForm Headei of the Process FMEA Form (fields A-H) Body ofthe PFMEA Fonn(fields a-n) Mainlaining PFMEAs L«veiagingPFMEAs Linkages ToDFMEA To Conaoi Plan APPENDICES Appendix A; Sample Foims DFMEAFoims PFMEA Forms Appendix B: System Level FMEA Inteifaces Inteiactions Relationships Multiple Levels of Design F ME As Appendix C: Altemative Risk Assessments AItematives to RPN Altemative: SO (S x O) Alteinative: SOD, SD . . . . Appendi* D: Alternative Analyses Techniques Failure Modę, Effect and Ciiticality Analysis (FMECA) Design Review Based on Failure Modes (DRBFM) Fault Iree Analysis (FTA) Refeiences and Suggested Readings Index

!V

TABLESandFIGTJRES Figurę III la Błock (Boundaiy) Diagram Examples 19 Figures ID. Ib, c Błock (Boundary) Diagram Examples 20 Figurę IH2 Example of a Paiametei (P) Diagram foi aGeneiic Catalytic Converter 21 Table HI 1 Sample DFMEA Form with Minimal Infoimation Elemenls & Example Entries 24 labie 1H.3 Example Potential FailureModes . 32 labie m 4 Examp!e Potential EtTects 35 labie Ci l Suggested DFMEA Severity Evaluation Criteria 37 Table III 5 Example Potential Causes 42 Table Cr2 Suggested DFMEA Occurrence Eraluation Ciiteria 46 n Table III 6 Examples of Prevention and Detection Design Contiols .. 51 labie Cr3 Suggested DFMEA/PFMEA Prevention/Detection Evaluation Ciiteiia ... 54 labie III.7 Examplesof Causes, ConOols and Recommended Actions 64 Figurę III. 7 DFMEA Intbimation Intenelationships Flow 65 Figurę IV 1 Highl_evel toDetailed ProcessMaps .71 Figurę IV.2 Example Process Flow Diagiam — 72 Table IV 1 Sample PFMEA Foim with Minimal Infoimation Elements Sc Example Entries 74 labie TV 2 Example of Piocess Step/Function/Requiiements Columns on PFMEA Form including Potential FailureModes ... .81 IableIV3ExampleofEffects 85 Table Cr 1 Suggested PFMEA Seveiity Evaluation Ciiteiia 88 Table Cr2 Suggested PFMEA Occuirence Evaluation Ciiteria 93 Table IV.4 Examples ot Causes and Contiols 96 Table Ci 3 Suggested Process FMEA Detection Evaluation Criteria 100 Table IV.5 Examples of Causes. Controls and Actions 110 Figurę 1V.S PFMEA Infoimation Inteirelationship Flow 111 DFMEAFormA 115 DFMEA FoimB - 116 DFMEAFoimC... 117 DFMEA FoimD 118 DFMEAFormE 119 DFMEAFormF 120 PFMEAFoimA 122 PFMEA FoimB 123 PFMEAFoimC .' 124 PFMEAFoimD 125 PFMEAFoimE 126 PFMEAFoimF 127 PFMEA Form G 128 PFMEAFoimH 129 Figurę B 1 Interfaces and Inteiactions 130 F igure B 2 Item, Functions, andFailuie 132 Figurę B 3 DFMEA EffectsLinkages 134 labie C 1 Contiast among RPN, SOD and SD 136 Figurę D 1 ExampIeof DRBFM Elements 138 FiguręD2FTA TreeStructure 139

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Vi

Chapter I

Geneial FMEA Guidelines

Chapter I Generał FMEA Guidelines

Generał FMEA Guidelines

Chaptci I

Introduction This manuał introduces the topie of Potential Failure Modę and EtTects Analysis (FMEA) and gives generał guidance in the application of the technique

FMEA Process FMEA is an analytical methodology used to ensuie that potentia! problems have been considered and addiessed thioughout the product and process development process (APQP - Advanced Pioduct Quality Planning) Its most visible result is the documentaiion of the coIlective knowledge of cross-functional teams Part of the eva!uation and analysis is the assessment of risk The impoitant point is that a discussion is conducted regaiding the design (pioduct or process), ieview of the functions and any changes in application^ and the resulting risk of potential failuie. Each FMEA should ensure that attention is given to eveiy component within the product oi assembly Critical and safety related components oi processes should be given a highei priority One of the most important factois fot the successful implementation of an FMEA program is timeliness It is meant to be a "before-the-event" action, not an "after-the-fact" exercise To achieve the greatest valuc, the FMEA must be done before the implementation of a pioduct or process in which the failure modę potential exists Up-ftont time spem piopeily completing an FMEA, when pioduet/process changes can be most easily and inexpensively implemented, will minimize late change crises Actions iesulting fiom an FMEA can leduce oi eliminate the chance of implementing a change that would create an even larger concern. Ideally, the Design FMEA process should be initiated in the early stages of the design and the Process FMEA before tooling or manufacturing eąuipment is developed and purchased The FMEA evolves throughout each stage of the design and manufacturing development process and may also be used in problem solving

v

FMEA can also be applied to non-manufacturing areas. For example, FMEA could be used to analyze risk in an administration process or the evaluation of a safety system. In geneial, FMEA is applied to potential failures in product design and manufacturing processes wheie the benefits are cleai' and potentially significant

2

Chapter I

Geneial FMEA Guidelines

Purpose of Manuał This manuał describes the basie piinciples and iraplementalion of the FMEA1 process and how it is integialed within the product and process development cycle This includes the documentation of this process and how the analyses can be applied for timely necessary improvement of a product 01 a process in its early and fuli deveiopment stage This manuał also provides descriptions and examples of alternate and suppoiting methodologies for these analyses, their specific advantages and limitations, guidance of how the analysis is to be cariied out for the maximum icliability impiovement or mitigation of potential safety risks. The manuał provides guidance on how the risk can be represented, measuied and prioritized for cost eftective mitigation of the failure effects As a tool in risk evaluation, FMEA is considered to be a method to identiiy severity of potential effects of faiiuie and to provide an input to mitigating measures to reduce iisk In many applications, FMEA also includes an estimation of the probability of oceunence of the causes of faiiuie and theii tesultant faiiuie modes This broadens the analysis by providing a measure of the failure mode's likelihood To minimize iisk, the likelihood of failure occutience is reduced which inereases product or ptocess reliability FMEA is a tool that is instrumental in reliability impiovement Theie aie three basie cases for which FMEA process is to be applied, each with a diffeient scope 01 fbcus: Case 1:

New designs, new technology, or new process. The scope of the FMEA is the complete design, technology, or process

Case 2:

Modifications to existing design 01 process The scope of the FMEA should focus on the modification to design or process, possible interactions due to the modification, and field history This can include changes in regulatory recjuirements

Case 3:

Use of an existing design or process in a new environment, location, applicatlon, or usage profile (including duty cycle, regulatory requirements, etc) The scope of the FMEA should focus on the impact of the new environment, location, or application usage on the existing design or process

The F MEA present herein also is known as a Faiiuie Modes Effects and Ciiticality Analysis (FMECA) sińce it includes a quantification of the risks 3

Generał FMEA Guidelines

Chaptet I

Scopeof Manuał The analytical melhods presented in this manuał are applicable to any product or process. However, this manuał will focus on those applications pievalent within the automotive industry and its suppliers

Impact on Organization and Management FMEA is an impoitant activity within any company Because the development of an FMEA is a multi-disciplined activity affecting the entiie pioduct realization piocess, its implementation needs to be well planned to be firlly effective This piocess can take considetable time and a commitment of the iequired resouices is vital. Impoitant to FMEA development is a process ownei and senioi management commitment Implementation apptoach will vaiy depending on the size and stiucture of the company concemed, although the principles will be the same: •

The scope will cover FMEAs produced in house and by multitier supplieis.

•

Address Design and Piocess FMEAs, as applicable

•

Accomplish this by having the FMEA process an integral pait of the APQP piocess

•

Pait of engineeiing technical reviews

•

Pait of the regulai sign-off and appioval of the pioduct or process design An FMEA is deveIoped by a multi-functional (01 crossfunctional) team The team size will depend both on the complexity of the design and the size and organization of the company Team members need relevant expeitise, available time and authority sanctioned by management A comprehensive tiaining progiam should be implemented including:

•

Management Oveiview

•

Tiaining foi users

•

Supplier Training

•

Facilitaloi Training Ultimately, management has the responsibility and owneiship for development and maintenance of the FMEAs

4

Geaeial FMEA Guidelines

ned FMEAs are aa integiaL part of managing iisk and supporting continual improvement. Consequently, FMEA becomes a key patt of Product and Process development The Advanced Product Qua!ity Planning (APQP) process identifies five generał areas of focus in this deve!opment process: •

Plan and Define Program

•

Product Design and Development

•

Process Design and Developmenl

•

Product and Process Validation

•

Feedback, Assessment and Conective Action The APQP Reference manuał shows DFMEAs as an activity in the Product Design and Development section of the timing chart and PFMEAs in the Process Planning and Development section The development of eithei DFMEA 01 PFMEA is a process that helps to guide the tearas in developing product and process designs that meet expectations The FMEA analysis should not be consideied a single event, but a long-term commitment that complements the product and process development to ensure potential failures are evaluated and actions are taken to icduce their iisk One key aspect of continual improvement is the retention of knowledge fiom past learning which often is captured in FMEAs It is advisable for organizations to capitalize on prior analyses of similar product and process designs for use as the starting point for the next program and/oi application The language used in FMEAs should be as specific as possible when describing an item (for example, failure modę, or cause) and not extend or extrapolate beyond the team's level of understanding as to what the faihue effects may be Clear statements, concise terminology and focus on the actual effects are key to the effective identiftcation and mitigation of iisk issues

*

Chaptei I

Geneial FMEA Guideliaes

Follow-up and Continuous lmprovement The need foi taking effective pieventive/conective actions, wilh appiopiiate follow-up on those actions, cannot be oveiemphasized Actions should be communicated to all affected activities A thoroughly thought-out and well-developed FMEA will be of limited value without positive and effective preventive/conective actions. Team leadeiship (typically the team leadei/lead engineei) is in charge of ensuring that all iecommended actions have been implemented 01 adeąuately addressed The FMEA is a living document and should always reflect the latest level, as well as the latest relevant actions, including those occuuing aftei the staitof pioduction

The team leadei/lead engineei has seveial means of assuring that iecommended actions aie implemented They include, but are not limited to the following: •

Reviewing designs, processes, and related iecoids to ensiue that iecommended actions have been implemented,

•

Confuming the incorpoiation of changes to design/assembly/ manufactuiing documentation, and,

•

Reviewing Design/Piocess FMEAs, applications, and Coratiol Plans

6

special

FMEA

Chaptei II

Sbategy, Planning, Implementation

Chapter I! Overview of FMEA Strategy, Planning and implementafaon

7

Chaptei II

Strategy, Planning, Implementation

Introduction FMEA development, eithei design or piocess, usys a common appioach to addiess: •

Potential pioduct oi piocess failure to meet expectations

•

Potential conseąueaces

•

Potential causes of the failure modę

•

Application of cuirent controls

•

Level of iisk

•

Risk reduction

♦

Befoie the FMEA dokument is started, the team must define the scope of the project and collect existing infoimation which is necessaiy for an effective and efficiem FMEA development ptocess

Basic Structure The purpose of the recommended FMEA fbimats described in this manuał is to oiganize the collection and display of relevant FMEA infoimation Specific formats may vaty based on the needs of the oiganization and the requiiements of the customei

J

Fundamentally, the format utilized should addiess: • Functions, requirements, and deliveiables of the product 01 piocess being analyzed, • Failuie modes wheti functional reąuiiements aie not met, • Effects and conseąuences of the failuie modę, • Potential causes of the failure modę, • Actions and contr ols to address the causes of the failure modę, and, • Actions to pievent lecunence of the failure modę

Approach There is no single or unique piocess ioi FMEA development; howevei there aie common elements as described below

ł s

Chaptei II

Sttategy, Planning, Implemenlation

Identify the Team As pieviously mentioned, FMEA developraent is the responsibility of a multi-disciplinaiy (or cross-functional) team whose raembers encompass the necessary subject mattet knowledge This should include facilitation expeitise and knowledge of the FMEA piocess A team approach is recommended to benefit the FMEA development piocess to ensuie input and collaboration fiom all affected ftinctional aieas. The FMEA team leadei should select team membeis with the relevant expeiience and necessaiy authoiity In addition to the design and piocess engineeis, the following aie examples of additional resoiuces: FMEA development topie Scope

Relevant Resources or Expertise Program Management, Customer, Integiation responsible individual(s)

Functions, iequirements and expectations

Customei, Program Management, Integiation iesponsible individual(s), Seivice Opeiations, Safety, Manufactuiing and Assembly, Packaging, Logistics, Materials

Potential failure modę - the way a piocess 01 pioduct might taił

Customer, Piogram Management, Integiation responsible individual(s), Service Opeiations, Safety, Manufacturing and Assembly, Packaging, Logistics, Materials, Quality

Effects and conseąuences of the failure - to both the organization's piocesses 01 to a downstieam customer Causes of the potential failure

Customer, Program Management, Integiation responsible individual(s), Seivice Opeiations, Safety, Manufactuiing and Assembly, Packaging, Logistics, Materials, Quality

Freąuency of occunence of potential failuie

Application of cuirent controls-prevention Application of current contiols-detection Recommended actions requiied

Customei, Manufacturing and Assembly, Packaging, Logistics, Materials, (ûality, Reliability, Engineering Analysis, Equipment Manufactuier, Maintenance Customer, Manufacturing and Assembly, Packaging, Logistics, Materials, Quality, Reliability, Engineeiing Analysis, Statistical Analysis, Eąuipment Manufactuier, Maintenance Manufacturing and Assembly, Packaging, Logistics, Materials, Quality, Equipment Manufacturei, Maintenance Customer, Manufactuiing and Assembly, Packaging, Logistics, Materials, Quality, Maintenance Customer, Program Management, Integiation responsible individual(s),-Manufactuiing and Assembly, Packaging, Logistics, Materials, Quality, Reliability, Engineering Analysis, Statistical Analysis, Eąuipment Manufactuier, Maintenance

9

Chapter II

Stiategy, Planning, Łmplementation

Define the Scope Scope establishes the boundaiy ofthe FMEA analysis It defines what is included aod excluded, deteimined based on the type of FMEA being developed, i e., system, subsystem, 01 component Befoie the FMEA can begin, a elear undetstanding of what is to be evaluated must be deteimined What to exclude can be just as impoitant as what to include in the analysis The scope needs to be established at the stait ofthe piocess to assuie consistent diiection and focus Ihe following raay assist the team in defining the scope ofthe FMEA: •

Function Model

•

Błock (Boundaiy) diagiams

•

Paiameter (P) diagiams

•

Intei face diagiams

•

Process flow diagiams

•

Inteiielationship matiices

•

Schematics

•

Bili ofMateiials (BOM)

System FMEA A system FMEA is madę up of vaiious subsystems Examples of systems include: Chassis System, Poweitiain System, 01 Inteiioi System, etc The fbcus of the System FMEA is to addiess all inteifaces and inteiactions among systems, subsystems, the enviionment and the customei. Subsystem FMEA

A Subsystem FMEA is a subset of a system FMEA. An example of a subsystem is the fiont suspension subsystem, which is a subset ofthe chassis system The focus ofthe Subsystem FMEA is to addiess all inteifaces and inteiactions among the subsystem components and inteiactions with othei subsystems ot systems Component FMEA

»

A Component FMEA is a subset of a subsystem FMEA Foi example, a biake pad is a component of the biake assembly, which is a subsystem of the chassis system NOTĘ: Any subseąuent adjustments to the scope may icąuire a modification ofthe team structiue and membeiship

10

Chaptei II

Strategy, Ptanning, Implementation

Define the Customer There are foui major customeis to be considered in the FMEA piocess, all need to be taken into account in the FMEA analysis: •

END USER: the person or oiganization that will utilize the pioduct The FMEA analysis affecting the End Usei could include, for example, durability.

•

OEM ASSEMBLY and MANUFACTURING CENTERS (PLANTS): the OEM locations wheie manufactuiing opetations ( e g , stamping and poweitrain) and vehicle assembly take place Addiessing the inteifaces between the product and its assembly process is critical to an effective FMEA analysis

•

SUPPLY CHAIN MANUFACTURING: the supplier location wheie manufactuiing, fabiicating oi assembling of pioduction mateiials oi parts takes place This includes fabiicating pioduction and seivice paits and assemblies and piocesses such as heat tieating, welding, painting, plating oi othei finishing seivices This may be any subsequent or downstieam opeiation or a next tier manufactuiing piocess

•

REGULATORS: govemment agencies that define iequiiements and monitoi compliance to safety and enviionmental specifications which can impact the pioduct oi piocess Knowledge of these customers can help to define the functions, teąuiiements and specitications moie robustly as well as aid in deteimining the effects of related failuie modes

Indentify Functions. Requirements, and Specifications Identify and undeistand the functions, reąuiiements and specifications ielevant to the defined scope. The puipose of this activity is to claiify the item design intent or piocess puipose This assists in the deteimination of the potential failuie modę foi each attiibute or aspect of the function

.1

Chaptei n


Identify Potential Failure Modes Failure modę is defined as the way 01 mannei in which a pioduct or piocess could fail to raeet design intent 01 piocess ieąuiiements The assumption is madę that the failure could occur but may not necessaiily occur A concise and undeistandable failuie definition is impoitant sińce it piopeily focuses the analysis Potential failuie modes should be desciibed in technical teims and not as a symptom necessarily noticeable by the customer. A laige number of failuie modes identified for a single iequirement may indicate that the defined iequiiement is not concise

Identify Potential Effects Potential effects of failuie aie defined as the effects of the failuie modę as perceived by the customei The effects or impact of the failure aie desciibed in teims of what the customei might notice or expeiience The customei may be an intemal customei as well as the End User Deteimining potential effects includes the analysis of the consequences of the failures and the seveiity 01 seriousness of those conseąuences

Identify Potential Causes Potential cause of failuie is defined as an indication of how the failuie could occur, desciibed in teims of something that can be conected oi can be contiolled. Potential cause of failuie may be an indication of a design weakness, the cohsequence of which is the failuie modę. Theie is a diiect relation between a cause and its tesultant failuie modę (i e , if the cause occurs, then the failuie modę occuis). Identifying the ioot cause(s) of the failuie modę, in sufficient detail, enables the identification of appropiiate contiols and action plans A sepaiate, potential cause analysis is perfoimed foi each cause if theie are multiple causes

i 1/

Chapter II


Identify Controls Controls aie those activities that pievent oi detect the cause of the failuie oi failure modę In deve!oping contiols it is impoitant to identify what is going wrong, why, and how to prevent oi detect it Controls aie applicable to pioduct design or manufactuiing processes. Contiols fbcused on pievention will provide the gieatest return.

Identifying and Assessing Risk One oi the impoitant steps in the FMEA piocess is the assessment of iisk This is evaluated in thiee ways, severity, occunence, and detection: Severity is an assessment of the level of' impact of a failiue on the customei Occurrence is how often the cause of a failuie may occui. Detection is an assessment of how well the pioduct ot piocess contiols detect the cause of the failuie oi the failuie mode. Oiganizations need to undeistand theii customei iequiiements for iisk assessment

Recommended Actionsand Results The intent of recommended actions is to reduce oveiall iisk and likelihood that the failure modę will occur The recommended actions address ieduction of the severity, occuirence and detection. The fóllowing can be used to assuie that the appropiiate actions aie taken, including but not limited to:

„

•

Ensuiing design achieved,

reąuirements

•

Reviewing engineering drawings and specifications,

•

Confirming incorpoiation processes, and,

•

Reviewing telated FMEAs, control plans and opeiations instiuctions.

in

including

reliability

are

assembly/manufacturing

Responsibility and timing to complete the iecommended actions should be recoided. Once actions aie completed and results captured, the updated iatings for seveiity, occunence and detection should also be lecoided

13

Chapter II

Strategy, Planning, Impleraentation

Management Responsibility

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Management owns the FMEA piocess Management has the ultimate responsibility of selecting and applying iesources and ensuiing an effective risk management piocess including timing Management iesponsibility also includes providing diiect suppott to the team through on-going ieviews, eliminating loadblocks, and incoipoiating lessons leamed

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ł

14

Chapter III

Design Failuie Modę and Effects Analysis

Chapter !li DFMEA Design Faiiure Modę and Effects Analysis

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Chapter III

Introduction

$ The Design Failuie Modę Effects Analysis, lefened to as DFMEA, suppoits the design piocess in leducing the risk of failures by: •

Aiding in the objective evaluation of the design, including functional ieąuiiements and design alteinatives,

•

Evaluating the initial design for manufactuiing, assembly, ser vice, and recycling ieąuiiements,

•

Increasing the probability that potential failuie modes and theii effects on system and vehicle operation have been consideted in the design/develt>pment process,

•

Providing additional infoimation to aid in the planning of thotough and efficient design, development, and validation piograms,

•

Developing a ianked list of potential failuie modes accoiding to theii effect on ihe customer, thus establishing a piioriTy system for design impiovements, development, and validation testing/analysis,

•

Pioviding an open issue format for recommending and tracking risk-ieducing actions, and,

•

Pioviding mtuie refeience, ( e g , lessons learned), to aid in addiessing field conceins, evaluating design changes, and developing advanced designs

f

Ihe DFMEA is a living document and should: •

Be initiated befoie design concept finateation,

•

Be updated as changes occui 01 additional infoimation is obtained thioughout the phases of pioduct development,

•

Be fundamentally completed befoie the production design is ieleased, and,

•

Be a souice of lessons learned foi futurę design iteiations.

Customer Defined The definition of "Customei" provided in Chapter U applies to DFMEA It is important to conectly identify the customei(s) because such knowledge diiects the development of the DFMEA, including the impact of the function of the design

I.

16

Chapter Tli

Design Failure Modę and Effecls Analysis

Team Approach The DFMEA is developed and maintained by a multidisciplioaiy (oi cioss-functional) team typically led by the design responsible engineei fiom the responsible design source (e g, OEM, Tier 1 supplier or Tiei 2 supplier and below) The iesponsible engineei is expected to directly and actively involve iepresentatives fiom all affected areas The areas of expeitise and iesponsibility may include, but are not limited to, assembly, manutacturing, design, analysis/test, reliability, materials, quality, seivice, and supplieis, as well as the design aiea iesponsible for the next higher or tower assembly or system, subsystem, or component

Manufacturing, Assembly and Sen/iceability Considerations The DFMEA should include any potential failure modes and causes that can OCCUI during the manuractuiing oi assembly process which aie the result of the design Such failure modes may be mitigated by design changes ( e g , a design featute which prevents a part fiom being assembled in the wiong orientation i e., eiior-proofed) When not mitigated during the DFMEA analysis (as noted in the action plan foi that item), theii identification, effect, and control should be transfeired to and coveied by the PFMEA The DFMEA does not rely on process controls to overcome potential design weaknesses, but it does take the technical and physical limits of a manufacturing and assembly piocess into consideiation, foi example: •

Necessaiy mold drafts

•

Limited suiface finish capability

•

Assembling space (e g , access for tooling)

•

Limited haidenability of steels

•

Tolerances/process capability/per foi mańce The DFMEA can also take into consideiation the technical and physical limits of produci serviceability and iecycling once the pioduct has entered field use, foi example:

•

Tool access

•

Diagnostic capability

•

Materiał classification symbols (foi recycling)

•

Materials/chemicals used in the manufacturing piocesses

17

Design Failure Modę and Effects Analysis

Chaptei III

Development of a Design FMEA The DFMEA focuses on the design of the product that will be delivered to the finał custoraer (End Usei). The pretequisite tasks for an effective analysis of the product design include: assembling a team, deteimining scope, creating błock diagiams 01 P-diagrams depicting product function and requirements. A elear and complete deflnition of the desired product chaiacteiistics better facilitates the identification of potential failure modes A DFMEA foim is used to document the results of the analysis including any recommended actions and responsibilities (See Table III 1) The DFMEA piocess can be mapped to the customer or oiganization's product development piocess

Prereguisites A DFMEA should begin with the development of information to understand the system, subsystem, oi component being analyzed and define their flinctional requiiements and characteristics In ordei to determine ihe scope of the DFMEA, the team should consider the following as applicable to component, subsystem ot system DFMEAs: •

What processes, mating components, oi systems does the product inteiface with?

•

Are there functions oi features of the product that afłect other components or systems?

•

Aie there inputs provided by othei components or systems tha: are needed to peifoim intended functions of the pioduct?

•

Do the producfs functions include the prevention or detection of a possible failure modę in a linked component or system? The following sections describe tools that may be applied, as appropiiate, to assist Ihe team in developing the DFMEA

Błock (Boundary) Diagrams The błock diagram of the pioduct shows the physical and logical lelationships between the components of the product There aie different appioaches and foimats to the constniction of a błock diagiam The błock diagiam indicates the inteiaction of components and subsystems within the scope of the design This interaction may include: flow of information, energy, fbice, or fluid The objective is to understand the requirements or inputs to the

!S

i

Chapter HI

Design Failuie Modę and Effects Analysis system, the activities acting on the inputs or function peifotmed, and the deliverables or output The diagram may be in the form of boxes connected by lines, with each box corresponding to a major component of the pioduct oi a major step of the piocess. The lines coirespond to how the pioduct components aie related to, or interface with each other The organization needs to decide the best approach or foimat for the błock diagram. Figurę III.la, b, and c contain examples of błock diagrams Copies of the diagrams used in DFMEA pieparation should accompany the DFMEA

Lift Gale Bali Studs

LiftGate

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Figurę IH.la Błock (Boundary) Diagram Esamples

19


Chaptei III

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20

Chaptei III

Design Failuie Modę and EfFects Analysis

Parameter (P) Diagrams The P-Diagiam is a structuied tool to help the team undeistand the physics related to the function(s) of the design The team analyzes the intended inputs (signals) and outputs (responses 01 functions) for the design as well as those contiolled and uncontrolied factois wbici can impact peifoimance. Ihe inputs to the pioduct and outputs fiom the pioduct, i e., the intended and unintended functions of the pioduct, are usetul in identifying eiror states, noise factors, and control factois. The enot states conespond to the Potential Faiiure Modes in the DFMEA. Chamicą! Snai: lX-:iiyr. & Ma-uriai Mount Materiał / Wire / Seals Substrate

Wash coat Technology Ptecious Metal toadinc/Ratto

• Geometry fcontourilength) • Celi Denslty • WaJIthickness Packaglng Location & Volume Row Distribution

(Pip* & Cone Geometry)

Siana | Mass Exnaust Gas Composllion

—■■„■■■■■■■■•ff^foź; Control Factors

mm

Skt#fc

i

Effor States: Functional • Output gases do not meet emission requirernents

Non-Functionaf ■ Odor/Smell • • • • •

No«se/Raffle Power Loss Excessive Heat (internal) Excesslve Heal (extemal) Exhaust leak lnadvertant Chsck Engine signal

u--^ Energy • ThermaJ Mechanical Chemical Pr-essure

i . — - - '•-«■-'"■'

Respoosa; Y, = Regulated Emission (HC CO NOx) [gms/mile] Y, = Non-Regulated Emission (H2S) [ppm/test]

.

Changes Ov«r_Timc/Miie Btockage / restriction Weld cteterioration / taligue Substrate retenlion (Mount degradation) Subsirale efosion / breałooe Catatyst chemical ageing Corrosion of sheH Loosening of heat shield

Ł».t£rnąl Enyjronrnen.t Amblent temperaturę Road load / vibralion Off Road - debrls / rccks Road Saltf mud/ water

Custorncr Usage Short, Iow speed trips High speed with Irailei tow Fuel type & quality / sulfur tevel Service damage Shipping mishandling Driving with engine errora

Noise F a c t o r s yarialion

Materiał vartalion Substrate Wash Composftion Cannłng forces: • Clampjng farcs • Wrap tighiness • Crimping force Assembly process • Misbiald / mtslabets • Orientation and centralny • Mount gap IMatl/WlreJ/SheflOD • Dimension (Assembly) Welding process

1

Systurn Intoractions Heat SNeid / NVH PaCs 1 Wełded Exhaust Manlfokl Leaks Engine misfire Excessive Heat Oli contamlnatlon Power train load vibration Dynamie load (engine induced) Calibration Backpressure

Figurę III.2 Example of a Parameter (P) Diagram for a Generic Catalytic Converter

21

Chaptei III


Functional Requirements

i

Anothei step in the DFMEA process is a compilation of the functional and inteiface iequirements of the design I his list may include the following categoiies: •

Geneial: This category considers the puipose of the ptoduct and its oveiall design intent

•

Safety

•

Govemment Regulations

•

Reliability (Life of the Function)

•

Loading and Duty Cycles: Customei ptoduct usage profile

•

Quiet Opeiations: Noise, vibiation and hatshness (NVH)

•

Fluid Retention

•

Ergonomics

•

Appeaiance

•

Packaging and Shipping

•

Service

•

Design for Assembly

•

Design fot Manufactuiability

Other Tools and Information Resources Other tools and resouices that may help the team understand and define the design reąuirements may include: •

Schematics, diawingSj etc

•

Bill of Materials (BOM)

•

Intenelationship matiices

•

Intetface matrix

•

Quality Function Deployment (QFD)

•

Quality and Reliability Histoiy The use of these tools, suppoited by engineenng experience and histoiical information, can assist in deflning a comprehensive set of ieąuirements and functions

-v

Aftei considering these pteieąuisites, statt filling out the fbim (labie 111 lbelow)

22

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Chapter HI


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23

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24


Chapter III

ExampleDFMEA The example used with the saraple foim deals wilh a Fiont Door assembly The product has several fiinctiooal requirements: Peimit ingtess to and egress fiom vehicle Piovide oceupant piotection &om o

Weather (comfort)

o

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Maintain integrity of innei dooi panel The finał DFMEA would include analysis of all these requirements The example includes pait of the analysis of the requirement: "Maintain integrity of innei dooi panel"

Header of the Design FMEA Form (fields A-H) The following describes the infoiraation to be entered on the foim Ihe headei should cleaily identify the focus of the FMEA as well as infoimation lelated to the document deve!opment and control process. This should include an FMEA number, identification of the scope, design lesponsibility, completion dates, etc The header should contain the following elements2:

The letters at the end of each heading indicate the aiea referred to on the sample fbim

25


Chapler III

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Table III.I Sam ple DFMEA Form with Minima! Information Elements & Example Entries

26


FMEA Number (A) Enter an alphanumeiic stting which is used lo identify the FMEA document This is used foi document conool

System, Subsystem, or Cornponent Name and Number (B) Enter the name and number of the system, subsystem, or cornponent which is being analyzed (See section entitled Define the Scope)

Design Responsibiiity (C) Entei the OEM, oiganization, and depaitment or gioup who is design lesponsible Also entei the supply oiganization name, if applicable

Model Year(s)/Program(s) (D) Enter the intended model yeai(s) and piogiam(s) that will use 01 be aifected by the design being analyzed (if known)

Key Datę (E) Entei the initial DFMEA due datę, which should not exceed the scheduled production design ielease datę

FMEA Dates (F) Entei the datę the oiiginal DFMEA was compieted and the latest revision datę

Core Team (G) Entei the team members responsible for developing the DFMEA Contact infoimation ( e g , name, oiganization, telephone number, and email) may be included in a leferenced supplemental document

Prepared By (H) Enter the name and contact infoimation including the oiganization (company) of the engineer lesponsible for piepaiing the DFMEA

27

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28

Chaptei HI


Body of the DFMEA Form (fields a - n) The body of the FMEA contains the analysis of lisks idated to the potential failuies, and impiovement action being taken 3

Item / Function / Requirements (a) Item/Function can be sepaiated into two (or moie) columns ot combined into a single, bridged column which encompasses these elements Inteifaces (as "items" of analysis) can be eithei combined or separate. Components may be listed in the item/function column, and an additional column may be added containing the functions or iequiiements of that item "Item", "Function", and "Requiiements" aie desciibed below:

Item (a1) Enter the items, inteifaces, 01 pmts which have been identified thiough błock diagiams, P-diagiams, schematics and othei diawings, and othei analysis conducted by the team The teiminology used should be consistent with customei iequirements and with those used in othei design development documents and analysis to ensuie tiaceability.

Function (a1) Enter the runction(s) of the item(s) 01 inteiface(s) being analyzed which aie necessaiy to meet the design intent based on customei iequiiements and the team's discussion. If the item(s) or inteiface nas morę than one function with different potential modes of failuie, it is highly lecommended that each of these runctions and associated failure mode(s) is listed sepaiately Function becomes a2 if Item and Function are Split

Requirements (a2) An additional column, "Requirements", may be added to fuithei refine the analysis of the failure mode(s) Entei the iequirement(s) for each of the functions being analyzed (based on customei iequirements and the team's discussion; see also Chaptei II, Section: Pieiequisites) If the function has moie than one iequirement with different potential modes of failure, it is highly recommended that each of the ieąuiiements and functions are listed separately \ Requir©ment becomes a3 if Item and Function are Split into \ separate columns, e g , a1 and a2

The letters at the end of each heading indicate the area refeited to on the sample tbim 29

POTENTIAL FAILURE MODĘ ANO EFFECTS ANALWIS (DESIGN FMEA)

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Potential Failure Modę (b) Potential failure modę is defined as the manner in which a component, subsystem, or system could potentially fail to meet 01 delivet the intended function desciibed in the item column Identify the potential failuie mode(s) associated with the tunction(s)/requirement(s) Potential failuie modes should be desciibed in technical teims, and not necessaiily as a symptom noticeable by the customei Each function may have multiple failure modes A large numbei of failure modes identified for a single function may indicate that the iequirement is not well defined. The assumption is madę that the failuie could occur, but may not necessaiily occur, conseąuently the use of the woid "potential" i ! Potential failure modes that could occur only under certain : operating conditions (i.e., hot, cold, dry, dusty. etc) and under j certain usage conditions (i e., above-average mileage, rough terrain, city driving only, etc) should be considered After determining all the failure modes, a validation of the completeness of the analysis can be madę through a review of past things-gone-wrong, concems, reports, and gioup biainstorming The potential failure modę may also be the cause of a potential failuie modę in a higher Ievel subsystem 01 system, or lead to the effect of one in a lower level component Example failuie modes, as related to diffeient requiiements, aie shown in table III .3

31

Chaptei III


Item

Function

Disk Brake system

Stop vehicle on demand (consideiing enviionmental conditions such as wet, dry, etc )

Requirement Stop vehicle travelmg on dry asphalt pavement within specified distance within specified g's of force

Allow unimpeded vehicle movement on no system demand Biake Rotoi

'.■;'■

• : - '

'■'. .■ ••

Allows tiansfer of force from biake pads to axle

Must deliver specified toiąue lesistance at axle

Failure Modę Vehicle does not stop Vehicle stops in excess of specified distance Stops vehicle with morę than xx g's of force Activates with no demand; Vehicle movement is partially impeded ActWates with no demand Vehicle cannot move Insufficient torque lesistance delivered

. ; '

Tabie ffl.3 Example Potentia! Failure Modes

32

Chapter III


This page intentionally left blank.

33

POTENTlAl FAILUflf MOOE AND EFFECfS ANALYSIS (DfólOJ FMfAl

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Potential Effect(s) of Failure (c) Potential effects of failuie aie defined as the effects of the failure modę on the fiinction, as peiceived by the customei(s). Desciibe the effects of the failuie in teims of what the customei might notice or expeiience, iemembering that the customei may be an internal customei as well as the ultimate End User State clearly if the failuie modę could impact safety or noncompliance to regulations. The effects should always be stated in teims of the specific system, subsystem, 01 component being analyzed Remember that a hieiarchical relationship exists between the component, subsystem, and system levels4 For example, a pait could fiactuie, which may cause the assembly to vibrate, resulting in an inteimittent system opeiation The inteimittent system operation could cause peifoimance to degiade and ultimately lead to customei dissatisfaction The intent is to piedict the potential failure effects to the team's level of knowledge Typical failure effects should be stated in teims of product or system peifoimance Table III 4 shows example effects of the failure modes nom Table JII.3 Item Disk Biake System

Failure Modę

Effect

Vehicle does not stop Vehicle stops in excess of specified distance Stops vehicle with morę than xx g's of foice

Vehicle control impaired; Regulatory non-compliance Vehicle controE impahed; Regulatory non-compliance

Regulatoiy non-compliance

Activates with no demand; Vehicle movement is paitially impeded

Decreased pad life; dirninished vehićle control

Activates with no demand Vehicle cannot move

Customer unable to drive vehicle

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Tab!e HL4 Esample Potential Effects

4

See also Appendix B 35

POTENTIAL FAILURE MODĘ AND EFFECTS ANALYSIS (DESIGN FMEA)

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Severity (S) (d) Severily is Ihe value associated with the most seiious effect fot a given failuie modę Seveiity is a relatiye lanking within the scope of the individual FMEA Suggested Evaluation Criteria The team should agiee on evaluation criteiia and a ranking system and apply them consistently, even if modified for individual piocess analysis (See Table Crl below for criteiia guidelines) \ lt is not recommended to modify criteria ranking values of 9 and 3 10- Faiiure modes with a rank of severity 1 should not be a analyzed further

Criteria: Effect

Severlty of Effect on Product

Rank

(Customer Effect)_ Failurc to Meet Safety and/oi Regulatory Requh ements Loss oiDcgradation (lt PMTliaiy

Function Loss o» Degiadation of Secondaiy function

Annoyance

No effect

Potential faiiure modę afiects safe vehicle opeiation and/oi ińvolves noncompliance with goveinment legulation without waining

10

Potential failuie modę affects safe vehicle opeiation and/oi involves noncompliance with govemment regulation with waming

9

Loss of piimary function (yehicle inopeiable, does not affect sale vehicle operation)

8

Degiadation of piimary function (vehicle opeiable, but at reduced level of performance)

7

Loss of secondaiy function (vehicle opeiable, but comfort / convenience functions inoperable)

6

Degradation of secondaiy function (vehicle opeiable, but comfoit / convenience functions at reduced level of performance)

5

Appearance oi Audible Noise, vehicle opeiable, item does not confoim and noticed by most customeis (> 75%)

4

Appeaiance or Audible Noise, vehicle opeiable, item does not conform and noticed by many customeis (50%)

3

Appearance or Audible Noise, vehicle operable, item does not conform and noticed by disciiminating customeis (< 25%)

2

No disceraible effect

1

Table Crl Suggested DFMEA Severity Evaluation Criteria

37

POTENTIAL FAILURE MODĘ AND EFFECTS ANALYSIS (DESIGN FMEA1

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Classification (e) This column may be used to highlight high-piiority failuie modes and theii associated causes As a result of this analysis, the team may use this infoimation to identity special chaiacteiistics ; Customer specific requirements may identify special product or process characteristic symbols and their usage ■ A characteristic designated in the design record as special ; without an associated design failure modę identified in the ■ DFM6A is an indication of a weakness in the design process

Potential Cause(s)/Mechanism(s) of Failure Modę (f) This infoimation can be separated into multiple columns 01 combined into a single column In the development of the FMEA, the identification of all potential causes of the failuie modę is key to subsequent analysis Although vaiied techniąues (such as brainstoiming) can be used to determine the potential cause(s) of the failuie modę, it is recommended that the team should focus on an understanding oitbs failure mechanizm for each failuie modę

Potentia! Mechanisrn(s) of Failure Modę (f1) A failuie mechanism is the physical, chemical, electiical, theimal, 01 other process that results in the failuie modę It is impoiiant to make the distinction that a failuie modę is an "obseived" or "extemar effect so as not to confuse failuie modę with failuie mechanism, the actual physical phenomenon behind the failure modę 01 the process of degradation 01 chain of events leading to and resulting in a paiticular failuie modę To the extent possible, list eveiy potential mechanism for each failuie modę The mechanism should be listed as concisely and completely as possible. For a system, the failure mechanism is the process of enor propagation following a component failure which leads to a system failuie A product or process can have several failure modes which are : correlated to each other because of a common failure l mechanism behind them I Ensure that process effects are considered as part of the . DFMEA process

39

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Potential Cause(s) of Failure Modę (f2) Potential cause of failure is defined as an indication of how the design process could al Iow the failuie to occur, described in terms of something that can be corrected or can be contiolled Potential cause of failure may be an indication of a design weakness, the consequence of which is the failure modę ] Causes are the circumstances that induce or activate a failure i mechanism In identifying potential causes of failuie, use concise desciiptions of the specific causes of failures, eg., specified bolt plating allows for hydiogen embiittlement Ambiguous phtases such as, pooi design or impropei design, should not be used Investigation of causes needs to focus on the failure modę and not on the effect(s) In deteimining the cause(s), the team should assume the existence of Che cause under discussion will icsult in the failuie modę (i e , the failure modę does not iequiie multiple causes to occur) Typically, there may be several causes each of which can result in the failuie modę. This lesults in multiple lines (cause bianches) for the failure modę To the extent possible, list eveiy potential cause for each failure mode/failuie mechanism The cause should be listed as concisely and completely as possible Sepaiating the causes will icsult in a focused analysis for each cause and may yield different measuiement, contiols, and action plans Table III 5 shows sample causes fbi the failure modes in Table UJ 3 Although not reąuiied as pait of the minimum FMEA foim elements, the table includes the failure mechanism to show the relationships among failuie modę, failuie mechanism, and cause In piepaiing the DFMEA, assume that the design will be manufactuied and assembled to the design intent Exceptions can be madę at the teamłs discietion wheie histoiical data indicate deficiencies in the manufacturing piocess

■1

Chaptei III


Failuie Modę

Cause

Mechanisra

Mechaoical Unkage break due to inadequate corrosion protection Vehiciedoes not stop

Vehicle siops io exces$ of

yyfeet

Slops vehicle wilh morę than xx g's oi force

No transfer ot lorce from pedał to pads

Reduced transfer of force from pedał to pads

ExcessiveAapid transfer of force from

Master cylinder vacuum lock due lo seal design l oss of hydraulic fluid from loose hydraulic linę due to incorrect connector torque specification Loss of hydraulic fluid due to hydraulic lines crimped/compressed, inappropriate tubę mateiial specified Mechanical linkage joints stiff due to inappropriate lubrication specification Mechanical linkage joints corroded due to inadequate corrosion protection Partial loss of hydraulic fluid due to hydraulic lines crimped, inappropiiate tubę materiał specified Cumulative pressure build-up rn master cylinder due to seal design

ActWate with no demand; Vehic!e moveraent is impeded

Pads do not releasc

Corrosion or deposit build up on rails or pad eais due to surface frnish not promoting adequate self cleaning and corrosioa protection

Actfvate with no demand Vebicle cannot raove

Hydraulic pressure does not idease

Master cylinder vacuum lock due to sea! design

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42

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44


Occurrence (O) (g) Occunence is the likelihood ihat a specific cause/mechanism will occur resulting in tbe failuie modę within the design life The likelihood of occurrence ranking numbei has a ielative raeaning iather than an absolute value (See Table Cr2). A consistent occunence ranking system should be used to ensuie continuity Ihe occuirence numbei is a ielative tanking within the scope of the FMEA and may not ieflect the actual likelihood of occunence Suggested Eva!uation Critetia The team should agiee on evaluation criteiia and a ranking system and apply them consistently, even if modified foi individual piocess analysis Occunence should be estimated using a 1 to 10 scalę using Table Cr2 as a guideline. In deteimining this estimate, questions such as the following should be consideied: •

What is the seivice histoiy and field expeiience with similar components, subsystems, 01 systems?

•

Is the item a canyover or similar to a pievious level item?

•

How significant aie changes fiom a pievious level item?

•

Is the item ladically dif feient fiom a previous level item?

•

Is the item completely new?

•

What is the application 01 what are the environmental changes?

•

Has an engineenng analysis ( e g , ieliability) been used to estimate the expected comparable occunence late for the application?

•

Have preventive contr ols been put in place?

4.'

Chaptei m

Likelihood of Failure


Criteria: O c c u r r e n c e of C a u s e - DFMEA

Criteria: O c c u r r e n c e of C a u s e - DFMEA ( D e s i g n life/reliability of i t e m / v e h i c l e )

Rank

(Incidents per items/vehicles)

New tecbnology/new design with no hisiory

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Very High

10 £ 1 in 10

High

Failure is inevitable with new design, new application, or change in duły cycle/operating condilions

50 per thousand

Failure is Ukcly with new design, new application, or change in duty cycle/opetating conditions

20 per thousand

9 1 in20

'

Failure is uncenain wilh new design, new application, or change in duły cycle/operaiing condilions

8

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Fieąuent failurcs associated with sirnilai designs or in design simulation and testing

T.

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Modetale

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5 pei thousand

Isolated failurcs associated with sirnilai design 01 in design simulation and testing

I per thousand

5 1 in 2,000 4

1 in 10,000 Only isolated failures associated with almost idenlical design or in design simulation and testing

01 per thousand

Mo observed failurcs associated with almost identical design oi in design simulation and testing

£ 0 0 1 pet thousand

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Failure is eliminated through preventive contro! Veiy 1 ow

Failure is eliminated through preventive control.

Table Ci2 Suggested DFMEA Occurrence Evaluation Criteria

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Chapter IIT

Design Pailure Modę and Effects Analysis


47

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48


Current Design Controls (h) Cunent Design Controls aie those activities conducted as part of tbe design process that have been completed 01 committed to and that will assuie the design adeąuacy for the design functional and reliability leąuirements under consideiation. Theie aie two types of design controls to consider: PreventioD: Eliminate (prevent) the cause of the mechanism of failuie or the failuie modę fiom occuning, oneduce its tatę of occurrence. Detection: Identify (detect) the existence of a cause, the lesulting mechanism of failuie or the failure modę, eithei by analytical or physical methods, beibie the item is released foi pioduction. : The preferred approach is to first use prevention controls, if j possible The initial occurrence rankings will be affected by the l prevention controls provided they are integrated as part of the design intent Detection contro! should include identification of those activities which detect the failure modę as well as those that detect the cause. The team should consider analysis, testing, ieviews, and othei activities that will assure the design adeąuacy such as: Prevention Controls •

Benchmaiking studies

•

Pail-safe designs

•

Design and Mateiial standards (interna! and exteinal)

•

Documentation - records of best piactices, lessons Iearaed, etc fiom similar designs

•

Simulation studies - analysis of concepts to establish design reąuirements

•

Eiioi-proofing Detection controls

•

Design reviews

•

Prototype testing

•

VaIidation testing

•

Simulation studies - validation of design

•

Design of Expeiiments; including reliability testing

•

Mock-up using similai parts

49

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Tbe example Design FMEA foim in this manuał has rwo columns for the design controls (i.e, separate columns foi Prevention Contiols and Deteclion Controls) lo assist the team in cleaily distinguishing between these two types of design contiols. This allows fo-i a quick visual deteimination that both types of design contiols have been considered If a one-column (foi design contiols) foim is used, then the following prefixes should be used For prevention contiols, place a 'P' befoie each pievent»on contiol listed Foi deteclion contiols, place a 'D' befoie each deteclion contiol listed Preventing the causes of the failuie modę through a design change 01 design piocess change is the only way a reduction in the occunence ianking can be effected Table III 6 shows example pievention and detection contiols for the causes identified in Table III.5. Failure Modę Vehicle does not stop

Cause

Prevention controls

Mechanical linkage bieak due to inadeąuale conosion piotection Master cylinder vacuum lock due to seal design

Designed per mateiial standard MS-845 Carry-ovei design with same duty cycle leąuiiements Designed per torąue reąuirements 3993

Loss of hydraulic fluid trom loose hydiaulic Iine due to incoirect connectoi torąue specification Loss of hydiaulic fluid due to hydiaulic lines ciimped/compressed, inappropriate tubę materiał specified

,-,:..'

Designed pei materiał standaid MS-1178

Detection controls Enviionmental stress test 03-9963 Pressure vaiiabiiity testing - system level Vibiation stepstiesstest 18-1950

Design of Expeiiments (DOE) -tubeiesiliency

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Detection (D) (i) Detection is the iank associated with the best detection conttol listed in the Cuiient Design Con&ol Detection column When morę than one control is identified, it is recommended that the detection ranking of each control be included as pait of the description of the control Record the lowest ianking value in the Detection column A suggested appioach to Cuirent Design Control Detection is to assume the failure has occuned and then assess the capabilities of the cunent design contr ols to detect this failure modę Do not automatically presume that the detection ranking is Iow because the occuiience is Iow It is impoitant to assess the capability of the design contiols to detect Iow fieąuency failure modes 01 reduce the risk of them going futther in the design releaseprocess Detection is a relative ianking within the scope of the individual FMEA In order to achieve a lower ranking, geneially the design control (analysis or verification activities) has to be improved Suggested Evaluaticn Criteria The team should agiee on evaluation criteria and a ranking system and apply them consistently, even tf modified lor individual piocess analysis. Detection should be estimated using Table Cr 3 as a guideline The ranking value of one (1) is reserved for failure prevention : through proven design solutions

53


Chaptei III

Opportunity for Detection

Criteria: Likefihood of Detection by Design Control

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Rank

■-.■of

■.■.;,

Detection '.■I J.iiwii.i!'.

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No cuirenl design control; Cannot detect ot is not analyzed

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Design anaiysis/detection contiols have a weak detection capabilily; Virtual Analysis (e g , CAE, FEA, etc ) is not cprrclau-d ;o expeeted aciual operating conditions

Product verification/validation aftei design freeze and prioi to launch with pass/fail testing (Subsystem or system testing with acceptance criteria such as nde and handling, shipping evaluaiion, etc) Post Design Freeze and prior to launch

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Pioduct vetification/validaIion after design fieeze and prior to launch with riegradation testing (Subsystem or system testing after durability test. e g , function check) Product validation (ieliability testing, development or validation tests) prior to design freeze using pass/fali testing (e g , acceptance ctiteiia for performance, function checks, etc)

Prioi to Design Fjeeze

Product validation (reliability testing, dcvclopment ot validation tests) prioi to design freeze using test to failure (e g , until leaks, yields, cracks. etc )

Moderatply-

Product validation (reliability tesling, development or validation tests) prior to design freeze using degradation testing (e g , data trends, before/aftet values, etc)

Viitual Analysis Correlaled

Design anaiysis/detection contiols have a stiong detection capability Virtual analysis (e g , CAE, FEA, etc ) is hi«hlv corretated with actual 01 expected operating conditions prioi to design fieeze

Detection not applicable; Failuie Prevention

Failure cause ot failure modę can not occui because it is fully prevented through design solutions (c g , prowen design standard, best praclice or common materiał, etc)

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Table C t 3 Suggested DFMEA/PFMEA Prevention/Detection Evaluation Criteria

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Determining Action Priorities Once the team has completed the initial identification of failuie modes and effects, causes and controls, including lankings foi sevexity, occuiience, and detection, they must decide if fuithei efforts are needed to ieduce the risk Due to the inherent limitations on tesouices, time, technology, and other factots, they must choose how to best piioritize these eflbrts The initial focus ofthe team should be oiiented towards failuie modes with the highest seveiity iankings When the sevetity is 9 01 10, it is impeiative that the team must ensuie that the risk is addiessed thiough existing design contiols or recommended actions (as documented in the FMEA). For failure modes with severities 8 or below the team should considei causes having highest occuiience oi detection iankings It is the team*s lesponsibility to look at ihe infoimation identified, decide upon an approach, and deteimine how to best piioritize the risk reduction effoits that best serve theii organization and customeis

Risk Evaluation; Risk Priority Number {RPN) Q) One appioach to assist in action prioiitization has been to use the Risk Piioiity Numbei: RPN - Sevetity (S) x Occuiience (O) x Detection (D) Within the scope of the individual FMEA, this value can rangę between 1 and 1000 The use oj an RPN rhreshold te NOT a recommended ptactice fot determining the needfor actwm Applying thiesholds assumes that RPNs are a measuie of ielative risk (which they often are not) and that continuous improvement is not iequired (which it is) Foi examp!e, if the customei applied an arbitrary thieshold of 100 to the following, the suppliei would be reąuiied to take action on the chaiacteństic B with the RPN of 112.

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In this exaraple, the RPN is higher foi chaiacteristic B, but the priority should be to woik on A with the highei severity of 9, although the RPN is 90 which is lower and below the thieshold. Another concern with using the threshold approach is that theie is no specific RPN value that reauiies mandatory action. Unfoitunately, establishing such thiesholds may promote the wiong behavior causing team membeis to spend time trying to justify a lowei occurtence ot detection ranking value to ieduce RPN This type of behavioi avoids addressing the teal problem that underlies the cause of the failure modę and merely keeps the RPN below the thieshold It is impoitant to recognize that while determining "acceptable" risk at a particulai program milestone ( e g , vehicle launch) is desiiable, it should be based on an analysis of severity, occunence and detection and not thiough the application of RPN thresholds

: Use of the RPN index in the discussions of the team can be a i useful tool The limitations of the use of RPN need to be understood However, the use of RPN thresholds to detetmine l action priority is not recommended

Recomrnended Action(s) (k) In generał, prevention actions (i e , reducing the occunence) are preferable to detection actions An example of this is the use of proven design standard or best practice rather than product verification/vaIidation after design fieeze The intent of recommended actions is to improve the design fdentifying these actions should consider reducing rankings in the following order: severity, occunence, and detection Example approaches to ieduce these are explained below: •

To Re duce Severity (S) Ranking; Only a design ievision can bring about a leduction in the seveiity lanking

\ High severity rankings can sometimes be reduced by making | design revisions that compensate or mitigate the resultant • severity of failure For example: The requirement for a tire is to i "retain applied air pressure under use" The severity of the effect - of the failure modę "rapid loss of air pressure" would be lower for .- a "run fiat" tire \ A design change, in and of itself, does not imply that the severity I will be reduced Any design change should be reviewed by the l team to determine the effect to the product functionality and j process

59

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Design Failuie Modę and Effects Analysis Foi maximum effectiveness and efficiency of this appioach, changes to the pioduct and piocess design should be implemented early in the development piocess Foi example, altemate materials may need to be consideied eaily in the development cycle to eliminate conosion seveiity. To Reduce Occurrence (O) Ranking: A reduction in the occunence ianking can be effecied by removing 01 controlling one oi morę of the causes 01 mechanisms of the failure modę through a design ievision Actions such as, but not limited to, the following should be consideied: o

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If the assessment leads to no recommended actions foi a specific failure mode/cause/contiol combination, indicate this by enteiing "Nonę" in this column. It may be useful to also include a rationale if "Nonę" is enteied, especially in case of high severity For design actions consider using the following: Results of design DOE oi reliability testing Design analysis (ieliabilify, structural oi physics of failuie) that would confum that the solution is effective and does not introduce new potential faihue modes Diawing, schematics, ot model to confirm physical change of taigetedfeature Results fi om a design review Changes to a given Engineering Standard or Design Guidelines Reliability analysis lesults

61

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Design Failure Modę and Effects Analysis Table III .7 below provides an example of the application of causes (Column f), controls (Column h) and recommended actions (Column k)

Rssponsibility & Target Completion Datę (I) Entei the name of the individual and organization responsible for completing each lecommended action including the taiget completion datę The deslgn-responsible engineei/team leader is responsible for ensuiing that all actions iecommended have been implemented or adequately addiessed

Action Results (m-n) Ihis section identifies the results of any completed actions and their effect on S, O, D rankings and RPN

Action(s) Taken and Completion Datę (m) After the action has been implemented, entei a bfief description of the action taken and actual completion dale

Severity, Occurrence, Detection and RPN (n) Aftei die preventivev'conective action has been completed, determine and lecord the resulting seveiity, occuirence, and detection rankings Calculate and record the resulting action (lisk) priority indicatoi ( e g , RPN) All ievised rankings should be reviewed. Actions alone do not guaiantee that the problem was solved ( i e , cause addtessed), thus an appropriate analysis or test should be completed as verification If finthei action is considered necessary, repeat the analysis The focus should always be on continuous impiovement

63

Design Failure Modę and Efiects Analysis

Preventfon Controls

Item

Failure Modę

Cause

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Vebictc doesnot stop

Mechamcal linkage break, due lo inadequate coirosion proteclion

■"■ '

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Detection Controls

Recommended Actions

Designed pet materiał standaid MS845

Environraental stress test 03-9963

Change materiał to stainless steel

Maslet cylinder vacuum lock due to seal design

Carry-over design with same dury cycle reąuiieraents.

Pressure variability testing - system leve!

Use carry-over aeal design

Lossof hydraulic fluid from loose hydiaulic linę due to incoirect coiwectoi rorąue specificalioo

Designed per loiąue leąuirements 3993

Vibiation step-stiess test 18-1950

Modtfy connector &om bolt-style to quick-connect

Loss of hydiaulic fluid due to hydraulic lines ci imped;corapiessed, inappropriate tubę materia! specified

Designed per materiał standaid MS1178

DOE-tube resiliency

Modify hose design &om MS1178 to MS-2025 toincreasestiength

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Maintaining DFMEAs The DFMEA is a lLving document and should be reviewed whenevei there is a pioduct design change and updated. as iequiied. Recommended actions updates should be included into a subseąuent DF MEA along with the finał lesults (what wotked and what did not wotk) Anothei element of on-going maintenance of DFMEAs should include a peiiodic ieview of the rankings used in the DFMEA Specific focus should be given to Occunence and Detection rankings This is paiticularly impoitant where impiovements have been madę eithet thiough pioduct changes oi impiovements in design controls Additionally, in cases wheie field issues have occmred, the lankings should be ievised accordingly

M

Chaptei III

Design Failute Modę and Effects Analysis

Leveraging DFMEAs If a new pioject or application is functionally similai to the existing product, a single DFMEA may be used with customer concurrence Using a fundamentally sound baseline DFMEA as the staiting point piovides the gieatest opportunity to leverage past expeiience and knowledge If there are slight differences, the team should identify and focus on the effects of these differences

Linkages The DFMEA is not a "stand-alone" document. Foi example, the output of the DFMEA can be used as input foi subsequent product development processes It is the summaiy of the team's

discussions and analysis Figurę III 7 shows the linkages of some of the commonly used documents

Boundary (Biock) Diagram, P - Diagram, etc. DFMEA Design Verification Plan& Report (DVP&R), PRv1EA:etc. Figurę I H 7 DFMEA Information Inteirelationships Flow

65


Chapter Iii

Design Verification Plan & Report (DVP&R) DFMEA and DVP&R have an impoitant Iinkage The DFMEA identifies and documents the cunent design prevention and detection contiols which become input to the test desciiption included within the DVP&R The DFMEA identifies "what" the contiols are while the DVP&R provides the "how" such as acceptance ciitetia, proceduie and sample size

PFMEA Anothei impoitant Iinkage is between the DFMEA and PFMEA For example, a Piocess (PFMEA) failuie modę oi a Design (DFMEA) failuie modę can iesult in the same potential pioduct effect In this case, the effects of the design failuie modę should be ieflected in the effects and seveiity rankings of the DFMEA and PFMEA.

66

Chaptet IV

Piocess Failuie Modę and Effccts Analysis

)

PFMEA Process Faiiure Modę and Effects Analysis

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67

■■n->

Piocess Failuie Modę and Effects Analysis

The piocess FMEA, leferred to as PFMEA, supports manufactuiing piocess development in reducing the risk of failures by: •

Identifying and evaluating the piocess functions reąuiiemems,

•

Identifying and evaluating potential pioduct and piocessrelated failure modes, and the effects of the potential failures on the piocess and customeis,

•

Identifying the potential manufactuiing oi assembly process causes,

•

Identifying piocess variables on which to focus process contiols for occunence reduction or incieased detection of the failuie conditions, and

•

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•

Be initiated piior to tooling for production,

•

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•

Include all piocesses within the plant that can impact the manufactuiing and assembly opeiations, such as shipping, receiving, transporting of materiał, storage, conveyors or labeling

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Eaily review and analysis of new oi ievised piocesses is advised to anticipate, resolve, or monitoi potential process concerns duiing the manufactuiing planning stages of a new model ot component ptogram The PFMEA assumes the product as designed will meet the design intent Potential failuie modes that can occur because of a design weakness may be included in a PFMEA Theii effect and avoidance is covered by the Design FMEA The PFMEA does not rely on pioduct design changes to overcome limitations in the process Howevei, it does take into consideiation a pioducfs design chaiacteiistics relative to the planned manufacturing oi assembly process to assure that, to the extent possible, the resultant pioduct meets customer needs and expectations. Foi example, the PFMEA development generally assumes that the machines and eąuipment will meet their design intent and therefoie aie excluded frorn the scope Control mechanisms for incorning paits and mateiials may need to be considered based on histoiical data

68

Chaptei r v


Customer Defined The definition of "Customer" for a PFMEA should normally be the "End User" However, the customer can aiso be a subseąuent oi downstream raanufacturing oi assembly opeiation, a seivice opeiation, oi regulator5

Team Approach The Pf MEA is developed and maintained by a mulri-disciplinaiy (or cross-functional) team typically led by tire responsible engineer During the initial development of the PFMEA, the lesponsible engineei/team leadei is expected to directly and actively involve repiesentatives from all affected aieas These aieas should include but are not limited to design, assembly, manufactuiing, materials, quality, service, and supplieis, as well as the aiea responsible for the next assembly The PFMEA should be a catałyst to stimulate the inteichange of ideas between the aieas affected and thus promote a team approach

Design Considerations The team should assume the pioduct as designed will meet the design intent During the development of a PFMEA, the team may identify design oppoitunities which, if implemented, would either eliminate or reduce the occurrence of a piocess failuie modę For example, adding a feature to a part and a matching featute to a fixtuie will eliminate the possibility of an operator placing a part in the wtong orientation Such infoimation must be piovided to the responsible design engineer as well as the tooling / equipment / fixture design-iesponsible individual for consideration and possible implementation

See discussion in Chapter IT, Customer Defined 69

Chapter IV


Development of a Process FMEA The process-iesponsibie engineer/team leader has at his or her disposal a number of documents that will be useful in pieparing the Pf MEA. The PFMEA begins by developing a list of what the process is expected to do and what it is expected not to do, i.e., thepiocess intent The PFMEA should begin with a flow chait of the generał process This flow chart should identify the pioduct/process chaiacteristics associated with each opeiation Identification of product effects ftom the corresponding DFMEA should be included Copies of the flow chart used in the PFMEA prepaiation should accompany it In ordei to facilitate documentation of the analysis of potential failures and theii conseąuences, example PFMEA forms have been developed and aie piovided in Appendix A The minimum infoimation content ieąuired foi a PFMEA is discussed below (AlsoseeTablelYl)

Prerequisites A PFMEA should begin with the development of infoimation to understand the manufactuiing and assembly opeiations being analyzed and define theii reąuiiements. The process flow diagiam is a piimaiy input to the PFMEA The flow diagiam is used as a tool to help establish the scope of analysis duiing manufactuiing system design

Process Flow Diagram and linkage to PFMEA A process flow diagiam6 describes the flow of the pioduct through the process - fiom incoming to outgoing This should include each stęp in a manufactuiing or assembly piocess as well as theii related outputs (pioduct chaiacteristics, teąuirements, deliveiables, etc) and inputs (process characteiistics, souices of vaiiation, etc) The detail of the process flow depends on the stage of piocess development discussion Ihe initial flow diagiam is generally considered a high level piocess map It needs morę detailed analysis to identify the potential failure modes.

6

The Process Flow Diagram is also refeired to as a Process Flow Chart 70

Chapter IV

Piocess Failwe Modę and Effects Analysis

High Level Process Map

B-B-S-0 Detailed Process Flow Diagram

Figurę IV 1 High Level to Detailed Process Maps

The PFMEA should be consistent with the information in the process flow diagram The scope of the piocess flow diagram should include all manufactuiing operations ftom processing of individual components to assemblies including shipping, ieceiving, transportation of materiał, stoiage, conveyois, labeling, etc A pieliminary tisk assessmenl using the process flow diagram may be peifbimed to identify which of these operations or individual steps can have an impact on the pioduct manufactuiing and assembly and should be included in the PFMEA The PFMEA development continues by identifying the iequiiement(s) for each process/function Requiiements aie the outputs of each operation/step and relate to the reąuirements for the producl The Requirements provide a desciiption of what should be achieved at each operation/step The Reąuirements provide the team with a basis to identify potential failure modes In order lo assure continuity, it is highly recommended that the same cioss-functional team develop the Process Flow Diagiam, PFMEA, and Contiol Plan See Figurę IV 2 foi an example process flow diagram

71

Piocess Failuie Modę and Effecls Analysis

Chaptei IV

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Materiał consistency Tool (insert) consistency Improper setup Poof chip removał (ie Iow coolant pressure Improper setup Toollng consistency Cootant flow Dress/compensation consistency & accuracy Dirty/oily parts Poor gage maintenance Consistency of maintenance

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72

Chapter IV

)

Process Failuie Modę and Effects Analysis

Other Tools and Information Sources Othei sources of infoimation that aie useful in pioviding the team with ways to focus and captuie discussions on the ieąuirements of the piocess include: DFMEA Diawings and design recoids Bill of Process Inteiielationship (Characteiistic) matiix Intemal and extemal (customer) nonconfoimances (i e , known failute modes based on histoiical data)

Quality and Reliability Histoty

Research Information Aftei establishing the scope of the analysis effoit, the team should begin by ieviewing histoiical information. The areas to ievie\v should include: • |

Lessons that have been learned from pievious product and piocess design implementation, and Any information available that establishes best piactices including items such as guidelines and standards, standard pait identification, or enor-pioofiiig methods Quality peifoimance infoimation available from similar, pievious product and process designs, including items such as: process yield7, first time capability (both end of linę and at each opeiation), Paits pei Million (PPM), piocess capability indices (Cpi; and PPk), and wananty metiics The infoimation can be useful input for deteimination of seveiity, occunence and detection rankings After consideiing these pieiequisites, siait filling out the form f Table IV 1 below)

7

Fiist Time Qualiry (f TQ); First Time Ihiough (FTT) 73

POTENTIAL FAILURE MODĘ AND EFFECTS ANALYS1S (PROCESS FMEA) Het,,.

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Chapter IV

Piocess Failure Modę and Effects Analysis

Example PFMEA Form The foim used in the examples in this refeience manuał is a guide to document the team*s discussions and analysis ot the PFMEA elements It contains the minimum content that is noimally expected by the OEMs Column oider can be modified and columns can be added to this foim depending on the oiganization and customer needs and expectations. In any case, any form submitted must be acceptable to the customci.

Headerof the Process FMEA Form (fields A-H) The following desciibes the infoimation to be entered on the foim The PFMEA headei should cleaily identify the focus of the PFMEA as well as infoimation telated to the document development and contiol process This should inelude an FMEA number, identification of the scope, design iesponsibility, completion dates, etc The headei should contain the following elements8:

FMEA Number (A) Entei an alphanumeiic stiing which is used to identify the PFMEA document This is used foi document control

Itern (B) Entei the name and number of the system, subsystem 01 component for which the piocess is being analyzed.

Process Responsibility (C) Entei the OEM, oiganization, and depaitment 01 gioup who is piocess design lesponsible Also entei the supply oiganization name, if applicabte

Model Year(s)/Program(s) (D) Entei the intended model year(s) and progiam(s) that will use 01 be atfected by the process being analyzed (if known)

The letters at the end oi each heading indicate the aiea refeired to on the sample foim 75

POTENTIAL

-1

FUEANdltier-

FAILURE MOOt ANO EFFECTS ANALYSIS (PROCESS FMEA1

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Potentlal Effectfs) of r

Cause(s) ot

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Failure

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Chaptei IV

Process Fjriluie Modę and Effects Analysis

Key Datę (E) Enter the initial PFMEA due datę, which should not exceed the scheduled start of production datę In case of a supply oiganization, this datę should not exceed the customer reąuiied Production Pait Approval Process (PPAP) submission datę

FMEA Datę (Original) (F) Entei the datę the original PFMEA was completed and the (atest revision datę

Core Team (G) Enter the team members responsible for developing the PFMEA Contact information ( e g , name, organization, telephone number, and email) may be included in a referenced supplemental document

Prepared By (H) Enter the name and contact information inciuding the organization (company) of the engineei/team leader responsible for pieparing the PFMEA

Body of the PFMEA Form (fields a

n)

Ihe body of the PFMEA contains the analysis of risks related to the potential failures and impiovement action being taken 9

Process Step / Process Function / Requirements (a) Process Step/Function can be sepaiated rnio two (or morę) columns or combined rnto a single, biidged column which encompasses these elements Piocess Steps may be listed in the Piocess Step/Function column ot additional column(s) may be added containing the functions 01 iequiiements of that piocess step "Process Step", "Function", and "Requirements" are desciibedbelow:

9

The letters al ihe end of each heading indicate the area releiied to on the sample fbim

POTENTtAl f A1LURE MOC* AND EFFECTS ANALYSIS IPROCESS FMEA1

SI

B.

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ProcessStep (a1) Entet the identiiicalion of the piocess step ot opetation being analyzed, based on the numbering piocess and teiminology Foi example, entei the numbei and identifier (eg., name) Piocess numbei ing scheme, seąuencing, and teiminology used should be consistent with those used in the process flow diagiam to ensure tiaceability and lelationships to othei documents (Control Plans, operator instiuctions, etc) Repaii and iewotk opeiations should also be included.

Process Function (a1) List the piocess function that coiresponds to each piocess step 01 opeiation being analyzed. The piocess function desciibes the puipose ot intent of the opeiation A lisk analysis is recommended in oidei to limit the numbei of steps to be included to only those that add value 01 othei wise aie seen as likely to have a negative impact on the pioduct If theie aie multiple process functions being analyzed with iespect to a given opeiation, each should be aligned on the foim with its iespective "Requiiements" to aid in the development of the associated failuie modes

Process Function becomes a2 if Process Step and Process Function are split

Requirements (a2) List the ieąuiiements foi each piocess function of the piocess step ot operation being analyzed Reąuiiements aie the inputs to the process specified to meet design intent and othei customei iequirements If theie aie multiple ieąuiiements with iespect to a given ninction, each should be aligned on the foim with the respective associated failuie modes in oidei to facilitate the analysis

Requirements become a3 if Process Step and Process Function are split into separate columns, e g , a1 and a2

79

o

poreNriAL FW-AhuniMf.

FAILURE MODĘ AND Eff ECTS ANALYSIS (PROCESS FMEA) Iient. Model

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Moce

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Chaptei IV

Piocess Failure Modę and Effecls Analysis

Potential Failure Modę (b) Potential failure modę is defined as Ihe manner in which the piocess could potentially fail to meet the piocess icąuiiements (including the design intent) In prepaiing the FMEA, assume that the incoming part(s)/mateiial(s) aie correct Exceptions can be madę by the FMEA team where histoiical data indicate deficiencies in incoming part ąuality The team should also assume that the basie design of the product is coirect; howevet, if there are design issues which result in ptocess conceins, those issues shouid be communicated to the design team foi resolution List the potential failuie mode(s) foi the patticular opeiation in teims of the piocess iequiiement(s) ( e g , as documented in the piocess flow diagiam) Assume that the failure could occui but may not necessarily oceur Potential failure modes should be desciibed in technical teirns, not as a symptom noticeable by the customer See the example table below. Process Step/Function Operation 20:

Requirement

Artach seat cushion to track using a toique gun

■*& ; ■

Potential Failure Modę

Four sciews Specified screws Assembly sequence: Fiist screw in right front hole

Fewer than four sciews Wiong screw used (laiger dia) Sctew placed in any othei hole

Sciews fully seated

Screw not fully seated

Screws torąued to dynamie toique specification

Screw toiqued too high

wm::.

Screw toiqued too Iow

■ . : ■ ; , ■ ' ■ ■ : ■ ; ■ ; ■

Table IV.2 Example of Ptocess Step/Fu nction/Req u irements Columns on PFMEA Form including Potential Failure Modes If the requirements have been well defined, then the potential failure modę is ieadily identifiable by deteimining the condition when a specific leąuiiement is not met Each iequirement may have multiple failure modes A laige number of failure modes identified foi a single iequirement usually indicates that the iequirement is not weil defined The assumption is madę that the failure could oceur but may not necessarily oceur - consequent!y the use of the woid "potential". Veiification of completeness of the potential failuie modes can be madę thiough a review of past things-gone-wTong, concerns,

81

POTINTIAL FA1LURE MOOE AND EFFECTC ANALYSli (PROCESS FMEAJ

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A

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f

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Rai(u«eii*
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Potenlial Eflecl(s) of Failure

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reject 01 scrap lepoils, and group biainstoiming Souices for this should aiso include a compaiison of similai pfocesses and a review of customei (End Usei and subseąuent opeiation) claims relating to similar components

Potential Effect(s) o f Failure (c) Potential effects of failure are defined as the effects of the failure modę as peiceived by the customer(s) The effects of the failure should be desciibed in teims of what the customei might notice or expetience, iemembeiing that the customei may be an inteinal customei as wdl as the ultimate End Usei The customei(s) in this context could be the next opeiation, subsequent opeiations oi locations, the dealer, and/or the vehicle owner Each must be consideied when assessing the potential effect of a failure The pioduct effects in the PFMEA should be consistent with those in the coiresponding DFMEA If the failure modę could impact safety oi cause noncompliance to regularions, this should be cleaiiy identifled in the PFMEA For the End Usei, the effects should be stated in teims of pioduct or system performance If the customei is the next opeiation or subsequent operation(s) / Iocation(s), the effects should be stated in terms of piocess / operation peifoimance See Table IV 3 Example ot Effects In ordei to determine the Potential Effect(s), the following questions should be asked: 1. Does the Potential Failure Modę physically prevent downstteam processing or cause potential harm to equipment or operator s? This includes an inability to assemble or join to a mating component at any subseąuent customeiłs facility If so, then assess the manufacturing impact No further analysis is iequired If not, then go to ąuestion 2 Examples could include: •

Unable to assemble at opeiation x

•

Unable to attach at customei facility

•

Unable to connect at customei facility

•

Cannot borę at operation x

•

Causes excessive tool weai at opeiation x

•

Damages equipment at opeiation x

•

Endangeis opeiator at customei facility

S3

Piocess Failure Modę and Effects Analysis ! 3 Notę: The location, station or operation at which the effect occurs ] should be identified. (f at a customer's facility, this should be i stated. 2. What is the potential impact on the End Usei ? Independent of any controls planned or implemented including error 01 mistake-proofing, consider what the End User would notice 01 expeiience This infbimation may be available within the DFMEA. Once determined, go to ąuestion 3 Examples could include: •

Noise

•

High effoit

•

Unpleasant odoi

•

Intermittent opei ation

•

Watei leak

•

Rough idle

•

Unable to adjust

•

Difficult to contiol

•

Poor appeaiance 3. What would happen if an effect was detected prior to reaching the End User? The potential effect at the cunent oi receiving locations also needs to be consideied Examples could include:

•

Linę shutdown

•

Stop shipment

•

Yaidhold

•

100% of product sciapped

•

Decreased linę speed

•

Added manpower to maintain reąuiied linę iate

I i | i :

Notę: If morę than one potential effect is identified when considering questions 2 and 3, all may be listed, but for purposes of the analysis, only consider the worst case when documenting the resulting Severity ranking

84

Piocess Failute Modę and Effects Analysis

Example of Effects Reąuirement

Failure Modę

Effect

Fotu screws

Fewer than foui sciews

EndUuser Loose seat cushion and noise Afanufacturing and A$sembly Stop shipment and additional soit and rework due to affected portion. Afanufacturing and Assembly Unableto install sciew in station

Specified screws

Wrong sciew used (largei dia)

Assembly seąuence: Fiist sciew iitright fiont hole

Screw placed in any othei hole

Afanufactur ing and Assembly Difficult to install iemaining screws in station

Screws fully seated

Screw not fully seated

Sciews toiqued to dynamie toiąue specification

Sciew torqued too high

End User Loose seat cushion and noise Afanufacturing and Assembly Soitand rewoik due to affected poition. End User Loose seat cushion due to subseąuent fmctuie of sciew and noise Afanufacturing and Assembly Sottand rewoik due to affected poition. End User Loose seat cushion due to giadual loosening of screw and noise Afanufacturing and Assembly Soit and iewoik due to affected portion.

Screw torqued too Iow

'

■ ■ < ' ■ " ' ' '

■

* '■'■■** * *

*

! * • "

Table IV.3 Example of Effects

85

POTENTIAL

A

FAILURE MODĘ A N D EFF ECTS ANAlYSiS

—

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.

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Polentia! Cause{s) of Failure

Potential Effect(s) of

■ ..urr.ii

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Severity (S) (d) Severity is Ihe value associated with the most seiious effect for a given failuie modę Seveiily is a ie!ative lanking within the scope of the individual PMEA Suggested Evaluation Criteria The team should agree on evaluation ciiteiia and a lanking system and apply them consistently, even if modified fot individual piocess analysis (See Table O l fot criteria guidelines)

It is not recommended to modify criteria for ranking values 9 and 10. Failure modes with a rank of 1 should not be analyzed further.

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Process Faiiure Modę and Effects Analysis


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Chaptet IV

Process Failure Modę and Effects Analysis

Classification (e) This column may be used to highlight high piiority faiiute modes ot causes that may teąuire additional engineering assessment Ihis column may also be used to classiry any special pioduct oi piocess chaiacteristics ( e g , critical, key, major, significant) foi components, subsystems, or systems that may require additionaf ptocess controls

i Customer specific requirements may identify special product or | process characteristic symbols and their usage

Wheie a special characteiistic is identified with a seveiity of 9 or 10 in the PFMEA, the design lesponsibie engineer should be notified sińce this may affect the engineering documents.

Potential Cause(s) of Failure Moda (f) Potential cause of failure is defined as an indication of how the failure could occur, and is described in teims of something that can be coirected 01 can be conttolled Potential cause of failuie may be an indication of a design or piocess weakness, the conseąuence of which is the failure modę To the extent possible, identify and document eveiy potential cause for each failure modę The cause should be detailed as concisely and completely as possible Sepaiating the causes will result in a focused analysis for each and may yield different measurement, controls, and action plans There may be one ot moie causes that can result in the failure modę being analyzed This tesults in multiple lines for each cause in the table or form.10 In preparing the PFMEA, the team should assume that the incoming pait(s)/material(s) ate correct. Exceptions can be madę at the team's discietion wheie histoiical data indicate deficiencies in incoming part quality Only specific enors ot maltunctions ( e g , seal not installed oi seal installed inveited) should be listed Ambiguous phiases ( e g , opeiatoi enoi oi seal mis-installed, etc) should not be used See Table TV 4 Example of Causes and Controls

In preparing the PFMEA, the team needs to ensure that any limitations of the design that may iesult in a potential process failure modę aie communicated to the design function 0;

Chapter IV

Process Failure Modę and Eiiects Analysis

Occurrence (O) (g) OccuueDce is the likelihood that a specific cause of failuie will occui. The likelihood of occunence ianking numbei has a relative meaning iathei tham an absolute vaiue (See Table Cr2) Estimate ihe likelihood of occunence of a polential cause of failuie on a 1 lo 10 scalę A consistent occunence ianking system should be used to ensuie continuity The occunence ianking numbei1 is a ielative ianking within the scope of the FMEA and may not leflect the actual likelihood of occunence The "Incident pei items/vehicles" is used to indicate the numbei of failuies thal aie anticipated duiing the piocess execution. If statistical data aie available ftom a similat piocess, the data should be used to deteimine the occunence ianking In othei cases, a subjeciive assessment can be madę by using the woid desciiptions in the left hand column of the table, along with input ftom the appropiiate process knowledge souice to estimate the ianking Suggested EvaIuation Ctiteria The team should agree on eva!uation criteiia and a ianking system and appiy them consistently, even it modified for individual piocess analysis Occunence should be estimated using a 1 to 10 scalę based upon Table Ci2 as a guideline.

92

Chapler IV


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Current Process Controls (h) Cunent Process Conti ols are desciiptions of the contiols that can either prevent to the ex.tent possible, the cause of failure fiom occuning oi detect the failuie modę or cause of failuie should it occui Thete aie two types of Piocess Contiols to consider: Prevention: Eliminate (pievent) the cause of the failure oi the failuie modę fiom occutring, oi leduce its tatę of occurrence Detection: Identify (detect) the cause of failure ot the failure modę, leading to the development of associated corrective action(s) oi countermeasuies.

J The preferred approach is to first use prevention controls, if j possible The initial occurrence rankings will be affected by the i prevention controls provlded they are integrated as part of the j process The initial detection rankings will be based on process ] controls that either detect the cause of failure, or detect the \ failure modę j Because statistical charting methods ( i e , Statistical Process | Control)11 typically use sampling to assess process stability and | detect out-of-control conditions they should not be considered ;! when evaluating the effectiveness of specific Detection Controls i SPC may, however, be considered as a Prevention Control for j specific causes whose trends are identifiable in advance of an | actual non-conformance being produced, such as tool wear

The example PFMBA form in this manuał has two sepaiate columns foi Pievention Contiols and Detection Contiols to assist the team in cleaily disttnguishing between these two types of contiols This allows foi a quick visual determination that both types of piocess contiols have been considered If a one-column (foi piocess contiols) foim is used, then the following piefixes should be used For prevention contiols, place a 'P' befoie or aftei each pievention contiol listed Foi detection contiols, place a 'D' before oi aftei each detection contiol listed (see labie IV 4 Example of Causes and Contiols)

See Chryslei, Foid, GM; SPC Manuał, AIAG 95

Chaptei IV"

Piocess Failute Modę and hffects Analysis

Failute Modę Screw not fiilly scated

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Training of set-up personnel

Torąue validation box included in set-up piocedure to validate setting pnoi to running

Senings added to set-up instructions Screw toiąued too Iow

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Training of set-up personne!

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98

Piocess Faituie Modę and Effecis Analysis

Detection (D) (i) Detection is the rank associated with the best detection control listed in the Detection Conttols column Detection is a telative ranking within the scope of the individual FMEA In oidei to achieve a lower ranking, geneially the planned detection control has to be improved When morę than one control is identified, it is recommended that the detection ranking of each control be included as part of the desciiption of the control Record the Iowest ranking value in the Detection column. Assume the failure has occirrred and then assess the capabilities of all "Cunent Process Controls" to pievent shipment of the part having this failure modę Do not automatically presume that the detection ranking is low because the occurrence is low, but do assess the ability of the process controls to detect low fiequency failure modes or prevent them from going further in the piocess

j Random qualily checks are unlikely to detect the existencs of an i isolated problem and should not influence the detection ranking Suggested Evaluation Cnteria The team should agree on evaluation criteria and a ranking system and apply them consistently, even if modified for individual product analysis Detection should be estimated using Table Ci 3 as a guideline a

I The ranking value of one (1) is reserved for failure prevention j through proven process design solutions

99

Chapter IV


. 1 O p p o r t u n i t y for Detection No detection opportunity

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Not likely to detect at any stage

Failure Modę and/oi Error (Cause) is not easily detected ( e g , iandom audits)

Problem Detection Post Piocessing

Failure Modę detection post-piocessing by opeiator through visual/tactile/audible means.

Problem Detection at Souice

Failure Modę detection in-station by operator through visual/tactile/audible means or post-piocessing through use of ataibute gauging (go/no-go, manuał toiąue check/clicker wiench, etc)

Problem Detection Post Processing

Failure Modę detection post-processing by operator through use ot vaiiable gauging oi in-station by operator through use of ataibute gauging (go/no-go, manuał toiąue check/clicker wiench, etc).

Problem Detection at Souice

Failure Modę or Error (Cause) detection in-station by operator through use of variable gauging or by automated controls in-station that will detect disciepant part and notiiy operator (light, buzzer, etc) Gauging performed on setup and first-piece check (for set-up causesonly)

Pioblem Detection Post Processing

Failute Modę detection post-piocessing by automated controls that will detect discrepant part and lock part to prevent iurthei processing

Pioblem Detection at Souice

Failute Modę detection in-station by automated controls that will detect discrepant pait and automatically lock pait in station to pievent turther processing

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Detection not applicable; Enor Pievention

Error (Cause) pievention as a result of fixture design, machinę design or pait design Disciepant paits cannot be '% madę because item has been enor-proofed by piocess/product design

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Table Cr3 Suggested Process FMEA Detection Evaluation Criteria

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Determining Action Priorities Once the team has corapleted the initial identification of failure modes and effects, causes and contiols, including rankings for sevetity, occuiieoce and detection, they must decide if further efforts aie needed to icduce the iisk Due to the inherent limitations on resouices, time, technology, and other factors, they must choose how to best piioiitize these efforts The initial focus of the team should be oiiented towards failure modes with the highest sevetity rankings When the seveiity is 9 oi 10, it is imperative that the team ensuie that the iisk is addressed through exisring design controls or tecommended actions (as documented in the FMEA) For failure modes with seveiities of 8 oi below the team should consider causes having ihe highest occurrence or detection iankings It is the team's lesponsibility to look at the infoimation, decide upon an approach, and determine how to best prioritize their iisk leduction effoils which best seive their organization and customers

Risk Evaluation; Risk Priority Number (RPN) (j) One approach to assist in action piioiitization has been to use the Risk Prioiity Numbei: RPN - Seveiity (S) x Occuirence (O) x Detection (D) Within the scope of the individual FMEA, this value can rangę between 1 and 1000 The use of an RP>\ thtes/toid is NOT a tecommendedpractice fot determining the need for actions Applying thresholds assumcs that RPNs are a measuie of ielative risk (which they often aie not) and that continuous improvement is not requiied (which it is) For example, if the customei applied an aibitraiy thieshold of 100 to the following, the supplier would be requiied to take action on the characteiistic B with the RPN of 112

Item A B

Severity 9 7

Occunence 2 4

Detection 5 4

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In this example, the RPN is higher for characteiistic B than chaiacteiistic A. Howevei, the piioiity should be lo woik on A with the higher severity of 9, although its RPN is 90 which is lower and below the threshold

103

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Piocess Failuie Modę and Effects Analysis Another concem with using the Ihieshold approach is that there is no specific RPN value ihat requires mandatory action Unfoitunately, establishing such thiesholds may piomote rhe wiong behavioi causing team members to spend time tiying to justify a lower occunence ot detection lanking value to teduce the RPN This type of behavioi avoids addressing the ieal problem that underlies the cause of the failure modę and meiely keeps the RPN belo w the thieshold. It is impoitant to recognize that while deteimining "acceptable" risk at a particular program milestone (e g , vehicle launch) is desiiable, it shouid be based on an analysis of seveiity, occunence and detection and not thiough the application of RPN thiesholds Use of the RPN index in the discussions of the team can be a 1 useful tool The limitalions of the use of RPN need to be 1 understood However, the use of RPN thresholds to determine action priorfty is not recommended

Recommended Action(s) (k) In generał, pievention actions (i.e , reducing the occunence) are piefetable to detection actions An example of this is the use of piocess design enoi pioofing tather than landom ąuality checks oi associated inspection The intent of any recommended action is to reduce iankings in the following order: seveiity, occunence, and detection. Example approaches to icduce these are explained below: •

j j I |

To Reduce Sevetity (S) Ranking; Only a design or process ievision can bring about a reduction in the severity ranking

A product/process design change, in and of itself, does not imply that the severity will be reduced Any product/process design change shouid be reviewed by the team to determine the effect on the product functionality and process

j For maximum effectiveness and efficiency of this approach, J changes to the product and process design shouid be I implemented eatly in the development process For example, I process technology needs to be considered very early in the j process development if severity is to be reduced

•

To Reduce Occunence (O) Ranking: To reduce occunence, process and design tevisions may be reąuired A reduction in the occunence lanking can be effected by iemovrng or contiolling one oi morę of the causes of the failuie modę through a product oi process design revision

Studies to undeistand the souices of vaiiation of the piocess using statistical methods may be implemented These studies

105

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Process Failure Modę and Effects Analysis may lesult in aclions that reduce occunence Fuither, the knowledge gained may assist in the identification of suitable contiols including ongoing feedback of infbrmation to the appropiiate operations for continuous improvement and problem ptevention •

To Reduce Detection (D) Ranking: The prefened method is the use of enor/mistake proofing A redesign of the detection methodology may result in a reduction of the detection ranking In sonie cases, a design change to a process step may be requiied to increase the likelihood of detection (i.e, ieduce the detection ranking) Generally, improving detection contiols iequires the knowledge and undeistanding of the dominant causes of process vaiiation and any special causes Incieasing the fiequency of inspection is usually not an effective action and should only be used as a tempoiaiy measuie to collect additional infoimation on the piocess so that peimanent preventive/conective action can be implemented12

If the assessment leads to no recommended actions fot a specific failure mode/cause/contioi combination, indicate this by enteiing "Nonę" in this column It may be useful to also include a rationale if "Nonę" is enteied, especially in case of high severity For ptocess actions, the evaluation may include but is not limited to a rt:view of: •

Results of piocess DOE 01 othei testing when applicable

•

Modified process flow diagram, flooi plan, work instiuctions or preventive maintenance plan

•

Review of equipment, fixtuies or machineiy specifications

•

New or modified sensing/detection device Table IV 5 below provides an example of the application of causes (Column f), controls (Column h) and iecommended actions (Column k)

Responsibility & Target Complstion Datę (I) Enter the name of the indśvidual and oiganization responsible foi completing each iecommended action including the target completion datę The piocess-tesponsible engineei/team leader is responsible for ensuiing that all actions recommended have been implemented or adequately addressed

) 12

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Action Results (m-n) I his section identifies the results of any completed actions and their effect on S, O, D lankings and RPN

Action(s) Taken and Compietion Datę (rn) After the action has beea implemented, enter a biief desctiption of the action taken and actual compietion datę

Severity, Occurrence, Detection and RPN (n) After the pieventive/coirective action has been completed, deteimine and tecord the lesulting seveiity, occurrence, and detection iankings Calculate and recoid the lesulting action (iisk) piioiity indicatoi ( e g , RPN) AU revised iankings should be reviewed Actions alone do not guaiantee that the problem was so!ved (i e , cause addressed), thus an appropriate analysis 01 test should be completed as verification If furthei action is considered necessary, repeat the analysis The focus should always be on continuous improvement

Chaptei IV Process Step/Function Op 20(attach seat cushion to tiack using a torąue gun) Sclect four screws


Reąuiiemem Four screws

Failuie

Mode Fewer than foui screws

Cause Too few screws inadvertently installed

Prcvention Conti ols Visual aids illusttating correct ąuantity

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Visual inspection in slation

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labie I V 5 Esamples oiCauses, Contr ols and Actions

Maintaining PFIVlEAs The PFMEA is a living document and should be ieviewed whenevei theie is a pioduct oi piocess design change and updated, as iequiied. Anothei element of on-going maintenance of PFMEAs should include a peiiodic revie\v Specific focus should be given to Occuirence and Detection iankings This is particulaity impoitant wheie theie have been pioduct oi process changes oi impiovements in process conttols Additionaily, in cases wheie either field issues oi pioduction issues, such as dismptions, have occuned, the iankings shoitld be ievised accordingly

Lęyęraging PFMEAs The use of a fundamentally sound PFMEA is the staiting point that provides the gieatest oppoitunity to !everage the use ofj>ast expeiience and knowledge

110

Chaplei IV

Piocess Failuie Modę and Effects Analysis If a new project or application is functionally similar to the existing pioduct and the piocess to be used is similar; a single PFMEA may be used with customer concunence If there are differences, the team should identify and focus on the effects of these diffeiences

Linkages Ihe PFMEA is not a "stand-alone" document Figurę IV 5 shows some common linkages

DFMEA, Process Flow Diagram, etc.

Process Control Plans Figurę IV.5 PFMEA Infbrmaiion Inteirelationship Flow

To DFMEA In the development of a PFMEA it is impoitant to utilize the infoimation and knowledge gained in the creation of me DFMEA However, the link between the two documents is not always obvious The difftculty occuis because the focus of each FMEA is diffeient The DFMEA focuses on pait function whereas the PFMEA focuses on the manufactuiing steps 01 process Infoimation in the columns of each foim is not directly aligned For example, Item/Function-Design does not equal Piocess Functions/Reąuirements; potential design failure modę does not equal potential piocess failure modę; potential design cause of failuie does not eûal potential process cause of failure However, by comparing the oveiall analysis ol design and process, a connection can be madę. One such connection is between the chaiacteiistics identified duiing the DFMEA and PFMEA analysis Another connection is the lelationship between potential design cause of failure (DFMEA) and potential process failuie modę (PFMEA) For example, the design of a feature such as a hole can cause a particular failuie modę The conesponding piocess

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Piocess Faiiuie Modę and Effects Analysis faiiuie modę is rhe inability of the piocess to manufacture the same featuie as designed In this example, the potential design cause of faiiuie (hole diameter designed too laige) would appeai to be similai to the potential piocess faiiuie modę (hole drilled too laige) The potential effect of the failure modę foi both design and process may be identical if' theie weie no additional piocess ielated effects In other words, the end iesult (effect) of the failure modę is the same, but there are rwo distinct causes While developing the PFMEA, it is the team's iesponsibiliry to ensure that all piocess reJated potential faiiuie modes which Iead to pioduct ielated effects are consistent between the DFMEA and the PFMEA

To Control Plan In addition to the list of Recommended Actions and their subsequent follow-up as a iesult of the PFMEA activity, a Control Plan should be developed13 Some organizations may elect not to specifically identify the ielated pioduct and piocess charactetistics" in the PFMEA In this siruation, the "Pioduct Chaiacteiistics" poition of the Control Plan may be deiived fiorn the "Reąuirements" poition of the "Piocess Function/Requiiements" column and the "Piocess Chaiacteiistics" poition may be derived ftom the "Potential Cause(s) of Failure Modę" column When the team develops the Control Plan, they need to assuie that the PFMEA cunent controls aie consistent with the connol methods specified in the Control Plan

13

Guidelines for Conttol Plan developmem aie included in Chiyslei, Foid, GM; Advanted P>oduct Quality Planning and Conttol Plan (APQP), AIAG. 112

I

APPENDICES

113

Appendix A

Saraple Forms

Appendix A: Sample Forms DFMEA Forms •

Foim A: Basic form (with minimal information)14 o

•

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To assist in the deteimination of failure modes

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•

Form D: Fotm B and C combined

•

Form E: Form D with sepaiate columns for Cunent Detection Design Contiols (Cause and Failuie Modę) o

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15

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Appendix B

System Level FMEA

Appendix B: System Level The piocess for a System FMEA is geneially the same as the deveIopment of other FMEAs The majoi differences between System level FMEAs and other types of FMEAs is the focus on functions and relationships that are unique to the system as a whole (i.e, do not exist at lowei levels) The System level FMEA includes failure modes associated with inteifaces and interactions in addition to consideiing single point failuies which is the primaiy focus of product level FMEAs Io help illustiate the meaning of System, Subsystem, and Component FMEAs, two examples have been constiucted below in Figuie B 1 (for Inteifaces and Interactions) and in Figurę B 2 (foi Item, Function, and Failure Modes.)

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130

Appendix B

System L evel FMEA

interfaces In Figurę B 1, intetiaces between subsystems aie shown where Subsystem A touches and (connects with) Subsystem B, B touches or connects with C, and a clearance between D and B, signified by the dashed linę The Enviionment also touches each of the subsystems listed in Figuie B 1, which reąuires the "Environmental Inteifaces" be consideied when completing the FMEA Also, the inteifaces to major and minoi subsystems, whethei direct or indiiect, should be included

The interfaces which are identified in the System FMEA should be included in the respective Subsystem FMEA

Figurę B.2 shows a system and its intenelationships in a "haidware" oriented appioach

Interactions A change in one subsystem or component may cause a change in anothei subsystem or component In Figuie B I , inteiactions between subsystems and components can occui among any of the interfacing systems For example, Subsystem A heats up, lesulting in Subsystem B and D gaining heat through their respective inteifaces, as well as Subsystem A giving ot? heat to the enviionment Interactions might also occur among 'nofl-contacting' systems via transfer through the 'ero/iionmenl' For example, if the environment is composed of high humidity and Subsystems A and C are dissimilai metals sepaiated by a non-metal composing Subsystem B, Subsystem A and C can still have an electrolytic reaction due to the moisture ftom the enviionment. Thus, inteiactions among non-contacting subsystems can be ielatively difficult to piedict but aie impoitant and should be consideied

131

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, Function: -Provides pleasing appearance

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Bicycie

Potential Failure Mode(s): -Finish (shlne) detenorates -Paint chips

Function: -Ease of use Potuntial Failure Mode(s|: -DifflcuU lo sleer •Diflicufl lo pedał

Front Wheel Assembly

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Rear Wheei Assembly

Potential Failure Mode(s): -Structural failure -Excessive deflection Function: -Provides dimensional control (or correct firushed frame geometry Potential Failure Mode(s): -Length of frame mounling poinls toolong -length of frame mounling points too short

Lower Front Tubę Lower Rear Tubę Sprocket Tubę

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Function: -Provides structural support

Handle Bar

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Component Levei

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Appendix B

Sys(em L e v d F M E A

Relationships Multiple Levels of Design FMEAs Moie likely than not, the focus of a DFMEA is an item which is a subset of a larger system The FMEAs at the different levels of the design hieiarchy (i e , system, subsystem and component) aie linked tbiough the cause -> failure modę -> effect ot failure lelationships This is a two way linkage (see Figuie B 3): Ftom Lower to ffighei Levei: The effect of a failure modę at a given level is a failure modę at the next highei level Fot example, the effect of a part 2 failuie modę would be a failure modę of module 3 eithei diiectly or indirectly by causing another pajt to fail The effect of a module 4 failure modę is a failuie modę of subsystem 4 Conseąuently, the effect of a failure modę at any sublevel may ultimately become a system tailure modę with its customer/ user related effects. Ftom Highei to Lower level: The linkage ftom a higher level to the next lowet Ievel is iclated to the physics of failure lather than a pure cause and effect relationship sińce in the development of a DFMEA, the causes identified at any level deal with the design piocess and only indirectly with the failure mechanisms. Undeistanding these relationships will piovide a consistency of analysis and an economy of etfoit in the development of DFMEAs

133

System Level f MEA

B

Effect on the end user

System

Subsystem 5

4 The effect of a ! Subsystem 4 Failure Modę is a V System Failure Modę j ; SubsystemJ| .Module 1

Module 2

r

Module

The effect of a Module 3 Failure Modę is a - Subsystem 4 Failure Modę

Design Process

Causes Y1, Y2, ..... Yn

Figuie B 3 DFMEA Effects Linkages

134

The effect of a sublevel Failure Modę is ultimately a System Failure Modę and its customer effect

■■HJaÊSI^^SEEfflffW

Appendk C

Altemative Risk Assessments

Appendix G: A!ternative Risk Assessments Alternatives to RPN The risk piiority numbei is the product of the severity (S), occuirence (O), and detection (D) iankings (S) x (O) x (D) = RPN Wirhin the scope of the individual FMEA, this value (between 1 and 1000) can be used to assist the team in ianking the concems in the design of the pioduct and process. Ihe table below, however, illustiates how differenl Seveiity (S), Occuiience (O) & Detection (D) scenaiios result in eąual RPN values 18 Upon ieview of each scenario, priorities would not be established by the team based on the RPN alone Fifteen Different Situations with an RPN=360

1 2 3 4 5 6 7 3 9 10 -1 12 :3 14 15

Severity of Problem Hazardous Hazardous Hazardous Hazardous Hazardous Hazardous Hazardous

High High Moderate Moderate Moderate Moderate Moderate Moderate

1C 1C 1C 9 9 9 9 8 8 6 6 5 5 4 4

Likelihood of Ccci; rrerice High Moderate Moderate Very High High Moderate Moderate

9 6 4 10 8 5 4

High

9

Moderate Very High Moderate High High Very High High

5 10 6 9

s 1C 9

Likelihood of Detection Moderate Low V97 Rcrô:o Mod High Moderate Remote fmpossible Moderate Very Remote Low Impossible Remote Very Remote \Zery Remote Impossible

4 6 9 4 5 8 '0 5 9 6 10 8 9 9 10

The ease of calculation and soiting of this index has led many to use it exclusively and without consideiation to what may be a more appioptiate means of piioiitizing Examples of some such altematives follow

Used wilh peimission ftom Whiilpool Coipoialion, ©2005, 2006 135

Altemative Risk Assessmenls

Appendbc C

Alternative: SO (S x O) Some organizations may choose to piimaiily focus on Seveiity and Occurrence The SO index is the pioduct of the Seveiity, and Occuirence rankings In using this index, the otganization may focus on how to ieduce SO by leducing the value of "O" thiough preventive actions Fuitheimoie this may lead to subseąuent detection impiovements for those with the highest SO value

Alternatfoe: SOD, SD Some organizations have chosen to use SOD 01 SD as a piioiitization tool SOD is the non-arithmetic combination of the Seveiity, Occunence and Detection iankings SD is the nonarithmetic combination of the Seveiity and Detection rankings Example (SOD): Severity,

S=7

Occunence,

O- 3

Detection,

D=5

The resulting SOD is 735 Esample (SD): Seveiity,

S =7

Detection,

D=5

The resulting SD is 75 The SOD, when soited in numeiical, descending oidet, will

piioiitize the scenaiios fitst by severity, second by occunence and lastly by detection

s 7 7 3

O 7

D 3

RPN 147

3 7

7 7

147 147

SOD 773 737

SD ,

377

37

73 77 al

Veiy Diffeient Scenaiios

Equal RPN Values Table C l Contrast among RPN, SOD and SD 1 Just as with RPN. use of the SOD/SD index should be used in 1 context of team discussion Defining priorities simply based on j the SOD has limitations just as with the RPN For example, a i failure modę with a SOD of 711 would be ranked higher (i.e., j have to be considered before) a failure modę with 599

136

Appendix D

Alteinative Analysis Techniąues

Appendix D: AIternative Analyses Techniques Failure Modę and EfFects Analysis is one of many lechniques used to evaluate and analyze design risk Other methods have beeii deve!oped fot specillc aieas and can be used to complement the analysis in the FMEA piocess They raay be used as a ieplacement foi an FMEA with authoiization by the customei These aie only a few of the examples.

Failure Modę, Effect and Criticality Analysis (FMECA) FM£CA is similar to FMEA The C in FMECA indicates that the ciiticality (01 sevetity) of the various failuie effects aie consideied and ianked Today, FMEA is often used as a synonym foi FMECA

Design Review Based on Failure Modes (DRBFIM) Design Review Based on Failuie Modes is a cause and effect analysis of conceins related to a design change It is a tool used to guide and manage good discussion in relation to the change DRBFM fbcuses on the impact of the change on design, evaluation piocedures, and manufactuiing systems with the intent of anticipating and preventing problems A design ieview by subject mattei expeits to evaluate the change{s) and related impiovements is an integial pait of DRBFM. (Reference Figuie

Dl)

Fault Tree Analysis (FTA) FTA is a techniąue fot system analysis wheie system faults are analyzed 6om a single potential failuie to identily all possible causes FTA consideis combinations of inteidependent as well as independent causes In addition to the structute of the fault tree and all of the logie inteidependencies, the FTA noimally inciudes the failuie piobabilities identification This allows the calculation of system reliability given the component leliabilities [9 (Reference Figuie D 2).

19

References: IEC 61025; QICID (ASQ-20352)

137

Appendix D

AIteinative Anaiysis Techniques

Action Status '"■'riap.".: .- - I! "'■ Target Cwrptółlon Dato

3 _ o OJ

Manufacturing

K

Targeł Compłelion Data

c_

Evaluation

cc

£3 8

LI CO O s

(ł) "O

o
ii r;

cc

a

s

■o o . Responsib*ty a

i?

8S a:

Taccjet Complelion Dale

;.r.

Design

ci

Design Actions to elimtnate concerns

c o

(provitfe dełaits and best practices used)

"O

_^2 fc u)

V)

go

co CO

5 •<—«

Severity

r^

Effect Cody

Li

Customer and System or Subsystem Effeci

a E co

ia

Other Causes

QL

(Review)

II

a U C;'

o: c .?? "w

Q

;ro Other Concerns (Review)

ł

CC

■6 L e s s o f Functlon

or Va)ue to Customer

o

Part Function

I

Change to Design or Environment

I

I-Iguie D-! Example of DRBFM Elements

138

n

Appendix D

Alternative Analysis lechniąues

CODECand anatog m t 8 2 not oparaflooal

I One or Bom

'

1

IC Faisd: No er noisy yffliage s:.ppy

analog tnputs r.ot | avaitebłe

Comocnents &iling - any fańjre

CD

ICfatlsd i * to random faiiure

Cne or mora pins shorted due to CeDns on bcord

Ccnnectłon(s) openofshorttó du« to m(g defect

5V analog not awfciaHo

Voltjge nas high or tow freąuertey n.oise

IC (Ms due to manufacTunog

Cold or insufnaent sołdsr on ora er morę pins

One or morę pins snerted du» to cxcessve scJdcr

IC damaged t y ESD dunng assemblyor test

IC erackad Cunnp assemWy

T [ Solder A l short_G13 J

Figurę D.2 FTA Tree S t i u c t u r e

139

[Brc*en_C13 j

Refeiences and Suggested Readings

References and Suggested Readings IEC 60300-3-1, Dependability management - Pan 3-1 Apphcatlon guide - Analysis techniąues for dependabiłity - Guide on merhodology LEC 60812, Edilion 2; Failure modes andeffects analysis, lanuaiy 2006 IEC 61025, Edition 2; Fault ttee analysis, lanuary 2007 QICID (ASQ-20352) "System Reliability Thtough Fault Ttee Analysis" SAE ARP 5580, Recommended Faiłute Modes and Ejfects Analysis (FMEA) Practices for NonAutomotive AppHcations (Repiaceraent for MIL-SID-1629A, 1998 (withdrawn)) SAE 11739:2002, Potential Failure Modę and Ejfects Analysis in Design (Design FMEA) and Potentiał Failure Modę andEffects Analysis in Manufactutmg and Assembly Processes (Process FMEA) Alfledo, H S Ang and Wilson, H Tang (1990). "Ptobability Concepts in EngineeringPlanningand Design, Volume II ~ Decision Risk and Reliability", WUey Publications Bowles, J (2003) "An Assessment of RPN Piioritization in a Failure Modes Effects and Ciiticality Analysis", Ptoceedings Annual Reliability and Maintainability Symposium, pp 380-386; aiso in Joutnal oj the IEST, Imtitute ofEnvitonmental Sciences and Technology, Vol47, 2004, pp 51-56 Krasich, M (2007) "Physics of Failure Appioach to FMEA", Tutorial Ptoteedings Reliability and Maintainability Symposium Kjasich, M (2005) "Fault Tree Analysis in Pioduct Reliability Improvernent", Tutonal Ptoceedings Reliability and Maintainability Symposium 0'Connei, PD.T,(2002) Piactical Reliability Engineeiing 4thedition, (Wiley) Shu-Ho Dai and Ming-0 Wang (1992), Reliability Analysis m Engmeetmg Apphcations, Van Nostiand Reinhold Wheelei, D J (2005) The SixSigma Ptactitioner'% Guide to Data Analysis, SPC Piess, Knoxvi!le, pp 311315 Rausand, M (2004) System Reliability Theoty (2nd ed), Wiley, 2004

140

Ind es

lnćex APQP (Advanced Pioduct Quality Planning), 2, 5 błock diagiam, 18, 19,29 classification, 39, 91 continuous impiovement, 6, 57,63, 103,107, 109 contro! plans, 6,13,111 cioss-functional, 2, 9,17, 69,71 cunent design contiols, 49, 53 design improvements, 16 design intent, 11,12,22,29,41,49, 68, 79 design life, 45 detection, 13, 18,49, 51, 57-64, 68,73,95,99110,135,136 detection contiols, 49,66,99,107 DFMEA (Design Failure Modę and Effccts Analysis), 5, 16-19,22,25,29, 39,41, 64-66, 70,73,83,84,111,133 DOE (Design of Expeiiments), 61, 107 DRBFM (Design Review by Failure Modę), 137, enoi proofing, 73,105 evaluation critetia, 37,45, 53, 87,92,99 flow diagiam, 70, 71,81, 107 FMECA (Failuie Modę, Effect and Ciitical Analysis), 3,137 Follow-up, 6 F1A (Fauli Ilee Analysis), 137,139 iunction, 16,18,19,21 , 29 ,31, 35, 71, 79,111 fiinctional requiiements, 8,16,18,25 inteiactions.3,10,130, 131 inteifaces, 10, 11,29, 130,131 item,73, 75, Ul, 133 linkages, 65,111,134 mistake pioofmg, 61, 107

occunence 3 13,45,46,49,53,57,59,61,63, 64,68, 69, 92, 93,95,99,103, 105,107,109, 110,135,136 OEM (GM, Foid, Chrysler), 11, 17,27, 75 PFMEA (Process Failure Modę and Effects Analysis), 5, 17,66, 68-71, 75, 77, 83, 91,95. 110,111 potential cause, 12,39,41,91,92 potential failuie modę, 11,16-18, 31, 61, 70-71, 81, 112 preventive contiols, 45 process step, 77, 79, 107 recommended actions, 6, 13,18, 57, 59, 61,103, L07 responsible engineei, 17, 63, 69, 70,91,107 RPN (Risk Priority Numbei), 57,59,63,103, 105,109,135,136 scope, 3,4, 8,10,11,18,25,68,70,71, 73, 75, 130 SD (Ranking by Seveiity and Detection), 136 Seveiity, 13, 37, 57, 59,63, 84, 87,103,109, 135,136 SO (Ranking by Seveiity and Occunence), 136 SOD (Ranking based on Seveiity, Occunence and Detection), 136 SPC (Statistical Piocess Contiol), 95, 107 special chaiacteristic, 39, 91 specification, 11,13, 61,107 team, 2,4,5, 8, 9,10,14,17,18,21,22,27, 29, 35, 37,41,45,49,53,57,59,69, 71, 73,81, 87,91,95,99,103,105,11! team leadei, 6, 9, 69, 70,107 thresholds, 57, 59,103,105 va!idation, 16, 31,49,59,61

141

FMEA_4th_en

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