12) Sistem Produksi Berbasis Proyek

2003/12/10

生産システム研究室

Departemen Teknik Industri

TI3122 PERENCANAAN & PENGENDALIAN PRODUKSI

SISTEM PRODUKSI BERBASIS PROYEK

Department of Industrial Engineering Instit Institut ut Teknol Teknologi ogi Bandun Bandung g Jala Jalan n Ganes Ganesha ha 10, 10, Band Bandun ung g 4013 40132 2


Definition Project can usually be defined as a series of related tasks directed toward a major output The characteristics of a project: It has a specific goal and deadline It is unique or somewhat unfamiliar to the existing work It contains complex interrelated tasks requiring specialized skills It is temporary but critical to the company 







TI-3131 Perencanaan dan Pengendalian Produksi

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A hierarchical view of the project environment

•

.

Program 1

...

Program x

...

...

Program n

Project xm-1

Project x1

Project x2

Project xm

Task x21

Task x22

Task x23

...

Activity x221

Activity x222

Activity x223

...

Task x2p

Activity x22q


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A hierarchical view of the project environment

• •

•

•

Program: the term commonly used to denote very large and prolonged undertakings. Project: the term generally applied to timephased efforts of much smaller scope and duration than programs. Programs are some time viewed as consisting of a set of project Task: an elemental content of a project. A project is normally composed of contiguous arrays of tasks that all contribute to the overall project goal Activity: the atom of a project. Activities are smaller than tasks TI-3131 Perencanaan dan Pengendalian Produksi

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Project management (PM)

•

• • •

Project management (PM) is the process of managing, allocating, and timing resources in order to achieve a given objective in an expedient manner The objective may be in terms of time, monetary, or technical results PM is the process of achieving objectives by utilizing the combined capabilities of available resources PM represents a systematic execution of tasks needed to achieve project objectives 5



Planning Scheduling

Organizing

Training Optimization

Project management

Risk management

Contract management

Cost control

Resource management

Software tools

Project design Performance control

Multidimensionality of project management TI-3131 Perencanaan dan Pengendalian Produksi

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Project management (PM)

• PM covers the following basic functions: Planning, •

•

Organizing, Scheduling and Control Project planning provides the basis for the initiation, implementation, and termination of a project. It sets guidelines for specific project objectives, project structure, tasks, milestones, personnel, cost, equipment, performance, and problem resolutions Project organization specifies how to integrate the functions of the personnel involved in a project. Directing (which involves guiding and supervising the project personnel) is an important aspect of project organization


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Project management (PM) • Project scheduling is the time phased arrangement of project activities subject to precedence, time, and resource constraints in order to accomplish project objectives. It is often the core of project management efforts because it involves the assignment of time periods to specific tasks within the work schedule


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Project Planning 1. Setting goals 2. Defining the project 3. Tying needs into timed project activities 4. Orginizing the team

Tools Time and cost estimates Budget, Cash flow Personnel Material ability Engineering diagram

Project scheduling 1. Tying resources (people, money, supplies) to specific activities 2. Relating activities to each other 3. Updating and revising on regular basis

Tools Gantt Chart, CPM, PERT Cash flow schedules

Project controlling 1. Monitoring resource, costs, quality, budgets 2. Revising and changing plans 3. Shifting resources to meet time, cost, and quality demands

Before project

Tools PERT charts Reports describing 1. budget by department 2. delayed activities 3. slack activities 4.quality of work completed

During project Start of the project


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The project of manufacturing • In a large organization, the manufacturing system may be • •

configured as a multi-project endeavor The following figure shows the typical components of a manufacturing enterprise organized as a project The project starts with a conceptualization of a product and needs some of distinct tasks for getting t he product to the market


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Systems integration Market survey Process planning

Idea

Feasibility study

Cost

Quality specs

Training

Financing

Operations planning

Production

Schedule

Facilities Technology assessment


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Project Management Technique:

1. Critical path method (CPM) was developed in 1957 by J.E. Kelly of Remington Rand and M.R. Walker of duPont

2. Program Evaluation and review technique (PERT) was developed in 1958 by the Navy with Booz, Allen and Hamilton


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The framework of CPM and PERT Basic steps: • Define the project and all its significant tasks or activities • Develop the relationship among the a ctivities. Decide which activities must precede and which must follow others • Draw the network connecting all of the activities • Assign time and cost estimates and required resources to each activity • Compute the longest time path through the network. This is called the critical path • Use the network to help plan, schedule, monitor and control the project TI-3131 Perencanaan dan Pengendalian Produksi

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The questions answered by CPM or PERT

• • • • •

When will the entire project be completed? What are the critical activities in the project, that is, the ones that will delay the entire project if they are late? Which are the noncritical activities, that is, the ones that can run late without delaying the whole project’s completion? What is the probability that the project will be completed by a specific date? At any particular date, is the project on schedule, behind schedule, or ahead of schedule? TI-3131 Perencanaan dan Pengendalian Produksi

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The questions answered by CPM or PERT • On any given date, is the money spent equal to, less than, • •

or greater than the budgeted amount? Are there enough resources available to finish the project on time? If the project is to be finished in a shorter amount of time, what is the best way to accomplish this at the least cost?


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Conventions

• •

Activities: a task that occurs between 2 events Event arrows and nodes

•

Activity-on-Arrow (AOA) Arrows are used to represent activities, while nodes represent starting and ending points of activities

•

Activity-on-Node (AON) Nodes represent activities, while arrows represent precedence relationships TI-3131 Perencanaan dan Pengendalian Produksi

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Convention .

Name and Symbol

Description

A point in time, usually a completion date or a starting date

Event (node)

An activity or a certain amount of work required in the project

Activity (arrow)

Activity A Event 1

Activity B Event 2

Event 3

(network) A sequence of activities with beginning and ending events


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Example 1 Activity A B C D

Immediate predecessor A B

2 C A

1

4

B

D 3


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Example 2 Beginning event 1 1 2 3 3 4 5

Ending event 2 3 4 4 5 6 6

Activity 1-2 1-3 2-4 3-4 3-5 4-6 5-6

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Example 2 .

2

4

6

1

3

5


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Example 3 Activity A B C D E F G H

Immediate Predecessor(s) A B C, D D E F


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Example 3 .

2

5

A

C

G

E

1

7

4 B

F

D

H 6

3 E

C 2

5

Dummy

G

A Dummy activity

1

7

B

C 3

4 D

6 F


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Critical Path Method (CPM) CPM is to determine the following quantities for each activity • ES: Earliest start time. All predecessor activities must be completed before an activity can be started. The ending time of the predecessor activities is the earliest time an activity can be started • LS: Latest start time. All successor activities must be completed without delaying the entire project This is the latest time an activity can be started without delaying the entire project • EF: Earliest finish. EF=ES+t • LF: Latest finish. LF=LS+t


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Critical Path Method (CPM)

•

•

TS: Total slack time. TS is the amount of time an activity may be delayed from its ES without delaying the latest completion of the project. TS=LS-ES or TS=LF-EF FS: Free slack time. FS is the amount of time an activity may be delayed from its ES without delaying the starting time of any of its immediate successors

⎧ ⎫ ⎩ i∈S ( j ) ⎭

FS ( j ) = Min ⎨ ES (i ) ⎬ − EF ( j ) S(j): immediate successors of activity j TI-3131 Perencanaan dan Pengendalian Produksi

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Critical Path Method (CPM) • The critical path is the group of activities in the project that

•

have a total slack time of zero. This path is critical because a delay in any activity along this path would delay the entire project The total project completion time is calculated by adding the time values of those activities on the critical path

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Example 4 Activity 1-2 1-3 2-3 2-4 3-4

Duration 2 7 4 3 2

2 3 2 4

1

7

4

2 3


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Example 4 .

ES, EF

2 3

LS, LF

2

6

6

2

2

1

3

2

3 2 9

0

9

4

0

1

5

0

0

4

9

0

6

9

7

7

7

7

9

2

7 7

7

3 9

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Example 4 Activity Duration 1-2 2 1-3 7 2-3 4 2-4 3 3-4 2

ES 0 0 2 2 7

EF 2 7 6 5 9

LS 1 0 3 6 7

LF

TS 3 7 7 9 9

1 0 1 4 0

• Determine free slack times for the respective activities.


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Program Evaluation and Review Technique (PERT) One distinguishing PERT and CPM is the use of 3 activities time estimates for each activity in the PERT technique. Only one time factor is given for each activity in CPM. The time estimates are: a=optimistic time b=pessimistic time m=most likely time te=expected time v=variance of activity completion time


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Program Evaluation and Review Technique (PERT) • The expected time of completion time for activity i of4completion time for activity i a+ m+b • The variance t e =

6

completion time • The variance of project 2 ⎛ b − a ⎞ vi = ⎜ ⎟ ⎝ 6 ⎠

V =

∑v

i i∈critical path


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Program Evaluation and Review Technique (PERT)

Activity 1-2 1-3 2-4 3-4

a 3 1 5 6

m 4 3 6 7

5 5 7 8

tb

v

4

1/9

3

4/9

6

1/9

7

1/9

If the expected project completion time is 20 weeks and the project variance is 100 weeks, what is the probability that the project will be Perencanaan dan Pengendalian Produksi finished on orTI-3131 before Week 25?

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Gantt chart • When the results of a CPM/PERT analysis are fitted to a • • •

calendar time, the project plan becomes a schedule The Gantt chart showing planned (or actual) progress of activities is one of the most widely used tools for presenting the schedule The horizontal axis indicates the time scale The horizontal bars/lines represent activities


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Gantt chart .

Activity

Duration W1 W2 W3 W4 W5 W6 W7 W8 W9

1-2

2 weeks

1-3

7 weeks

2-3

4 weeks

2-4

3 weeks

3-4

2 weeks

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Gantt chart The basic Gantt chart does not show the precedence relationships among activities but it can be modified by linking appropriate lines

Activity

Duration

A

2 weeks

B

7 weeks

C

4 weeks

D

3 weeks

E

2 weeks

W1

W2

W3

W4

W5

W6

W7


W8

W9

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Crashing

• • •

Additional resources can reduce activity time for certain activity within the project Although it can be expensive to shorten activity times, doing so might be worthwhile The questions are: 





•

What activities should be shortened? How much will this action cost? Will a reduction in the activity time in turn reduce the time needed to complete the entire project?

The least expensive method of shortening the entire project should be determined TI-3131 Perencanaan dan Pengendalian Produksi

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Cost-time Curves

Cost

Time

Cost

8 weeks 7 weeks 6 weeks

$300 $400 $600

$600

$500

s i x A Y

$400

$300

6 days

7 da ys

X-Axis 8 da ys

Time (weeks)


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Cost of reducing activity time • The objective is to reduce the entire project completion •

time by a certain amount at the least cost If Mi = maximum reduction of time for activity i Ci= additional cost associated with reducing activity time for activity i C Ki= cost of reducing activity time by one time unit K = M for activity i i

i

i

K i =

C i M i 37



Determining the least cost Activity

Duration

M

C K

1-2

2

1

$300

1-3

7

4

2-3

4

2-4 3-4

Critical

$2000

$300 $500

No Yes

2

$2000

$1000

No

3

2

$4000

$2000

2

1

$2000

$2000

No Yes

Min

2 3 2 4

1

7

4

2 3


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Determining the least cost Activity 1-3 is to be shortened by 1 week in order to reduce the project completion time to 8 weeks Note that any further reduction in activity time along the critical path would cause the critical path to include activities 1-2, 2-3 and 3-4.


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Further Readings • Badiru, A.B., 1996, Project management in manufacturing •

and high technology operations, John Wiley and Sons, Inc., New York Heizer, J. and Render, B., 1996, Production and operations management, Prentice Hall International Editions, New Jersey


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