ME 333 Manufacturing Process I Lecture 09
Ca st s t i n g D ef e f e ct ct s • • • • • •
Type Types s of of Def Defec ects ts Insp Inspec ecti tion on Me Meth thod ods s Mould Mouldin ing g Rel Relate ated d Defec Defects ts Fill Fillin ing g Rela Relate ted d Defec Defects ts Solidi Sol idifica ficatio tion n Related Related Defects Defects Defe Defect cts s An Anal alys ysis is
© 2006 Prof. B. Ravi, Mechanical Mechanical Engineer Engineering ing Department Department,, Indian Institute Institute of Technolo Technology, gy, Bombay.
Types of Defects
B a se se d o n L o c a t i o n : ¾ External ¾ Internal
B a se se d o n T y p e : ¾ Geometric ¾ Integrity
B as a s e d o n Si Si ze z e / Se v e r i t y : ¾ Small/Minor ¾ Large/Major
B a se s e d o n P r o c e ss ss : ¾ Moulding-related ¾ Filling-related ¾ Solidification-related.
B a s e d o n Ca u s e : ¾ Raw materials ¾ Product design ¾ Tooling design ¾ Process parameters ¾ Process control
B a se se d o n St a g e : ¾ Casting ¾ Rough machining ¾ Finish machining ¾ Service B a se s e d o n Re Re p a r a b i l i t y : ¾ Repairable ¾ Irreparable
Inspection Methods
Destructive: ¾ Sectioning, Machining ¾ Mechanical testing ¾ Chemical testing
Non-Destructive: ¾ Visual: large external defects ¾ Dimensional: size defects ¾ Pressure testing: leakage ¾ Radiography: internal holes ¾ Ultrasound: internal discontinuities ¾ Eddy current: hardness, structure ¾ ¾
Magnetic Particle: sub-surface discontinuities Dye Penetrant: defects with opening to surface.
Moulding-related Defects
I m p r o p e r Cl Cl o su su r e c r o s s p a r t i n g p l a n e : flash A cr A l o n g p a r t i n g l i n e : mismatch
MISMATCH FLASH [Atlas of Casting Defects, Institute of British Foundrymen]
Filling-related Defects
] n e m y r d n u o F h s i t i r B f o e t u t i t s n I , s t c e f e D g n i t s a C f o s a l t A [
I n c o m p l e t e F i l li l i n g : cold shut, misrun. Ga se s e o u s En En t r a p m e n t s : blow hole, gas porosity. S o l i d I n c l u s io i o n s : sand inclusion, slag inclusion.
COLD SHUT
MISRUN
BLOW HOLE
GAS POROSITY
Solidification/Cooling-related Solidificatio n/Cooling-related Defects
S o l i d i f i ca c a t i o n S h r i n k a g e : cavity, porosity, centerline, sink. H i n d e r e d Co Co o l i n g Co Co n t r a ct c t i o n : hot tear, crack, distortion. SHRINKAGE CAVITY
] n e m y r d n u o F h s i t i r B f o e t u t i t s n I , s t c e f e D g n i t s a C f o s a l t A [
SINK
CORNER SHRINKAGE
POROSITY
CRACK
Defects Analysis
I n d i v i d u a l D ef e f e ct ct : ¾ Defect identification ¾ Cause identification ¾ Remedy specification
D e f ec ect s o v e r a b a t c h / p e r i od : ¾ Quality control charts ¾ Defect frequency (histogram) ¾ Defect spectrum (pattern over time)
Ex p e r t S y s t e m s f o r D ef e f e ct c t s An An a l y s i s ¾ Knowledge base (IF-THEN rules with confidence) ¾ Inference Engine
Summary
Ca st s t i n g d e f e c t s are significant: typically 1-10% About 20 major types of casting defects: Flash, mismatch, cold shut, misrun, blow hole, gas porosity, shrinkage cavity, porosity, centerline, sink, hot tear, crack, scab, swell, metal penetration, rough surface. Other defects: improper composition and properties.
Implications: ¾
Minor defects can be repaired, with cost increase.
¾
Major defects lead to rejection, with loss of productivity.
S t a t u s a n d P r o g r e ss ss : ¾ ¾ ¾ ¾
Quality control and defects analysis: experts/systems. Quality certification and assurance gaining importance. Responsibility shifting to manufacturer; legal implications. Toward zero defects: prevention is better than cure!
Home Exercise • Draw the cause-ef cause-effect fect (Ishikawa) (Ishikawa) diagra diagram m for the following following defects: defects: Shrinkage porosity, Blow hole, Mismatch. Include causes related to moulding, filling and solidification. • For each each of above above grou group p of caus causes, es, iden identify tify the the sub-c sub-caus auses es (ex. improper improper filling), filling), and sub-sub-caus sub-sub-causes es (ex. ingate ingate too small). small). • Write the IF-THEN IF-THEN rules rules for identifying identifying and and troubleshootin troubleshooting g (cause) (cause) the following defects: shrinkage porosity, gas porosity.
