The document outlines various casting defects encountered in manufacturing, categorizing them based on location, type, size, cause, and stage of production. It also details inspection methods for these defects, both destructive and non-destructive, as well as analyses to identify and remedy the defects. Overall, it emphasizes the importance of quality control and the shift in responsibility for defect management towards manufacturers.

1. ME 333 Manufacturing Process I
© 2006 Prof. B. Ravi, Mechanical Engineering Department, Indian Institute of Technology, Bombay.
Lecture 09
Casting Defects
• Types of Defects
• Inspection Methods
• Moulding Related Defects
• Filling Related Defects
• Solidification Related Defects
• Defects Analysis

2. Types of Defects
ƒ Based on Location:
¾ External
¾ Internal
ƒ Based on Type:
¾ Geometric
¾ Integrity
ƒ Based on Size/Severity:
¾ Small/Minor
¾ Large/Major
ƒ Based on Process:
¾ Moulding-related
¾ Filling-related
¾ Solidification-related.
ƒ Based on Cause:
¾ Raw materials
¾ Product design
¾ Tooling design
¾ Process parameters
¾ Process control
ƒ Based on Stage:
¾ Casting
¾ Rough machining
¾ Finish machining
¾ Service
ƒ Based on Reparability:
¾ Repairable
¾ Irreparable

3. Inspection Methods
ƒ Destructive:
¾ Sectioning, Machining
¾ Mechanical testing
¾ Chemical testing
ƒ 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 Magnetic Particle: sub-surface discontinuities
¾ Dye Penetrant: defects with opening to surface.

4. Moulding-related Defects
ƒ Improper Closure
ƒ Across parting plane: flash
ƒ Along parting line: mismatch
FLASH
MISMATCH
[Atlas of Casting Defects, Institute of British Foundrymen]

5. Filling-related Defects
ƒ Incomplete Filling: cold shut, misrun.
ƒ Gaseous Entrapments: blow hole, gas porosity.
ƒ Solid Inclusions: sand inclusion, slag inclusion.
COLD SHUT MISRUN BLOW HOLE GAS POROSITY
[Atlas
of
Casting
Defects,
Institute
of
British
Foundrymen]

6. Solidification/Cooling-related Defects
ƒ Solidification Shrinkage: cavity, porosity, centerline, sink.
ƒ Hindered Cooling Contraction: hot tear, crack, distortion.
SHRINKAGE CAVITY POROSITY
SINK CORNER SHRINKAGE CRACK
[Atlas
of
Casting
Defects,
Institute
of
British
Foundrymen]

7. Defects Analysis
ƒ Individual Defect:
¾ Defect identification
¾ Cause identification
¾ Remedy specification
ƒ Defects over a batch/period:
¾ Quality control charts
¾ Defect frequency (histogram)
¾ Defect spectrum (pattern over time)
ƒ Expert Systems for Defects Analysis
¾ Knowledge base (IF-THEN rules with confidence)
¾ Inference Engine

8. Summary
ƒ Casting defects are significant: typically 1-10%
ƒ 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.
ƒ Implications:
¾ Minor defects can be repaired, with cost increase.
¾ Major defects lead to rejection, with loss of productivity.
ƒ Status and Progress:
¾ Quality control and defects analysis: experts/systems.
¾ Quality certification and assurance gaining importance.
¾ Responsibility shifting to manufacturer; legal implications.
¾ Toward zero defects: prevention is better than cure!

9. Home Exercise
• Draw the cause-effect (Ishikawa) diagram for the following defects:
Shrinkage porosity, Blow hole, Mismatch.
Include causes related to moulding, filling and solidification.
• For each of above group of causes, identify the sub-causes
(ex. improper filling), and sub-sub-causes (ex. ingate too small).
• Write the IF-THEN rules for identifying and troubleshooting (cause)
the following defects: shrinkage porosity, gas porosity.