Text Book:

1
Chapter 12
Metal Casting Design, Materials, Economics
2
Design Considerations

• Developed over many years
• Established though practical experience
• Analytical methods
• Process modeling
• CAD
• Manufacturing techniques
• Improving productivity
• Cost savings

3
Design for expandable-Mold Casting

• Corners, angles, and section thickness
• Flat areas
• Shrinkage
• Parting line
• Draft
• Dimensional tolerances
• Machining allowance
• Residual stresses

4
Casting design modifications

• Fig Suggested design modifications to avoid
  defects in castings. Note that sharp corners are
  avoided to reduce stress concentrations.

5
Design for expandable-Mold Casting Cont

• Fig Examples of designs showing the importance
  of maintaining uniform cross-sections in castings
  to avoid hot spots and shrinkage cavities

6
Avoiding shrinkage cavities

• Fig Examples of design modifications to avoid
  shrinkage cavities in castings.

7
Chills

• Fig The use of metal padding (chills) to
  increase the rate of cooling in thick regions in
  a casting to avoid shrinkage cavities.

8
Normal Shrinkage Allowance for some Metals Cast
in Sand Molds
9
Solidification Contraction of various Cast Metals
10
Parting Line

• Fig Redesign of a casting by making the parting
  line straight to avoid defects.

11
Casting Design Modifications

• Special consideration
• Draft angle
• Galling
• Eamples of casting design modifications.

12
Desirable and Undesirable Die-Casting Practices

• Examples of undesirable and desirable design
  practices for die-cast parts. Note that
  section-thickness uniformity is maintained
  throughout the part.

13
Nonferrous Casting Alloys

• Aluminum-based alloys
• Magnesium-based alloys
• Copper-based alloys
• Zinc-based alloys
• High-temperature alloys

14
Ferrous Casting Alloys

• Cast Irons
• Gray cast iron
• Ductile iron
• White cast iron
• Malleable iron
• Compacted graphite iron
• Cast steels
• Cast stainless steels

15
The Economics of Castings

• Casting Processes
• Some involve more labor than others
• Some take a more time than others
• Some more time to produce
• Cost of a product
• Materials
• Labor
• Tooling
• Equipment
• Cost of casting process
• Sand casting little cost
• Die-casting
• Materials
• Machining
• Preparation
• Melting and pouring of molten metal
• Cost for furnaces
• Related machinery
• Cost of finishing the casting

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THE END