ME 455/655 Casting
Session Overview
Basic principles of metal casting processes p rocesses
Different type of metal casting process –
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Sand Casting Investment Casting Die casting
Process
Equipment
Materials
Design guides
Die Casting: Total relative part cost
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1/31 2009.02.24
ME 455/655 Casting
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Melt metal alloy Pour into mold
Allow solidification Remove from mold
Advantages: Advantag es: –
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Casting
Basic Process –
Many alloys Complex shapes
NOTE: not all alloys alloys can be cast
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2/31 2009.02.24
ME 455/655 Casting
Casting Processes
3/31 2009.02.24
Metal Casting Processes
Expe Ex pend ndab able le Mo Mold ld Ca Cast stin ing g
NonNo n-ex expe pend ndab able le Mo Mold ld Ca Cast stin ing g
Sand Casting
Permanent Mold Casting
Shell mold Casting
Die Casting
Investment Casting
Centrifugal Casting
Carbon Dioxide Mold Casting
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ME 455/655 Casting
4/31 2009.02.24
Molten metal is poured into a mold cavity formed out of sand –
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Sand Casting
Natural Sand Synthetic Sand
Pattern is an approximate duplicate of the real part –
Typically made of wood, sometimes metal
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Sand casting
ME 455/655 Casting
Molding
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Pattern Making
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Core Making
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Gating System
5/31 2009.02.24
Sand
Melting of metal
Pouring into molds &Solidification
Shakeout & Removal of gating system
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Cleaning and Finishing
ME 455/655 Casting
Sand Casting
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6/31 2009.02.24
Sand Casting
ME 455/655 Casting
Advantages –
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Castings can be up to several tons Least expensive casting process Can be used with most metals
Disadvantages –
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Rough Surface Finish Large dimensional variation Usually require Secondary Machining Parts have internal porosity Low production volume
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7/31 2009.02.24
Sand Casting
ME 455/655 Casting
Gating system –
Sprues Holes through which molten metal is poured
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Runners Networks through which the metal flows in the mold
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Gates
Risers –
Areas where the metal enters the impression (part)
Reservoirs of molten metal to ensure complete part filling
Vents –
Holes allowing escape of gasses from the melt
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8/31 2009.02.24
ME 455/655 Casting
Sand casting
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9/31 2009.02.24
ME 455/655 Casting
Sand Casting
Consideration –
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Metal Match Plates
Used for large production volume
Two halves are mounted to this
Runner Patterns
A pattern may be used to imprint the runner system (high volume) System is made by hand (low volume)
Cores –
10/31 2009.02.24
Use cores in the same way as in injection molding
Drafts –
Need draft angle to easily remove the pattern
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ME 455/655 Casting
Guidelines
When uniform cross-sections cannot be maintained, then changes in cross-sections must be gradual.
Avoid intersection ribs because they create regions of heavy cross-section
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11/31 2009.02.24
ME 455/655 Casting
12/31 2009.02.24
This process is one of the oldest manufacturing processes. –
Investment Casting
Used by Egyptians 5000 years ago to make gold jewelry
Similar to Sand Casting –
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DIFFERENCE: pattern is made of wax (or foam) lost foam/wax casting
Low production volume (
