Casting process and different types of castings

ME 455/655 Casting

Session Overview

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Basic principles of metal casting processes p rocesses

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Different type of metal casting process  –

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Sand Casting Investment Casting Die casting 

Process

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Equipment

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Materials

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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  –

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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 

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Risers  –

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 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  [email protected]

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

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Two halves are mounted to this

Runner Patterns  

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 A pattern may be used to imprint the runner system (high volume) System is made by hand (low volume)

Cores  –

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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 

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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

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12/31 2009.02.24

This process is one of the oldest manufacturing processes.  –

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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

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Low production volume (