Casting

2

Casting since about 4000 BC…

Ancient Greece; bronzestatue casting circa 450 BC

Iron works in early Europe,e.g. cast iron cannons fromEngland circa 1543

Two Categories of Casting Processes1. Expendable mold processes - mold is

sacrificed to remove part

2. Permanent mold processes - mold is made of metal and can be used to make many castings

Casting Methods

• Sand CastingHigh Temperature Alloy, Complex Geometry, Rough Surface Finish

• Investment CastingHigh Temperature Alloy, Complex Geometry, Moderately Smooth Surface Finish

• Die CastingHigh Temperature Alloy, Moderate Geometry, Smooth Surface

Sand Casting

Uses sand to hold the desired shape to be

cast

Bonded with chemicals or clay with water or

oil

Many different types of sand casting

Sand Casting

Sand Casting Steps

cope: top half

drag: bottom half

core: for internal cavities

pattern: positive

funnel sprue runners gate cavity {risers, vents}

Investment CastingA refractory material (investment) is poured

around or built up on a pattern

The investment is hardened by drying or

heating

The pattern is removed by melting or

burning

Metal is poured into the resulting cavity

Investment Casting

(a )Wax pattern( injection

molding)

(b )Multiple patterns assembled to wax

sprue

(c )Shell built immerse into ceramic

slurry immerse into fine

sand( few layers)

(d ) dry ceramic melt out the wax fire ceramic (burn

wax)

(e ) ) (Pour molten metal gravity cool, solidify

[ Hollow casting : pouring excess metal before

solidification

(f ) Break ceramic shell ( vibration or water

blasting)

(g )Cut off parts( high-speed friction

saw) finishing (polish)

Investment Casting Steps

Die CastingHuge numbers of small, light castings can

be produced with great accuracy.

Little surface finishing is required.

Permanent mold (dies can be used over and

over)

Die Casting

Die CastingSteps

• Reference:

Metal Casting book

http://en.wikipedia.org

Casting