1. Permanent Mold Casting
molten metal is poured into mold more than one time without any variance in dimensions or details of the castings

2. Method of introducing metal into mold
Gravity or Pressure
England - permanent mold casting process is called Gravity Die Casting
U.S. - Use of pressure (Other than gravity) to fill the mold is called Die Casting or Pressure Die Casting
Permanent mold casting is classified as intermediate between sand casting and die casting

3. Molds
Usually made of cast iron or graphite - any refractory metal can be used
gating system machined into mold
best suited for large quantities
200,000 low temp alloy castings before mold wears out
usually made in two halves to open and close

4. Molds (Cont.) must stay cool - possibly water cooled
venting at parting line or ejector pins
wall thicknesses of 3/4 to 2”
sections 1/4” and thinner, gravity alone will not force metal in mold
thicker cross sections than die casting

5. Molds (Cont.) ejector pins in mold
coating of release to assist in removal
molds usually heated 300 to 400 deg to assist metal flow

6. Cores metal, sand, plaster allow for intricate internal shapes
Note: external shapes are difficult to make with this process

7. Advantages normally automated high production rates
good surface finish
close tolerances (.010”)
good mechanical properties

8. Applications auto pistons cylinder heads connecting rods kitchen wear
parts usually less than 50 lbs

9. Slush Casting form of Permanent mold casting
works off principle that a solidified skin develops in a casting that becomes thicker as the metal cools

10. Process pour molten metal into mold desired skin thickness is reached
mold is inverted or slung
remaining metal is poured out
mold halves opened
casting removed

11. Application ornamental and decorative objects
toys from low melting allows
zinc
tin
lead