Permanent Mold Casting molten metal is poured into

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

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

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

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

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

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

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

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

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

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

Application • ornamental and decorative objects • toys from low melting allows – zinc – tin – lead