An often overlooked manufacturing process combines graphite molds with a low-turbulence-filling method and a zinc-aluminum alloy. It turns out parts with tolerances of ±0.005 in./in. or less, and at lower cost than other casting methods. The material, alloy ZA-12, is about 11% aluminum. “It's harder, stronger, and more durable than aluminum, brass, bronze, and plastic,” says Val Zanchuk, president of Graphicast Inc., Jaffrey, N.H., (graphicast.com).

Tooling costs for graphite molds are lower than those for die casting or plastic injection. Graphite costs less than tool steel and requires no heat treating. “In addition, equipment for low-turbulence casting controls fill rates, cycle times, and temperatures. Because molds fill from the bottom, it minimizes turbulence in the molten metal, producing excellent parts time after time,” says Zanchuk.

Compared to conventional sand and investment casting, low-turbulence casting creates parts in volume with accuracies and surface finishes as good or better. And graphite molds are long lasting and reusable. Molds for sand and investment castings, on the other hand, are destroyed when extracting parts. “The accuracy and lustrous surface finish of ZA-12 almost eliminates the additional finishing steps needed with other casting methods”, adds Zanchuk. He points out that parts can be chromated, plated, painted, power coated, and more.