In subtractive patternmaking, a CAD file is programmed into a machining center, which works in layers to suit the lengths of the cutters.


custom metalcasting operation in Hoagland, Ind. As CNC machining capabilities


develop, as well as additive manufac- turing, users among metalcasters and independent patternmaking shops are evolving their methods in step with the technologies. “[Companies] positioned to offer these latest techniques will use the various ‘tools’ to build more complex components with shorter lead times at lower costs, producing a win-win for the project,” said Hockemeyer.


A Variety of Choices Among the rapid methods for


metalcasting are several additive manufacturing (AM) technologies for “printing” plastic, wax, sand or metal tooling. “Each of these typically offers


advantages over traditional CNC machined foundry tooling in the way of less lead time and lower


costs,” said Hockemeyer. “One way in which they excel is that they are not affected by part complexity. In fact, the more complex the part ge- ometry, the more effective AM is at producing an efficient solution. “For example, when a complex wax pattern made with conventional techniques requires a soluble core, a die with moving action or challeng- ing draft requirements, a printed wax pattern can be made in one piece. The layering process elimi- nates those concerns and the need for the wax die altogether,” he said. “Similarly, when a complex sand mold pattern requires draft, cores, multiple glued cores, offset parting or loose pieces, a printed sand mold can avoid those concerns by building a complete mold ready to be poured with metal, without the need for a pattern. Printed plastic patterns offer advantages since they require less programming and setup time as


20 | METAL CASTING DESIGN & PURCHASING | Nov/Dec 2014


compared to a machined pattern, and the AM machine itself can run 24/7 unattended.” Soft tooling produced using


additive manufacturing methods can be ready quickly and maintain the metal casting supplier’s ability to make up to several hundred parts. “This commonly takes place when a plastic master model is printed, followed by a mold off the master model, and ends with a cast polymer pattern impression made from a material with good wear characteristics allowing for hun- dreds of sand molds to be made,” Hockemeyer explained. Thomas Mueller, CEO of Ex-


press Prototyping in Keego Harbor, Mich., prints investment casting patterns in PPMA (Plexiglas). “3-D printing technology allows us to print every thinkable shape and form. No draft angle is needed,” he said. The firm specializes in plastic


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