Metaltek provides rapid castings for Army cleaning tool.

When Benet Laboratories, a Department of Army research, development and engineering facility located at the Watervliet Arsenal in upstate New York, wanted to develop a single-piece casting to replace a four-piece multi-metal fabrication, it required a rapid prototype to verify the castability and functionality of the design. The American Metalcasting Consortium (AMC), which provided technical input to Benet Laboratories during the design of the part, located Metaltek International's Wisconsin Investcast facility in Watertown, Wis., to provide quick castings to prove out the design.

The part, a cleaning mesh holder, is used for cleaning the barrel of an 81 mm mortar. Originally a four-piece fabrication, the piece incorporated parts that were made from two different metals (aluminum and steel), which were brazed together to form the assembly. The manufacture of the fabrication was expensive, particularly because of the use of two different metals.

Once it was determined the part could be a good fit for casting, AMC put Benet Laboratories in touch with Wisconsin Investcast. "Prototype parts were needed to demonstrate the casting could achieve the necessary geometry and to prove the concept through testing," said Dave Poweleit, application engineer for AMC.

Benet Laboratories used its stereolithography machine to produce QuickCast patterns--plastic patterns that are created layer by layer from a CAD file. The patterns were sent to Wisconsin Investcast to produce prototypes using investment casting.

After solidification analysis to determine the proper gating, Wisconsin Investcast assembled the pattern on a tree, invested it into a slurry and stucco to produce a shell coating and then burned out the plastic pattern from the shell. "We had some concerns about the plastic from the QuickCast patterns because they can sometimes cause cracking in the mold, but we did not run into that problem this time around," said Dave Kirmse, mechanical engineer at Wisconsin Investcast.

The castings were poured within a week of receiving the patterns. For small runs of this nature, the casting facility uses a "mini producer" to dry the patterns between dippings. This machine is a miniaturized replica of the plant's full-size drying operation. It incorporates the same environment, drying chamber and air speeds as the large-scale version but allows small-run and prototype parts to be produced without interrupting regular production.

The final casting, which incorporated two helical tines, measured 9 x 3 in. (22.86 x 7.62 cm) and weighed 3 lbs. (1.36 kg), was provided to Benet Laboratories free of charge. The prototype helped prove the part could be investment cast and meet the physical requirements. The collaboration also helped steer the current redesign of the casting for improved castability.

"Rapid prototyping can generate anything you want, but that doesn't mean it's cost-effective tooling-wise," Kirmse said. Wisconsin Investcast passed along the suggestion to change the shape of the tines in order to cut tooling costs, which AMC and Benet Laboratories incorporated into the redesign. Once the design is finalized, the component will go into full production at an investment casting facility.

Visit www.amc.aticorp.com for more information.

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