Additive Manufacturing

FEB 2013

Modern Machine Shop and MoldMaking Technology present ADDITIVE MANUFACTURING, a quarterly supplement reporting on the use of additive processes to manufacture functional parts. More at additivemanufacturinginsight.com.

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F E AT U R E an AM pattern. This can include basic room temperature vulcanizing (RTV) molds poured onto an AM pattern or rotocasting (spincasting) of urethane. When higher quantities are needed than an RTV mold can accommodate with its average life of 25-50 units, epoxy tooling is an attractive option. Used for reaction injection molding (RIM) or standard injection molding, epoxy tooling can be a cost-effective method to produce bridge tooling. Sacrificial (one-time) molds also can be useful in AM, and FDM technology has been used successfully for wash-out mandrels in the composites arena. Other pattern-based RT processes include cast kirksite tooling (epoxy tooling with filler), 3D Keltool, MetalCopy, PHAST, V-Process and rubber plaster molding (plaster casting). High-Performance Tooling Metal casting tool made with Sandform. Courtesy of Voxeljet. Indirect Tooling Several pattern-based processes have been developed for creating a tool rapidly through AM, with varying costs, lead times and process capabilities. In general, any process—whether additive, subtractive or formative—can be used for indirect tooling. The accuracy of these processes depends, in large part, on the accuracy of the method used to create the pattern. Few areas of manufacturing have been impacted as much by AM as investment casting. Early on in the development of AM, Helisys's laminated object manufacturing (LOM) system used layered paper for casting patterns because of the low ash content. Companies now make casting patterns via QuickCast (a stereolithography build style), jetted wax and resin systems such as PolyJet and Multi-Jet Modeling (MJM), and with selective laser sintering (SLS) for polystyrene and FDM for ABS. In the plastics field, many companies that need to produce a relatively small run of plastic parts employ silicone rubber tooling made from 6— AM Supplement With high-performance tools, molding cycle time is more important than the time it takes to produce the actual tool, and creating conformal cooling channels within the tool using AM can help speed the molding cycle. These channels conform to the shape of the mold cavity and enable coolant to pass through, removing heat from the mold or die faster and more evenly than straight-line channels. Tests suggest that conformal cooling can reduce cycle time by 30 percent or more and improve part quality. The result can have a significant impact on part costs and production rates. Another method of thermal management is the use of functionally graded materials. The idea

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