ing, visual aids and for patterns for metal castings or polyurethane plastic parts,” Caffrey said. “But in regards to metals, we’re seeing a real increase in uses for end-use parts, for direct part production. That application category has been growing very quickly.”
Metal Powder Bed Fusion By far the most common method
By building components one layer at a time, powder bed fusion can produce complex shapes.
for printing metal parts involves directing a heat source onto a bed of powdered metal to fuse granules together. With so-called “metal powder bed fusion” techniques—also called laser melting, selective laser melting or direct metal laser sinter- ing (DMLS)—a laser or other heat source binds the materials together in a micro-welding procedure accord- ing to a 3-D model that is sliced into thin layers. As the part is printed, it will be
supported by lattice structures of the same material. Once printing is complete, the supports are removed by hand and/or CNC machining. Research has shown objects created by powder bed fusion, with proper heat treatment, can exhibit physical and mechanical properties similar to cast parts, though further stud- ies are ongoing. “Te main difference is the grain
structure,” said Bry Ewan, product manager of metals, Stratasys Direct Manufacturing, Valencia, Calif., a service provider of additive and ad- vanced manufacturing including 3-D printing. “If you cut a DMLS part in half, the internal grain structure will look different when compared to a cast part. But if you’re using an alloy that can be cast, the part will behave just like its cast or forged cousin.” Powder bed fusion has made
significant inroads in the aerospace, medical and oil/gas industries. (See the sidebar for a case study involv- ing a hinge for the Airbus A320.) GE Aviation recently announced plans to invest $50 million to introduce high volume additive manufacturing to its facility in Au- burn, Ala. This facility will produce the 19 fuel nozzles in its LEAP jet engine via powder bed fusion. The
32 | METAL CASTING DESIGN & PURCHASING | May/Jun 2015
Photo courtesy of EOS
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