Production Machining

DEC 2017

Production Machining - Your access to the precision machining industrial buyer.

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companies. e EBM system replaces the laser or thermal print head with an electron beam, most typically to produce dense metal parts. "e decision between EBM and laser comes down to the part. Both systems have their advan- tages, and 3D printed parts need to be designed for the intended system," Mr. Rappach says. e printers at Slice are geared more toward produc- tion work than they are for prototypes. Setup can take six to eight hours, including extensive prep work such as cleaning and maintenance necessary to qualify the machine, alignment of the beam and a preheat warming cycle to get to the correct temperature. "EBM machines are a different mindset," Mr. Rappach says. "A lot of job shops are looking to 3D printing for one-off prototypes, making parts quickly and easily. We are using the technology for production of parts that cannot be created any other way." During the build process, a layer of powder is spread inside the chamber. e full chamber is under vacuum, filled with helium. e powder is preheated to semi- solidify it. e end product is a brick of powder that has already been heat treated and annealed during the printing process (as opposed to laser 3D printed parts, which have Anodizing the Hip Cups Although Slice's acetabular hip cups are currently being anodized by an outside firm, the company is looking to bring that operation in-house as well for further control. Why are the parts anodized? Mr. Rappach says, "Because we can." Most medical implanted parts are anodized for color coding to identify a size. But forged or cast titanium parts have a plasma-sprayed or glued coating on them that cannot be anodized. The 3D printed parts, however, have no foreign matter on them, so they can be anodized to follow suit with the screws and plates and other complementary components in that environment. residual stresses after completion and are heat treated afterwards). e part is then ready for its next steps. Additive's Secondary Operations Once the powder brick comes out of the machine, it goes into the next room to run through the powder recovery system (PRS). In this blasting cabinet, the brick is blasted to get the parts out of the 3D print build. e powders from the build are collected, and a sample of the powder is tested for chemical composition. Several random pieces from the 3D build are also tested to make sure the printer is not burning off more of any one element, which could cause lower chemical makeup in the finished part relative to the correct makeup in the powder. All of the powder that comes off of the build is put in a reblending to have it recertified. Slice is currently not reusing the powder, but the goal is to work toward a better understanding of how much of the material and chemical makeup has burned off and how to compensate for that accurately in a reblend. Slice was set up with a good mix of turning and milling machines along with the 3D printers. Swiss machines are typically key compo- nents of a medical shop, and this requirement is filled at the company by three Tornos GT 26 CNC Swiss turning centers, along with a high production Tornos EvoDeco 32. While these machines are not associated with the production of any of the 3D printed parts, they do serve to create corresponding parts such as screws, along with unrelated components for other applications. "We do complex machining, mill-turning, 3D printing," Mr. Rappach says. "ese jobs always come with a screw or an instrument that needs to be used with those compo- nents, and the Tornos machines provide the capabilities we need for that work." Directly related to the company's 3D printed parts, though, is a lineup of several Willemin-Macodel 508 MT machining centers with turning capabilities. Medical 3D printed parts require significant finishing, and these machines serve this integral role. Aside from the engineered surfaces that are specifically related to the 3D printing, all other surfaces need to be finished, polished or touched in some way outside of the printer. Currently, one of the primary 3D printed parts at Slice is a line of acetabular cups for hip replacement. In other shops, this part is often forged, then machined after forging. e finished part would then have a coating glued or plasma sprayed on it. Because that coating is not Manufacturing with Additive :: 37

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