Additive Manufacturing

SEP 2018

ADDITIVE MANUFACTURING is the magazine devoted to industrial applications of 3D printing and digital layering technology. We cover the promise and the challenges of this technology for making functional tooling and end-use production parts.

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Page 30 of 43

AM / Perfect and Scale 29 within the factory" that currently holds five 3D printers with space to accommodate between eight and 12 total machines. Two of the machines remain reserved for R&D, while the other three are dedicated to production. Each of these machines prints and mills green parts made from MIM powder within an 8 by 8-inch print bed. Using MIM powder is cost-effective and avoids the need to develop and vali- date AM-specific materials. 3DEO currently offers 17-4PH stainless steel, primarily used for medical and defense applications, and MIM 316L stainless steel, used for applications that require higher corrosion resistance. Additional materials including Inconel, cobalt-chrome, titanium and tool steels are also in testing. A recoater blade spreads a thin layer of the metal powder and then binder is sprayed evenly across the entire layer. Note that the printer is not jetting the binder—that is, depositing droplets point-by-point over a cross-section—but binding the entire layer at once, which 3DEO says results in better consis- tency throughout the build. "We're essentially creating a cake," Petros says. "If we do it properly, material properties will be consistent throughout." The spray approach also enables greater resolution versus binder jetting, where the droplets of binder tend to be larger than the powder particles they bind. After binding, micro end mills cut the perimeter and cavities of each part while a vacuum tip removes scrap pow- der. The modular cutting tool carriage can carry as many as eight end mills along parallel tool paths simultaneous- ly, creating multiple parts at once. The three-axis motion of the machine is controlled by G code and the company's own toolpath software. Cutting the parts green like this has several advantages. First, tool wear is greatly reduced compared to milling a solid piece of stock or a final sintered part. In fact, the micro end mills currently in use at 3DEO's facility have never been replaced in the company's history. Second, machining during the build process leaves smooth, clean walls with good surface finishes, re- ducing the need for postprocessing. Machining as a step in the print- ing process also enables different process along the way. Rather than selling AM equipment out- right, 3DEO is commoditizing its technology by selling parts. As a parts producer, developing and retaining a process in- house made business sense. Using another provider's technology would come with a learning curve, one that is reduced when em- ployees have input on the equipment they use. And as a builder, this arrangement avoids outside beta testers and the need to market the system. Because 3DEO doesn't need to convince potential users of the value of its technology, it can focus on pro- ducing good parts and letting those parts speak for themselves. Binding Plus Milling What 3DEO has developed is a hybrid process that McGough describes as "traditional manufacturing with an additive funk." Distinct pieces of the process are familiar—from machining, MIM, binder jetting additive manufacturing—but in 3DEO's case, combined in a new way that enables the rapid production of small metal parts in series. 3DEO's 3D printing capacity is housed in a temperature- and humidity-controlled "pod" inside the Gardena facility, a "factory California-based startup 3DEO originally set out to commercialize a metal 3D printing technology, but changed tactics to apply that technology to making parts instead. Marty McGough (left) came onboard to help the three founders, Payman Torabi, Matt Sand and Matt Petros, shepherd the company toward production. t 3DEO's process involves spraying layers of MIM powder with a binding agent, and then milling the green parts one or multiple layers at a time. The machine's modular tool carriage can hold as many as eight micro end mills to trim a group of parts simultaneously. 3DEO's production metal AM process is capable of printing thousands of pieces per machine each day. The batch of production parts shown here has been printed and sin- tered, and will undergo secondary operations of polishing and drilling before completion.

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