Additive Manufacturing

MAY 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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MAY 2018 Additive Manufacturing 10 TAKING SHAPE Applying Material Like Toner Promises AM at Speeds Like Injection Molding By Peter Zelinski An example of a component produced via STEP. The process can produce parts without the layer lines typical of 3D printing. When Evolve Additive Solutions Chief Business and Marketing Officer Bruce Brad- shaw refers to the Evolve's new "STEP" technology for additive part production, he is careful to avoid the term 3D printing. The technology is for high-speed, high-volume additive manufacturing, nothing like the one-off applications where 3D printing began. But the irony in avoiding this term is that STEP has as much in common with actual printing as any additive system so far. The technology achieves high-speed material layering by applying polymer onto rollers like toner in a document printer. Indeed, to understand the concept of STEP is to realize that many of the additive technologies to date have been performing essentially like dot- matrix printers. By contrast, here is an approach to additive that is both metaphorically and literally very much like a laser-jet printer. In the STEP (Selective Thermoplastic Electrophotographic Process) technology, the material layers that are applied like toner are delivered by belt onto a preheated part that is moving at a matching speed. The belt carries an entire layer at once, precisely meeting the part as it moves in a straight line beneath the belt on a conveyor of its own. Thus, in applying material to the part, there is nothing like a nozzle or beam that moves through one small area at a time. Rapidly delivering each layer in this way allows for build rates unlike previous additive processes. The first machine model developed offers a build chamber measuring 24 × 13 × 6 inches. One layer across its 24 × 13 area can be applied in 4 seconds. Filling the entire volume with parts—however many parts can be fit into that space—takes 3 hours. Established 3D printer maker Stratasys developed the technology to its current point, then spun it out into Evolve, a separate company in which Stratasys is a minority owner. Steve Chillscyzn, co-inventor of the technology, is the company's CEO. He says the plan is to fully commercialize the technology in 2020, but Evolve is announcing STEP this year in part because it is searching for beta users, and in part because the technology is potentially a solution for major manufacturers that will need time to evaluate it and adapt their plans. Bradshaw says the capabilities of STEP are more comparable to short-run injection molding than to other additive processes. STEP provides a way to obtain a 2,000-piece run of plastic parts within one day, versus the lead time necessary to wait for mold tooling. And because the mold is absent, the new technology also delivers a cost per piece at this quantity level that is lower than molding. One other way the process is comparable to molding is this: It can produce parts missing the layer lines typical of 3D printing. STEP mates heated layers to a heated part, producing fusion that is more complete than in a process such as FDM. Candidate materials for STEP are the same polymers available for injection molding, the company says. Delivering the materials as toner requires materials- engineering techniques proprietary to Evolve. It also affords possiblities that are typical of printing. That is, just as a laser-jet printer can apply several toners, the STEP machine has multiple print heads providing the chance for multiple materials in the same build. Various polymers applied at the voxel level could achieve combinations of material properties unobtainable in any single material alone. Thus, the technology offers a means of realizing some parts that were previously unthinkable, then manu- facturing them at production scale. Here is the alpha version of the STEP machine. In a process similar to laser-jet printing, it uses a roller system to deliver complete layers of material to the part.

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