Page 27 - 3D Metal Printing Summer 2019

Binder Jetting 3D
be slow and costly, we basically jet a binder into a metal powder.”
Weber refers to jetting as “area-wide” technology, a much more efficient method than a “point process,” as he describes laser-bed printing.
“So this process runs about 50 times faster than other presently available binder jetting and selective laser melting metal-AM processes,” he says, stressing that the result is efficient batch produc- tion, with multiple parts produced quickly within the build area. “The Metal Jet deliv- ers an HP binding agent to a powder- metal bed and industry-standard metal- injection-molding (MIM) metal powders. The inkjets spray in a layer via a print head traveling side to side, with another print head alternately traveling in a per- pendicular direction and spraying the next layer.”
Weber attributes speed, density and accuracy in part to inkjet-nozzle redun- dancy, with the Metal Jet reportedly fea- turing four times the number of nozzles and two times the number of print bars as presently available systems.
Density after sintering is greater than 93 percent, similar to densities achieved via MIM. In addition, HP officials report, the Metal Jet can produce multiple parts simultaneously, and parts can be arranged freely in multiple levels within the bed to optimize packing density, productivity and cost. And, no build plate is required.
The machine spreads lower-cost (com- pared to powders developed for AM) off- the-shelf MIM powder, according to Weber. The powder measures about 10 microns, as compared to 50-micron poly- mers used in HP’s nonmetal machines. Why 10 microns?
“When sintered, it provides great mate- rial properties, which the MIM industry figured out over the last 40 years or so,” Weber says. “Then, instead of a fusing agent we jet a binding agent and build layer by layer. With no support structures required, there’s no need to machine them off, which eases automation of the process.”
Obviously, HP paid attention to MIM when developing the Metal Jet, and sees
At IMTS 2018, HP signaled its entry into 3D metal printing with the introduction of its Metal Jet printer, employing binder jetting technology that promised print speeds to 50 times faster than current AM machines.
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MIM markets as good possibilities for its technology, along with investment casting. “We see market opportunities relative to what’s consumed in iron and steel,” says Weber, “including not only stainless but also low-alloy and workhorse steels used in the automotive industry. We’re not going to focus on aviation and reactive materials such as titanium, but automo- tive, industrial and medical can be ideal
applications.”
Though not achieving tolerances
attained with MIM, “We can get 99-per- cent of the way there,” says Weber, “with a secondary operation to achieve critical dimensions in certain areas of a part.”
Considering the tooling required in these other processes, printing proves more economical up to a certain volume point. As an example, Weber showed a valve lifter, produced via MIM and using a mold that costs $50,000.
“From a break-even standpoint, it’s cheaper to print 50,000 of these than to use MIM,” he says. “Over time, as our pro- ductivity improves as it has with our non- metal printers, we think the break-even point will move out farther and farther.”
GKN, VW Bullish on Binder Jetting
Representatives from GKN and Volk- swagen again were on hand—HP part- nered with these and other companies to gain insight into metals materials and part manufacturing—to detail their metal- printing efforts. GKN, a powder producer
and maker of sintered and AM parts, con- sumes 300,000 tons of powdered metal each year, while the AM industry worldwide consumes less than 2000 tons/yr., claim company officials. It launched an AM-parts business unit about 2 years ago, according to Guido Degen, president of additive man- ufacturing for GKN Powder Metallurgy, and seeks mass production via AM.
“Binder jetting allows us to bridge from low volumes (via laser-bed processes) to volumes of 50,000 or 100,000 pieces, or more,” Degen says, citing technology advantages such as competitive costs, time to market and design freedom. “It adds to our portfolio. We now become a solution for customers needing one part or 1 million (MIM gets the call for volumes surpassing 100,000 parts).”
For its part, Volkswagen sees binder jetting as a solution first for its low-volume parts (5200 different VW parts fit in this category), and then later on for higher- volume parts, according to Sven Crull, Volkswagen Group’s head of design for new manufacturing technologies. He sees the technology as ideal as the automaker works toward its goal of mass customiza- tion, with AM finding its way from cos- metic parts to more functional applica- tions. Crull expresses confidence in AM providing for these needs as materials and the process evolve. Of more concern to him: designers accepting AM and real- izing the possibilities inherent in the process. 3DMP