ASME AM3D chair Tim Simpson steps inside the Penn State CIMP-3D electron beam additive manufacturing system, which prints metal parts up to 30” x 20” x 18” in size. Image: Penn State CIMP-3D
Imagine a 3D printer able to print any material at any location in three-dimensional space. You could create functionally graded metallic parts, combined with plastics, electronics, and ceramics—perhaps integrated into bone tissue as a bionic implant.
It's crazy to think about, right?
But it's not so crazy to Tim Simpson, professor of mechanical and industrial engineering at Penn State University and the 2015 chair of ASME's Additive Manufacturing and 3D Printing Conference and Expo.
Simpson is also the co-director of the Center for Innovative Materials Processing Through Direct Digital Deposition (CIMP-3D), a manufacturing demonstration facility for additive manufacturing (AM) of metallic components.
CIMP-3D—pronounced "simp-three-D"—serves as a metals node for America Makes, a national leader in the development of AM.
The center capitalizes on the expertise of more than 35 faculty and researchers across Penn State in all of the disciplines required to make 3D printing a viable force in American industry.
The faculty and researchers' combined task is “to develop an integrated, comprehensive, physics-based approach to describe and link the important relationships that govern additive manufacturing."
CIMP-3D officially opened its doors in January 2013 with initial funding from the Defense Advanced Research Projects Agency under their Open Manufacturing Program. It has continued to add new types of equipment and now works with many other clients from the Department of Defense and industry on various research and applied-3D-printing projects.
“Additive technology is redefining everything," says CIMP-3D co-director Simpson. “How we design parts, how we make them, how we inspect them, how we qualify them, the supply chain that produced them—everything is being rewritten right now."
Part of the challenge, Simpson says, is that "we don't truly know and understand the physics of what's going on inside additive systems."
So, for example, in a metallic powder–based 3D printer, the laser hits the powder and melts the particles together, slowly building up a 3D object layer upon layer.
But depending on the speed and energy of the laser as it interacts with the powder, each object will heat and cool a bit differently, Simpson says. This “thermal history" will affect the microstructure of the object, which in turn affects its material properties—strength, stiffness, elasticity, and so on.
“So if you design your part thinking you're going to get [certain] properties, but you don't understand actually how it's made, then you may not get those," Simpson says.
Post-processing still required
The game's not over once a part has finished printing.
“A common misconception with 3D printing—and particularly for metals—is that you hit 'go' and then you pull the part off the machine and you're done, and rarely is that the case," Simpson says.
Most 3D-printed metal objects require some post-processing heat treatment because of the stresses that build up from the repeated heating and cooling caused by the laser, he says.
In fact, post-processing machining is often an essential step in creating the exact material properties you are looking for in a 3D-printed metallic part.
"Unlike for traditional subtractive processes, you start with a known material and then create the shape," Simpson says. "But in this case, you 3D-print to create the shape, and then you heat treat it or solution anneal it to actually get the material that you want."
This hydraulic manifold was printed as a single piece using 3D printing—it weighs 70% less than the original 17-piece assembly that it replaced, yet withstood the same pressure and fatigue testing. Image: Penn State CIMP-3D
Part of the technology required to print Simpson's imagined multimaterial bionic implant is already taking shape.
One of the machines undergoing tests at CIMP-3D is the Optomec LENS 3D printer, a laser-based directed energy system that allows its user to feed different metallic powders through it at different rates in order to create different alloys.
Changing the alloy on a microscale as the part is built up layer by layer makes it possible to grade the material composition and properties from, say, hardened steel at one end, to improved wear resistance in another spot, with corrosion resistance throughout.
Simpson expects advances in AM to continue rapidly.
“Two years ago when we started CIMP-3D, everybody was asking if you could actually print metal parts that are structurally sound," he remembers.
Now that question has been answered definitively, he says, and people are asking if metal and plastic can be printed at the same time—"So they're already moving on to the next phase," Simpson says.
At this rate, it won't be long before a 3D-printed multimaterial bionic implant will become a reality.
The new frontier of additive manufacturing can be intimidating to navigate; fortunately, there’s the ASME AM3D conference to help guide you as you integrate AM into your business. Learn more about the ASME Additive Manufacturing and 3D Printing Conference and Expo here.
Holly B. Martin is an independent writer.