David Go and Richard Billo
Two College of Engineering professors at the University of Notre Dame devised a solution to metal warping in 3D printing that was commercialized by Atlas 3D of Plymouth, Ind. The firm was acquired last year by Siemens Digital Industries Software.
Richard Billo, associate vice president for research and professor of computer science and engineering, and David Go, Rooney Family Collegiate Professor in the Department of Aerospace and Mechanical Engineering, along with colleague, David Hoelzle, currently associate professor in the Department of Mechanical and Aerospace Engineering at the Ohio State University, identified the reasons for the warping and how to avoid it. Their solution became the basis of the Sunata cloud-based software that enhances the simulation process for optimal manufacturing. They received funding for the development from the federal America Makes program that focuses on additive manufacturing.
“This problem was brought to us by Johnson & Johnson,” Billo says. “When you print the metal part, it often warps, what we call distortion. As you print it, it begins to warp. They were not sure why. We discovered that you could find an orientation to build that part where the warping would be minimal.”
Go, an expert on principles of heat transfer, said the warping results from uneven cooling of the materials in the manufacturing process.
“From a physics perspective, what happens is you are essentially melting a metal powder with a laser,” he says. “As it cools, that’s where the distortion happens. We needed to create a computational model that could simulate the heating and cooling processes in time and predict the mechanical distortion or warping and use that tool to optimize the orientation.
“When doing simulation, if you know what you’re simulating, it’s really easy. You can break down the equations and apply them to components of interest. Here, we had to do it without knowing what we had to print. It had to be very general, suitable for any possible 3D printed part. The other problem was it had to be very fast.”
The process might involve choosing among hundreds of simulated orientations that must be calculated fast enough to be practical for commercial manufacturing.
“The challenge for us was to take complex heat transfer and thermal physics, complex mechanics, and make something really simple that could run really fast,” Go says.
The solution was borrowed from the principles used to evaluate electrical circuits and apply them to thermal circuits. Postdoctoral associate Hao Peng developed representative thermal circuit components for the range of possible shapes, such as holes and features, found in complex parts such as knee replacement implants.
“The thermal circuits simplify the physics so it’s really fast,” Go says. The system was able to predict warping within 15 percent of experimental results with less than one-thousandth-inch distortion.
Indiana Technology and Manufacturing Companies (ITAMCO) of Plymouth, a leading advanced manufacturing and technology firm, created the spinoff Atlas3D to commercialize the solution.
“They really took our university algorithms and software and ruggedized it, made it more of a product, made it user-friendly,” Billo says. “They licensed that from the university. Their objective was to grow that product, grow the customer base, and sell the company.”
“They made a nice interface that looks nothing like what came out of Notre Dame,” Go says. “We put the engine together. They made the rest of the car.”