Progress Toward a Model for DMLS

Distortion, delamination and failure are common challenges with direct metal laser sintering (DMLS). A project funded by America Makes and sponsored by the Air Force Research Laboratory aims to help manufacturers meet these challenges. At the 2016 Additive Manufacturing Conference, Joel Neidig, development and technology manager at ITAMCO, outlined the progress being made toward a model that could minimize these problems through automated design of functional support structures. The project is led by the University of Pittsburgh, in conjunction with Johnson & Johnson, ITAMCO and the University of Notre Dame.

The project partners have created a model called the thermal circuit network (TCN) for modeling thermal distortion in DMLS builds. TCN models each super layer (a subset of the real layer in the part) using thermal circuit elements to determine the total stress accumulation and distortion in each build cycle. The model can be applied to any parts using STL files as model output, and has the advantage of speed.

According to researchers, TCN’s computational time is much faster than FEM. In one test part, it took 1 hour and 53 minutes to compute a test part with FEM, while the same task was accomplished with TCN in just 38 seconds. Loss of accuracy is less than 10 percent with this model.

According to Neidig, next steps will be to incorporate more models to take into account material plasticity and different types of materials. The project also aims to put its work into a package that doesn’t require an extremely experienced person to use.

“Our goal is to create it so that a novice engineer can come in and get a successful print right off the bat,” Neidig says. “There may still be some tweaking, but it gives you a good place to start.”