Current selective laser melting additive manufacturing (AM) systems do not have adequate process control features for wide-spread adoption across NASA. In this project Mound Laser & Photonics Center (MLPC) will work with Wright State University (WSU) to implement a novel system for layer-by-layer in-process monitoring for AM. The key innovation in this work will be the use of a line-laser profilometer (LLP) for 3-dimensional, in situ, sub-micron profilometry on every layer during an AM process, both before and after the layer has been melted. Several advantages will be gained from this approach: (1) Measurements on the spread powder layers will determine powder distribution and quality, enabling correlation between powder distribution and finished part material properties such as microstructure and density; (2) Measurements on the melted layer profile will determine the geometric accuracy of the melted layer (both in depth and lateral dimensions), compared to the CAD file, and allow correlations between geometric accuracy to powder distribution, laser parameters, and material properties; and (3) simple layer defects will be easily identified before the next layer is spread. This technology could enable real-time process qualification, and eventually automatic powder re-spreading or layer re-melting to fix defects in the layer. In this project, the SBC (MLPC) will build test coupons in their custom-built, fully tunable, research-grade AM testbed and monitor the build process with the LLP. The RI (WSU), who has tremendous expertise in AM sample characterization, will then perform in-depth material analysis on the test coupons to determine material properties. At the time of this proprosal, MLPC has already determined that the LLP can measure the AM testbed with micron-scale accuracy. Therefore, achieving success with this approach is very likely, the primary needs for implementation are the development of experimental methods and process control correlations.
