Influence of optical system operation on stability of single tracks in selective laser melting

Abstract

Additive manufacturing (AM) technologies are increasingly being studied and introduced into the modern industry, but for wide applications there exists some "lack of confidence" about the quality of the parts produced by AM. This distrust has an objective basis: it was shown that the final 3D object is a superposition of a huge number of tracks and layers, and deviations from the optimal process parameters can lead to non-regular shape, unmelted places (lack of fusion) and porosity. Experiments with different bare substrates were performed to classify instabilities and artifacts in single tracks derived from laser beam characteristics, the optical system, scanning strategy, etc. demonstrating an adjustment scheme for testing and verifying LPBF equipment. An important point is that this research can be useful for the custom experimental setup. The paper describes the importance of checking the system before each build to identify problems caused by optical system operation. Also, possible deviations from the stable process, methods of their diagnostics and solutions are described. The proposed method is a cost-free way to diagnose the stability of the selective laser melting, which does not imply the necessity of having additional systems for detecting problems. The diagnostic scheme was used to evaluate in situ diagnostics of the LPBF processes on the Additive Manufacturing Metrology Testbed (AMMT) at the National Institute of Standards and Technology (NIST).