Laser Powder Bed Fusion In-situ Sensing

While commercial LPBF machines are relatively robust and can produce near-net shapes with sub-mm features, there are still opportunities to improve the process.  This requires continuing to improve the understanding of the process dynamics as well as adding feedback control for optimal laser power and beam speed.  In addition, the complex nature of parts created with LPBF and the desire to use them in critical applications makes validation essential.  This is because limited production runs prevent statistical validation.  Instrumenting LPBF machines with radiometric sensors (e.g. infrared/visible cameras and spectrometers) provides valuable insight into the process. In particular, radiometric data can be related to process features such as melt-pool size, temperature, and recoil pressure. This data can also be correlated with ex-situ measurements to create predictions of part quality as well as real-time feedback for control and process planning in subsequent layers. We have explored various techniques to extract local thermal features from radiometric data and mapped these to microstructure and part strength. IR camera data also forms the basis for control oriented thermal modeling using in-situ measured melt-pool data to predict and correct the effects of beam path and part geometry. We are also investigating spectroscopic techniques to non-intrusively measure species content, temperature, and pressure as well as more conventional in-situ thermographic inspection of parts and the powder bed.