Lawrence Livermore National Laboratory

Real-time Melt Pool Sensor

The deep understanding of the process afforded by simulation and modeling is not sufficient for certification. real-time process monitoring will be required to ensure the process developed through modeling and simulation was in fact executed as planned in the production of the part.

For example, the LLNL metal AM machines has a sensor that monitor fabrication as the laser melts the powder. The real-time melt pool sensor is based on work at the Katholieke Universiteit Leuven. It includes a photodiode detector and a high speed IR camera for imaging the melt pool. This high speed IR camera generates 5,000, 100x100 pixel images each second. These data can be used in real-time to control the process or after the fact to certify the component.

The diode detector sees the powder bed. Changing brightness of the melt pool results in a different intensity value in the diode. This is useful to observe long-term drift of the laser energy. The high speed IR camera senses the melt pool area and its integrated intensity. The results are recorded on a layer by layer basis.