Volumetric heat source calibration for laser powder bed fusion

Computationally efficient models that consider only conduction are increasingly used in powder bed fusion (PBF) to predict the thermal history for relatively large build volumes. We propose a systematic method to calibrate experimentally representative heat sources for use in such models. An inverse heat conduction problem (IHCP) methodology is applied to determine the parameters that characterise a double-ellipsoid volumetric heat source, based on temperature measurements taken from the solidification boundary of the melt pool. We demonstrate that these fitted parameters follow well-defined trends across a range of laser powers and scan speeds, for melt pools in the conduction and transition modes typically used in laser PBF. Furthermore, we found that these trends in the fitted parameters are related to the energy density of the scanning laser beam, enabling an appropriate source to be calculated even at intermediate laser powers and scan speeds where calibration experiments have not been undertaken. These results enable a heat source to be selected for conduction-only models that incorporates experimentally calibrated effects such as the laser absorption and the penetration of the vapour depression into the melt pool, which are computationally expensive to calculate from first principles. The approach could also be used to characterize laser PBF systems, for example to monitor the drift in process settings that occur over time.