Analytical modelling of scanning strategy effect on temperature field and melt track dimensions in laser powder bed fusion

Abstract

The manufacture of defect-free and dimensionally accurate parts in laser powder bed fusion (LPBF) is influenced by temperature field, deposited track geometry, and process-induced thermomechanical stress. The selection of an appropriate scanning strategy is key to achieving this goal. Well-tested numerical models of heat transfer and thermal stress are possible routes to design for the LPBF process, but these models are computationally expensive and arduous for practicing engineers. Here, we introduce an analytical heat transfer model tailored for part-scale LPBF simulations, encompassing widely used scanning strategies such as linear, circular, spiral, and circular beam oscillation paths. Notably, our model integrates exact curvilinear trajectories of the laser beam, enhancing fidelity in representing non-linear scanning paths. The computed melt track profiles and thermal cycles are tested rigorously with the corresponding experimentally measured independent results. The computational times for various scanning strategies are examined. A unique temperature non-uniformity metric is defined as the sum of the normalized deviations between the computed temperature field in a layer and the average layer temperature at any time instance. The computed temperature non-uniformity metric is shown to work well as a susceptibility factor for the thermal stress along a layer. Ultimately, the work underscores the potential of an efficient analytical heat transfer model, reducing trial-and-error tests and helping to select optimal scanning strategies in part-scale LPBF.