Method to maximize the productivity of laser powder bed fusion systems through dimensionless parameters

Abstract

Productivity in laser powder bed fusion systems can be increased by using high layer thickness (>40 μm). The process parameters for high layer thickness are typically found by one-factor-at-a-time, design of experiments, or computationally intensive numerical simulations. In this paper, a method to scale-up the process parameters from low to high layer thickness is proposed. The method is based on dimensionless parameters from the analytical model. Through the proposed scale-up method, the build rate increase was proportional to an increase in layer thickness. The scale-up method was demonstrated for laser powder bed fusion of stainless steel 316L from 30 to 50 μm layer thickness and from 50 to 70 μm layer thickness. For both cases, no detriment to part density was observed—measured densities before and after the scale-up were above 99.6%. The density results obtained were within high density windows with variation of parameters resulting in the same respective volumetric energy densities and one-factor-at-a-time parameter studies. There was no significant change in tensile properties after the scale-up except reduction in elongation at break in the XY direction. The comparable mechanical properties before and after the scale-up method were attributed to the observed similarities in microstructure features such as the crystal orientation, cell sizes, and proportions of low and high angle grain boundaries.