Exploring the fabrication limits of thin-wall structures in a laser powder bed fusion process

Abstract

Although additive manufacturing (AM) is becoming increasingly popular for various applications, few studies have addressed design and potential problems in thin wall fabrication for the laser powder bed fusion (LPBF) process. In the LPBF process, rapid cooling induces thermal shrinkage, which in turn, results in high residual stress and complicates thin wall fabrication. The minimum wall thickness is limited by the parameters and machine settings while the dimensional accuracy is controlled by the powder size, scan strategy, and part geometry. The ability to fabricate thin-wall components is important for applications such as heat exchangers (HX). This study explores the performance of the LPBF process by fabricating thin walls with extreme geometries in different processing conditions and alloys using an EOS M290 LPBF machine. Results show that the material, part design, and scanning strategy contribute to the variation in thin wall dimensions. A maximum inclination angle of 60° and a minimum wall thickness of ~ 100 μm in Ti-6Al-4V, Inconel 718, and AlSi10Mg were achieved using optimized part design and processing conditions. The effects of part design and material on the thermal distortion and surface finish of thin walls were also investigated leading to a discussion on how the scan mode assigned by the EOS software affects design and fabrication. Additionally, synchrotron-based X-ray micro-tomography (μSXCT) was utilized to quantify the porosity in thin-wall structures and to correlate it with the integrity of the structures. Comprehensive design guidelines presented in this work can increase the success rate of fabricating thin-wall geometries.