Approaches to minimize overhang angles of SLM parts

Abstract

Purpose For geometries exhibiting overhanging surfaces, support structures are needed to dissipate process heat and to minimize geometrical distortions attributed to internal stresses. The use of support structures is often time- and cost-consuming. For this reason, this study aims to propose an approach which minimizes the use of such structures. Design/methodology/approach For minimizing the use of support structures, process parameters in combination with a contour-like exposure strategy are developed to realize support-less overhanging structures of less than 35°. These parameters are implemented in a shell-core strategy, which follows the idea of applying different processing strategies to the critical (overhanging) shell and the uncritical core of the part. Thereby, the core is processed with standard parameters, aiming a dense material. On the critical shell, optimized processing parameters are applied, reaching good results in terms of surface quality, especially at extreme overhang situations. Findings The results show that the selective laser melting (SLM) technology is able to realize support-less overhanging surfaces by choosing suitable scan strategies and process parameters. Particularly good results are always obtained when the exposure direction of the shell is parallel to the contour of the sample. Originality/value The validity of the results is demonstrated through the successful reproduction of the build strategy on two commercial SLM machines, reaching support-free builds of surfaces with an angle to the horizontal of less than or equal to 30°.

Fast Detection of Heat Accumulation in Powder Bed Fusion Using Computationally Efficient Thermal Models

“…The degree of overheating typically increases with decreasing the overhang angle defined as the angle between part surface and the base plate. Therefore, heuristic AM design guidelines are used, where features with overhang angles smaller than a critical value are avoided [ 15 , 16 ]. Although overhangs are a salient example of features which cause overheating, the phenomenon is not uniquely linked to them.…”

Support-Free Metal Additive Manufacturing: A Structured Review on the State of the Art in Academia and Industry

“…Residual stresses in x-direction were affected in reversed order with the smallest values for continuous scan paths and the largest for the chess pattern. Cloots et al (2017) also investigated adapted process parameters with a shell and core exposure strategy.…”

A design framework for additive manufacturing

“…Some AM technologies can produce angled overhangs of certain gradient where others cannot (Table 3). These numbers can diverge highly in certain parts whose surface quality is acceptable to be poor and if the process parameters have been set up correctly [21]. For extrusion AM technologies, extreme angled overhangs cannot be created as material cannot be deposited in midair [12].…”