Load Capacity of Support Structures for Direct Machining of Selective Laser Melted Parts

Selective Laser Melting (SLM), as a fast-growing metal-based Additive Manufacturing technology, allows to produce high strength parts with complex geometries. However, limited part properties in the as-built condition require effortful post-processing tasks (e.g. milling, drilling, polishing) to meet technical specifications and tolerances. This significantly increases the manufacturing costs of SLM parts. To address this problem, the concept of Direct Machining is presented. Direct Machining is defined as the post-processing of SLM parts via machining without prior removal of the parts from the build platform to achieve economic benefits. For this, the support structures have to withstand the occurring cutting forces during machining — a task for which they were not initially designed.
The aim of this study is to investigate the load capacity of 316L SLM support structures. For this, machining experiments on a five-axis milling machine were conducted. Cutting parameters, support geometries and support volume were varied and the cutting forces were measured to investigate their influence on the stability of the support structures. Results show, that deliberate SLM support structures allow precise machining directly on the build platform. Furthermore, a theoretical load model of Direct Machining is developed. Based on this, further optimization of the support structures regarding cutting force absorption and material volume are presented.