This paper was produced for the 2019 NAFEMS World Congress in Quebec Canada
Throughout the last decade, additive manufacturing (AM) processes have become increasingly relevant in different industries, e.g. medical, aerospace and tools, being on the verge to broad industrial application. Especially in selective laser melting (SLM) of metals, support structures have a strong influence on the successful production of parts: They are responsible for supporting overhanging features as well as preventing distortion by anchoring the part to the build plate and dissipating process-induced heat. Today, support structures are often more massive than necessary, leading to high post-processing efforts as well as increased material consumption. Additionally, they often do not fulfil all of their respective tasks, posing a risk of failure during the manufacturing process. To reduce the manufacturing and finishing efforts in SLM, support structures have to be optimized in terms of material consumption, strength and thermal conduction.
To decrease material consumption, the use of topology optimization to generate support structures offers various possibilities. Combined with a process simulation of SLM, the support structures can be adapted to the individual part, ensuring the fulfilment of every respective task as well as minimum material consumption. The validity of this approach for mechanical loads has been proven in a previous publication . This study presents a continuation of the conducted work by applying thermal loads to the general concept.
The case study is carried out using a cantilever beam made of Ti-6Al-4V. As a first step, a finite element simulation of the manufacturing process’ thermal history is set up. Specific characteristics of SLM such as layer-by-layer manufacturing, laser heat source and powder material are implemented. The simulation result shows artificially high temperatures along the bottom of the overhanging part with the expected general shape of temperature distribution. Employing the simulation results as input load, topology optimization of the support structures is conducted in the second step. Here, the Solid Isotropic Material with Penalization (SIMP) method is applied. The resulting optimized geometry exhibits a tree-like shape, with branches leading from the overhanging beam to the build platform, which is acting as heat sink. This is in accordance to the results obtained for mechanical loads, suggesting further investigation of tree support structures.
|Date||18th June 2019|
|Organisation||Technische Universität Hamburg-Harburg iLAS|