Topology optimization of support structure for selective laser melting process

• Main Author: Wu, Lingyun
• Other Authors: Li Hua
• Format: Thesis-Master by Research
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Manufacturing; Engineering::Mathematics and analysis::Simulations
• Online Access: https://hdl.handle.net/10356/151396
• Institution: Nanyang Technological University

As a kind of additive manufacturing technologies, selective laser melting (SLM) is widely used in various industries. In the three-dimensional (3D) printing process, support structure is often used to enhance the overhang structure and prevent the structure from collapsing. In addition, as the energy is highly concentrated during the printing process, it may cause a large temperature gradient, forming internal stress and warping deformation. Therefore, it is necessary to add support structures, which are usually generated excessively by the existing additive manufacturing technology, for avoiding warpage and enhancing thermal diffusion to reduce temperature gradient. As such, this thesis mainly studies the support structure in SLM using topology optimization methods. The main contributions of this thesis are detailed as follows: 1) Optimization of support structure subject to mechanical load, based on structural topology optimization methodology. Modelling is presented for simulation of the support structure for SLM, based on structural topology optimization. This is performed to find the best distribution of structure materials with the objectives for minimizing compliance, and subject to certain volume fraction constraint. 2) Optimization of support structure subject to heat flux load, based on thermal topology optimization methodology. Similar to structural topology optimization, thermal topology optimization is conducted, in which the objective of the optimization is to minimize temperature, that is, to minimize thermal compliance, and subject to heat flux load generated during printing progress. 3) Optimization of support structure subject to thermo-mechanical coupled load, based on structural topology optimization methodology. For structural topology optimization with consideration of heat flux load, a thermal compliance is used as an additional constraint in optimization, in order to obtain an optimized support structure subject to thermo-mechanical coupled load. 4) Optimization of support structure subject to thermo-mechanical coupled load, based on thermal topology optimization methodology. For thermal topology optimization, the present procedure is similar to that for structural topology optimization subject to thermal-mechanical coupled load. A structural compliance is introduced as an additional constraint in thermal topology optimization, for the support structures subject to thermal-mechanical coupled load. Through the studies mentioned above, four kinds of support structures for a same printed part are generated optimally for comparison, namely (1) the uniform support structure, (2) the mechanical-loading support structure optimized by the structural topology optimization, (3) the heating-loading support structure optimized by the thermal topology optimization, and (4) the thermo-mechanical-coupled-loading support structure obtained by structural topology optimization. It is shown through comparisons that the optimized structures are more effective than the uniform structures for supporting the overhang structure and transferring heat. The printing efficiency is also improved and thus material consumption reduced.