Design Optimization for Additive Manufacturing in OptiStruct with Consideration of Overhang Angle in Topology Optimization

Across multiple industries including automotive and aerospace, topology optimization continues to play a crucial role in the design of structural parts for light-weighting and performance gains. In the topology optimization process within OptiStruct, the optimal material distribution of a structure is determined for a given set of boundary conditions and constraints, within a certain design region. However, one of the traditional challenges involved with topology optimization includes manufacturability of the optimized designs using traditional processes. The results of topology optimization, given complete freedom over a set design space, often do not produce parts that can easily be cast or formed, and thus manufacturing constraints introduced into the optimization formulation are necessary to be able to realize the design for production.

OptiStruct has offered manufacturing constraints for traditional forms of manufacturing such as casting and extrusion for several years now. Since additive manufacturing (AM) brings a level of increased design freedom compared to typical casting, machining and stamping processes, it has generated increased interest as a method to manufacture near optimal structures generated by topology optimization. In addition, the consolidation of multiple parts into a single additively manufactured part can save significant tooling and other overhead costs for manufacturers interested in light weighting and reducing total production costs. However, AM brings its own set of design challenges, including the necessity of support structures in part production, thermal distortion, and amount of post-processing required. To accommodate this, overhang angle (OHA) consideration for topology optimization in the form of a full constraint and a more lenient penalty method has been implemented in OptiStruct. Overhang angle (OHA) consideration helps to determine optimal structural topology in a design space while either avoiding all overhanging members or finding a good compromise between structural performance and the need for support structure. This paper gives a technical review and guidelines for positioning the current capabilities.

Note: This example uses OptiStruct version v2018. There have been some changes to the discussed algorithms compared to previous versions. Generally, version 2017.2.3 can be used to reproduce all the presented results.