Topology Optimization for Additive Manufacturing Considering Overhang Angle

This presentation was made at NAFEMS Americas Seminar "Engineering Analysis & Simulation in the Automotive Industry: Creating the Next Generation Vehicle Accurate Modelling for Tomorrow's Technologies".

The automotive engineering community is now confronting the largest technology transformation since its inception. This includes the electrification of powertrains for more efficient consumption and cleaner emissions, the reinvention of the battery with fast wireless charging capabilities and finally the advent of a fully autonomous vehicle. Compounding to these technology changes, the automotive companies design verification process is moving away from a major reliance on physical testing to almost a full virtual simulation product verification process. The challenges to the automotive engineers are enormous and require a significant increase in the upfront use of numerical simulation capabilities, methods and processes such they’re able to efficiently design, manufacture and deliver these very innovative technologies to the market in greater speeds than ever before.

Resource Abstract

Throughout the automotive industry, topology optimization plays a crucial role in the design of structural parts for light-weighting and performance gains. In the topology optimization process, 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.

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. 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.

In metal powder-based additive manufacturing, structures produced by the path of the laser in the powder-bed setup can only be printed up to a certain maximum overhang angle (OHA) from the vertical. This angle depends on the machine parameters and material characteristics, and is typically about 45º from the normal to the powder bed. At OHA greater than this, the powder, which is melted several layers at a time to cool and form the structure, burns underneath the structure without enough reinforcement underneath to anchor the structure to the build plate. For this reason, the standard practice is to create support structures, which are generated underneath the main structure, to support these areas. However, support structures can complicate postprocessing, build time, and part surface quality, so it is often desired to effectively minimize their usage.

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 talk gives a technical review and workflow examples for considering OHA in topology optimization.

Document Details

AuthorHoglund. R
Date 8th November 2018
OrganisationAltair Engineering, Inc.


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