Topology Optimization for additive manufacturing with distortion constraints

Grzegorz Misiun,Emiel Van De Ven,Matthijs Langelaar,Hubert Geijselaers,Fred Van Keulen,Ton Van Den Boogaard,Can Ayas

doi:10.1016/j.cma.2021.114095

Abstract

An important cause of failure in powder bed additive manufacturing is the distortion of the part due to thermal shrinkage during printing and the relaxation of residual stresses after its release from the base plate. In this paper, Additive Manufacturing simulations are coupled with Topology Optimization in order to generate designs that are not susceptible to failure associated with distortion. Two possible causes of failure are accounted for: recoater collision and global distortion of the product. Both are considered by simulation of the build process and defined as constraints in the context of a Solid Isotropic Material with Penalization method based topological optimization. The adjoint method is used to derive the sensitivities of the additive manufacturing constraints. The method is demonstrated with the 2D and 3D optimization of a bracket. Next to global topological changes, the obtained designs show features that are aimed at facilitating the printing process. These features resemble supports that are routinely applied to powder bed additive manufacturing. The formulated constraints were found to prevent excessive part distortion and associated build failures in all cases, against a modest increase in the compliance of the bracket.

Highlights

Additive manufacturing (AM) of 3D objects comprises deposition of layer-upon-layer of material
An important cause of failure in powder bed additive manufacturing is the distortion of the part due to thermal shrinkage during printing and the relaxation of residual stresses after its release from the base plate
Additive Manufacturing simulations are coupled with Topology Optimization in order to generate designs that are not susceptible to failure associated with distortion

Summary

Introduction

Additive manufacturing (AM) of 3D objects comprises deposition of layer-upon-layer of material. AM is characterized by a short lead time, low material waste, the possibility to process hard-to-produce materials (e.g., TiAl and NiCrFe alloys) and the fabrication of products that require less machining due to near-net-shape production. For these reasons, AM techniques are gaining popularity for metals [2]. At every build cycle a thin layer of metal powder, typically 40–60 μm thick, is spread by a recoater assuring that the deposited powder layer has a constant thickness

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