Topology Optimization for Cost and Time Minimization in Additive Manufacturing

Abstract

The ever-present drive for increasingly high-performance designs realized on shorter timelines has fostered the need for computational design generation tools such as topology optimization. However, topology optimization has always posed the challenge of generating difficult, if not impossible to manufacture designs. The recent proliferation of additive manufacturing technologies provides a solution to this challenge. The integration of these technologies undoubtedly has the potential for significant impact in the world of mechanical design and engineering. This work presents a new methodology which mathematically considers additive manufacturing build time and cost alongside the structural performance of a component during the topology optimization procedure. Three geometric factors are found which have influence on the additive manufacturing build time and cost: total surface area, total overhung supported area, and total support structure volume. An innovative methodology to approximate each of these factors dynamically during the topology optimization procedure is presented. The methodology, based largely on the use of spatial density gradients, is developed in such a way that it does not leverage the finite element discretization scheme. This is done in order to overcome some of the shortcomings of the methods in the existing literature. Moreover, it investigates a problem which has not yet been explored in the literature: direct minimization of support material volume in density-based topology optimization. The entire methodology is formulated in a smooth and differentiable manner, and the sensitivity expressions required by gradient based optimization solvers are derived. In two numerical examples, minimization of compliance and total surface area was performed, and reduced build time by an average of 13% over minimization of compliance alone. For the same two numerical examples, minimization of compliance and support volume was performed. Support volume was reduced by an average of 40%, and build time by 25%, but came at the cost of increased compliance.