  In the industrial practice, additive manufacturing processes are often
followed by post-processing operations such as subtractive machining, milling,
etc. to achieve the desired surface quality and dimensional accuracy. Hence, a
given part must be 3D printed with extra material to enable such finishing
phase. This combined additive/subtractive technique can be optimized to reduce
manufacturing costs by saving printing time and reducing material and energy
usage. In this work, a numerical methodology based on parametric shape
optimization is proposed for optimizing the thickness of the extra material,
allowing for minimal machining operations while ensuring the finishing
requirements. Moreover, the proposed approach is complemented by a novel
algorithm for generating inner structures leading to reduced distortion and
improved weight reduction. The computational effort induced by classical
constrained optimization methods is alleviated by replacing both the objective
and constraint functions by their sparse-grid surrogates. Numerical results
showcase the effectiveness of the proposed approach.
