Challenges in topology optimization for hybrid additive–subtractive manufacturing: A review

Hybrid additive–subtractive manufacturing (HASM) is a revolutionary technique that fabricates complex-shaped parts in high precision. One setup to finish complicated manufacturing operations ensures high efficiency, and the interlacement of additive–subtractive operations fabricates conventionally difficult-to-process complex geometries. On the other hand, the expensive hybrid manufacturing equipment, the tedious preprocessing and extended processing time, the costly raw materials all make the utilization of HASM to process simply-designed mechanical components uneconomical. Hence, this paper is focused on design for HASM, to create the suitable mechanical structures for HASM endowed of superior functionality and light-weight features over the traditional counterpart. The performance enhancement is in general realized by expanding the geometric complexity to the level that is difficult-to-process or even unmanufacturable by traditional manufacturing techniques. HASM-oriented topology optimization is specifically focused and the state-of-the-art is reviewed and analyzed in this comprehensive paper. Starting from topology optimization for additive/subtractive manufacturing, the existing methods are thoroughly reviewed and their potentials to address design for HASM issues are carefully analyzed. Then, two critical problems: (i) topology optimization for HASM addressing residual stress/distortion constraints and (ii) process planning-assisted topology optimization for HASM addressing tool accessibility constraints, are illustrated and discussed on related technical challenges and potential solutions. At the end, the unaddressed technical issues on topology optimization for HASM are summarized to provide guidance for future research.