Hybrid manufacturing: a review of the synergy between directed energy deposition and subtractive processes

Additive manufacturing (AM) is one of the pillars of Industry 4.0, where automation to create smart factories is the main target. The hybridization of processes is one of the leading strategies to implement a more flexible, efficient, and interconnected manufacturing environment. Nowadays, different researches are focused on the hybridization of metal AM and subtractive manufacturing (SM). Based on the working principles of AM and SM, it can be established that they are complementary processes. Hence, a synergy between them allows conceiving a unique process. As a result, the advantages are magnified, and the limitations of each one are minimized or eliminated. This review presents the latest developments, challenges, limitations, and future perspectives for the integration between directed energy deposition (DED) and SM. DED is a versatile AM process for metal parts fabrication, where the geometrical complexity is its main advantage. Nevertheless, the low surface quality and the difficult dimensional control of the parts create the need for post-processing. Traditional post-processing involves a higher production time, and the barriers cannot be completely overcome. Then, a hybrid process constitutes a powerful concept to combine both technologies efficiently, to produce complex parts with less waste of material and energy.