Hybrid Manufacturing

Additive Manufacturing (AM) involves material growth in a layer-by-layer manner over a substrate as against Subtractive Manufacturing (SM) in which material is chipped away from a bulk stock. Both approaches have advantages and limitations and hence have their own windows of applications. Hybrid Manufacturing (HM) aims to synergically combine these competing processes so as to deploy them in complementary ways. This approach will retain their advantages while bypassing their limitations. HM discussed here makes use of wire cladding for near-net material addition using arc or laser. This is followed by finish-machining. There are at least five levels of hybridization in terms of (a) approach, (b) energy source, (c) layering strategies, (d) kinematics, and (e) materials. AM’s incremental growth and very high aspect ratios result in non-uniform heat distribution and hence residual stresses and associated warpages/cracks. Therefore, Residual Stress Management (RSM) assumes significance in HM. RSM is implemented through pre-/in-situ/post-processes. Inspecting each layer is important before proceeding to the next layer; if the layer is defective, it can be either rectified or removed. The technologies for RSM and inspection require integration of a few tools such as preheater, hammer, and camera on the same platform. The need to have all these hybrid processes and multiple technologies in one platform has evolved into a Multi-Station Multi-Axis – Hybrid Layered Manufacturing (MSMA-HLM) system in IIT Bombay. It is a 5-axis system with different stations for various operations, viz., preheating, cladding, face milling, inspection & RSM, and finally finish-milling.