Development of cryogenic assisted machining strategy to reduce the burr formation during micro-milling of ductile material

Micro-milling is an inevitable machining process for the fabrication of products with complex shapes and high dimensional accuracy. However, this process usually needs post-processing operations to remove the burrs formed from the ductile materials. This research work focuses on the development of a micro-milling strategy to suppress the formation of burrs during machining and hence avoid post-processing operations, consequently reducing the cost of the products. During micro-milling, a LN2 jet was positioned ahead of the tool movement loci resulting in a change of microstructure at the top layer of the workpiece surface, enhancing its mechanical properties with the subsequent reduction of excessive plastic flow during the shearing process. Micro-hardness tests were performed below the top layer to conform the speculation and evaluate the effect of cryogenic treatment and a significant increase in micro-hardness was found. The experimental results reveal a significant decrease in the burrs formation due to the cryogenic treatment with an enhanced machining quality in terms of cutting forces, chip morphology and surface roughness.