Effect of temperature buildup on milling forces in additive/subtractive hybrid manufacturing of Ti-6Al-4V

An additive/subtractive hybrid manufacturing (ASHM) combines the advantages of both additive and subtractive processes for fabricating complex parts of a better quality. While in an additive manufacturing process, temperature buildup is fast because of heat accumulation from a laser or electron beam, which exerts a great influence on the successive subtractive process. This study firstly measures the temperature variation of a Ti-6Al-4V workpiece in the direct material deposition (DMD) process, and then designs a heating device for a milling experiment at elevated temperatures. The effect of temperature buildup on milling forces is investigated through the experiment and a 2D thermal-mechanical coupling model. For work hardening effect and rapid tool wear, the milling forces are hardly decreased when the preheating temperature is lower than 300 °C. At a preheating temperature of 300 °C or higher, a significant reduction in milling forces is recorded, which may be attributed to the thermal softening effect on the workpiece material. The decreasing trend is more obvious at a larger feed-per-tooth. The thermal softening effect is reflected in the deformation layer in the subsurface of the machined workpiece. The study provides a guide to the determination of ASHM process parameters for Ti-6Al-4V.