Analytical modeling of micro-milling operations on biocompatible Ti6Al4V titanium alloy

Abstract

Among the biocompatible materials, Ti6Al4V titanium alloy is widely spread due to its properties, such as corrosion and fatigue resistance combined with low density. Ti6Al4V can be processed by Additive Manufacturing technologies, such as Power Bed Fusion (PBF). The biomedical applications require good surface finishing to ensure biocompatibility with tissues and organs. Machining is an adequate process to ensure low final roughness of components. The necessity to realize miniaturized features implicates the usage of micro mills with diameter lower than one millimeter. It implicates several issues, such as size effects, higher than expected cutting forces, rapid tool wear which can be addressed by experimental tests and process modeling. This work reports the results of micro-milling performed on additively manufactured samples in Ti6Al4V. PBF process was utilized to manufacture the samples by employing laser source (PBF-LB). The machining center was equipped with a loadcell to acquire cutting force signal. An analytical cutting force model was calibrated on the experimental data with the purpose of predicting loads on the tool by considering ploughing- and shearing- regimes. Specific machining tests were performed to calculate the Minimum Uncut Chip Thickness (MUCT) and to calibrate the unknow parameters of the model, while further tests allowed to verify the reliability of the model about the cutting force prediction. The elaboration of the cutting force data was performed by an iterative methodology based on the Particle Swarm Optimization (PSO) algorithm.