Cutting tool wear during precision boring operations in lathe of a grade 4 titanium for biomedical implants

Abstract

The titanium devices manufacturing present some challenges to be aborded, specially to produce biomedical implants. Considering machining, there are issues to be solved to improve part quality and production. The finishing produced by boring in lathe is related to the part precision during titanium machining, which can be affected by tool wear. This work aims to evaluate the cutting tool wear during boring in lathe of a grade 4 titanium. A combination of roughness parameters and radius of machined hole measured by 3D laser microscopy was applied to establish a relation between surface topography, workpiece geometrical deviations and tool wear. Cylindrical bars of grade 4 titanium with diameter of 4.2 mm were machined with 11 and 16 m/min cutting speed, 15 μm/r feed, 70 μm depth of cut and 2 500 μm length of cut per workpiece. Uncoated and TiN coated carbide cutting tools were applied for machining tests. Tool wear was evaluated by optical microscopy after machining of 3 000 workpieces per cutting tool. Results indicated a strong correlation between pairs Rq/Ra-Kurtosis and Rp/Rz-Skewnees for machined surface formed by worn out tools. Coated tools machined a rougher surface than uncoated ones. Crater wear and flank wear was noticed as well as geometrical deviations increased with higher cutting speed. The combination of uncoated cutting tools with lower cutting speed to machining grade 4 titanium showed a good agreement to increase production of biomedical implants.