Quality of Machined Surface and Cutting Force When Milling NiTi Alloys

The machining of shape memory alloys, such as NiTi, presents challenges due to their specific physical, chemical, and mechanical properties. This study investigated the effect of the helix angle of milling tools-both uncoated and coated-on the cutting forces and the surface roughness of the milling process for a NiTi alloy. Experiments were conducted using the tools with and without coatings at various helix angles (20°, 30°, and 40°) and under different machining conditions. Optimization of the process was employed the Taguchi method to identify the best combination of the corresponding parameters. The results of the cutting force and the surface roughness measurements were analyzed and discussed in the context of optimizing the cutting conditions to achieve the desired outcomes. The results show that the lowest surface roughness values (Sa = 0.301 μm and Sz = 3.41 μm) were achieved with the coated tool at a helix angle of 30°, a feed per tooth of 0.02 mm, and a cutting speed of 45 m/min, while the lowest cutting force (F = 143.6 N) was observed with the coated tool at a cutting speed of 55 m/min, helix angle of 40°, and feed per tooth of 0.02 mm. This research provides valuable insights for industrial applications requiring the precise machining of NiTi in terms of the cutting forces and the surface quality. The findings reveal that the presence of the coating, along with an increase in the helix angle, significantly reduces the cutting forces, positively influencing the quality of the machined surface.