Effect of Tool Orientation on Surface Integrity during Ball End Milling of Titanium Alloy TC17

During milling process of ball end mill, the tool orientation is important to the surface quality of workpiece. In this work, a series of milling experiments are done by carbide ball end mill on a workpiece of titanium alloy TC17, using the rotational angle and the inclination angle of tool axis to describe the tool orientation and the effect of tool orientation on surface integrity are studied. The results show that the surface roughness in both directions (feed direction and step direction) is optimal when the rotational angle is within the scope of 0°to 90°with a constant inclination angle. The change of the inclination angle has little effect on the roughness in feed direction, but much larger or smaller angle leads to a bigger roughness in step direction. The various tool orientations have an enormous impact on surface morphology. Compressive residual stress can be detected on all machined surface during changing the rotational angle and reached the maximum when it is 90°. The surface residual stress reduces with the increase of the inclination angle. The tool orientation makes little effect on the microhardness due to the lower degree of work hardening.