Side Milling of Helical End Mill Oscillated in Axial Direction with Ultrasonic Vibration

Abstract

This paper is focused on the cutting performance in the side milling of a small-size end mill with vibrations generated by an ultrasonic vibration spindle apparatus in the axial direction with a helix edge. In side milling with ultrasonic vibration in the rotational direction, the mean value of the cross-sectional chip area per cutting time decreases owing to the frequent repetition of the cutting and non-cutting phases. As a result, the cutting force decreases and provides an optimal cutting performance as compared to that in conventional side milling. First, the cross-sectional chip area is calculated using three-dimensional computer aided design (CAD) with its mean value relative to the cutting time. The ultrasonic vibration spindle apparatus is then attached to the machine spindle, and cutting tests are performed for conventional and ultrasonic vibration machining. Next, the flank wear, surface roughness, cutting force, and residual stress are measured. The results obtained from the cutting tests of the two machining methods are compared. The main results are as follows: (1) A comparison of the flank wears of conventional machining and ultrasonic vibration machining shows that the former is larger than the latter. The maximum flank wear increases as the cutting length increases for both the machining methods. (2) The maximum height of the machined surface in ultrasonic vibration machining is larger than that in conventional machining because of the marks caused by ultrasonic vibration. (3) The mean cross-sectional chip area relative to the cutting time decreases with ultrasonic vibration machining and the tool deformation decreases with a decrease in the mean cutting force relative to the cutting time. (4) With ultrasonic vibration machining, residual stress is generated on the machined surface not only in the feed direction but also in the axial direction because of the repetitive sliding actions in the axial direction of the flank of the cutting edge.