Effect of circular tool path on cutting force profile in micro-end-milling

Micro-end-milling requires high spindle rotational speed to achieve effective material removal. This results in the requirement of tool stoppage or slowdown during a micro-end-milling operation, a deterrent to productivity and to part acceptability. A circular tool path geometry can avoid discontinuities in the tool movements leading to a more consistent and smooth material removal. However, optimal process planning for such a tool path will require detailed understanding of the chip-formation mechanism in circular end-milling. The cut geometry during end-milling along a circular tool path is often approximated as that of a linear tool path. Although this assumption works well for circular tool paths with higher tool path radius, this is not the case for lower tool path radius often used in micro-milling. In this study, the effect of circular tool path on the cutting force for varying tool path rotation angle, tool path radius, and feed rate is experimentally investigated. Systematic signal processing was applied to analyse the measured cutting force signal along linear and several circular tool paths. Qualitative as well as quantitative differences were observed in the cutting force profiles obtained using different tool path radii, tool path orientations, and feed rates. This implies the need for an improved chip thickness formulation dedicated to micro-end-milling with circular tool path rather than approximating it with formulations derived for linear tool path.