Cutting Force Analysis in Transient State Milling Processes

This paper proposes a method for predicting transient state forces in milling processes as the cutter engages with and disengages from a workpiece. Analysis of this nature can contribute to the fundamental understanding of forced vibrations, deflections, and dynamic stability of multi-flute milling systems at the start and end of a cutting pass, thereby facilitating process planning, tool geometry optimisation, and on-line diagnostics. The calculation of transient cutting forces is commonly performed with the determination of local forces and numerical integration along cutting edges. In an effort to provide an estimation of transient cutting forces without resorting to numerical integration, this paper uses the result of a frequency domain model obtained from convolution integration as a basis for examining the temporal discretisation of a transient state cutting into steady-state conditions with various engagement and disengagement positions. The resulting milling forces in axial, feed, and cross-feed directions are expressed explicitly in terms of workpiece material properties, tool geometry, cutting parameters and process configuration. The process of end milling is presented to illustrate the applicability of the proposed method. End-milling experiments were performed and results compared to the force predictions for the verification of the analytical models.