Cutting force prediction based on study of cutter-workpiece engagement in flexible ball-end milling of panel molds

Abstract

In this paper, the flexible cutting force forms the basis for investigating the stability of the process involved in milling hardened steel mold with a curved surface. The cutter-workpiece engagement, which changes along the curved tool path, is inevitably affected by cutter deflection. An analysis of cutter-workpiece engagement therefore plays a critical role in predicting the flexible cutting force. First, the influence of the curved surface milling force on ball-end cutter deflection is analyzed, and the effect of tool load on the deflection of the cutting edge at different discrete positions is evaluated. A model of the uncut thickness of the milling surface is then constructed, based on the three-dimensional trochoidal trajectory of the milling process. The rules relating to the cutting process of the uncut thickness with the cutting edge at different discrete positions are analyzed. A milling force prediction model relating to the milling of the curved surface is constructed that considers cutter deflection as a part of the cutter-workpiece engagement. Finally, a hardened steel mold milling experiment is carried out. This confirms that the amplitude and trend predicted by the milling force model and the experimental results are consistent. The results validate the capacity of the proposed method to accurately predict the cutting force for different cutter teeth with tool deflection. Application of the method shows that the milling forces are relatively stable when the lead angle is between 6° and 12° or − 6° and − 12°. When the lead angle exceeds 12° or is less than − 12°, both the milling forces and cutter deflection increase rapidly.