The concept of an effective orthogonal cutting edge in turning is considered. The orientation of this edge in the radial-longitudinal plane, as commonly modeled through an effective lead angle, is studied. The methods of effective lead angle prediction used in numerous previously developed force models are plagued with large errors over ranges of process inputs, in particular feed rate and depth of cut. Four previously developed methods of effective lead angle prediction are reviewed and compared to a new method presented here. This new method accounts for the size effect as introduced through the variation in chip thickness along the cutting edge, especially along the tool nose region. The difference in the new method is that the effect of continuous chip thickness variation along the cutting edge is included when evaluating the specific machining energies rather than using an average chip thickness, which has been used in the other methods. Therefore, the differential normal and friction force components acting on the rake face are functions of chip thickness through both the elemental chip load and the specific energies. Their directions are characterized by the orientations of the rake face and edge. By numerically integrating the differential force components modeled in this fashion, a significant improvement in effective lead angle prediction accuracy is realized. This improved accuracy is verified using experimental data obtained for 1018 steel and 304 stainless steel at varying levels of feed rate, depth of cut, cutting speed, nose radius and tool lead angle.


Industrial Engineering | Manufacturing



URL: http://digitalcommons.calpoly.edu/ime_fac/54