Process planning for corner machining based on a looping tool path strategy

Abstract

A corner is an elemental machining feature for internal pockets that is difficult to plan and execute. During machining of a corner, there is continuous variation in radial depth of cut and frequent changes in magnitude as well as direction of the feed rate. These result in inconsistent machining leading to machine tool jerk, excessive cutting force, and poor surface finish. In this paper, an integrated process planning approach for optimal corner machining has been proposed that combines the tool path generation and machining parameter selection tasks. As a first step a looping tool path strategy was implemented to progressively remove material in multiple loops in order to keep the radial depth under a permissible limit. The tool path consists of G1 continuous biarc and arc spline segments which allow a constant feed rate to be held over the entire tool path. The geometries of the corner and cutting tool and the kinematics of the machine tool structure were considered in the calculation of the allowable constant feed rate. In the next step, the machining time was minimized by iteratively adjusting the feed per tooth value under cutting force constraints. The constraint ensured that the tool deflection was always under a tolerance limit. The resulting tool paths for different test cases indicated the ability of the tool path generation strategy to minimize the number of loops. A comparison of the results on machining times based on initial and optimal feed values and their corresponding tool path lengths indicated the potential for the improvement in productivity of corner machining. The proposed integrated approach that combines both geometric and machining parameters can generate more optimal process plans than approaches that consider these parameters separately.