Less interference tool-path correction model for half revolution penetration and retraction trajectories in internal straight thread side milling

Abstract

Unreasonable tool-path generation in the penetration and retraction processes of the internal thread milling can easily result in severe interference errors, therefore, this study proposes a less interference tool-path correction model for the half revolution penetration and retraction trajectories to further reduce the tool-path interference errors. Firstly, the parametric equations of the initial penetration and retraction trajectories are derived from the half revolution penetration and retraction angle α. Then, an offsetting coefficient e is defined to adjust the X-coordinate components of the starting point of the penetration trajectory and the end point of the retraction trajectory, the Z-coordinate components of the penetration and retraction trajectories are calculated by substitute the angle α with the cutter spiral rotation angle θ. As a result, the correction parametric equations for adjusting the penetration and retraction trajectories with the e are established. Finally, according to the influence of e on the interference errors, the appropriate value of the e is determined to control the interference errors within the allowable tolerance range. Taking the milling of M16 × 1.5 thread hole with M8 × 1.5 thread milling cutter as an experimental example, the experimental results show that the maximum interference error of the proposed correction model (e = 0.9) can be reduced by 73.6% and 33.82% compared with the initial uncorrection model and the existing optimization method, respectively. This study indicates the proposed model can significantly decrease the interference occurred in internal thread milling and smoothly achieve the demands of more precision threaded connections.