Prediction and Experimental Validation of Cutting Force for Bull-Nose End Mills with Lead Angle

Abstract

This study focuses on cutting force predictions with the tool-workpiece inclination angle in bull-nose milling based on the semimechanistic force model. By analyzing kinematics and mechanics of the bull-nose end mills during cutting, force expressions including lead angle are stated and the model is exerted on each discrete element as oblique cutting with coordinate transformation and numerical integration to obtain the dynamic cutting force components. An improved identification method considering speed variations along the tool axis is applied to calibrate coefficients. Coefficients are regarded as the function of each elemental elevation. Then, a geometry-based method to acquire cutter workpiece engagement (CWE) is proposed. Also acquisition of accurate start and exit angles on each slice is deliberated elaborately for cutters with lead or tilt angle in milling processes. Thereby, to verify the validity of the force prediction model and start-exit angle acquisition method, experiments with variable lead angles are conducted under different axial immersions. The results reveal that the presented model and approaches can predict cutting forces with high accuracy. Finally, the cutting force components under different cutter postures and conditions are analyzed to provide instructions for parameter selections.