Prediction Of Cutting Force In3D Curved Surface Milling Based On A Semi-Analytical Cutter Workpiece Engagement Model

Ball-end milling of3D curved surface is widely used in die and mold, automobile, aerospace and other manufacturing industries. Cutting force which affects all aspects of the milling process is one of the most important parameters of CNC milling. Cutter workpiece engagement (CWE) which is the foundation of cutting force research defines the practical contact situation between cutter and workpiece. The CWE usually changes along cutter path in surface machining. Therefore, determining accurately the CWE of ball-end milling of3D curved surface is the core content of cutting force prediction for3D curved surface milling. In this paper, the CWE modeling and cutting force prediction for ball-end milling of3D curved surface are investigated. The main contents and work are as follows:(1) Contraposing3D curved surface milling along arbitrarily cutter path, using differential method, the milling process of3D curved surface can be taken as a combination of a series of sequential tiny inclined plane milling at an interval of feed per tooth along the cutter path. According to the coordinates of start and end cutter location of each tiny inclined plane cutting, the mathematical models which can describe arbitrarily changing feed direction in surface machining are established.(2) Taking the tiny inclined plane milling as the object, the boundary curves of cutter workpiece engagement are determined by means of spatial coordinate system rotation transformation. And the intersection point coordinates of boundary curves which can precisely define the spatial enclosed geometry of the CWE are confirmed. Then a semi-analytical cutter workpiece engagement model which is applied to ball-end milling of3D curved surface are proposed.(3) Based on the above-mentioned model, a calculation method which is used to determine the intersection point between cutting edge curve and the CWE boundary curves is put forward. Then a program module that can confirm the cutting edge engagement which participates in the cutting process is developed for ball-end milling of3D curved surface.(4) The undeformed chip thickness calculation model is modified to adapt to the variation of cutting geometry conditions for ball-end milling of3D curved surface. Based on the suggested program module, the cutting force of whole3D curved surface machining can be obtained by simulating the cutting force of each differential inclined plane milling along the cutter path. And the validity of cutting force prediction method proposed in this paper is confirmed through actual milling experiment.