Machining, Measurement, and Control Laboratory

A Study on End milling of Hardened Steel (3rd Report)
-- A Prediction Model of Cutting Forces for Ball End mills and Control for Constant Cutting Forces Using this Model --

Hirotoshi Otsuka (Oita Industrial Research Institute)
Iwao YAMAJI (Kyoto University)
Yoshiaki Kakino (Kyoto University)
Heisaburo Nakagawa (The University of Shiga Prefecture)

This paper deals with the mathematical model for cutting forces by (Al,Ti)N-coated micro-grain carbide ball end mill cutters during end milling of hardened steel for dies and molds. Since it is known that cutting characteristics changes depending upon the location of cutting edge and its chip thickness in ball end milling, a quadratic polynomial model is proposed for the prediction of cutting forces based on the response surface methodology. The model contains three variables of the engagement length of cutting tool, the maximum undeformed chip thickness and the nose engagement angle. The obtained prediction model is shown to be applicable for this problem. In end milling of hardened steel, the control of cutting forces is especially important because chipping occurs easily if the cutting edge is subject to severe cutting force. Furthermore, constant cutting force is required for improving the accuracy of machined surfaces. The prediction and control of cutting forces in pick feed ball end milling which includes both straight and concave contour cutting is very effective using this model.

Key words: hardened steel, (Al,Ti)N-coated tool, mathematical model, cutting force, response surface methodology, ball end mill