Improved chip thickness model for serrated end milling

Abstract

This paper presents an improved chip thickness model for serrated end mills that accounts for the actual trochoidal path traced by the tooth. The model includes the influence of radial run-out on teeth. We also present a method to infer radial run-out on serrated tools using a combination of measurements and scanned geometry of the serration profiles. We present results for cutters with serrations of the trapezoidal and circular kinds. We observe differences in chip thickness and cutting forces evaluated using the proposed model and with those evaluated using a circular tool path approximation to increase with feed and radial engagements. However, the differences are negligible, being at most 2%, suggesting that the circular chip thickness model is indeed a reasonable approximation for predicting cutting forces with serrated cutters. Experiments confirm predictions. For run-outs of the order of feed, i.e., 0.02–0.05 mm/tooth/rev, or less, we find that cutting force profiles and levels are not significantly altered. The resultant force with moderate levels of run-out included in the model is at most 1% different than the case without run-out, suggesting that serrated cutters may be used even with moderate levels of run-outs when the feed is low. Results can instruct the design and use of serrated cutters that reduce forces and make easier the high-performance machining of difficult-to-cut materials across industries.