Geometric models of non-standard serrated end mills

Abstract

Serrated end mills reduce process forces and improve chatter-free material removal rates. Improvements in cutting performance are governed mainly by the serration profile on these cutters. The geometric models of serration profiles are necessary to guide the design of improved cutters. Since these geometric models are usually not available a priori, this paper presents two methods to reconstruct geometric models from scanned measurements of eight different serrated cutter types available commercially. One representation is parametric-based, and another is NURBS-based. Reconstructed serration profiles are classified as the standard sinusoidal, circular, and trapezoidal profile types; and the non-standard semi-circular, circular-elliptical, semi-elliptical, inclined semi-circular; and the inclined circular types. For all eight profiles, the variation in local radius and irregular chip thickness distribution that are a characteristic of serrated cutters are captured by both approaches to approximate the geometry. Force models with the proposed geometric models as inputs are used to predict forces and those forces were experimentally validated. Validated forces confirm that the proposed geometric models are indeed correct. Comparing the cutting performance of all eight serrated cutters suggests that the circular and non-standard serrated end mills can preferentially reduce cutting forces as compared to the standard sinusoidal and/or trapezoidal profiles. However, in terms of the ratios of maximum to minimum peak resultant cutting force, we find that the standard sinusoidal profiled cutter outperforms the other four-fluted cutters, whereas the non-standard inclined circular profiled cutter retains its advantages over other three-fluted cutters.