On modelling the cutting forces and impact resistance of honed milling tools

In milling operations, cutting tools are subjected to cyclic thermal and mechanical loads due to their intermittent engagement with the workpiece. As a result, they commonly fail due to edge chipping and thermal cracking, among which the former is directly related to the impact at the entry or exit, respectively, in downmilling or upmilling where the chip thickness is maximum. Among the many design factors that affect the impact resistance of milling tools, cutting-edge radius is one of the most important; however, it is often omitted in classic force models. In this paper, a force model that accounts for the edge radius was developed to predict the milling forces. Five sets of milling inserts with custom-made edge radii ranging from 25 to 45 mu m were produced and tested. Test results were used to validate the force model and capture the effects of edge radius on the impact resistance of the prepared inserts. Results showed that increasing the edge radius initially improved the impact resistance and increased the tool life. However, increasing the edge radius beyond a certain threshold was proven to be detrimental since it made the tool blunt and drastically increased the cutting forces.