Correlating surface roughness, tool wear and tool vibration in the milling process of hardened steel using long slender tools

High speed milling is an operation frequently used in finishing and semi-finishing of dies and molds. However, when it is necessary to produce molds with deep cavities and/or with small corner radius, long tools with small diameters are required. This represents a challenge for manufacturing professionals: how to minimize tool vibration using a tool with such low rigidity and obtain good workpiece surface quality and long tool lives. This paper attempts to answer this question. Milling experiments on hardened AISI H13 steel were carried out using integral and indexable insert tools with different tool overhangs and different diameters. Tool wear, workpiece surface roughness and cutting forces were measured and these parameters were correlated with the frequency response function (FRF) obtained with the tools fixed in the machine tool. The main conclusion of this study is that good workpiece surface roughness allied to long tool lives for long tools with small diameters can be achieved, provided the tooth passing frequency used in the milling process (and its harmonics) does not produce high FRF values.

► The harmonics of the tooth passing frequency must not produce high FRF values. ► Even after a very long cutting time, tool flank wear was very small. ► The small tool wear stimulated even more tool vibration in the unstable process. ► In the stable process, wear stimulated tool runout, but did not increase roughness.