The influence of cutting forces on surface roughness in the milling of curved hardened steel surfaces

The milling of dies and molds involves the machining of complex shapes from hardened steel. To allow deep cavities to be manufactured, milling cutters are usually long with a small diameter. Because of this and because of the cutting forces involved, they have a tendency to vibrate. In finishing operations, vibration is more critical as it can damage the surface quality of the die or mold, affecting end-product quality. Determining the components of the cutting forces may therefore help choose milling parameters that reduce surface roughness. In light of this, the present work seeks to provide a better understanding of the influence of milling parameters on cutting forces and surface finish when milling dies and molds. Milling tests were performed to investigate the effects of cutting strategy, lead angle and tool overhang (input variables) on cutting force components, and workpiece surface roughness (output variables). The results were evaluated by analysis of variance. The main conclusion was that surface roughness is directly related to radial force and that the cutting conditions that provided the lowest radial load (an upward strategy with a lead angle of 0°) produced the best surface roughness.