High speed machining of moulds and dies for net shape manufacture

Abstract

High speed machining (HSM) generally refers to end milling or ball nose end milling at high rotational speeds (10 000–100 000 rev./min). The paper initially reviews the development and application of HSM for the manufacture of hardened moulds and dies. Following on from this, experimental work is detailed relating to the use of indexable insert ball nose end mills to machine hardened (∼52 HRC) AISI H13 hot work tool steel. Tool wear, workpiece surface roughness and cutting force data are presented. The effects of tool material (TiCN and TiAlCrYN coated carbide and uncoated cermet) and cutting speed (150–350 m/min) were investigated using a full factorial experiment incorporating test replications. Limited performance data for solid carbide tooling are also presented. The use of indexable insert cutters, generally resulted in lower tool life values (approx. 50% length cut at a cutting speed of 250 m/min) compared to equivalent solid carbide. The highest tool life values were obtained with TiCN coated inserts and TiAlN coated solid carbide cutters. Workpiece surface roughness was typically 1–4 μm R_a, with slightly lower values for insert cutters. Cutting forces were relatively high (up to ∼1300 N) with the indexable cutters, as a result of a relatively large axial depth of cut (1 mm), a negative rake angle (−10°) and a blunt insert edge condition.