THE EFFECTS OF PROGRESSIVE TOOL WEAR AND TOOL RESTRICTED CONTACT ON CHIP BREAKABILITY IN MACHINING

Chip breakability plays an essential role in automated machining systems. This paper presents an experimental investigation of the effects of progressive tool wear and the resulting formation of the tool restricted contact on chip breakability in a turning operation. Six parameters of tool wear, namely, major flank wear (VB), crater wear depth (KT), crater wear length (KK), crater wear width (KB), wear retract of cutting edge (KS) and nose wear (N), are shown to contribute to the variations of chip breakability with tool wear progression. The results show that the chip breakability varies significantly with tool wear progression, especially with the combined crater and flank wear progression, and contributes to the development of a restricted rake face land, making the tool behave like a restricted contact grooved tool. The chip curling and breaking action is largely influenced by the nature and magnitude of the restricted contact and the groove profile being developed on the tool face. The results presented in this paper are also intended to provide guidelines for designing effective chip grooves on the tool face.