On-machine measurement technique for cutting tool wear monitoring

Abstract

This paper presents a novel measurement technique for cutting tool wear (attrition and abrasive) by using knife-edge interferometry (KEI) in a simple, high-accuracy, low-cost and convenient way. Unlike an amplitude splitting interferometry, such as the Michelson interferometry, the proposed KEI utilizes interference between a transmitted wave and a diffracted wave at the cutting tool edge. In this study, a laser beam is incident on the cutting tool edge and the photodetector measured the interference fringes by scanning a cutting tool edge along the cutting direction. The relationship between the cutting tool wear and interferometric fringes produced by edge diffraction phenomena is established by using cross-correlation of KEI fringes of two different cutting tool edge conditions. The cutting tool wear produces the phase shift (attrition wear) and the decay of oscillation (abrasive wear) in the interferometric fringe. The wear characteristics of the cutting tool with a radius of curvature of 6 mm was investigated by measuring the interferometric fringes of the tool while cutting an aluminum workpiece in a lathe. As a result, the cutting tool attrition wear and lags of the KEI fringes between a new tool and used tool showed a linear relationship 5.62 lag/wear(μm), and a significant abrasive wear was not observed under given cross-correlation conditions. This measurement technique can be used directly for cutting tool radius compensation in on-machine measurement applications, and will allow for a high-resolution diagnosis of precision cutting tool wear.

Keywords: Cutting tool wear; Knife-edge diffraction; Knife-edge interferometry; Cross-correlation