Development of an optical probe for evaluation of tool edge geometry

Abstract

This paper proposes a non-contact and on-machine measurement method for evaluating tool edge geometry. In the proposed method, a focused laser beam having a diameter of several micrometres traces over the tool edge. By utilizing a light intensity of the laser beam passed around the tool rake face, the gap between the centre of the optical axis of the focused laser beam and the tool edge can be obtained. By combining the measured gap and the information on the XY positions of the focused laser beam, the tool edge contour can be evaluated. In the proposed method, stability of the laser power emitted from a light source would affect measurement accuracy of the tool edge contour. A modified optical design was therefore applied to the evaluation system so that a laser power drift and influences of common-mode noise could be compensated in real time. A modified evaluation system consisting of a laser diode, a beam splitter, a pair of lenses and two photodiodes was developed. Experiments were carried out to test the basic performances of the developed evaluation system with the modified optical design. Possible sources of measurement errors in the tool edge contour evaluation were also discussed. Furthermore, computer simulation was carried out to confirm measurement resolution of the developed system along the tool edge contour.

Keywords

• on-machine measurement
• non-contact measurement
• focused laser beam
• tool edge measurement
• light intensity