Measurement of nose radii of multiple cutting tool inserts from scanned images using sub-pixel edge detection

The nose radius of a cutting insert is known to affect the surface roughness and dimensional accuracy of the finished product. Thus, accurate measurement of tool nose radius is important in tool quality monitoring. In this paper we present a new approach in measuring nose radii of multiple cutting inserts from scanned images using image processing. Batch processing of inserts solves the problem of the conventional method of measuring tool nose one at a time. Comparison of the measurement accuracy with a profile projector and the high resolution variable focus 3-D metrology system (Alicona InfiniteFocus) shows that the developed method using scanned images yields only 2.0 % error and gives about 3.0% of error with the repeated scanning of nose radius on various locations. In contrary, the conventionally digital profile projector methods gives error of radii measurement of 10.0% and high uncertainty compared to the InfiniteFocus. The specification limits of nose radius suggested by ISO 3685 are ±10% of the nominal radius. Hence the proposed measurement method using scanned images of inserts provides a low-cost yet fast and accurate assessment of automated tool nose measurement.