Development of a Computer Vision Flank Wear Measurement System for Microdrills

摘要

The objective of this study is to develop an image processing measurement system by integrating a CCD camera with a toolmaker microscope to inspect the wear on microdrills used to drill printed circuit boards (PCB) and the stainless steel sheet-SUS420. The design and manufacture of a circular multi-LED lighting device and a micro-drill holder were first accomplished in this study, in order to get a clear image of the flank area. Two wear parameters, namely the flank area wear and the average flank width wear, were used to evaluate the wear on the microdrill. A set of image analysis software, written in Visual BASIC, was also developed to carry out the image preprocessing tasks, such as filtering, thresholding, edge enhancement using spatial convolution calculation, and calculation of the wear parameters. The developed system was calibrated with a standard glass scale under different magnifications, namely 30X and 100X. The resolution of the developed system was about 3.3 microns per pixel in both x- and y-directions under 30X magnification. The flank area wear vs. the number of hits and the flank width wear vs. the number of hits of the tested micro-drills, were obtained based on the experimental results. The tool life of the microdrill was about 20,000 hits for the microdrilling of six-layered PCB using tungsten 1.8m/min. The tool life of the microdrill was about 200 hits for the microdrilling of SUS420 sheet using carbide microdrills with diameters of 0.3 mm when the spindle speed was 100,000 rpm and the feed was tungsten carbide microdrills with diameters of 1.0 mm when the spindle speed was 3,000 rpm and the feed was 10 mm/min.