Experimental analysis of chip formation in micro-milling

This study investigates the mechanism of chip formation when milling 360 brass with a 2-flute flat end-mill of diameter 635 mu m. Experiments reveal how chips are formed in the micro-milling process, which differs from conventional milling in that the feed per tooth is often smaller than the cutting edge radius of the tool. Several slots are milled in the workpiece using a speed of 80,000 rpm and feeds per tooth ranging from 0.188 mu m to 6 mu m. For each set of cutting conditions, the volumes of the resulting chips and the feed marks on the machined workpiece surface are analyzed. The data indicate that when the feed per tooth is relatively small compared to the cutting edge radius of the tool, the volume of the chips is significantly larger than the nominal volume, and the spacing between feed marks is significantly larger than the feed per tooth. The data indicate that for a small feed per tooth, a chip is not formed with each pass of a cutting tooth, meaning that chips are produced intermittently.