Monitoring System for Behavior of Small-diameter End Mill by Use of CCD Image (2nd Report)

Abstract

Milling with small-diameter end mill is sensitive process, since the end mill is weak and flexible. This paper proposes a monitoring technique for the in-process measurement of cutting force and the prediction of tool breakage in the high speed slotting with the small-diameter end mill, which is based on the newly developed visualization system with high-speed CCD camera, image acquisition and image processing. In order to remove the effect of cutting chip and fluctuation of tool rotation on the projection image of tool, the continuous 200 frames of image was used for the image processing of tool shape. As a result, this measuring system enables the precise measurement of tool deflection in the high speed milling process.It was shown from the comparison between monitoring system and experiment that the tool deflection had good correlation with the cutting force, in which the static compliance and the geometrical moment of inertia were introduced in the prediction of the cutting force. The cutting force predicted by the static compliance was well agreed with the one measured by the dynamometer at the high speed milling of pre-hardened steel and brass in the various cutting conditions. It was also shown that the breakage force was estimated by the principal stress due to the bending moment and was nearly equal to the strength of tool. Since this system is able to measure the tool deflection and to predict the cutting force in process, it is useful for the monitoring of the cutting state in high speed milling with the small-diameter tool.