Diamond cutting of ultrasmall-diameter micropins of difficult-to-cut material

Abstract

Diamond cutting was carried out to fabricate micropins of a difficult-to-cut material. Although difficult-to-cut materials can be processed using superhard cutting tools, no studies on the cutting of micropins of such materials have been reported thus far. In the present study, therefore, we attempted to turn and mill sintered WC micropins using polycrystalline diamond microtools processed by electrical discharge machining and a microcutting device designed especially for microtools. As a result, micropins approximately 2 μm in diameter and 15 μm in length, and 1.5 μm in diameter and 4 μm in length were successfully turned, indicating that micropin cutting is possible even for a difficult-to-cut material. Furthermore, a triangular-prism pin with a cross-section side of 20 μm, a square-prism pin with a cross-section side of 12 μm, and a semicylindrical pin 35 μm in diameter were milled with tool rotation and the workpiece held stationary. Micropin grinding tools were also finished by turning and then employed for drilling microholes by ultrasonic grinding. As a result, a microhole 4 μm in diameter was drilled in crown glass. In addition, thrust force during turning operations was measured using an electronic balance. The thrust force increased with the depth of cut, cutting speed, or approach angle. Finally, in order to predict tool life, Taylor's tool life equations were obtained by measuring tool wear during turning at different cutting speeds, feeds per revolution, and depths of cut.