Solution of dynamic cutting mechanism of ultrasonic viration assisted micro drilling

点击翻译按钮获取中文摘要

The purpose of the present research is to make clear the effect of ultrasonic vibration on drill behavior at the hole entrance in micro drilling to the normal plane and the inclined plane, and the effect on chip discharge characteristics in deep drilling of normal plane. Drill behavior is deduced from the shape of the drilled hole preserved using a quick stop device. In deep drilling the chip disposal condition is observed and chip formation mechanism is considered.In micro drilling to the normal plane the ultrasonic vibration prevents the drill wandering motion at the entrance, which results from the decrease of radial force due to the increase of effective rake angle on chisel edge, the hammering motion of chisel edge and the prevention of accumulation of drill displacement due to infinitesimal intermittent cutting. As a result, the accuracies of hole shape and size at the entrance are improved. The area occupied by chip in drill flute becomes smaller with vibration than that without vibration. Chip fiow angle becomes larger and curvature of side curl becomes smaller with vibration. These features may be caused by the decrease of difference between cutting velocities at corner side and center side of a cutting edge and by the increase of radial chip fiow velocity due to the improvement of cutting performance at chisel edge with vibration. In vibration-assisted deep drilling smooth disposal of chip prevents drill breakage due to chip jamming, needs no step feed and improves cutting efficiency. The deterioration of hole wall integrity caused by the rubbing of chip is reduced.ln drilling to the inclined plane the out-of-roundness becomes smaller with vibration than without vibration due to the improvement of drill centering although radial force is acting until the start of engagement of full cutting edges.