Effect of cutting fluid on ultra high speed micro drilling

摘要

This report is concerned with ultra high speed micro drilling. To investigate drilling performance precisely, a fine measuring system for drilling forces is presented. Measuring resolutions for thrust and torque are 0.1 mN and 0.1 mu Nm respectively. Drill sizes 0.1-0.04 mm in diameter are used in drilling of copper and print circuit board (PCB). The maximum rotating speed used in the experiment is 10x10~4 rpm. The results obtained are as follows. In dry drilling, tool wear is rapidly developed in several drilling operations. Both torque and thrust under dry conditions increases as tool wear increases, however, its initial increasing rate of the torque is greater than that of the thrust. After several drilling operations, increasing rate of thrust and torque become slow down gradually. Drill breakage in micro drilling is mainly caused by high torque. A proper application of cutting fluid reduces torque and drill breakage significantly. Rotating speed does not affect thrust in wet drilling while it has significant effect on torque. It is the best way to use HSS drill with wet condition at 4x10~4 rpm in micro drilling copper and PCB. Step feed is also effective to reduce drilling forces.