Effects of ultrasonic vibration on machining accuracy in microdrilling

The purposes of the present paper are to investigate the effects of ultrasonic vibration on machining accuracy of duralumin and to clarify the mechanisms for the improvement of machining accuracy in microdrilling. Ultrasonic vibration of 40 kHz considerably reduces the friction on the rake face, makes chips thinner and then decreases cutting forces. This decrease in cutting forces, especially the mean radial force, leads to the improvement of cutting accuracy, i. e. smaller hole oversize, a little better roundness at hole entrance and smaller displacement of hole center under ultrasonic vibration. The thinner chip increases the velocity of chip flow and results in better characteristics of chip disposal and less tendency of drill breakage.