Characteristics of Longitudinal and Torsional Vibration for Hole Machining by Ultrasonic Vibration

We are developing a new method using ultrasonic longitudinal and torsional vibration of a hollow-type stepped horn for hole machining. We foresee that the equipment can be simplified and miniaturized. In this paper, ultrasonic vibration sources of a hollow-type stepped horn without a diagonal slits vibration converter and with a diagonal slits vibration converter are used. The longitudinal and torsional vibration characteristics of the horn are clarified and the shape of the horn is examined. First, the longitudinal vibration characteristics of a hollow-type stepped horn without diagonal slits are clarified. As a result, the hollow-typed stepped horn has the best shape in all cases of the crosssectional ratio when the hollow part depth is 1/4 wavelength. The amplification factor was decided by the crosssectional ratio when the hollow part depth is 1/4 wavelength. The amplification factors are proportional to the crosssectional ratio, but if the amplification factor exceeds 4.6, it was not proportional to the cross-sectional ratio. The longitudinal vibration adding the static pressing force has a resonance of 1/2 wavelength for this hollow-type stepped horn length in all cases. Second, the longitudinal and torsional vibration characteristics of a hollow-type stepped horn with diagonal slits are clarified. As a result, the longitudinal vibration amplitude is proportional to the cross-sectional ratio, but the torsional vibration amplitude is the same value in all cases of cross-sectional ratio. The torsional vibration amplitude of the tip side becomes larger when the hollow part contains diagonal slits.