Experimental investigation of ultrasonic vibration-assisted tapping

Vibration-assisted tapping was studied for fabricating internal threads for titanium metal. High frequency imposed on the workpiece, was generated by a piezoelectric actuator. The axial thrust force and the tapping torque were respectively plotted against the tap's traveled distance relative to the workpiece. Each of the plots demonstrated that the entire tapping process could be divided into six characteristic stages. The implication associated with each characteristic stage was discussed for each plot. The stages where there was maximum thrust force and maximum torque located were identified. The frequency, which was adjustable through a control unit, was found to generate the minimum tapping torque when it equalized the resonance frequency of the tapping setup, a significant finding, which could be applied to decrease the tapping torque, and in turn the likelihood of tap breakage. The effect of tap size employed and the role played by cutting oil were also identified and discussed. No adverse effect on the teeth's shapes fabricated by the vibration-assisted tapping was found.