Research On Kinematic Analysis And Experiment For Step Vibration Tapping

Vibration tapping is an unconventional and pulse tapping. Researchers and industrial corporations in home and abroad have been attracted by its technological advantages in recent decades. Based on the study of the conventional vibration tapping, the step-vibration tapping is approached from theory and experiments in this thesis. And some conclusions which beneficial to machining in practice are drown out.Firstly, the developments of technology and equipments of the vibration tapping are summed up. A method to make the step-vibration tapping come true is established based on the study of the conventional vibration tapping. The kinetic mathematical model of the step-vibration tapping is set up. And the curves of displacement and velocity changing along with the time for a cutting edge are given out.Through comparing the displacement and velocity curves of the step-vibration tapping with the one of the conventional vibration tapping, it is shown that the two methods are different in the process of machining, but both of the curves are periodic. Finally the changes of the net cutting time ratio, the maximum cutting velocity and the movement locus of cutting edge under the tapping parameters (amplitude, frequency, rev) are analyzed.Secondly, Owing to reveal the cutting mechamsm of step-vibration tapping, the characteristics torque of tapping, the chip formation mechanism and the effect of precision processing with radial force and axial force are discussed . Furthermore, the chip of formation by applied metal crystal dislocation theory are explained which provides foundation for further study subsequently.At last , In order to study the step-vibration tapping in practices, stainless steel is used to experiment on vibration tapping based on the step-vibration cutting device, the following three contents are approached: first the law which the cutting parameters (spindle speed, frequency , amplitude) influences the measurement of clearance on quantity ratio of screw combined is approached. And through comparing the clearance of conventional tapping and conventional vibration tapping and step-vibration tapping, it is shown that the step vibration tapping may obtain with relative less quantity ratio of screw combined with clearances. Secondly, the law of chip shaping influenced by the processing parameters is investigated. In contrast to common tapping and conventional vibration tapping, it is found that the step-vibration tapping may obtain with relative less in length of chip shape and less crookedness for conventional tapping. Thirdly , the law of thread profile effect by the processing parameters is investigated, and in contrast to conventional tapping and vibratory tapping, it is found that the unilateral tooth type of trapped shear is produced for the step-vibration tapping and conventional tapping, and the double tooth type of trapped shear is produced for the conventional vibration tapping. The cause produced the tooth type of trapped shear is explained.