Investigation of a new-type precision cropping system with variable-frequency vibration

To investigate a new-type precision cropping system with variable-frequency vibration, it is necessary to obtain the characteristics of vibrating force and displacement of shearing die in different exciting frequencies. The model and equations of a six-degree-of-freedom vibrating system are established, and the six natural frequencies of the system are achieved by means of classical analysis method, the amplitude–frequency characteristics are described according to Cramer's rule, and the theoretical analysis results are verified by experiments. The approximate relationship between the vibrating force and exciting frequency are achieved and the experimental results show that crack will propagate along z direction, which is in agreement with the theoretical results. The work-piece cross-section obtained by the experiments has no radial distortion and deviation angle, moreover, the cutting force is lower and the die lifetime is longer compared with common bar cropping method. A new cross-section quality assessment method is proposed for the work-piece obtained under the control of different frequency–time characteristic curves. The assessment results show that the linear decrement control mode is better for producing good-quality work-piece.