Abstract: Ultrasonic elliptical vibration cutting (UEVC) can effectively reduce tool wear and improve the workpiece surface quality, which is widely used in ultra-precision machining of various difficult-to-cut materials. In order to improve the machining efficiency of UEVC, a kind of ultrasonic elliptical vibration cutting device with multi-stage amplification function is designed, which can effectively increase the output amplitude. The first amplification of the amplitude is realized by using the analytical method to design the stepped longitudinal vibration transducer. Combining with Timoshenko's theory and Finite Element Method, a stepped bending vibration horn is designed to amplify the amplitude for the second time. The designed longitudinal vibration transducer is used to excite x and z direction of the bending vibration horn respectively to make it in the double bending vibration mode. The ultrasonic elliptical vibration generator is used to adjust the phase difference of the two longitudinal vibration excitation, so as to output the ultrasonic elliptical vibration on the cutting tool installed at the front end of the bending vibration horn. The vibration performance test of the device shows that the resonant frequency is 35.3 kHz and the maximum output amplitude is 8 μm, which can effectively improve the critical cutting speed of "tool-separation". The device and diamond tool are used to machine pure iron, the effect of amplitude and cutting speed on surface roughness is analyzed, and the machined surface with roughness of 20 nm is obtained.

Key words: ultrasonic elliptical vibration cutting, finite element method, two bending vibration mode, amplitude, pure iron