具有多级放大功能的超声椭圆振动切削装置的设计

Development of Ultrasonic Elliptical Vibration Cutting Device with Multi-stage Amplification Function

超声椭圆振动切削可有效降低刀具磨损,提高零件表面加工质量,被广泛应用于难加工材料的超精密加工。为提高超声椭圆振动切削的加工效率,设计了一种具有多级放大功能的超声椭圆振动切削装置,有效提高了输出振幅。利用解析法设计阶梯式纵向振动换能器,实现了对振幅的第一次放大;结合Timoshenko理论及有限元仿真,简便设计了一种阶梯式弯曲振动变幅杆,对振幅进行第二次放大。利用纵向振动换能器在弯曲振动变幅杆的x方向和z方向分别激励,使其处于双弯曲振动模态,利用超声椭圆振动发生器调整两个激励的相位差,从而在安装在弯曲振动变幅杆前端的刀具上合成超声椭圆振动。对装置进行振动性能测试,其谐振频率为35.3 kHz,振幅最高可达8μm,可有效提高“刀-工分离”的临界切削速度。利用该装置及单晶金刚石刀具对纯铁进行切削,分析了振幅和切削速度对表面粗糙度的影响,得到粗糙度22 nm的加工表面。

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 8μm,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.