| Elliptical vibration assisted cutting(EVC) technology has lots of advantages. Generally speaking, the tool wear is significantly reduced due to the force being decreased, which would improve the surface quality. In this paper, the working principle of non-resonant elliptical vibration is analyzed, after that, two non-resonant type EVC(NT-EVC) devices are designed for both laser processing and turning. Also this paper proposes one design method based on ABAQUS by finite element calculations. A test is conducted on the devices to prove that their off- line dynamic performance, which proves that they are both of high precision. This paper also proposes a modified elliptical vibration cutting(MEVC) method to eliminate cutting residual height brought by conventional EVC, which will result in improvement of the surface quality. The specific work is as follows:1. This paper simplifies the system made of piezoelectric actuator and flexible hinge structure to a second-order vibration system with viscous damping. Also, the paper presents the frequency response formula of the second-order vibration system, which is used to get the steady output of the second-order vibration system under harmonic wave input conditions. The influence of motion coupling rate between the two-axis is analyzed on the aspect accuracy of the el iptical motion.2.Based on ABAQUS, one finite element analysis software, the article gives the common design methodologies for NT-EVC devices and the specific steps is given. Two EVC devices with high frequency for turning and laser processing are designed based on the method. The design details involve t he selection of flexible hinge, the calculation and the design of structure, the preloading of piezoelectric drive unit, the dynamics and statics simulation, lightweight design and optimization for higher frequency.3. Parallel structure is used in these two designed devices, which aims to reduce the motion coupling between the two motion axes and lower the mutual motion interference of the two piezoelectric stacks. So, the damage to each piezoelectric stack caused by mutual force interference is declined. The kinematic coupling rates of the NT-EVC device for laser processing are 1.6% and 2.5% in the later test.4. Offline test is conducted to verify the performance of the devices. As to NT-EVC device for laser processing, its maximum strokes of X-axis and Y-axis are both 7.6μm, and the resolution is 10 nm, the maximum operating frequency is 600 Hz. As to NT-EVC device for turning, its maximum strokes of X-axis and Y-axis are both 4μm, the maximum operating frequency is 1600 Hz. As above, it’s confirmed that these performances already meet the requirements of the EVCdevices..5. NT-EVC device for laser processing is tested in generating an elliptical motion with high precision. In this paper, respectively, we achieve the elliptical motion control of the device in both open- loop control mode and closed- loop control mode. After setting the PID controller of the closed- loop control system, the system has good dynamic properties.The device can achieve elliptical motion with long axis range from 20 nm to 7.8μm. Besides, we test the device in elliptical motion with different eccentricity, proving that the device is of high motion accuracy.6. Using the device for turning, we conduct the MEVC test. Firstly, we study the formation mechanism of the cutting residual height of EVC cutting in the perspective of micro-geometric. Then we proposed the MEVC method aiming to improve machining quality. We turn the end face of brass rod with the MEVC method in 1000 Hz.After the turning, we observe the surface using a microscope and the experimental results show that the MEVC method can improve the surface quality. |
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