RESEARCH ON ULTRASONIC AIDED FIXED-ABRASIVE LAPPING TECHNOLOGY FOR ENGINEERING CERAMICS CYLINDRICAL PART

摘要

As the final machining procedure of precision components, lapping is often regarded as an important step affecting surface quality, machining accuracy and machining efficiency. Due to some drawbacks of free-abrasive lapping such as deep scratches on the lapped surface, lower lapping efficiency for lower lapping speed, severe waste of abrasive, high processing cost, and so on, fixed-abrasive lapping technology was put forward and developed recently. Meanwhile, considering the unique advantages of the ultrasonic vibration aided machining in the processing of hard-brittle materials such as engineering ceramics, optical glass, etc. and the influence of ultrasonic vibration on the self-sharpening characteristic of abrasive pellet, a novel ultrasonic aided fixed-abrasive lapping technology for engineering ceramics cylindrical part is put forward and corresponding lapping device is developed in this paper. Through theoretical analysis on the ultrasonic aided lapping mechanism, it is found that the value and direction of grain movement speed will change due to the superimposition of ultrasonic vibration, which will lead to the change of cutting angles and further affect the lapping performance. Assuming every abrasive particle is a cutting insert, under the assistance of axial ultrasonic vibration, negative rake of the grain will increase, even change to positive value, so as to sharpen the lapping grains and benefit the lapping processing. Moreover, when ultrasonic vibration is superimposed to the lapping tool, motion locus of abrasive grains will present sinusoid. As a result, the locus of single grain may self-interfere in actual lapping process and make blank cutting. So the depth of cut of abrasive grain will increase under the same lapping pressure, leading to the increase of MRR under the same lapping conditions. Finally, a series of contrast lapping experiments were carried out and some lapping characteristics were researched. Experimental results show that ultrasonic vibration assistance can help to heighten material removal rate, smoothen the waveform of tangential force, reduce the average tangential force and improve surface quality. Ultrasonic aided lapping with fixed abrasive is a high efficiency and precision processing technology for engineering ceramics cylindrical part.