Study On Piezoelectric Self-adaptive Micro Electrical Discharge Machining System

With the development of scientific technology, the application of micro-structural parts increase quiekly. Micro-EDM is an important method for machining micro structural parts, but it has some disadvantages in machining process, for examples, debris is difficult to be removed, the machining condition is unstable, which will restric the development of micro-EDM. So development of a new micro-EDM device, improving the speed of removing the debris and the stability of machining condition, and furthermore to improve the machining efficiency is the important research direction of mico-EDM.. Based on this, a new method called piezoelectric self-adaptive micro-EDM is developed based on inverse effect of piezoelectric ceremics.The principle of the piezoelectric actuator is analyzed at first in this paper. And then the working process of piezoelectric self-activated micro-EDM is explained in detail. The discharge energy of the system is obtained by theoretical calculation and the calculation results show that the discharge energy is mainly provided by C2. The calculation results are verified by specific experiments, and the experiment results are consistent with the theoretical analysis.Based on the deep analysis of the features and the requirement of the equipment of micro-EDM, piezoelectric self-adaptive micro-EDM device is developed. The design process of each part of the device is introduced in detail. It is composed of a mechanical system and an electrical system. The mechanical system is consists of granite pedestal, high precision three-axis motion platform, precise rotary spindle, micro-feed mechanism and reverse copying of electrode unit, etc. The electrical system includes micro energy pulse generator, servo control system, discharge detecting circuit and contact sensing circuit, etc.The static analysis and modal analysis of column on the machine is performed by ABAQUS software. The force model and the corresponding boundary conditions is established and determined, the forced state is analyzed. The statics characteristic (stress and strain) of the column is obtained by static analysis. The first six natural frequencies and corresponding modes of the column are obtained from modal analysis. The first six natural frequencies of the column are far away from the frequency of the applied force. The rationality and reliability of the designed column is verified.Experiment is performed by using the self-designed micro-EDM machine. The motion performance of the piezoelectric actuator and the processing property of the machine are tested, and the test results show that the machine can improve the machining efficiency. The relationship between discharging gap and open circuit voltage is analyzed, and the discharging gap increases with the increase of open circuit voltage. The discharge characteristic of this new technology is studied in detail and the unstable phenomenon in the experiment is explained. The analysis results show that short circuit and electric arc are the main factors which affect the machining stability Micro holes and micro grooves have been machined successfully by using the machine and the experimental results show that this new technology can achieve good results.