Study On Micro Energy Pulse Generator Used For Micro EDM

With the increasing demand for micro devices and MEMS technology, the EDM has been put forward higher requirements, and the improvement of the micro-EDM capability limit becomes a goal for researchers to pursue. In the micro-EDM , one of the key factors that determine the limit of miniaturization is the discharge crater size. In order to obtain smaller discharge craters, the single pulse energy must be reduced as smaller as possible. In the process of actual micro-EDM , RC pulse generator is generally used in micro-EDM. Lower discharge voltage and smaller capacitance C are the tranditional methods to reduce single pulse energy .Generally considered to reduce the capacity value of capacitance is an ideal choice, but the it is constrainted by the whole device stray capacitance C'(generally about a few hundreds pF ~ several thousands pF) .The method of lower discharge voltage also has some disadvantages. The lower discharge voltage ,the smaller discharge gap, which means poor discharge environment and requires more precise gap control technique.For the tranditional single pulse discharge energy reduction methods have some disadvantage, this paper presents a new method, adding a resistance R to the discharge circuit to reduce the discharge energy single pulse. Based on the basic principles of micro-EDM, this paper established an analytical model of this improved micro energy pulse generator. With this analytical model , relations among peak current, open circuit voltage and other parameters were analyzed, and then analyzed how those effect the single pulse energy. This paper also explore if the resistance R can reduce the negative effect of stray capacitance C' on the discharge energy of single pulse.Based on theoretical analysis, this paper analyzed the key technologies of micro energy pulse generator ,designed and made a micro energy pulse generator with PIC and CPLD (Complex programmable Logic Device) as the control center。At the same time , against practicable need of micro-EDM, the design scheme for Multi-mode pulse power was put forward. This scheme combing merit of RC type pulse generator and Transistor type pulse generator, assure rough machining, medium precision machining and fine machining can be proceed in the same micro-EDM system,and it can also work as micro energy single pulse generator.Finally, micro energy pulse generator was debugged and tests were done. It was indicated by the test that the theoretical analysis was verified. The results showed that: improved RC micro pulse generator has sustain voltage and it doesn't change with R; when R increases, the peak current and discharge energy of single pulse turn down; R can help reduce the disadvantage influence of stray capacitance on discharge energy.