Develop Of Ultra Short Pulse Generator For Micro-EDM

From the day when EDM was developed, it had been playing a more and more important part in the area of national defense and civil industry because of its special machining principle and the extensive adaptability to the machining material. One of the most popular research contents of EDM is to lead it to the research of precision and minuteness using the EDM's characteristic of none macroscopical cutting force. The key technology of achieving precision and minuteness for EDM is the single machining amount must be as little as possible.The energy of single pulse of the pulse generator directly affects the single machining amount of micro-EDM. In order to reduce the energy of single pulse of the pulse generator, the duration of the output pulse must be shorten.The several factors affected the turn-off and turn-on processes were analyzed to get the relationship of the turn-off time, turn-on time, driver current and output current. The output waveform of using different MOSFET driver currents, output currents and different types of MOSFET were obtained using PSPICE simulation. The conditions of getting short pulse duration were summarized. These would be the base theory of developing the ultra short pulse duration pulse generator.Based on the above theory, matched the signal source, MOSFET driver and MOSFET, an ultra short pulse generator for micro-EDM was developed. Its minimum output pulse duration could be 20ns. It had a well designed human interface using a micro controller. Its pulse interval and duration were adjustable and it could output the group waveform. These provided a reliable, controllable, micro energy output for micro-EDM.The output waveforms of the developed ultra short pulse generator were analyzed. Some experiments of the generator were performed on a home built micro-EDM machine tool. The micro shaft and the micro hole were made. The machined surfaces using different pulse durations were compared. The results showed that the surface roughness of that made by the developed pulse generator was better compared to the surface roughness of that machined by RC type pulse generator. The machining gap experiment showed that the machining gap of the developed pulse generator was less. The experiments indicate that the output energy of the developed pulse generator was smaller and controllable. The developed pulse generator is more suitable for micro-EDM.