Study On Hybrid Micro EDM System And Process

Micro electrical discharge machining(EDM), as an important micro machining technology, for the special advantages such as lower cost, untouched machining process, higher aspect ratio and better capability in machining micro 3D structures, becomes a promising method for micro machining in many fields and has been paid intense attention to by domestic and overseas researchers. But it also has some disadvantages like narrow discharge gap, difficult removal of discharge debris, serious tool-electrode wear, low availability of pulsed power supply and etc, which makes it calling for improved techniques in choosing machining parameters and the performance of servo-feed electrode for micro EDM.First of all, the structure of the micro EDM system is introduced. Then the PID tuning for the servo control system has been carried out to find the best motion performance of the precision 3-axis workstage, As to the discharge gap control system, the threshold-control method has been used to feed the electrode. In this method, the federate of the electrode must be suitable for the best discharge condition according to the discharge waveform. Hence, the voltage between electrode and workpiece is gathered. Then the open circuit threshold and short circuit threshold are set to identify the present discharge condition from three different types as open circuit, normal discharge and short circuit. So that, the electrode could be moved upwards or downwards according to the discharge condition to keep discharge gap steady.Subsequently, experiments have been made to study the effect of the machining parameter such as the voltage and RC parameters to the machining result by micro-hole machining situations based on the principle of EDM. Meanwhile, the efficient and steady machining process can be determined by optimizing the machining parameters according to the different machining requirements.At last, the micro cylindrical electrode has been used in micro EDM scanning machining layer by layer During this scanning machining, the electrode path is designed by utilizing CAD/CAM and the real-time compensation of the electrode has been studied. In this part, micro 3D structures such as micro slot and micro rectangle cavity have been completed to validate the ability of the servo scanning micro EDM. And the influence of the scanning velocity and the track span on the machining efficiency and accuracy has been discussed detailedly. In the end, the online method of machining the micro electrode has been studied, and a micro electrode ofФ30μm has been accomplished by electrical discharge grinding. Furthermore, if the electrode is replaced by micro milling tool, micro milling machining can be realized, then micro milling and micro EDM could be integrated on a single machine tool. As a result, the workpiece are able to be machined by micro milling and micro EDM with fixing only once. Therefore, the machining accuracy could be improved by eliminating the positioning error induced by fixing the workpiece twice.