Research Of Micro-Energy Pulse Generator For EDM

After sixty years of development, Electrical Discharge Machining(EDM) has become one of important parts in modern manufacture areas. Its characteristic of non-contact and little cutting force established its advantage position in the fields of micromachining. The accurate control of single pulse discharge energy is one of key techniques in micro-EDM. The peak current and pulse duration of single pulse determine the size and depth of discharge crater, so they determine the machining surface roughness and size and shape accuracy. They are key factors to limit the machining ability of micro-workpiece and micro-electrode.Firstly, the process of electrical breakdown in liquid is analyzed; there is a breakdown electric field which can be deduced using some theories. Experiments were done to validate that, which provides theoretically basis for low open-circuit power EDM. The electrode for micro-EDM is usually extremely thin, so the electric field in the gap is extremely uneven. The process of dielectric breakdown in uneven electric field is analyzed and the influence of electrode polarity on gap breakdown is researched.Next to that, the single pulse energy of independent pulse generator is analyzed, it found that isopulse mode can control the energy accurately and suits for micro-EDM. Based on that, A micro-energy pulse generator is developed. A circuit is designed to generate current pulse, which can switch off the main circuit when discharge is detected. The minimum pulse duration can reach 115ns. The pulse generator output can be selected as isopulse mode, voltage mode, grouping pulse mode, which ensures the energy for micro-EDM reliably.In the end, as an important part of horizontal spindle micro-EDM machine tool, after debugging with mechanical structure, movement control and monitor software sections, it works reliably. In small energy condition during experiments, compared with voltage mode the isopulse mode has obvious advantages.