Study On Large Area Edm Based On Capacitance Coupling

In the background of "Made in China 2025",the manufacturing industry of our country tends to be precision,intelligent and high-efficient.Die industry is the foundation of manufacturing industry.And the die with high precision,long life,short manufacturing cycle and low cost can greatly promote the development of manufacturing industry.In the general EDM,as the machining area increases,the finished surface roughness becomes rough no matter how small the supplied electric power is.This is because as the machining area increases,the capacitance between the workpiece and the electrode increases,the stored energy increases,resulting in the discharge of the energy stored in the capacitor is released to increase the discharge energy,making it difficult to obtain a small surface Roughness.The large area EDM method based on capacitance coupling is that the pulse power supply and the working gap are separated by the feeding capacitance.Compared with the traditional RC relaxation pulse power supply and the independent transistor pulse power supply,it is characterized by only the induced current,no conduction current,avoiding the impact of the gap capacitance.In this dissertation,the principle of large area EDM based on capacitance coupling is analyzed.The simulation model of large area EDM based on capacitance coupling is constructed,and the charging and discharging characteristics simulation of large area EDM based on capacitance coupling is carried out.The three axis precision EDM platform of large area EDM based on capacitance coupling is completed.The charging characteristic experiment of large area EDM method based on capacitance coupling is conducted,and the experimental results are in agreement with the simulation results,and the relationship between the open gap voltage and the distance of gap is obtained when the distance of gap is longer than and close to the working gap.The discharging characteristic experiment of large area EDM method based on capacitance coupling is conducted,and the general discharge waveform is showed.And the influence of the open gap voltage,the feeding capacitance,the pulse frequency,the feeding mode and the working area in this method is analyzed by the experimental results.The experimental phenomena of large area EDM based on capacitance coupling is observed and analyzed,and the processing characteristics of this method are studied experimentally and theoretically.And the effects of flow conditions,pulse width and discharge polarity on the carbon deposition and discharge are confirmed.The phenomenon of discharge state with regular change in continuous machining is observed and analyzed.Two ways to reduce the discharge energy are proposed,and the experimental equipment and process requirements of the two methods are analyzed.The surface roughness of Ra0.3~0.5 ?m is obtained by using the large area EDM method based on capacitance coupling on the surface of SKD61 die steel with diameter of 100 mm.