Simulation Research On Temperature Field And Stress Field Of The Single Pulse Dry EDM Using Finite Element Method

Electrical Discharge Machining in gas (dry-EDM, or gas-EDM) is expected to become one of green processing methods in the 21st century, because this method does not produce harmful gases, refractory material, and the processing is environment- friendly. Besides, the processing method owns good processing characteristics, such as, low electrode wear ratio. However, dry-EDM process still has the problem of low efficiency. Study the characteristics of single pulse EDM in gas can contribute to the mechanism research of gas-EDM, and it is helpful to improve the processing performance of the dry-EDM. Therefore, in this paper, finite element method (FEM) is used to study the single pulse thermal conductivity model and the corresponding temperature field and stress field of dry-EDM.Firstly, after comparing, debugging and analyzing several programs of single pulse power, an experimental independent-type single pulse EDM power supply was developed. The single pulse power supply has a MCU as core and it owns detecting gap voltage function. The power supply has been used in gas and oil medium experiments and good waveforms were obtained. It was found, under certain experimental conditions, the maintain voltage is 12V for single pulse discharge (Steel-steel electrode).Secondly, based on the principle of the EDM thermal erosion, and considering the discharge channel expansion time-varying radius and the boundary conditions, heat transfer model of single pulse discharge in gas was established using the Gaussian heat source model, and the heat flux formulas were derived for the air and kerosene medium.Next, according to the above model, the temperature field of single pulse discharge in gas was simulated. Temperature curve and temperature distribution were simulated for spark discharge process in gas and oil, and the simulation results of the two different medium were contrasted and analyzed. Single-pulse test results verified the validity of the simulation model.Finally, based on the temperature field model, thermal stress of single-pulse EDM in gas was simulated and analyzed. It was found that the maximum tensile stress exceed the yield strength. By comparing the stress and strain simulation in gas and kerosene, it was found that less stress and strain can be achieved on condition of effective chip removal in dry-EDM process. Hence, it is predicted that the smaller surface cracks and longer service life of parts machined in gas-EDM.