Multiphysics Modeling and Validation of Material Removal in Conventional and Vibration-Assisted Micro-EDM

Abstract

With the ever-increasing demand for small and precise products across various industries, micromanufacturing has become more critical than ever. Micromanufacturing processes must continuously improve to produce components with tighter tolerances, higher accuracy, and superior surface integrity to meet the growing demand for such products. Non-conventional machining methods have gained immense importance in the manufacturing industry due to the high demand for precise and micro components of hard-to-cut materials. Electrical discharge machining (EDM) comes with the advantage of machining materials irrespective of their hardness. Still, it has inherent disadvantages, such as low material removal rate (MRR), debris adhesion, high surface roughness, tool wear, etc. Most of these issues are magnified when the process of EDM is downscaled to micro-EDM. Despite numerous experimental attempts, there is still less understanding of all the interactions between the plasma and electrodes in the micro EDM process, emphasizing the necessity for process modeling. A numerical model using the multiphysics finite element method is developed to estimate the plasma parameters, such as the plasma channel diameter and temperature distribution in the radial and axial directions. The numerical model also predicts the heat flux distribution and explains the plasma-electrode interactions via different heat transfer mechanisms such as conduction, convection, radiation, and thermionic effect. Experimental plasma diameters obtained from high-speed imaging of the discharge process were compared with the simulation results to discuss the validity of the proposed model. Percentage errors varying from 5.06 % to 14.5 % are observed. A pulse monitoring system (PMS) is then presented to monitor the discharge pulses for a controlled RC-based micro-EDM in real-time. The acquired information from the developed PMS explains the variations in discharge energy, material removal, and tool wear with increasing machining depth. After exploring the fundamentals of the process, the Hybridization of the micro-EDM process is analyzed to improve the machining performance by conducting a comparative study between the unassisted and ultrasonic vibration-assisted micro-EDM. Vibrations assistance enhanced the machining stability by increasing the percentage of contributing discharges by 19%. The ultrasonic vibrations proved beneficial in addressing the primary issue associated with the micro-EDM process, i.e., low MRR with a maximum of 35% increment. Finally, the output of the plasma model is utilized to predict the crater formation with and without vibration assistance. The crater model is validated using single discharge experiments to discuss the material removal mechanism with vibration assistance.