Thermal-electrical modelling of electrical discharge machining process

Abstract

Non-traditional machining has grown out of the need to machine exotic engineering metallic materials, composite materials and high tech ceramics having good mechanical properties and thermal characteristics as well as sufficient electrical conductivity. Electric Discharge machinery developed in late 1940’s has been accepted worldwide as a standard process in manufacturing and is capable of machining geometrically complex or hard material components, that are precise and difficult-to-machine such as heat treated tool steels, composites, super alloys, ceramics, hastalloys, nitralloy, nemonics, carbides, heat resistant steels etc. being widely used in die and mold making industries, aerospace, aeronautics and nuclear industries The thermal erosion theory is the most accepted mathematical model for evaluating material removal from electrodes during EDM process. It postulates that the process involves melted electrode and its evaporation by the discharge energy dissipated on electrode surface. Part of the melted and evaporated material is then ejected from electrode by force of different natures. Keeping this in view, the present work has been undertaken to generate a thermal-electrical model for sparks generated by electrical discharge in a liquid media and to determine the temperature distribution of tool and work piece. For a single discharge test, copper and En- 19 was used as specimens. The amount of heat dissipated varies with the thermal-physical properties of the conductor. The model is developed by using ANSYS software. ANSYS uses the finite-element method to solve the underlying governing equations and the associated problem-specific boundary conditions. Material Removal Rate, Surface Roughness and the maximum temperature reached in the discharge channel is determined.