Investigation of Magnetic Field assisted Electrical Discharge Sinking of Ti6Al4V

Electrical discharge sinking (EDM) is a high-precision manufacturing technique. During the shaping process, the workpiece surface is simultaneously modified as a result of material transfer and thermal effects. To increase productivity, there is a variety of solutions to improve material removal rate, e.g. through using ultrasonic vibration assistance or powders that are admixed to the dielectric. However, sizes of the components too large for ultrasonic stimulation or challenges with the dielectric circulation system with admixed powders limited their applications. Applying external magnetic fields to assist EDM, showed a promising potential by means of significant increases of the material removal rate. Nevertheless, the mechanism of the external magnetic field assistance in EDM is still not understood well. In this study, effects of an external magnetic field with a strength of 0.66 T on the material removal of single discharge craters, the material transfer from a copper tool electrode to Ti6Al4V workpiece surfaces, and surface roughness are investigated during the magnetic field assisted EDM process. Discharge durations of 30 µs and 60 µs with different polarities were applied. Results show that the external magnetic field plays a vital role in increasing material removal volume up to approx. 130 %. Lorentz force is identified as main phenomenon, which significantly influences the generation of the cavity and peak areas of the crater. However, the magnetic field has a negligible effect on enhancing the material deposition from tool electrode to the workpiece surface layer. Magnetic field assisted EDM is a potential technique for improving the productivity of the EDM process of Ti6Al4V without reducing the modification of the workpiece surface caused by changes of the chemical composition.