An Investigation of Magnetic-Field-Assisted Material Removal in Micro-EDM for Nonmagnetic Materials

Abstract

Previous magnetic-field-assisted microelectrical discharge machining ͑-EDM͒ techniques have been limited to use with magnetic materials. Therefore, a novel process has been developed and tested to improve material removal rate in magnetic-field-assisted -EDM for nonmagnetic materials. The workpiece electrodes were oriented to promote directionality in the current flowing through the workpiece, while an external magnetic field was applied in such a way as to produce a Lorentz force in the melt pool. Singledischarge events were carried out on nonmagnetic Grade 5 titanium workpieces to investigate the mechanical effects of the Lorentz force on material removal. Erosion efficiency, melt pool volume analysis, plasma temperature, electron density, and debris field characterization were used as the response metrics to quantify and explain the change in material removal with the applied Lorentz force. By orienting the Lorentz force to act in a direction pointing into the workpiece surface, volume of material removed was shown to increase by up to nearly 50%. Furthermore, erosion efficiency is observed to increase by over 54%. Plasma temperature is unaffected and electron density shows a slight decrease with the addition of the Lorentz force. The distribution of debris around the crater is shifted to greater distances from the discharge center with the Lorentz force. Taken together, these facts strongly suggest that the Lorentz force process developed produces a mechanical effect on the melt pool to aid in increasing material removal. The application of the Lorentz force is not found to negatively impact tool wear.

Atomized Dielectric Spray-Based Electric Discharge Machining (Spray-EDM) for Sustainable Manufacturing

“…Magnetic field-assisted flushing Several research efforts have been made into the use of magnetic field for improved flushing in EDM [17,96,97,18,98,19]. The concept of using magnetic field to assist in gap cleaning for EDM was first developed by De Bruijn et.…”

“…In order to develop a novel EDM technique that aims to improve process performance, it is pertinent to understand both the material removal mechanism and the flushing of debris particles. The flushing of debris deals with how the material is removed from the inter-electrode gap to prevent short-circuiting [1]. …”

“…al. (2011) [19] developed a method to improve the performance of µ − EDM for non-magnetic materials. When a directional current is flowing through the non-magnetic workpiece placed in a magnetic field, a Lorentz force is produced when the current and the magnetic field are non-parallel.…”

“…The effect of debris on the discharge is more significant in µ-EDM due to smaller gap distances employed in the process compared to macro-EDM. Hence effective flushing of the debris is crucial to improving the efficiency and stability of the EDM process [1]. It has been determined that effective flushing of debris enhances the efficiency of the process and reduces machining time by a factor of six [57].…”

Effect of Magnetic Field on Electrode Wear Ratio in Electro-Discharge Machining

“…Lorentz force technique is utilized to flush debris during machining operation to avoid instability. This force is perpendicular to current per unit area and magnetic field (T) [9].…”