Fundamental study of magnetic field-assisted micro-EDM for non-magnetic materials

Micro-EDM;material removal rate;magnetic field;non-magnetic material;Lorentz force;micro-machining

Heinz, Kenneth G., Jr. ; Kapoor ; Shiv G. ; DeVor ; Richard E.

关键词: Micro-EDM;    material removal rate;    magnetic field;    non-magnetic material;    Lorentz force;    micro-machining;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/16966/Heinz_Kenneth.pdf?sequence=2&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Micro-Electrical Discharge Machining (µ-EDM) is a unique machining method capable of removing material in the sub-grain size range (0.1-10 µm) from materials irrespective of their hardness.This process is valuable in the manufacturing of miniaturized products where industry demand for increasingly hard materials has reached the limitations of conventional micro-machining techniques.However, the current material removal rates (MRR) for µ-EDM range from 0.6-6.0 mm3/h, which is far below the desired minimum level of 10-15 mm3/h required for industrial viability.Many techniques have been previously developed to close this gap; however, they have all either fallen short of the industry goal or have been developed for specific materials, limiting widespread industrial use.This research seeks to develop a technique for improving MRR in µ-EDM that can be applied to any material, with a focus on non-magnetic materials.Two processes have been developed in an attempt to solve this problem, one aimed at altering the discharge plasma channel through the use of magnetic fields to affect plasma confinement and/or plasma stability and the other aimed to improve the material removal mechanism of the µ-EDM process through the use of Lorentz forces induced in the melt pool.Single-discharge events were carried out on non-magnetic Grade 5 titanium workpieces to investigate the mechanics of material removal and evaluate the effectiveness of these two techniques.Discharge crater area analysis, high-speed imaging, melt pool volume analysis, erosion efficiency, plasma temperature, electron density, and debris field characterization were used as the response metrics to quantify and explain the change in the process mechanics with the application of these techniques.By orienting the Lorentz force to act in a direction pointing into the workpiece surface, volume of material removed increases by 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 in the melt pool to aid in increasing material removal.The application of the Lorentz force is not found to negatively impact tool wear.