The influence of magnetic field controlled electrical discharge milling on the surface quality of grooves

Abstract

In electrical discharge machining (EDM), the concentration of discharge debris in the machining gap will affect the discharge stability, thereby determining the surface quality of the machining. As a commonly used special machining method, discharge milling often encounters the problem of residual debris in the discharge gap during the machining process, resulting in poor machining results. In order to improve the machining efficiency and surface quality of discharge milling, this study proposes magnetic field control for discharge milling. Firstly, establish a discharge milling model and discuss the changes in the flow direction and speed of the working fluid in the bottom gap and around the electrode caused by changes in the flushing direction, while keeping the electrode feed direction unchanged. And it is stipulated that the flushing direction is the same as the electrode feed direction (same direction flushing machining), and the flushing direction is the reverse as the electrode feed direction (reverse direction flushing machining). The simulation found that there is a phenomenon of Flow around circular cylinder (FACC) around the electrode, which has adverse effects on machining. By changing the flushing direction, flushing speed, and magnetic field strength, the number of debris trapped in the machining gap was compared. The results showed that reverse flushing machining is more conducive to the discharge of debris from the machining gap, and increasing the flushing speed and magnetic field strength can accelerate the discharge of debris in the machining gap. Subsequently, a verification experiment was conducted, and the experimental results showed that compared with the same direction flushing machining, the material removal rate of the reverse direction flushing machining increased from 0.93 μg/s to 2.42 μg/s, an increase of 160.22 %. The surface roughness decreased from 4.79 µm to 2.91 µm, a decrease of 39.25 %. After applying a 200mT Halbach array magnetic field control, the material removal rate increased from 2.8 μg/s to 3.67 μg/s, an increase of 31.07 %. The surface roughness decreased from 2.58 µm to 2.21 µm, a decrease of 14.34 %.