Slow walking wire is a kind of machining machine tool that uses continuously moving thin metal wires (called electrode wires) as electrodes to perform pulse spark discharge to remove metal from the workpiece and cut it into shape. The phenomenon of loose contact light pressure discharge between the wire electrode and the workpiece during slow wire walking machining. When the flexible electrode wire and the workpiece are close to the commonly considered discharge gap (such as 8-10 μ m) Spark discharge does not occur, even when the electrode wire has come into contact with the workpiece and the gap is no longer visible from the microscope, sparks are often not visible. Normal spark discharge occurs only when the workpiece bends the electrode wire and deflects it for a certain distance (from a few microns to tens of microns). At this time, every 1 feed of the wire electrode μ m. The discharge gap does not decrease by 1 μ m. Instead, the electrode wire increases a bit of tension between wires, and the workpiece increases a bit of lateral pressure. Obviously, spark discharge can only be formed after maintaining a certain slight contact pressure between the electrode wire and the workpiece. Based on this, it is believed that there is an electrically generated insulating thin film medium between the electrode wire and the workpiece