EDM (Electrical Discharge Machining) is a kind of machining equipment mainly used for EDM. Widely used in the manufacture of various metal molds and mechanical equipment. It is a special processing method for etching conductive material by electric erosion generated when the two-pole pulse discharge is immersed in the working fluid. It is also called electric discharge machining or electric erosion machining.

Edit this paragraph spark machining principle

When EDM is performed, the tool electrode and the workpiece are connected to the two poles of the pulse power supply, respectively, and immersed in the working fluid, or the working fluid is charged into the discharge gap. The gap automatic control system controls the tool electrode to feed the workpiece. When the gap between the two electrodes reaches a certain distance, the pulse voltage applied on both electrodes breaks down the working fluid to generate a spark discharge.

A large amount of heat energy is instantaneously concentrated in the microchannels of the discharge, the temperature can be as high as 10000°C or more, and the pressure also drastically changes, so that the local minute amounts of metal materials on the working surface are immediately melted, vaporized, and splashed into the working fluid in an explosive manner. Rapid condensation, the formation of solid metal particles, was taken away by the working fluid. At this time, a tiny pit mark is left on the surface of the workpiece, and the discharge is suspended for a short time, and the working fluid between the two electrodes is restored to the insulating state.

Immediately afterwards, the next pulse voltage breaks down again at another point where the two electrodes are relatively close to each other to generate a spark discharge, and the above process is repeated. In this way, although the amount of metal to be removed by each pulse discharge is very small, because there are tens of thousands of pulse discharges per second, more metals can be removed and the productivity is certain.

While maintaining the constant discharge gap between the tool electrode and the workpiece, the workpiece electrode is continuously fed to the workpiece while the workpiece metal is removed, and finally the shape corresponding to the shape of the tool electrode is machined. Therefore, as long as the shape of the tool electrode and the relative movement between the tool electrode and the workpiece are changed, various complicated profiles can be processed. The tool electrode is commonly used for electrical conductivity, high melting point, easy processing of resistance to corrosion materials, such as copper, graphite, copper-tungsten alloys and molybdenum. In the machining process, the tool electrode also has a loss, but less than the amount of metal removal of the workpiece, and even close to no loss.

The working fluid acts as a discharge medium and plays a role of cooling, chip evacuation, etc. during the processing. Common working fluids are lower viscosity, higher flash point, stable performance media such as kerosene, deionized water, and emulsions. The EDM machine is a kind of self-excited discharge. Its characteristics are as follows: Between the two electrodes of the spark discharge, there is a high voltage before discharge. When the two electrodes are close to each other, after the medium is broken down, spark discharge occurs. With the breakdown process, the resistance between the two electrodes sharply decreases, and the voltage between the two electrodes also sharply decreases. The spark passage must be extinguished in a short period of time (usually 10-7-10-3s) in order to maintain the “cold pole” characteristic of the spark discharge (ie, the thermal energy of the channel energy conversion is too late to reach the depth of the electrode). Channel energy acts on a very small area. The effect of channel energy can cause the electrode to be locally corroded. The method of sizing a material by using the corrosion phenomenon generated by the spark discharge is called EDM. EDM is a spark discharge in a liquid medium at a lower voltage range. EDM machining According to the form of the tool electrode and the relative movement between the tool and the workpiece, EDM machining methods can be divided into five categories: EDM machining using a forming tool electrode and a simple feed movement relative to the workpiece; An axially moving wire is used as a tool electrode, and the workpiece is moved in a desired shape and size to make a trajectory motion to cut a wire-cut electric wire of a conductive material, and a wire or formed conductive grinding wheel is used as a tool electrode to perform grinding or forming of small holes. Grinding EDM grinding; EDM conjugate revolving machining for thread ring gauges, thread plug gauges, gears, etc.; other types of machining such as small hole machining, engraved surface alloying, and surface hardening. EDM can process difficult-to-cut materials and complex-shaped workpieces by ordinary cutting methods; there is no cutting force during machining; no burrs, knife-mark groove, etc.; tool electrode materials are not harder than workpiece materials; Automated; after processing, the surface has a degenerating layer that must be removed in some applications; the purification of the working fluid and the smog pollution generated during the processing are troublesome.

The main role of EDM

Spark machining is mainly used to process molds and parts with complex shapes of holes and cavities; to process various hard and brittle materials such as hard alloys and hardened steels; to process deep holes, shaped holes, deep grooves, and narrow holes. Sewing and cutting sheets, etc.; processing tools such as various forming tools, templates and thread ring gauges.