If before an EDM machine was a rarity, today such equipment will not surprise anyone. By electric erosion is understood the destruction of interatomic forces of interaction in metals under the influence of an electric charge. The EDM machine owes its appearance to the development of Soviet scientists B. R. Lazarenko and N. I. Lazarenko. Such equipment is universal. It allows you to process and shape any brands of metals and alloys. Moreover, the hardness of the processed material does not matter. The ability to process any materials is one of the main advantages of EDM over traditional machining.
The principle of the EDM machine
When familiarizing themselves with the principle of operation of such equipment, many have an association with electric arc welding. And this is quite logical. Indeed, for the course of erosion processes, it is necessary to obtain an electric discharge. To this end, a potential difference is created between the electrodes. In this case, one of the electrodes is the workpiece, and the second is the machine electrode.
When the electrode approaches the workpiece at a critical distance, a so-called breakdown occurs. In other words, the electrons perform the work of exit and rush through the air to the cathode (workpiece).
Electrons colliding with the surface of the workpiece, in a matter of fractions of a second, they heat it to incredibly high temperatures (10,000 or more degrees Celsius). The melting point of even the most refractory materials is several times lower. Thus, the metal layer instantly evaporates, depressions are formed in the form of a working tool of an EDM machine.
Why is electrolyte needed?
To enhance the effect, the anode and cathode are placed in a dielectric solution. As such, kerosene can be used. However, it can ignite at any time. Therefore, preference should be given to special mineral oils. Oil can also burn, but flash points are significantly higher than kerosene. In addition, kerosene exudes vapors that are harmful to production personnel.
The dielectric fluid is very hot and forms the so-called steam jacket (small air bubbles). It is through the air that is enclosed in a dielectric fluid that current flows (directed motion of electrons). This allows you to concentrate the flow of electrons and enhance the beneficial effect.
Effect of processing on the strength characteristics of the treated surface
After processing, the chemical composition and concentration of various elements in the surface layer of the workpiece are slightly changed. For example, carbon concentration may increase. In addition, the surface layer can be doped with elements that are contained in the molten electrode. By selecting the electrodes, it is possible to alloy the surface with elements such as aluminum, zinc, chromium, nickel, tungsten and others. Depending on the conditions of subsequent operation of the part, this can play both a positive and a negative role.
Advantages of EDM technology and equipment
One of the main advantages of this technology is the very high accuracy of product processing. This led to the widespread use of electroerosion technology in industries such as the military industry, precision engineering, as well as in the production of critical medical devices.
The shortage of production space is one of the main problems of modern engineering companies. EDM machines, as a rule, are quite compact and partially solve this problem. Thus, the compactness of the equipment is also an indisputable advantage of machines of this type.
EDM device
There are many types of machine tools. However, the above principles of operation are true absolutely for each of them, whether it is an electroerosive piercing machine or a machine for electrospark processing.
It may seem that this technological equipment is incredibly complex and expensive. Costly, maybe. Especially if the machine will produce a famous brand. However, the principle of operation of the equipment is quite simple. A lot of videos have appeared on the Web in which craftsmen reproduce these processes. Moreover, they collect electrical discharge machines with their own hands in the conditions of home amateur workshops.
The machine itself, like any other machine for processing metals and other materials, includes a bed (base), an electrolyte bath, a spindle head, a control panel for the operator (this can also be a full-fledged numerical control system), various automation. These are the main components. Individual machines can be additionally equipped with an electrolyte filtration system and other devices.