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Electrical Discharge Machining of metals

This type of metal machining is based on the use of electrical erosion associated with electrical discharge between the machine’s work electrode and the workpiece. This is why it is also referred to as EDM, which is short for Electrical Discharge Machining – to put it simply „machining using electrical discharge”. It can therefore be successfully used for any material with a specific conductivity of more than 10-2S/cm.

Electrical Discharge Machining is particularly suitable for difficult-to-cut materials such as cemented carbide or hardened tool steels, which are harder to cut due to their high level of hardness. The advantages of EDM technology also include the ability to achieve very complex shapes and high accuracy. Electrical Discharge Machining is also used to regenerate plastic machining tools such as injection molds.

EDM Electrical Discharge Machining is divided into two main types: sinker EDM and wire EDM. They differ mainly in the type of work electrode that is being used. Sacher realizes orders that require both of these types of electrical discharge machining to be used.

Electrical Discharge Machining – how does it work?

EDM Electrical Discharge Machining is a process that removes material from the workpiece. It is carried out by using electric erosion which occurs during a series of electric shocks between the working electrode and the surface of the workpiece immersed in dielectric. There is no contact surface and no mechanical contact between them during electro-erosion. However, there is a gap of 0,01 to 0,8 mm depending on the specific conditions.

Electro-erosion is caused by the use of electricity in the form of electric arc shocks or periodic spark discharges that occur between the tool and the workpiece surface. These discharges occur in a dielectric work center. However, machining capabilities are limited due to the fact that dielectrics do not conduct the electric current or do so poorly. For this reason, the electrospark machining only applies to electrical conductive materials. During the electric shock, a plasma channel is formed around which a gas bubble increases its diameter. A local temperature rise of approximately 13 725 degrees Celsius (14 000 K) causes melting and partial evaporation of a limited volume of material.

After the electrical shock has been discharged, the pressure drops and the molten material evaporates. Rapid pressure changes can lead to micro explosions. The liquid material is thrown away. A part of it clots in the crater that is formed and some of it solidifies in the form of balls. The structure and properties of the solidified substance are different from those seen prior to the electro-erosion process. Subsequent electrical discharges occur in other areas, which are characterized by better conditions for creating the plasma channel and consequently the discharge.

Electrical Discharge Machining efficiency

The amount of material removed depends on the energy used in a single discharge. The higher the energy, the higher the machining efficiency and surface roughness. Since the discharges never occur at the same time, it is not easy to determine clearly how long the CNC Electrical Discharge Machining process will take. The efficiency of this process is affected by several factors like power, pulse duration, current and other pulse generator parameters, as well as the machined surface or electrode material. These elements are also important to the length of the process, the condition of the top layer and the accuracy of the electrical discharge machining.

The energy value parameter of a single discharge pulse has a significant impact on the quality of the resulting surface. The higher the values of the current parameters, the more rough the surface is. More powerful discharges lead to creating larger craters.

CNC Electrical Discharge Machining

Sacher provides complete CNC Electrical Discharge Machining services, which means using specialist microcomputer devices integrated into the control sections of these machines. The entire machining process is computer controlled and requires no manual intervention by the operator. As a result, the machining process is much more efficient and effective than what can be achieved using conventional methods.

CNC Electrical Discharge Machining provides excellent flexibility for the entire production process, which is demonstrated by i.e. ease of producing different workpiece varieties. This technology also significantly reduces production time, which saves time, but also material. As a result, the manufacturing and processing costs of the individual components are optimized. The CNC process becomes more economical and efficient.

Electrical Discharge Machining – uses and advantages

Electro-erosion is widely used in industry. This process allows for machining of very hard materials, including problematic materials such as carbide and hardened steels. EDM is recommended for die and mold applications. The production of these components must be conducted with extreme precision due to the presence of particularly demanding construction points such as deep ribs, narrow gaps, sharp internal corners and other complex shapes. In this case, Electrical Discharge Machining is irreplaceable.

Moreover, the ability to process EDM to achieve the highest accuracy, superior surface integrity and very fine finish eliminates or significantly reduces the need for polishing and other secondary processes. In addition, this process allows for creating very complex shapes and small pieces that would be difficult to perform with other methods and tools. Electro-erosion also provides excellent surface finish, well-finished tapered holes and very small diameter holes.