• June 21, 2024
  • Shatou, Changan, Dongguan, CN
Electrical discharge machining

What is electrical discharge machining?

EDM is a non-traditional metal processing method. The principle is to form a high-intensity electric field on the electrode by applying a high-frequency pulse voltage between the workpiece and the electrode, thereby forming an electric spark discharge. When discharging, a plasma area with extremely high temperature is generated on the surface of the workpiece, which causes local melting and evaporation of the metal material, and at the same time causes a small blasting effect, through the evaporation and blasting of the material on the surface of the workpiece, the removal of the workpiece material is realized.

Types of EDM

According to different processing methods and process requirements, EDM can be divided into three common types: drilling EDM, wire cutting and sinker EDM.

Drilling EDM

Drilling EDM is a method of metal processing using electrochemical principles. It forms a discharge channel on the surface of the metal workpiece, and melts and evaporates the material of the workpiece through electric spark discharge to achieve the purpose of drilling.

Wire cutting

Wire-cut EDM is a commonly used part cutting method, which is often used for fine cutting of metal materials. It uses high-frequency electric spark corrosion, mechanical extrusion and impact heat to make the workpiece material form a thin electric spark discharge channel between the electrode and the workpiece, and generates high temperature, high pressure and other conditions during the discharge, melting and evaporating the workpiece material locally. Oxidation and condensation processes are combined, and the cutting of the workpiece is realized through the irregular corrosion of electric spark discharge.

Sinker EDM

Deposition EDM, also known as electrical discharge machining or die engraving, is a machining process that uses electrical discharges or sparks to remove material from a workpiece. It is mainly used for precision machining of hard conductive materials such as metals.

Advantages and disadvantages of EDM

EDM is an advanced metal processing technology with the following advantages:

1. High-precision processing: EDM can realize the processing of small, complex and precise parts, and can meet the requirements of high-precision processing.

2. Non-contact processing: EDM is a non-contact processing technology that will not cause any physical damage to the surface of the workpiece, avoiding problems such as scratches and dents caused by tool contact.

3. Wide applicability: EDM is not limited by the hardness of the workpiece, and can process metal materials of various hardness, including hard alloy, high-speed steel, stainless steel, etc., and has unique advantages for the processing of parts with high hardness or complex processes.

4. Controllable discharge energy: By adjusting the EDM parameters, the discharge energy and discharge form can be controlled to meet the processing requirements of different workpieces and optimize the processing effect.

However, EDM also has some disadvantages:

1. Slow processing speed: EDM is a point-by-point processing method, and the processing speed is relatively slow, which cannot meet the processing needs of large quantities and high efficiency.

2. The surface quality is limited: due to the pulse energy generated by the electric spark discharge, it will cause tiny melting and splashing on the surface of the workpiece, resulting in a high roughness of the processed surface, which requires subsequent polishing, grinding and other treatments.

3. The processing depth is limited: EDM can only be used for micro-machining, and the processing depth is limited to a certain extent, which cannot meet the processing requirements of some large-sized parts.

Generally speaking, EDM has the advantages of high precision and wide applicability, but the disadvantages of slow processing speed and limited surface quality limit its application in certain processing fields.

Comparison between EDM and traditional machining methods

The comparison between EDM and traditional processing methods mainly includes the following aspects:

1. Wide range of processing materials: EDM can be used to process various conductive materials, including difficult-to-machine materials such as cemented carbide, tool steel, ceramics, etc., while traditional processing methods have higher requirements on the conductivity of materials.

2. Small damage: EDM is non-contact processing, which will not generate mechanical stress on the surface of the material, so the damage to the processed material is small, and the original hardness and precision of the material can be maintained.

3. High-precision machining: EDM can achieve very high machining accuracy, and can process complex and small parts and molds.

4. Machinable hard materials: Traditional processing methods may encounter difficulties in processing materials with high hardness, such as tool steel and cemented carbide. However, because EDM uses the principle of spark discharge, the hardness Higher material processing effect is remarkable.

5. Slower speed: Compared with traditional processing methods, EDM has slower processing speed and lower processing efficiency.

In general, EDM is suitable for processing high-hardness, high-precision materials and complex-shaped parts and molds, but the processing speed is slow and the scope of application is relatively narrow. The traditional processing method is suitable for the processing of general materials and parts with relatively simple shapes, and the processing speed is fast, but there may be certain restrictions on the processing of difficult-to-machine materials and high-precision requirements.

EDM equipment and process parameters

EDM is a processing method that utilizes spark erosion and is widely used in processing hard materials such as metal materials, ceramics and composite materials. This processing method usually requires the following equipment and process parameters:

Equipment:

1. EDM machine tool: including processing table, processing head, electrode, working fluid circulation system and control system, etc.
2. Working fluid: Water or oil is usually used as the working fluid to cool the gap between the electrode and the workpiece and remove the bubbles of the spark.

Process parameters:

Mach. ParameterEDM
Discharge voltage40 to 400V
Discharge current0.5 to 500A
Discharge durationup to 1000 μm
Pulse frequency1 to 2000 μm

1. Discharge voltage: refers to the voltage applied between the electrode and the workpiece during processing. Generally speaking, the higher the discharge voltage, the faster the spark erosion rate. But too high a voltage will lead to overheating of the discharge and increased electrode wear.

2. Discharge current: refers to the magnitude of the current passing between the electrode and the workpiece. The larger the discharge current, the faster the spark erosion. However, excessive current will cause excessive burning and carbonization on the surface of the workpiece.

3. Discharge time: refers to the length of time the electric spark stays on the workpiece. The longer the discharge time, the greater the depth of spark erosion.

4. Pulse frequency: refers to the number of discharges per unit time. The higher the pulse frequency, the faster the electric spark erosion.

5. Flow rate of working fluid: The flow rate of working fluid has an important influence on the cooling effect of EDM and the control of the gap between the electrode and the workpiece.

The above are some commonly used equipment and process parameters for EDM. When using it, it is necessary to choose the appropriate parameters according to the hardness and shape of the processed material.

Key Technology of EDM

The key technologies of EDM include the following aspects:

1. EDM machine tool technology: refers to the design and manufacturing technology of EDM machine tools, including the structure, transmission system, electrical system and control system of the machine tool. The design and manufacturing quality of machine tools directly affect machining accuracy and machining efficiency.

2. Electrode material selection and manufacturing technology: In EDM, electrodes are important components that generate sparks through discharge. The material selection and manufacturing process of the electrode have a great influence on the processing effect. Commonly used electrode materials include copper, tungsten-copper alloy, molybdenum-copper alloy, etc.

3. Discharge parameter control technology: discharge parameter control refers to the technology of controlling parameters such as voltage, current, discharge time and discharge energy of electric spark discharge. Reasonable discharge parameter control can achieve stable discharge process and high processing efficiency.

4. Process research and optimization technology: The process research and optimization of EDM refers to exploring the best processing technology suitable for different materials and processing requirements through experiments and simulations. Process research and optimization can improve machining accuracy and machining efficiency.

5. Loop control technology: Loop control technology refers to the technology to control parameters such as polarity, pulse number, and pulse width in the spark discharge loop. Reasonable loop control can achieve stable discharge process and high processing speed.

6. Processing parameter monitoring and feedback adjustment technology: processing parameter monitoring and feedback adjustment technology refers to the technology of real-time monitoring of processing parameters in the process of EDM and adjustment of processing parameters according to the monitoring results. This allows for good process control and improved machining accuracy.

The historical development of EDM

EDM is a process method that uses electric discharge sparks to process metal materials. It originated in the United States in the late 1940s. The following is the historical development of EDM:

1. In the late 1940s, American scientist Joseph Priestley discovered the phenomenon of electric spark for the first time, and began to study the use of this phenomenon for material processing.

2. In the early 1950s, engineers from General Electric Company (GE) in the United States invented the first commercial electric discharge machine and began to apply it to the manufacturing industry.

3. In the mid-1950s, EDM technology began to be widely used in industries such as aerospace, automobile manufacturing and mold manufacturing.

4. In the 1960s, with the rapid development of electronic technology and material science, EDM technology was further improved and enhanced.

5. In the 1970s, EDM technology began to gain international attention and was widely adopted by the Japanese manufacturing industry.

6. In the 1980s, with the introduction of computer control technology, the degree of automation of EDM machine tools was greatly improved, and the machining accuracy and efficiency were further improved.

7. After the 1990s, EDM technology has gradually matured, and its application fields have continued to expand, involving medical equipment, electronic components, mold manufacturing and other fields.

8. In recent years, with the continuous emergence of advanced materials and complex parts, the requirements for EDM technology are getting higher and higher, such as high-speed EDM, micro EDM, etc.

Application fields of EDM

EDM is widely used in the following fields:

1. Mold manufacturing: EDM can be used to manufacture molds of various shapes and complexity, such as plastic injection molds, die-casting molds, forging molds, etc.

2. Parts processing: EDM can be used to process precise and complex metal parts, such as aerospace parts, semiconductor parts, auto parts, medical device parts, etc.

3. Radar antenna manufacturing: EDM can be used to manufacture structures such as small holes, thin grooves and waveguides in radar antennas, which can improve the performance and reliability of antennas.

4. Gemstone processing: EDM can be used for cutting, engraving and drilling of gemstones, and can achieve fine and complex gemstone processing effects.

5. Precision bearing processing: EDM can be used to manufacture structures such as inner holes, outer rings and raceways in precision bearings, which can improve the precision and service life of bearings.

6. Die processing: EDM can be used to manufacture structures such as small holes, fine grooves and concave-convex surfaces in the die, which can improve the service life and processing accuracy of the die.

In short, EDM plays an important role in the manufacturing industry and is widely used in mold manufacturing, parts processing, radar antenna manufacturing, gemstone processing, precision bearing processing, and die processing.

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