Spark machine knowledge

Brief introduction of spark machine (EDM, full name of EDM)

A mechanical processing equipment mainly used for EDM. Widely used in manufacturing various metal molds and mechanical equipment.

Electrical discharge machining (EDM) is a special machining method to remove conductive materials by electrical corrosion generated by pulse discharge between two electrodes immersed in working fluid. It is also called electrical discharge machining or electrical corrosion machining, or EDM for short.

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The development course of spark machine 1943, the Soviet scholar Lazarenko and his wife researched and invented EDM, and then developed rapidly with the improvement of pulse power supply and control system. At first, the pulse power supply is a simple resistance-capacitance circuit. In the early 1950s, it was improved into a resistor-inductor-capacitor circuit. At the same time, the so-called long pulse power supply such as pulse generator is used to improve the etching efficiency and reduce the relative loss of tool electrodes.

Then high-frequency pulse power sources such as high-power electron tubes and thyratrons appeared, which improved the productivity under the same surface roughness. In the mid-1960s, transistor and thyristor pulse power supply appeared, which improved the energy utilization efficiency, reduced the tool electrode loss and expanded the adjustable range of rough and finish machining.

By the 1970s, high and low voltage composite pulse, multi-loop pulse, constant amplitude pulse and adjustable waveform pulse appeared, and new progress was made in machining surface roughness, machining accuracy and reducing tool electrode loss. In the control system, from the initial simple maintenance of the discharge gap to control the advance and retreat of the tool electrode, it has gradually developed into the timely control of various factors such as electrical parameters and non-electrical parameters by a microcomputer.

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When EDM is carried out according to the machining principle of spark machine, the tool electrode and workpiece are respectively connected to the two poles of pulse power supply and immersed in working liquid, or the working liquid is filled 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 to the two electrodes will break through the working fluid and generate spark discharge. A large amount of heat energy is instantly concentrated in the discharge microchannel, the temperature can be as high as 10000 degrees Celsius, and the pressure changes sharply, so that a small amount of metal materials on this working face are immediately melted and gasified, and explosively splashed into the working liquid, which quickly condenses to form solid metal particles and is taken away by the working liquid. At this time, tiny pits were left on the surface of the workpiece, and the discharge stopped for a short time, and the working fluid between the two electrodes returned to an insulating state.

Then, the next pulse voltage breaks down at another point where the two electrodes are relatively close to each other to generate spark discharge, and the above process is repeated. In this way, although the amount of metal etched by each pulse discharge is very small, more metal can be etched due to the action of thousands of pulse discharges per second, which has a certain productivity.

Under the condition of maintaining a constant discharge gap between the tool electrode and the workpiece, the tool electrode is continuously fed to the workpiece, and the workpiece metal is removed at the same time, 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 motion mode between the tool electrode and the workpiece are changed, various complex contours can be machined. Tool electrodes are usually made of corrosion-resistant materials with good conductivity, high melting point and easy processing, such as copper, graphite, copper-tungsten alloy and molybdenum. In the process of machining, the tool electrode also has loss, but it is less than the erosion of the workpiece metal and even close to no loss.

Working fluid, as a discharge medium, also plays the role of cooling and chip removal during machining. Commonly used working fluids are media with low viscosity, high flash point and stable performance, such as kerosene, deionized water and emulsion. The EDM machine tool is a kind of self-excited discharge, which is characterized in that there is a high voltage between the two electrodes of spark discharge before discharge. When the two electrodes are close, the dielectric between them is broken down, and then spark discharge occurs. With the breakdown process, the resistance between the two electrodes drops sharply, and the voltage between the two electrodes also drops sharply. The spark channel must be extinguished in time after a short time (generally 10-7- 10-3s) to maintain the "cold electrode" characteristics of spark discharge (that is, the heat energy converted by channel energy cannot reach the electrode depth too late), so that the channel energy acts in a small range. Under the action of channel energy, the electrode will be partially corroded. The method of sizing materials by using the corrosion phenomenon produced by spark discharge is called EDM. EDM is a kind of spark discharge in liquid medium in low voltage range. According to the form of tool electrode and the characteristics of relative motion between tool electrode and workpiece, EDM methods can be divided into five categories: EDM with simple feed motion relative to workpiece by forming tool electrode; Using the axially moving metal wire as the tool electrode, the workpiece moves along the track according to the required shape and size, and the conductive material is cut by WEDM. Using metal wire or special-shaped conductive grinding wheel as tool electrode, small hole grinding or electric spark grinding of special-shaped grinding is carried out; It is used for EDM rotary machining of yokes such as thread ring gauges, thread plug gauges and gears. Small hole processing, carving surface alloying, surface strengthening and other processing. EDM can process materials and complex workpieces that are difficult to cut by ordinary cutting methods. No cutting force during machining; No burr, knife marks, grooves and other defects; The tool electrode material need not be harder than the workpiece material; Direct use of electric energy processing, easy to achieve automation; After processing, the surface produces a metamorphic layer, which must be further removed in some applications; It is very troublesome to purify the working fluid and treat the smoke pollution produced in the process.

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The main function of EDM is mainly used to process molds and parts with complex cavity shapes; Processing all kinds of hard and brittle materials, such as cemented carbide and hardened steel; Machining deep fine holes, special-shaped holes, deep grooves, slits and slices; Processing tools, such as various molding tools, templates and thread ring gauges.

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The types of spark machines are 1 and mirror spark machine, which can produce mirror effect and are the best spark machines at present. The processed mold can be directly used in production, without saving mold, saving manpower and improving efficiency. Moreover, mirror spark machine has high precision and obvious advantages in the application of precision molds. The cost in mirror spark machine is relatively high, ranging from 700,000 to 800,000 to several million imported from mirror spark machine. In recent years, China has also introduced mirror spark machine, all of which are joint ventures with foreign mirror spark machine manufacturers.

2. Plastic mold EDM machine, which is our common spark machine, is mainly used for plastic mold EDM, which is relatively common in China, cheap and widely used, with an average price not exceeding100000. 3. Fine-hole discharger is also a kind of electric spark. Its main purpose is to punch holes in the mold.

In addition, there are some special machines, such as those specializing in the production of graphite and tungsten steel.

5, ZNC spark machine, Z-axis CNC, X-axis and Y-axis manual, is a more practical spark machine.

6, CNC spark machine, XYZ three-axis CNC. Numerical control spark machine has many functions, such as automatic copying, automatic centering, automatic programming, G code programming, three-axis linkage discharge and so on.

Spark machine maintenance

Daily maintenance

The workbench of spark machine should be kept clean, otherwise it will rust.

Check whether the oil pump pressure is normal.

The appearance of the equipment should be kept clean and tidy.

Two-week maintenance

Hand oiler oil, each time the pressure is 3 times.

Check the oil quantity of the manual oiler.

Three months maintenance

Lubricate each guide rail of the spark machine.

Check the accuracy of the disk. (Is the flatness measured with a dial indicator correct? )

Four seasons maintenance

Check whether the liquid level of spark machine is normal. (Check whether the level of the workbench is correct with a level gauge)

Check the three-axis accuracy of spark machine. (Whether the stroke is measured correctly with a pitch gauge)

Five-year maintenance

1 Check and clean the fuel tank of the spark machine.

2 Check and replace Z-axis lubricating oil of spark machine. (Please contact Qunji Service Department for details)

Check and clean the electrical cabinet. (Please contact Qunji Service Department for details)

Six opinions

Lighter oil: it is related to the frequency of use and the amount of erosion. It is recommended to check once every six months to confirm whether to replace it according to the actual situation.

About filtration: it is related to the frequency of use and the amount of loss. It is recommended to check it once every quarter to confirm whether to replace it according to the actual situation.

About cotton filtration: because of the frequency of use and the loss. It is recommended to check it once every quarter to confirm whether to replace it according to the actual situation.

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Future development direction of spark machine: precision of spark machine

The core of EDM is mainly reflected in the requirements of dimensional accuracy, copying accuracy and surface quality. By adopting some advanced machining technologies, the mirror machining effect can be achieved, and the EDM of high-precision die parts such as micro connectors, IC plastic packages, mobile phones and CD boxes can be successfully completed. Therefore, EDM has comprehensively promoted the further development of existing NC machining technology and continuously improved the machining accuracy of molds.

Intelligent spark machine Intelligent spark machine adopts intelligent control technology. The intelligence of EDM machine tool is embodied in accurate detection technology and fuzzy control technology. Online automatic monitoring and adjustment of machining process can realize the optimal control of machining process. Fuzzy control technology is to judge the state of EDM gap through computer monitoring, and automatically select machining conditions within the range of maintaining arc stability to achieve the highest machining efficiency.

Spark machine automation

When the spark machine is equipped with electrode library and standard electrode fixture, as long as the electrodes are put into the tool library and the machining program is compiled before machining, the whole EDM process can run automatically day after day without manual operation. The automatic operation of machine tools reduces the labor intensity of operators and improves the production efficiency. The functions of automatic measurement and alignment, automatic positioning, and continuous processing of multiple workpieces of spark machine have played a good role in its automation performance. The automatic operation process does not need manual intervention, which can improve the machining accuracy and efficiency.

High efficiency of spark machine

Spark machine can greatly improve the rough and finish machining efficiency on the premise of ensuring machining accuracy. Such as mobile phone case, household appliances, electrical appliances, electronic instruments and other fields, it is required to greatly shorten the discharge time of large-area workpieces and reduce the roughness at the same time. Therefore, manual polishing treatment is not required after discharge. This not only shortens the processing time and saves the trouble of post-treatment, but also improves the quality of the die. The powder processing type of spark machine can meet the requirements.