Do-it-yourself electric spark machine diagram. The main features of electroerosion. Machine work table

1. Essence and purpose of electroerosive machining

electroerosion- this is the destruction of the surface of the product under the action of an electric discharge. The founders of the technology are Soviet technologists B.R. Lazarenko and N.I. Lazarenko.

Electrical Discharge Machining (EDM) is widely used for resizing metal products- for obtaining holes of various shapes, shaped cavities, profile grooves and grooves in parts made of hard alloys, for hardening tools, for electroprinting, grinding, cutting, etc.

Rice. 1.9. 1 - tool electrode, 2 - workpiece, 3 - environment in which the discharge is performed, 4 - capacitor, 5 - rheostat, 6 - power source, 1p - electric spark processing mode, 2p - electric pulse processing mode

The scheme of electroerosive processing of materials is shown in fig. 1.9. The circuit is powered by a pulsed voltage of different polarity, which corresponds to the electric spark mode (1p) and the electric pulse mode (2p). The supply voltage charges the capacitor (4), parallel to which is the discharge gap between the electrode-tool (1) and the workpiece (2), which are placed in a liquid with a low dielectric constant. When the voltage on the capacitor exceeds the ignition potential of the discharge, breakdown of the liquid occurs. The liquid is heated to the boiling point and a gas bubble is formed from the vapors of the liquid. Further, the electric discharge develops in a gaseous medium, which leads to intense local heating of the part, the surface layers of the material melt and the melt products in the form of balls solidify in the flowing liquid and are removed from the processing zone.

2. Stages of electroerosive machining Electrospark machining mode

The workpiece is an anode (+), that is, in this case, the workpiece is processed by an electron flow, that is, the electronic streamer works, melting the volume of the anode-workpiece in the form of a hole. In order for the ion flow not to destroy the tool electrode, voltage pulses with a duration of no more than 10 -3 s are used. The electric spark mode is used for finishing, precise machining, since the metal removal in this case is small.

Electropulse processing mode

The workpiece is a cathode, that is, a negative pulse with a duration of more than 10 -3 s is applied to it. During electropulse processing, an arc discharge is ignited between the electrodes and the processing of parts is carried out by an ion stream. This mode is characterized by a high metal removal rate, which exceeds the productivity of the electrospark mode by 8–10 times, but the processing cleanliness is much worse. In both modes, kerosene or insulating oils are usually used as the working fluid.

3. Physics of EDM

The phenomena occurring in the interelectrode gap are very complex and are the subject of special studies. Here, the simplest scheme for removing metal from the processing area by means of electrical erosion will be considered.

As shown in fig. 1.10, a voltage is applied to the electrodes 1, which creates an electric field in the interelectrode gap. When the electrodes approach a critical distance, an electric discharge occurs in the form of a conductive channel. To increase the intensity of the discharge, the electrodes are immersed in a dielectric liquid 2 (kerosene, mineral oil, etc.). On the surface of the electrodes there are microroughnesses of various sizes. The electric field strength will be greatest between the two protrusions closest to each other on the surface of the electrodes; therefore, it is here that conductive bridges from impurity liquid particles arise. The current through the bridges heats the liquid until evaporation and a gas bubble (4) is formed, inside which a powerful spark or arc discharge develops, accompanied by a shock wave. There are flows of electrons and ions (positive and negative streamers) that bombard the electrodes. A plasma discharge channel is formed. Due to the high concentration of energy in the discharge zone, the temperature reaches thousands and tens of thousands of degrees. The metal on the electrode surface melts and evaporates. Drops of molten metal as a result of the movement of the liquid flow in the working area are thrown out of the electrodes and solidify in the liquid surrounding the electrodes in the form of small spherical particles (5).

From the interaction of liquid with sections of electrodes heated to a temperature of 100-400 0C, pyrolysis of the dielectric liquid occurs at the boundaries of the plasma channel of the discharge. As a result, gases are formed in the liquid, as well as asphalt-resinous substances. Carbon is released from the gaseous medium, deposited on the heated surfaces of the electrodes in the form of a thin film of crystalline graphite. At the site of action of the current pulse, small depressions remain on the surfaces of the electrodes - holes formed as a result of the removal of a certain amount of metal by the discharge.

In table. 1.2 shows the dependence of the erosion of the steel electrode on the energy and duration of a single pulse.

Table 1.2

Dependence of the erosion value of the steel electrode (anode) on the energy and duration of a single pulse

Rice. 1.10. 1 - electrodes, 2 - liquid, 3 - wells, 4 - gas bubble, 5 - erosion products

After the discharge, for some time, the channel column cools down and the plasma substance in the interelectrode gap deionizes. The electrical strength of the interelectrode gap is restored. The deionization time of the liquid dielectric is 10 6 -10 -2 s. The next discharge usually occurs already in a new place, between the other two nearest points of the electrodes.

The duration of the intervals between pulses should be sufficient to remove erosion products from the discharge zone, as well as a gas bubble, which is the main obstacle to the next discharge. In this regard, the frequency of discharges decreases with increasing energy.

This happens until the discharges remove from the surface of the electrodes all parts of the metal that are at a breakdown distance at the magnitude of the applied voltage. When the distance between the electrodes exceeds the breakdown distance, the electrodes must be brought closer to resume the discharges. Usually, the electrodes are brought together during the entire treatment time so that the electrical discharges do not stop.

Parameters of working impulses owls. The main parameters of electrical pulses applied to the interelectrode gap are their repetition frequency, duration, amplitude and duty cycle, as well as the shape, which determine the maximum power and energy. The shape and parameters of the pulses have a significant impact on the wear of the tool electrode, productivity and roughness of the machined surface.

Let us denote the pulse repetition rate, i.e., their number per second, through f. Then T = 1/f will be a period. It determines the time interval after which the next impulse follows.

The pulse is characterized by the amplitude value (or amplitude) of the voltage and current Um and Im. These are the maximum values ​​that the voltage and current acquire during the pulse time. During electroerosive machining, the voltage amplitude varies from a few volts to several hundred volts, and the current amplitude varies from a fraction of an ampere to tens of thousands of amperes. The range of duty cycles of the pulse during electroerosive machining is in the range from 1 to 30.

Polar effect and pulse polarity. The high temperature in the discharge channel and the ongoing dynamic processes cause erosion of both electrodes. The increase in erosion of one electrode compared to the other electrode is called the polar effect. The polar effect is determined by the material of the electrodes, the energy and duration of the pulses, and the sign of the potential applied to the electrode.

The processes of voltage and current changes have an oscillatory character relative to their zero value. In electroerosive machining, it is customary to consider the working or direct polarity of the pulse to be that part of it that causes the greatest effect of erosion of the workpiece being machined, and the reverse is the part of the pulse that causes increased erosion of the tool electrode. The workpiece to be processed is attached to that pole, the effect of erosion of which is greater under given conditions. An electrode-tool is attached to the opposite pole. For example, with short pulses of electrospark processing, energy is predominantly supplied to the anode, which should be used here as a workpiece (straight polarity). With an increase in the duration of the pulses, a redistribution of the heat flux on the electrodes occurs. This leads to the fact that under certain modes of electropulse processing, the anode erosion becomes less than the cathode erosion. In this case, reverse polarity should be used, using the workpiece as the cathode.

Electrical discharge machinability. The effect of erosion of various metals and alloys, produced by electric pulses of the same parameters, is different. The dependence of the intensity of erosion on the properties of metals is called electroerosive machinability.

The different influence of pulsed discharges on metals and alloys depends on their thermophysical constants: - melting and boiling points, thermal conductivity, heat capacity. If we take the electrical discharge machinability of steel as a unit, then the electrical discharge machinability of other metals (under the same conditions) can be represented in the following relative units: tungsten - 0.3; hard alloy - 0.5; titanium - 0.6; nickel - 0.8; copper - 1.1; brass - 1.6; aluminum - 4; magnesium - 6 (the indicated data are valid only under specific conditions: pulse energy 0.125 J, duration 1.4-10 -5 s, frequency 1200 1/s, current amplitude 250 A).

Working environment. Most EDM operations are carried out in a liquid. It provides the conditions necessary for the removal of erosion products from the interelectrode gap, stabilizes the process, and affects the dielectric strength of the interelectrode gap. Fluids suitable for electrospark processing must have the appropriate viscosity, electrical insulating properties, and chemical resistance to discharges.

With an increase in the pulse frequency and a decrease in the operating current, the stability of the working process deteriorates. This makes it necessary to increase the duty cycle of the pulses. The use of rectangular pulses significantly improves performance.

Processing productivity can be increased if forced removal of erosion products from the interelectrode gap is applied. To do this, liquid is injected into the interelectrode gap under pressure (Fig. 1.11).

Rice. 1.11.

Good results are obtained by applying vibrations to the tool electrode, as well as rotating one or both electrodes. The liquid pressure depends on the depth of the hole and the size of the interelectrode gap. Vibrations are especially necessary for electrospark processing of deep holes of small diameter and narrow slots. Most EDM machines are equipped with a special vibrating head.

Surface quality and machining accuracy. The metal of the electrodes is subjected to a local, short-term, but very intense electrothermal effect. The highest temperature exists on the treated surface and decreases rapidly at some distance from the surface. Most of the molten metal and its vapors are removed from the discharge zone, but some remains in the hole (Fig. 1.12). When the metal solidifies, a film is formed on the surface of the hole, which differs in its properties from the base metal.

Rice. 1.12. 1 - the space left after the melting of the metal; 2 - white layer; 3 - roller around the hole; 4 - processed workpiece; BL, NL - diameter and depth of the hole

The surface layer in the molten state actively enters into chemical interaction with vapors and decomposition products of the working fluid formed in the high temperature zone. The result of this interaction is an intense saturation of the metal with the components contained in the liquid medium, as well as with the substances that make up the tool electrode. Thus, titanium, chromium, tungsten, etc. can be introduced into the surface layer. liquid hydrocarbons(kerosene, oil), the surface layer is saturated with carbon, i.e., iron carbides are formed. Therefore, during electroerosive machining, the surface of the part is hardened.

Intensive heat removal from the discharge zone through the masses of cold metal adjacent to it and the working fluid creates conditions for superfast hardening, which simultaneously with carburization leads to the formation of a very hard layer. The hardened surface layer of steel has an increased resistance to abrasion and a lower coefficient of friction than that of non-heat-treated steel. The structure of the surface layer differs significantly from the structure of the base metal and is similar to the structure of the chilled layer that occurs on the surface of some cast irons. Therefore, this layer is called the "white layer". The depth of the white layer depends on the energy of the pulses, their duration and the thermophysical properties of the processed material. With long current pulses of high energy, the depth of the white layer is equal to tenths of a millimeter, and with short pulses - hundredths of a millimeter and microns.

Hardening of the surface layer of metals (electroerosive alloying). One of the advantages of the electrospark method of processing materials is that, under certain conditions, the strength properties of the workpiece surface increase sharply: hardness, wear resistance, heat resistance, and erosion resistance. This feature is used to improve wear resistance. cutting tool, dies, molds and machine parts, strengthening metal surfaces by the electrospark method.

In electrospark alloying, reverse polarity is used (the workpiece is the cathode, the tool is the anode); processing is usually carried out in air and, as a rule, with electrode vibration. The equipment with which the hardening process is carried out is small-sized and very easy to operate. The main advantages of the electrospark coating method are as follows: the coatings have a high adhesive strength with the base material; surfaces to be coated do not require preliminary preparation; it is possible to apply not only metals and their alloys, but also their compositions. The processes occurring during electrospark hardening are complex and are the subject of thorough research. The essence of hardening is that during an electric spark discharge in air, a polar transfer of the electrode material to the workpiece occurs. The transferred electrode material alloys the workpiece metal and, chemically combining with the dissociated atomic nitrogen of the air, carbon and the workpiece material, forms a diffusion wear-resistant hardened layer. In this case, complex chemical compounds, highly resistant nitrides and carbonitrides, as well as quenching structures appear in the layer. According to experts, during electrospark hardening in the surface layer, for example, steel, the processes listed in Table 1 occur. 1.3.

Table 1.3

During electrospark hardening, the microhardness of the white layer in carbon steels can be increased to 230 MPa, the height of the microroughness of the treated surface is up to 2.5 microns. The thickness of the coating layer obtained on some installations is 0.003-0.2 mm.

4. Basic technologies of electroerosive processing of metals

Technologies for dimensional processing of metal parts.

The shaping of parts by the electroerosive method can be carried out according to the following schemes.

1. Copying the shape of the electrode or its section. In this case, the processed element of the workpiece in shape is an inverse reflection of the working surface of the tool. This operation is called stitching. There are direct and reverse copy methods. With direct copying, the tool is above the workpiece, and with reverse copying, it is below it. The stitching method is simple to perform and widely used in industry. On fig. 1.13 shows a diagram of electrical discharge machining by copying the shape of the electrode-tool. In the course of electroerosive machining, the electrode (1) is introduced into the part, providing copying of the electrode.

2. Mutual movement of the workpiece and the electrode-tool. With this scheme, the operations of cutting out complex profile parts and cutting blanks with electrodes, electroerosive grinding and boring of parts are possible.

Rice. 1.13. : 1 - electrode-tool, 2 - workpiece, 3 - liquid, 4 - vessel

Sewing windows, cracks and holes. This operation is carried out on universal machines. Slots with a width of (2.5-10) mm and a depth of up to 100 mm are stitched by the electroerosive method. To ensure the removal of erosion products from the interelectrode gap, the tool electrode is made T-shaped or the thickness of the tail part is reduced compared to the working part by several tenths of a millimeter. The speed of flashing the slots is (0.5-0.8) mm/min, the roughness of the treated surface is up to 2.5 microns.

Processing of parts such as nets and sieves. EDM machines have been created that allow processing mesh parts with up to several thousand holes. The machines can simultaneously process more than 800 holes with a diameter of (0.2-2) mm in sheets of corrosion-resistant steels, brass and other materials up to 2 mm thick. Processing capacity up to 10,000 holes per hour.

Electroerosive grinding. This is one of the varieties of electrical discharge machining, which is used for processing high-strength workpieces made of steels and hard alloys. Removal of metal in this case occurs under the influence of pulsed discharges between the rotating electrode-tool and the workpiece being processed, and not as a result of mechanical action, as in abrasive grinding.

The methods of direct and reverse copying have a significant drawback, which consists in the need to use complex shaped electrodes-tools. The wear of the electrodes affects the accuracy of the manufacture of parts, therefore, with one electrode-tool, it is possible to produce no more than 5-10 parts.

The electric spark method of complex contour wire cutting compares favorably with copying methods in that here the tool is a thin wire made of copper, brass or tungsten with a diameter of several microns to 0.5 mm, which is included in the electrical circuit as a cathode (see Fig. 1.14).

Rice. 1.14. : 1 - wire, 2 - workpiece, 3 - guide rollers, 4 - device for adjusting the wire drawing speed

To eliminate the influence of wire wear on the accuracy of processing, the wire is rewound from one coil to another, which allows all new elements to participate in the work. When rewinding, there is a slight tension. Near the workpiece to be processed, rollers are installed that orient the wire relative to the workpiece. Complex contour wire cutting is used for precision cutting of workpieces, cutting of precise slots, cutting of semiconductor materials, processing of cylindrical, conical outer and inner surfaces.

The main advantages of electrical discharge machining with a wire electrode-tool include high accuracy and the possibility of wide automation of the process.

Electrocontact method of processing. Electrocontact processing of materials is a kind of electroerosive processing. Its difference lies in the fact that pulses of electrical energy are generated as a result of the mutual movement of the electrodes or the interruption of the electrical discharge when pumping liquid under pressure. Electrocontact processing can be carried out at direct and alternating current, in air or liquid (water with anti-corrosion additives). During processing, the electrode-tool and the workpiece are completely immersed in a liquid, or liquid is sprayed into the interelectrode gap. Processing is carried out at significant currents (up to 5000 A) and voltages idle move power source 18-40 V. The electrocontact method produces semi-finish turning of bodies of revolution, fine cutting, flashing of cylindrical, shaped holes and volumetric cavities, milling, grinding. The electrocontact method is especially effective when processing workpieces made of hard-to-cut steels and alloys, as well as high-hardness cast irons, single crystals, and materials with high thermal properties.

Schematic diagram of the installation for electrocontact processing is as follows. The workpiece and the electrode-tool, having an axis of rotational symmetry and included in the circuit with a power source, after contact, perform rotary motion relative to each other.

Under the conditions necessary for the implementation of electroerosive processes, metal is removed from the workpiece.

Hardening of the surface layer of the metal (electroerosive alloying)

One of the advantages of electroerosive machining of metals is that, under certain conditions, the strength properties of the surface of the workpiece sharply increase. This feature is used to improve the wear resistance of cutting tools, dies, molds, etc. In electroerosion alloying, reverse polarity is used (the workpiece is the cathode, the tool is the anode), processing is usually carried out with the atoms of the tool-electrode in the electric pulse mode (see Fig. 1.15) in air and, as a rule, with electrode vibration.

Rice. 1.15 Scheme of electroerosive alloying: 1 - alloying electrode-tool, 2 - alloyed part

The main advantages of electroerosive alloying are as follows: coatings have a high degree of adhesion to the base material; surfaces to be coated do not require preliminary preparation; it is possible to apply not only metals and alloys, but also their compositions.

The processes occurring during electroerosive hardening are complex and are the subject of thorough research. However, the essence of hardening is that during an electric spark discharge in air, the electrode material is transferred to the workpiece (see Fig. 1.15). The transferred electrode material alloys the workpiece metal and, chemically combining with air nitrogen ions, carbon and workpiece material, forms a wear-resistant hardened layer consisting of nitrides, carbonitrides and other hardening structures.

With electrospark alloying, the microhardness of the white layer in carbon steels can be increased to 230 MPa. The thickness of the coating layer obtained on some installations is 0.003-0.2 mm. When hardening the surface of machine parts (for example, at the IE-2M installation), it is possible to obtain a layer depth of up to 0.5–1.6 mm with a microhardness of 50–60 MPa (when hardened with ferrochrome).

There is a distinction between clean processing, which corresponds to high voltages and low short-circuit currents (up to 20 A), and rough (rough alloying) at low voltages of 50-60 V and short-circuit currents over 20 A.

Work on electroerosive machines. Preparation of electroerosive machines for work consists in installing the workpiece and the tool electrode and aligning their relative position, preparing the bath for work and the working fluid pumping system, selecting and setting the generator modes. The workpiece is installed and fixed directly on the machine table or in the fixture. The tool electrode is installed with its tail into the head spindle. When aligning, indicators, optical instruments, devices are used that allow you to change the position of the tool in relation to the workpiece and the angle of inclination.

After adjusting the position of the electrode tool, fill the bath with working fluid, check the operation of the pumping system, set the required pumping pressure. The pulse generator mode is set (polarity, pulse shape, duty cycle, pulse repetition rate, average current), using the appropriate tables and nomograms. Changing the polarity of the voltage of the pulse generator is carried out by switching on the plug connector of the current leads to the machine. When working with direct polarity (electric spark mode), a negative potential is applied to the electrode, and a positive potential is applied to the workpiece. To work with reverse polarity (electropulse mode), reverse switching is performed. The installation of electrical parameters and operating modes is carried out using switches located on the control panel. Adjust the supply regulator by setting the recommended regulator voltage.

In the direction of metalworking, the method of electrical discharge machining (EDM) has become widespread. The electroerosive processing method was discovered by Soviet scientists in 1947.

This technology was able to greatly facilitate the process of metal processing, especially it helped in the processing of high-strength metals, in the manufacture of parts of complex design, as well as in other areas.

The operation of the method is based on the impact on the part by electric discharges in a dielectric medium, as a result of which the metal is destroyed or its physical properties change.

Application of the EEE method:

• When processing parts made of metals with complex physical and chemical properties;
• In the manufacture of parts of complex geometric parameters, with complex machining;
• When alloying the surface to improve wear resistance and give parts the required qualities;
• Improving the characteristics of the upper layer of the metal surface (hardening) due to the oxidation of the material under the influence of an electric discharge;
• Marking products without harmful effects, which is present in mechanical branding.

Used to perform various operations different types electroerosive processing. Numerical devices are installed on industrial machines. program control(CNC), which greatly simplifies the use of any type of processing.

Types of electroerosive processing of material:

• The electric spark type of processing is used when cutting hard-alloy materials, figured cutting and for making holes in high-strength metals. Gives high accuracy, but the speed is low. It is used in stitching machines.
• The electrocontact processing method is based on the local melting of the metal by arc discharges, followed by the removal of the spent material. The method has a lower accuracy, but more high speed work than the electrospark method. It is used when working with large parts made of cast iron, alloy steel, refractory and other metals.
• The electric pulse method is similar to the electric spark method, but arc discharges with a duration of up to 0.01 seconds are used. This gives high performance with relatively good quality.
• The anodic-mechanical method is based on a combination of electrical and mechanical effects on the metal. The working tool is a disk, and the working medium is liquid glass or a substance similar in characteristics. A certain voltage is applied to the workpiece and the disk, during the discharge the metal is melted, and the sludge is mechanically removed by the disk.

In industry, machines are used that work on the basis of the method of electroerosive metal processing. They are classified according to several parameters: principle of operation, control, availability of CNC, etc.

Types of machines operating on the principle of EDM:

• EDM wire machine;
• Electroerosive wire-cutting machine;
• Electroerosive piercing machine.

Due to its versatility, the EEO machine is needed on the farm, and sometimes it cannot be replaced at all. Everyone would like to have such a device in their garage. Unfortunately, buying such a factory-assembled machine is very expensive and often not possible. There is a way out of this situation - to collect with your own hands.

Cutting and stitching machine

Contrary to preconceived notions about the complexity and impossibility of such a task, this is not the case. This is quite a feasible task for a simple layman, although everything is not so simple. The simplest type of machine is a cut-out machine, designed for processing parts made of alloyed, refractory and other durable metals.

The electrical circuit contains: a power source, a diode bridge, a light bulb and a set of capacitors connected in a parallel circuit. An electrode and a workpiece are connected to the output. Note again that this circuit diagram for a figurative concept of the principle of operation of the device. In practice, the scheme is supplemented with various elements that allow you to adjust the piercing machine to the required parameters.

General requirements for the electrical circuit of the cutting machine:

• Consider the required power of the machine when choosing a transformer;
• The voltage on the capacitor must be greater than 320 V;
• The total capacitance of the capacitors must be at least 1000 uF;
• The cable going from the circuit to the contacts must be only copper and with a cross section of at least 10 mm;

One example of a working scheme:

As you can immediately see, the scheme differs significantly from the principle one, but at the same time it is not something supernatural. All the details of the electrical circuit can be found in specialized stores or simply in old electronic devices that have long been gathering dust somewhere in the garage. An excellent solution is to use CNC to control the machine, but this method of control costs a lot, and connecting it to a home-made machine requires certain skills and knowledge.

Machine design

All elements of the electrical circuit must be securely fixed in a dielectric housing; it is desirable to use fluoroplastic or another with similar characteristics as a material. You can display the necessary toggle switches, regulators and measuring instruments on the panel.

On the bed, you need to fix the holder for the electrode (must be fixed movably) and the workpiece, as well as the dielectric bath, in which the whole process will take place. As an addition, you can put an automatic electrode feed, it will be very convenient. The working process of such a machine is very slow, and it takes a long time to make a deep hole.

DIY wire machine

The electrical circuit of the wire machine is the same as on the cut machine, with the exception of some nuances. Consider other differences of the wire machine. Structurally, the wire machine is also similar to the cut-out machine, but there is a difference - it is a working element of the machine. On a wire loom, unlike a cut one, it is a thin copper wire on two drums, and in the process of work the wire is rewound from one drum to another.

This was done to reduce tool wear. A fixed wire will quickly become unusable. This complicates the design with a wire movement mechanism that must be installed on the frame for convenient processing of parts. At the same time, it gives the machine additional functionality. When cutting complex elements the best option will put the CNC, but, as mentioned above, this is due to some difficulties.

A simple electric spark setup (Fig. 1) makes it possible to easily and quickly process small parts made of electrically conductive materials of any hardness. With its help, you can get through holes of any shape, remove a broken threaded tool, cut thin slots, engrave, sharpen tools, and much more.

The essence of the process of electrospark processing is the destruction of the workpiece material under the action of a pulsed electric discharge. Due to the small area of ​​the working surface of the tool, a large number of heat that melts the substance of the workpiece. The processing process is most effective in a liquid (for example, in kerosene), which washes the place of contact between the vibrating tool and the workpiece and carries away the erosion products with it. The tool is brass rods (electrodes), repeating the shape of the intended hole.

Rice. 1. Small-sized electric spark installation:
1 - workpiece; 2 - tool; 3 - electromagnetic vibrator; 4 - clamping device; 5 - bath.

The circuit diagram of the installation is shown in fig. 2. The installation works as follows. The discharge capacitor C1 is connected with its positive terminal to the workpiece 1. Its minus is connected to the tool 2. The electromagnetic vibrator 3 informs the tool of continuous oscillations. This ensures a constant spark at the point of contact and prevents the tool from welding to the workpiece. The workpiece 1 is fixed in the clamping device 4, which has reliable electrical contact with the bath 5.

The power transformer is assembled on a Sh32 core made of ordinary transformer steel. The thickness of the set is 40 mm. The primary winding contains 1100 turns of PEV 0.41 wire with a tap from the 650th turn. The secondary winding has 200 turns of PEV-2 wire with a diameter of 1.25 mm. Between the primary and secondary windings, a shielding winding III is placed, consisting of one layer wound with a PEV 0.18 wire. The capacity of the discharge capacitor is 400 μF (two capacitors of the KE-2 type 200 x 50 V). Rheostat R1 is designed for a current of 3-5 A. This rheostat is wound with a nichrome wire with a diameter of 0.5-0.6 mm on the resistance BC-2.

Rice. 2. Schematic diagram of the electric spark installation.

Diodes D1-D4 type D304, other types of diodes can be used. At the output of the rectifier, the voltage is about 24-30 V. You can use power supplies with a lower voltage, but with a large current, so that the power consumed by the charge circuit is at least 50-60 watts.

During the operation of the installation, continuous sparking occurs. To reduce the interference generated by the installation, it is necessary to include a simple radio interference filter in its power circuit.

For the manufacture of non-standard equipment or products in production (at a factory, in a factory, in an industrial workshop), they usually do not think for a long time, and if they cannot make something themselves and on their own, then they order this equipment or products on the side, regardless of the costs. For a craftsman, this option for acquiring a non-standard product is not always acceptable.
So what to do?
Do not lose heart and remember that any technical problem has many solutions and you just need to find the most acceptable solution suitable for use in your particular case.
Example: You need to make a couple of products, the size of a medium-sized basin, from sheet steel.
For the sake of manufacturing two or three parts, which, quite possibly, will subsequently need a radical alteration or even a new design, renting a press and making a stamp (with alteration) for a craftsman can turn out to be an expensive pleasure. But you should not give up what you have planned, especially if you know how to work not only with your hands, but also with your head. In the middle of the last century, an electro-hydraulic effect was discovered, a spark in water excited a hydraulic shock with which you can stamp quite large and complex products on relatively simple equipment.
Hydraulic shocks for stamping have been used for a relatively long time. During the conquest of the American wild west, handicraftsmen stamped saucepans, bowlers and other products in primitive stamps, shooting into the water (stamp) from guns or revolvers.
The device of the stamp was as follows: A sheet blank was attached to the matrix, so that water did not get under the sheet blank, then the whole assembly was immersed in a thick-walled vat of water and fired. Hydraulic shocks gradually pressed the sheet of metal against the inner surface of the matrix. Air was bled from the matrix cavity through a special hole. Then, for the same purposes, instead of shooting, they began to blow up mini charges of explosives. The equipment was compact and simple, although a bit "" dangerous.
Would you say primitive? But it's simple. Bodies for ultra-long limousines are still stamped in this way, using water and explosives. It turned out that for the manufacture of such bodies it is too expensive to make a special press even for reputable firms. With the help of approximately the same equipment, ship armor is cut to size (thickness up to 0.8 meters), ore is crushed, etc. etc.
In our beloved Land of Prohibitions, no one will allow production pranks with firearms and explosives to a lone master, so for the execution of what was conceived at home, an electro-hydraulic effect would be very useful. Not prohibited, adjustable in power and relatively cheap. The matrix is ​​easy to make from ordinary polymer-coated concrete. As you can see, this idea is quite realistic in the end.
More details for those interested in the book: Yutkin L.A. ,Electrohydraulic effect and its application in industry.""
The following examples:
Processing of metals by electrical methods.
These are electrochemical, electroerosive and electrocontact methods of dimensional processing of metals and metal alloys of any hardness. Dimensional and volume cutting and processing, punching of simple and extra-deep, profiled holes, cavities. Milling, marking, sharpening, grinding, polishing, etc. In relation to the usual methods of processing (cutting), the tool used (for electrical processing) can be cheaper, home-made and from non-deficient materials, the machines are simpler, compared to the usual ones, to manufacture .
A well-known method of electrochemical dissolution of a metal under the action of electric current. If two metal electrodes are connected to a direct current source and the electrodes are lowered into the electrolyte solution, then the positive electrode (workpiece) will begin to dissolve, and the negative electrode (tool), depending on the electrolyte used, will remain unchanged or begin to be covered with a layer of metal dissolved in the electrolyte. In our case, only the dissolution of the metal on the workpiece is welcome, the dissolved metal precipitates and the unchanged state of the tool electrode. For this, a 25% solution is used as an electrolyte. table salt. The closer the electrode-tool is to the electrode-workpiece, the more accurate is the imprint "" of the tool on the workpiece. In reality, the distance between the tool electrode and the workpiece electrode is from hundredths of a millimeter and more.
The main difficulties are:
to keep the tool electrode at the same distance from the workpiece electrode during the entire processing process, the dissolution of the metal leads to a change in the dissolution area and other changes in various parameters.
remove dissolved metal from the processing zone and prevent its deposition on the workpiece and tool. This is usually done by supplying electrolyte under high (up to 20 atmospheres) pressure to the working gap.
The advantages of such processing are a relatively cheap and practically eternal tool, the ability to process metals of any hardness with very high accuracy, without subsequent changes in their properties and hardening in particular.
A simpler way to process metals is electroerosive. In essence, this is a continuation of the electrochemical method. When the gap between the tool electrode and the workpiece electrode approaches, a breakdown spark occurs. Holes appear on both electrodes at the place where the spark originated, but the hole is slightly larger on the workpiece. The metal in this case does not dissolve in the electrolyte, but evaporates and then condenses in the form of tiny metal balls in the working fluid. For electroerosive machining, it is no longer a conductive electrolyte that is used, but liquid dielectrics (or working fluids): engine oil, kerosene, descillated water, etc. Liquid dielectrics prevent the evaporated metal of the workpiece electrode from settling on the electrode tool. Thus, both the tool and the workpiece are destroyed, but the workpiece at the point of contact is destroyed more, and so after a series of contacts, the workpiece is eventually processed.
Wear (destruction) of the tool up to 30-80 percent in relation to the destruction on the workpiece. However, the tool can often be made from tin or pieces of non-deficient wire of the required diameter, for shaped cutting and punching complex and deep holes, not only in ordinary iron, but also for processing other metals, up to super-hard pobedite soldering. The punching of ultra-deep holes is carried out with a constant rotation of the tool and the supply of working fluid under low pressure. The processing accuracy is relatively low, but the processing itself is quite simple.
The machine for electrical discharge machining resembles a desktop drilling machine. Only the tool is attached to the solenoid connected in parallel to the electromagnetic coil. During the contact of the electrodes, the tool and the workpiece come into contact, the electrical circuit closes, a current appears in the coil, the electromagnetic coil raises the solenoid and the tool above the workpiece. But at this time, the electrical circuit is de-energized and the solenoid (and the tool) falls under its own weight down onto the workpiece and everything repeats. Repeats automatically as long as there are conditions for tool-to-workpiece contact.
Disadvantages: The tool quickly loses its original shape, which leads to a large distortion of the workpiece shape. Therefore, processing is sometimes carried out in several steps and different instrument, first in the draft version, then in the final version.
The electro-contact method of metal processing is even simpler. As a working fluid, a solution of liquid glass (sodium or potassium silicate) is already used. The tool is a metal, rotating disc made of thick tin. A solution of liquid glass (better known as clerical glue) forms an insoluble film on the metal, but microroughnesses on the metal tool peel off the film on the workpiece and immediately a discharge of electricity levels the protrusion on the tool and makes a new recess on the workpiece. And so continuously, at different points of contact, while the tool disk rotates and comes into contact with the workpiece. A solution of sodium silicate (potassium) is either poured into the contact zone, or both the workpiece and the tool are immersed in the solution. In an electro-contact way, you can cut and process metal in much the same way as a grinder or on an emery wheel.
Machine tools for electro-contact processing of metals are the simplest in design and must ensure the rotation of the tool, and the supply of high currents by the tool to the processing zone. Tool wear is significant, but finishing is carried out with the same tool as roughing.
Electro-contact grinding and polishing irregularities on the guide surfaces of metalworking machines. In this case, the cast-iron plate (tool) and the frame (workpiece) are connected to a low-voltage direct current source and poured with liquid glass (manually rubbed) grind the surface of the guides.
If you think that any of the above metal processing methods will suit you, then of course my description will not be enough for a serious study of this topic. But in essence, the machines are quite simple, and all of the above is not so difficult to use at home.

To change the shape of the dimensions of a metal workpiece, you can use the electroerosive processing method. It has been used for many years in various industries, it is characterized by high accuracy but low productivity. For application this method processing, you should use a special electric spark machine, which can be purchased or made by yourself. Homemade version can be used in everyday life in small-scale production. Its cost of making it yourself will be lower than buying an industrial version. Therefore, let us consider in more detail how you can make the electric spark machine in question with your own hands, what is needed for this and in what cases it can be used.

The principle of the considered processing method

A feature of processing with an electric spark installation can be called the fact that the evaporation of the metal occurs due to the effect of a certain charge on the surface of the workpiece. An example of such an impact can be called the closure of a capacitor on a metal plate - a hole of a certain size is formed. EDM creates a high temperature that simply vaporizes the metal from the surface. It is worth noting that a machine from this group has already been used over the past 50 years in various industries. The main condition for using such an electric spark machine is that the workpiece must be made of a certain metal. In this case, it is not the degree of machinability that is taken into account, but the electrically conductive properties.

Main structural element

The EDM has a spark generator that acts as a capacitor. For processing, a large capacity storage element should be used. The principle of processing is to accumulate energy for a long time, and then release it over a short period of time. The device of the laser installation also works according to this principle: a decrease in the time interval for the release of energy leads to an increase in the current density, which means that the temperature rises significantly.

The principle of operation of the generator, which is installed on EDM machine, is as follows:

1. the diode bridge conducts rectification of industrial current with a voltage of 220 or 380 volts;
2. the installed lamp limits the short circuit current and protects the diode bridge;
3. the higher the load indicator, the faster the charging of the electric spark machine;
4. after charging is completed, the lamp will turn off;
5. having charged the installed accumulator, it is possible to bring the electrode to the workpiece being processed;
6. after the circuit is opened, the capacitor starts charging again;
7. The charging time of the installed storage element depends on its capacity. As a rule, the time interval is from 0.5 to 1 second;
8. at the moment of discharge, the current strength reaches several thousand amperes;
9. the wire from the capacitor to the electrode must have a large cross section, about 10 square millimeters. In this case, the wire must be made exclusively of copper.

The generation frequency when the electrode of the electric spark machine is connected is 1 Hz.

The design of the electric spark machine

There are schemes that are quite difficult to implement. The scheme under consideration can be implemented with your own hands. Parts for the installed generator are not in short supply, they can be purchased at a specialized store. Capacitors are also very common, as is the diode bridge. At the same time, when creating a home-made electric spark machine, the following points should be taken into account:

1. on the capacitor, the indicated voltage should not be less than 320 volts;
2. the number of energy storage devices and their capacity are selected taking into account the fact that the total capacity should be 1000 microfarads. All capacitors must be connected in parallel. It should be borne in mind that the power of a home-made version increases if it is necessary to obtain a stronger spark strike;
3. the lamp is installed in a porcelain cartridge. It is necessary to protect the lamp from falling, a circuit breaker is installed with a current strength of 2 to 6 Amperes;
4. the machine is used to turn on the circuit;
5. electrodes must have strong clamps;
6. a screw clamp is used for the negative wire;
7. The positive wire has a clamp with a copper electrode and a tripod for guiding.

Homemade wire version has a relatively small overall dimensions.

The main elements of the scheme of electrospark equipment

The scheme is represented by the following elements:

1. electrode;
2. clamp screw used to fix the positive wire and electrode;
3. sleeve for direction;
4. housing made of fluoroplast;
5. hole used to supply oil;
6. tripod.

The body, which is used to connect all the elements, is machined from fluoroplastic. A grounding pin is used as a bushing, in which a threaded hole is machined along the axis for attaching the electrode. All structural elements are mounted on a tripod, which is made with the possibility of changing the height. A hole is also created through which oil is supplied.

Often, cutting is carried out using a device that is powered by a starter with a coil connected to 220V. The starter rod can have a stroke of 10 millimeters. The starter winding is connected in parallel with the lamp. That is why at the time of charging the capacitors, the lamp is on, and after this process is completed, it goes out. After the stem has been lowered, a spark charge occurs.