Homemade electrical discharge machines. DIY electric spark machine

Processing metals of various levels of hardness with high precision is possible using unconventional methods. These include cutting, grinding and strengthening the surface using electrical erosion. The electroerosive machine was invented a long time ago, but has become widespread only in recent decades.

The first industrial-grade machine was created by CHARMILLES TECHNOLOGIES in 1952, and the CNC EDM machine appeared in 1969. Compared to traditional methods of metal processing - forging, casting, grinding, milling, the electric spark method can be considered innovative. The first mentions of forged and cast products are several thousand years old.

All metals are conductive substances, so electrical discharge machining is applicable to all types of alloys. With its help you can perform a wide range of work, ranging from ordinary cutting and drilling to:

• fine grinding;
• increasing the surface and restoring the configuration;
• hardening;
• copying;
• firmware;
• engraving;
• spraying.

Electroerosive equipment is based on the principle of the occurrence of a short-term electric arc, which leads to the loss of substance by the cathode and anode. With a short pulse, the substance is removed from the anode, with a longer pulse, from the cathode. Modern electroerosive machines use both types of pulses in their work. Both the working tool and the workpiece can be connected to the positive or negative pole.

The only condition that is observed in all types of machines is that only direct current is used. The voltage level and current strength depend solely on the parameters of the metal being processed. The frequency of occurrence of pulses is determined by the mechanical approach and distance of the electrode and the working surface - breakdown occurs only at a certain distance between the contact surfaces.

Electric pulse processing of metals aimed at destroying the workpiece (cutting or drilling) is carried out in a dielectric medium, which is a special liquid. The most commonly used are oil, kerosene or distilled water. Surfacing, strengthening or spraying operations are performed in air or vacuum.

Electrical discharge cutting of metal

This type of processing is used in cases where it is necessary to produce small-sized parts with complex contours with high precision edges, to produce parts from particularly hard alloys, and in jewelry. Limitations on the size of workpieces and the thickness of the processed material are determined only by the design of a particular machine. In most cases, electrical discharge cutting is used in industrial enterprises focused on large-scale production of high-precision parts that do not require further processing.

But without much difficulty, you can build an electrical discharge machine with your own hands, if you have some metalworking skills and a certain knowledge of electronics and electrical engineering. The design of a homemade electrical discharge cutting machine is simple and can be implemented even at home, not to mention in a metalworking workshop or workshop of a small enterprise.

But it should be taken into account that in home-made machines it is very difficult to realize the main advantages of electrical discharge machining - high accuracy and versatility. Refractory metals and alloys are cut very slowly and require high power consumption.

When cutting metal, the workpiece is connected to the positive pole of the current source, and the working electrode is connected to the negative pole. The loss of substance at the anode is nothing more than erosion, a cut, the thickness of which depends on the geometry of the cathode. The type of dielectric with which a certain type of EDM machine works also plays a big role.

For industrial production, two main types of equipment are used - an electroerosive wire cutting machine and an electroerosive piercing machine. The first type is used when processing large parts made of thick-walled metal, the second - for more precise work on copying parts made of high-strength materials or strict requirements for their shape.

Wire cutting machines

The electroerosive industrial wire-cutting machine operates on the non-contact principle of interaction between a conductive wire (molybdenum, tungsten or other refractory metal) with a diameter of 0.1-0.2 mm and the workpiece. You can process metal of any level of refractoriness in different thicknesses of the part. A positive pole is connected to the wire wound on rotating drums, which moves in two directions - vertically and towards the workpiece, and a negative pole is connected to the workpiece.

As the wire line moves, a discharge occurs that burns a line of the required configuration into the part. In essence, electrical discharge machining on a wire machine performs milling operations, but on metals of special strength and with precision that is unattainable with mechanical processing. This includes:

• ultra-small angles;
• rounding of microdiameters;
• maintaining parallelism of lines throughout the entire depth;
• high precision edge surfaces.

The processing accuracy reaches 0.110-0.012 mm.

Electroerosive piercing machines

Electric contact piercing processing of metals involves the action of a point electrode with a given cross-sectional shape, on which the shape of the erosion depression in the workpiece depends. They are used for processing:

• stainless steels;
• tool alloys;
• titanium;
• hardened steel.

But they can work with all types of conductive materials when it is necessary to make holes or recesses of great depth with a minimum diameter and precise cross-section geometry.

One of the most difficult operations of a piercing machine is the production of threaded holes in high-strength, refractory materials. In this case, only CNC machines are used. An electrode made of thin wire is inserted into the hole and moves in the longitudinal and transverse directions (along the X, Y axes, with simultaneous movement along the Z axis). The result is a hole with a complex wall configuration, threaded or other profile.

Electrical contact processing allows you to obtain high-precision impressions of stamps, molds or other small parts. In this case, the electrode is a miniature copy of the required product, made of copper or graphite. Depending on the polarity of the connection, clear depressions or equally clear protrusions are obtained on the workpiece. Such electroerosive machines are produced in both stationary and desktop versions (for example, G11 ARAMIS (Czech Republic)).

Homemade EDM machines

It is advisable to assemble a homemade electrical erosive machine if high-precision work with metal is performed frequently and in relatively large volumes. This is difficult-to-manufacture equipment that is rarely used in everyday life. It is justified in metalworking shops and workshops as a finishing tool for processing workpieces after milling or lathes or manufacturing small parts of complex configurations.

The operating principle of an electroerosive machine requires the manufacture of both an electronic circuit that generates a high-power pulse current, and a complex mechanical part that ensures the movement of the electrode (wire or piece). The main difficulty is to make a generator that can accumulate a charge sufficient for a breakdown in a short time, throw it out in a split second and restore it in an equally short period. If the current density is insufficient, electrical discharge machining is impossible even on thin parts made of soft metals.

The main parts of a homemade wire EDM machine:

• bed - cast iron or steel;
• desktop - durable plastic or stainless steel;
• dielectric bath, which serves as a working area;
• wire feeding system (two reels, electric motor, drive, guides);
• electrode control system (for piercing);
• start and stop system;
• dielectric pumping unit - pump, filters, pipelines;
• generator;
• control system.

The last point is one of the most difficult; it is necessary to synchronize the wire feed in speed and direction, the pulse frequency and the supply of dielectric fluid. It should be taken into account that during operation the liquid is ionized, and its properties change significantly.

Depending on the circuit of the machine generator, it uses very dangerous currents of 1-30A at a voltage of 220 V. The insulation of all conductive parts must be extremely reliable. You can see how a homemade machine works in the video, or here.

After analyzing various information from the Internet, we can conclude that only industrial machines are truly efficient. Homemade products are suitable for engraving, writing, and sawing thin sheets of metal, which can be done with a high-quality professional jigsaw.

To produce elements with a complex profile from difficult-to-cut metals, an electrical discharge machine is used. Its work is based on the impact of electric current discharges, which create a high temperature in the processing zone, causing the metal to evaporate. This effect is called electrical erosion. The industry has been using machines operating on this principle for more than 50 years.

Types of equipment and processing methods

The operation of an electrical discharge machine can be described as follows:: take a charged capacitor and bring its electrodes to a metal plate. During a short circuit, the capacitor discharges. A bright flash is accompanied by the release of energy (high temperature). At the point of closure, a depression is formed due to the evaporation of a certain amount of metal from high temperature.

Various types of generating electrical discharges are implemented on technological equipment . Among the main schemes are:

• electric spark;
• electrical contact;
• electric pulse;
• anodic-mechanical.

By implementing one of the schemes in practice, machines are manufactured. Based on the principle of electrical erosion, the following machines were produced in different modifications:

• cut-out;
• wire;
• stitched.

To obtain precise dimensions and automate the process, the equipment is equipped with computer numerical control (CNC).

An electric spark machine works using a spark generator. A generator is an energy storage device that provides an electrical impulse. For constant supply of pulses, a capacitor bank is organized.

To organize an electrical circuit, the cathode is connected to the actuator, and the anode is connected to the workpiece. A constant distance between the electrode and the workpiece guarantees uniformity of the process. When the electrode is lowered vertically onto the part, the metal is pierced and a hole is formed, the shape of which is determined by the shape of the electrode. This is how an EDM piercing machine works.

A wire EDM machine is used to produce parts from hard-alloy and difficult-to-machine parts. A thin wire acts as an electrode. When metal evaporates, oxides with a high melting point are formed on the surface of the workpiece. To protect against them, the process is carried out in a liquid medium or oil. During sparking, the liquid begins to burn, taking oxygen and other gases from the working area.

Machines of this type are sometimes the only possible way to manufacture a structural element. But buying EDM equipment for infrequent jobs is a wasteful endeavor. Therefore, if the need arises, you can make an electrical erosion machine with your own hands.

Features of a homemade device

Before you start making a homemade EDM machine, you need to understand its structure. The main structural elements include:

Manufacturing a spark generator

To make a spark generator, parts can be found everywhere (in old TVs, power supply monitors, etc.). The principle of its operation is as follows:

Safety precautions when working

Since organized do-it-yourself electrical erosion is associated with the possibility of electric shock, safety precautions must be approached with all responsibility. The workpiece must not be grounded. Otherwise, an emergency will occur - a short circuit in the supply network. Capacitors rated at 400 V can be lethal with only 1000 µF of capacitance.

Connecting devices eliminates contact with the housing. To connect the capacitor to the electrode, a copper wire with a cross section of 6-10 square meters is required. mm. Large volumes of oil used to prevent oxide formation may ignite and cause a fire.

Modern devices, machines, instruments and mechanisms consist of more complex parts when compared with devices that came out earlier. At this stage of technological progress, devices are required to perform large amounts of work. People tend to mechanize everything in order to simplify their daily lives, as well as to achieve new results in research or in fields such as construction, industry, and so on. Along with the complexity of the parts, their processing has become correspondingly more difficult.

Various devices are used to process parts. They differ in operating principle, purpose, and other aspects. But a huge number of specialists emphasize the advantage of using electrical discharge machines, which designed for processing various parts, and with very convincing results and indicators.

Purpose of electroerosive machines

Electroerosive machines are used to cut various workpieces of various shapes and sizes. Processing occurs either at a right angle or at an angle from 1 to 30 degrees. The angle at which workpieces are processed depends primarily on the configuration of the machine. The beginning of the cut can occur from the edge of the workpiece, as well as from the inside through a hole that is pre-drilled. Electroerosive machines are designed to produce parts with an accuracy of up to 0.015 millimeters.

The main purpose of electroerosive machines is considered to be the replacement of stamping. Machines of this type Can cut several pieces at once, thanks to the possibility of batch processing. In this case, subsequent milling of the part is not required, since during processing there is no surface deformation of the workpiece being processed.

The machine also allows you to produce various matrices and templates. One of its big advantages is that it can be easily and quickly reconfigured. In principle, the entire reconfiguration of an electroerosive machine consists of performing several operations: first you need to download the required drawing from AUTOCAD, then perform several actions on the computer, then set up the generator and after that you can begin processing the next workpiece. Experienced operators spend an average of only 15 minutes setting up the device.

Machines of this type consist of the following components:

Machine bed

This part is cast from cast iron. The internal stresses in the chamber are relieved. Internal space of the bed intended for installation of electrical equipment, since the bed itself is box-shaped. The working part of the bed is precision scraped and ground in some places, namely: on the drum carriage, on the column fastenings and on the work table guides.

Machine work table

This is a very important component of the EDM machine. The work table consists of two plates, which are mounted on ball-roller guides. The plates are installed one above the other.

If there is a need to move the table, then you need to use two stepper motors. This is done using two ball screws. Also you can change the position of the desktop manually, while using the feed wheel, which are still attached to the same ball screw shafts.

Wire conveyor

This part of the machine consists of a wire drum, as well as a system of roller guides, which are located in the lower and upper arms.

The control computer and generator can be placed either in a rack or in a desktop with a cabinet. The only differences are in the cost of the device, the monolithic layout, as well as in the design of all equipment.

Operating principle of an electrical discharge machine

After the design aspects of existing electrical discharge machines have been discussed above, it is necessary to understand the principle of their operation. It is impossible not to mention that the procedures for processing parts that are used on devices of this type allow one to achieve simply amazing results.

First, a few words about what electrical erosion is, because as the reader might have already guessed from the name of the machine, it is this reaction that is the basis of the operation of such devices.

The destruction of the top layer of the surface of a material under the influence of external influences carried out by electrical discharges is called electrical erosion. Exactly this process became the basis for processing various materials and parts, which is called electroerosive.

Electrical discharge machining itself is carried out by changing the size, shape, roughness and surface properties of the workpiece under the influence of electrical discharges as a result of electrical erosion affecting the workpiece during processing.

Due to the fact that very high temperatures operate in the discharge zone (8000 - 12000 degrees Celsius), the metal undergoes the following changes: heating, then subsequent melting and even partial evaporation. In order to obtain such high temperatures in the discharge zone, a large concentration of energy is created, which is achieved thanks to an electrical pulse generator. The electrical discharge machining process itself takes place in a working fluid, namely distilled water. It fills the space between the existing electrodes. One of these electrodes is the workpiece itself, and the second is the tool electrode (tubular electrode).

Under the influence of forces that arise in the discharge channel, as well as due to the fact that the electrode rotates rapidly, liquid and vaporous metal is released from the discharge zone into the surrounding working fluid, and then it solidifies in it with the formation of separate small parts. A hole is formed in the workpiece under the action of a current pulse. Besides, you can observe the waste of the electrode-tool, occurring parallel to the formation of the hole.

It should be noted that the electrode tool must be made of a material with high erosion resistance. Such materials that have such an important quality and that can ensure the stability of the electrical erosion process are: tungsten, graphite, aluminum, brass, copper and graphite materials. Typically, these machines use copper or brass tubular electrodes.

Parameters that affect processing speed and accuracy

In order to understand even better the operation of electrical discharge machines and influence its quality, you can specify several important parameters, which directly affect the accuracy and speed of the processing process:

In addition to the above parameters, one more can be named, which can also have a great influence on the electrical discharge machining process. This parameter is the position of the universal cartridge for attaching electrodes, namely the straightness of its location relative to the X-axis. Therefore, the user of the machine It is strongly recommended to check the cartridge on a regular basis.

EDM Capabilities

After all the intricacies of the processing process on an electrical discharge machine have been discussed, we can mention the capabilities of this very useful device, with such impressive functionality.

Electroerosive machine:

conclusions

EDM machines are very useful devices that are capable of doing very complex work. The huge number of users who process various materials on machines of this type testify in favor of such equipment, which has proven itself to be the best.

A number of advantages, as well as an atypical operating principle, which allows achieving outstanding results when processing various workpieces, make this processing equipment a real titanium among devices of other types, but also intended for processing various workpieces.

The ease of operation of electroerosive machines allows them to work even for those users who previously had no experience or certain skills in working with the same equipment.

The principle of operation of electroerosive machines, which consists in the use of electrical erosion for processing workpieces, allows one to achieve very high-quality results.

To change the shape and size of a metal workpiece, you can use the electrical discharge processing method. It has been used for many years in various industries, characterized by high accuracy but low productivity. To apply this processing method, you should use a special electric spark machine, which you can purchase or make yourself. The homemade version can be used in everyday life in small-scale production. The cost of making it yourself will be lower than purchasing an industrial version. Therefore, let’s take a closer look at how you can make the electric spark machine in question with your own hands, what you need for this and in what cases it can be used.

Homemade electric spark machine

The principle of the considered processing method

A special feature of processing with an electric spark unit is that the evaporation of metal occurs due to the effect of a certain charge on the surface of the workpiece. An example of such an effect is the short circuit of a capacitor on a metal plate - a hole of a certain size is formed. EDM creates a high temperature that simply evaporates 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 machine has a spark generator that acts as a capacitor. For processing, a large capacity storage element should be used. The processing principle is to store energy over a long period of time and then release it over a short period of time. The laser device also works on this principle: reducing the time period of energy release leads to an increase in current density, which means the temperature increases significantly.

Electrical circuit of an electric spark installation

The operating principle of the generator, which is installed on an electrical discharge machine, is as follows:

1. the diode bridge rectifies 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 complete, the lamp will go out;
5. Having charged the installed storage device, you can bring the electrode to the workpiece;
6. after the circuit is opened, the capacitor begins to charge again;
7. The charging time of the installed storage element depends on its capacity. Typically, the time period is from 0.5 to 1 second;
8. at the moment of discharge the current reaches several thousand amperes;
9. the wire from the capacitor to the electrode should 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 is supplied to an electric spark machine is 1 Hz.

Design of an electric spark machine

There are schemes that are quite difficult to implement. The scheme in question 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 widespread, as is the diode bridge. At the same time, when creating a homemade 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 that the total capacity should be 1000 μF. All capacitors must be connected in parallel. It is worth considering that the power of a homemade version increases if it is necessary to obtain a stronger spark strike;
3. The lamp is installed in a porcelain socket. The lamp should be protected from falling; a circuit breaker with a current strength of 2 to 6 Amperes is installed;
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 direction.

The homemade wire version has relatively small overall dimensions.

Homemade electric spark machine

Basic elements of the electrical spark equipment circuit

The diagram is represented by the following elements:

1. electrode;
2. a clamp screw used to secure the positive wire and electrode;
3. guide bushing;
4. body made of fluoroplastic;
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 ability to change height. A hole is also created through which oil is supplied.

Electric spark machine diagram

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

If you find an error, please select a piece of text and press Ctrl+Enter.

stankiexpert.ru

Do-it-yourself machine for electrical discharge machining of metals

An electrical discharge machine is designed for cutting metal parts of complex shapes. Modern piercing equipment makes it possible to process conductive material along four axes at once, producing products of any shape, even from hard alloys that are difficult to machine.

Capabilities of EDM machines

wire EDM machine

The electroerosive machine copes with complex technological tasks:

• making recesses and holes of complex configuration, including blind openings;
• processing of titanium, tool and alloy steels, hard alloys and hardened steel of the highest hardness;
• making recesses of various configurations on the internal surfaces of the part;
• threaded holes in hard metal workpieces;
• production of parts that is impossible or difficult on computer-controlled lathes and milling machines.

Types of processing

There are several types of electrical discharge machining:

• combined - performed simultaneously with other types of processing;
• electroerosive abrasive - the material is destroyed by electricity and polished with abrasive particles;
• electrochemical - the metal dissolves in an electrolyte under the influence of current;
• anodic-mechanical - the metal dissolves with the appearance of a film of oxides, combined with the electrical erosion method;
• hardening;
• volumetric copying is a processing method that allows you to obtain a projection of a tool on a blank;
• marking;
• grinding - metal is polished under the influence of electricity;
• piercing - the tool cuts into the blank and forms a hole;
• cutting - the electrode tool makes feeding movements and constantly rewinds, removing the top layers of the workpiece, creating the required shape;
• cutting - dividing a blank into separate pieces;
• fine-tuning

Operating principle of the machine

Primary processing of the blank and removal of the main volumes of material occurs on a CNC lathe or milling machine. The principle of operation of electroerosive equipment is that the metal is processed by current discharges appearing between the workpiece and the tool. A stretched wire is used as a cutter.

The generator releases current in pulses without changing the properties of the working medium. When a voltage above critical appears between the electrodes, a plasma channel is formed, destroying the surface of the workpiece. A small notch appears. The polarity of the current is selected in such a way that the part is destroyed more strongly.

In order to reduce cutter wear, unipolar electrical pulses are created. Depending on the pulse length, the polarity is selected, since with a short duration the negative electrode wears out faster, and with a longer duration the cathode wears out. In fact, during processing, both principles of creating unipolar electrical pulses are used: an alternating positive charge and a negative charge are applied to the blank. Water reduces the temperature of the tool (wire) and carries away destruction products.

Under the influence of high-frequency pulses, erosion occurs evenly along the length of the gap, gradually widening the narrowest point. Gradually, the tool (wire) or part is moved in the required direction, increasing the area of ​​influence. A part made of any material that allows electricity to pass through can be processed using this principle.

Processing time depends on the physical properties of the material (electrical conductivity, thermal conductivity, melting point). The faster the work is done, the more roughness remains on the surface. The best effect is achieved by multi-pass processing with decreasing pulse power.

Machine design

Main elements of an electrical discharge machine:

• bed - made of special, highly durable cast iron, which gives strength and stability to the structure.
• desktop - rectangular stainless steel;
• stainless steel working bath;
• The wire feeder consists of drive reels (ceramics), wire guides and a drive system;
• automatic wire installation device (installed at the request of the customer);
• the dielectric block consists of cardboard or paper filters, a dielectric container and a container for the ion exchange mass, and a pump for driving water;
• an anti-electrolysis generator is used, which prevents the destruction of the workpiece;
• numerical control system with display.

Making a machine with your own hands

spark generator circuit

The main difficulty in making a machine with your own hands is assembling the spark generator. Over some time, it must accumulate a sufficient amount of electricity and throw it out in one gulp. It is necessary to achieve the shortest possible current surge so that its density is as high as possible. You can either pull out the components for it from an old TV yourself or buy it.

diagram of a homemade machine: 1 - electrode; 2 - electrode clamp screw; 3 - positive contact clamp screw; 4 - direction bushing; 5 - fluoroplastic body; 6 - opening for oil inflow; 7 - tripod

The capacitor must withstand 320 V, with a total capacity of 1 thousand uF. All parts are assembled in an insulated fluoroplastic box. You can make a guide sleeve for the electrode from the grounding pin of the Euro socket. It is moved forward as it evaporates, for which the clamp screw is loosened. The tripod for mounting the entire device must be height-adjustable. A tube is inserted into the hole for oil inflow, and the direction bushing drips oil along the longitudinal line of the electrode.

A drive (starter with a 230V coil) is connected to the electrode. The stroke of the rod fixes the depth of the hole. While the capacitors are charging, the lamp turns on and the starter rod is held inside. As soon as the capacitors are sufficiently charged, the lamp goes out and the rod moves down. He touches the workpiece and a discharge occurs in the form of a spark, the cycle repeats. The repetition frequency depends on the lamp power.

During operation, the oil may ignite. It is important to follow safety precautions! After all these steps, we will get a self-made erosion machine.

The video demonstrates the capabilities of the EDM machine:

stanokgid.ru

How to do it. - Erosion machine.

HOW TO MAKE AN ELECTRIC SPARK MACHINE

(garage)

I bought this tripod for the price of scrap. And I had a headache for a long time about what to do with it. As they say, the time has come. All this is being done so that small chill molds can be made in garage conditions. But to achieve good results you need to work hard and try hard.

The tripod itself. I started making the head. The head consists of el. coils, yoke and damper device.

The lower part of the head, with two screws, for attaching the soft insert and the electrode. The upper part of the head consists of a U-shaped bracket with a bolt for adjusting the springs. The yoke to the middle of the coil consists of iron and the extension is made of textolite. At the end there is a washer and between the washer there are two springs.

Head assembled. There is a groove in the iron part along the yoke into which we screw the stopper.

At the bottom of the bed I made a tray for kerosene. I collected according to this scheme. But the capacitor that stands between the working electrodes is selected during operation. Its capacity depends on many factors.

I assembled the electrical circuit in such a housing. But just in case, I placed everything on the left side of the cabinet. I left half the empty space for an electronic generator for the future.

To test the machine, I made the following electrode from bronze. Ready electrode.

Left a trace. It's far from perfect, but we'll work on it.

This should only happen with an electronic generator.

View work.

cazac.ucoz.com

Small-sized electric spark machine

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

The essence of the electric spark machining process is the destruction of the workpiece material under the influence of a pulsed electric discharge. Due to the small working surface area of ​​the tool, a large amount of heat is released at the discharge site, which melts the substance of the workpiece. The processing process most effectively occurs in a liquid (for example, kerosene), which washes the contact point between the vibrating tool and the part and carries away erosion products. The tools are 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 electrical circuit diagram of the installation is shown in Fig. 2. The installation works as follows. Discharge capacitor C1 is connected by its positive terminal to the workpiece 1. Its negative terminal is connected to tool 2. Electromagnetic vibrator 3 imparts continuous oscillations to the tool. This ensures constant sparking at the point of contact and prevents the possibility of welding the tool to the workpiece. The workpiece 1 is fixed in a clamping device 4, which has reliable electrical contact with the bath 5.

The power transformer is assembled on an Ш32 core made of ordinary transformer steel. Set thickness 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 there is a shielding winding III, consisting of one layer wound with PEV 0.18 wire. The capacity of the discharge capacitor is 400 μF (two capacitors of type KE-2 200 x 50 V). Rheostat R1 is designed for a current of 3-5 A. This rheostat is wound with nichrome wire with a diameter of 0.5-0.6 mm on a resistance VS-2.

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

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

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

Photo instructions included.

Erosion machine.pdf (542 kB)

An electrical discharge machine is designed for cutting metal parts of complex shapes. Modern piercing equipment makes it possible to process conductive material along four axes at once, producing products of any shape, even from hard alloys that are difficult to machine.

Capabilities of EDM machines

The electroerosive machine copes with complex technological tasks:

• making recesses and holes of complex configuration, including blind openings;
• , tool and alloy steels, hard alloys and hardened steel of the highest hardness;
• making recesses of various configurations on the internal surfaces of the part;
• threaded holes in hard metal workpieces;
• production of parts that is impossible or difficult on computer-controlled lathes and milling machines.

Types of processing

There are several types of electrical discharge machining:

• combined - performed simultaneously with other types of processing;
• electroerosive abrasive - the material is destroyed using electricity and polished with abrasive particles;
• electrochemical - the metal dissolves in an electrolyte under the influence of current;
• anodic-mechanical - the metal dissolves with the appearance of a film of oxides, combined with the electrical discharge method;
• hardening;
• volumetric copying is a processing method that allows you to obtain a projection of a tool on a blank;
• marking;
• grinding - metal is polished under the influence of electricity;
• piercing - the tool cuts into the blank and forms a hole;
• cutting - the electrode tool makes feeding movements and constantly rewinds, removing the top layers of the workpiece, creating the required shape;
• cutting - dividing the blank into separate pieces;
• fine-tuning

Operating principle of the machine

Primary processing of the blank and removal of the main volumes of material occurs on a CNC lathe or milling machine. The principle of operation of electroerosive equipment is that the metal is processed by current discharges appearing between the workpiece and the tool. A stretched wire is used as a cutter.

The generator releases current in pulses without changing the properties of the working medium. When a voltage above critical appears between the electrodes, a plasma channel is formed, destroying the surface of the workpiece. A small notch appears. The polarity of the current is selected in such a way that the part is destroyed more strongly.

In order to reduce cutter wear, unipolar electrical pulses are created. Depending on the pulse length, the polarity is selected, since with a short duration the negative electrode wears out faster, and with a longer duration the cathode wears out. In fact, during processing, both principles of creating unipolar electrical pulses are used: an alternating positive charge and a negative charge are applied to the blank. Water reduces the temperature of the tool (wire) and carries away destruction products.

Under the influence of high-frequency pulses, erosion occurs evenly along the length of the gap, gradually widening the narrowest point. Gradually, the tool (wire) or part is moved in the required direction, increasing the area of ​​influence. A part made of any material that allows electricity to pass through can be processed using this principle.

Processing time depends on the physical properties of the material (electrical conductivity, thermal conductivity, melting point). The faster the work is done, the more roughness remains on the surface. The best effect is achieved by multi-pass processing with decreasing pulse power.

Machine design

Main elements of an electrical discharge machine:

• bed - made of special, highly durable cast iron, which gives strength and stability to the structure.
• desktop - rectangular in stainless steel;
• stainless steel working bath;
• The wire feeder consists of drive reels (ceramics), wire guides and a drive system;
• automatic wire installation device (installed at the request of the customer);
• the dielectric block consists of cardboard or paper filters, a dielectric container and a container for the ion exchange mass, and a pump for driving water;
• an anti-electrolysis generator is used, which prevents the destruction of the workpiece;
• numerical control system with display.

Making a machine with your own hands

The main difficulty in making a machine with your own hands is assembling the spark generator. Over some time, it must accumulate a sufficient amount of electricity and throw it out in one gulp. It is necessary to achieve the shortest possible current surge so that its density is as high as possible. You can either pull out the components for it from an old TV yourself or buy it.



diagram of a homemade machine: 1 - electrode; 2 — electrode clamp screw; 3 — positive contact clamp screw; 4 — direction bushing; 5 — fluoroplastic body; 6 — opening for oil inflow; 7 - tripod

The capacitor must withstand 320 V, with a total capacity of 1 thousand uF. All parts are assembled in an insulated fluoroplastic box. You can make a guide sleeve for the electrode from the grounding pin of the Euro socket. It is moved forward as it evaporates, for which the clamp screw is loosened. The tripod for mounting the entire device must be height-adjustable. A tube is inserted into the hole for oil inflow, and the direction bushing drips oil along the longitudinal line of the electrode.

A drive (starter with a 230V coil) is connected to the electrode. The stroke of the rod fixes the depth of the hole. While the capacitors are charging, the lamp turns on and the starter rod is held inside. As soon as the capacitors are sufficiently charged, the lamp goes out and the rod moves down. He touches the workpiece and a discharge occurs in the form of a spark, the cycle repeats. The repetition frequency depends on the lamp power.

During operation, the oil may ignite. It is important to follow safety precautions! After all these steps, we will get a self-made erosion machine.

The video demonstrates the capabilities of the EDM machine: