From the beginning of the seventies of the last century, cutting-off electric tools from Bulgaria were supplied to the territory of the USSR and other countries. It was of good quality and was popular, for which it received the short name "Bulgarian".

Since then, it has been much clearer to a Russian person than the technical term - angle grinder or angle grinder for short. Thanks to a simple device and useful features, an angle grinder is necessary home master to renovate an apartment with your own hands.

How to choose it for your tasks, taking into account the performance of specific work, we explain in this article.

Purpose

The grinder was originally created for grinding surfaces. But due to significant design upgrades, it quickly began to perform such useful functions as cutting and processing any building materials, including cement, concrete, brick, tile, slate and all kinds of metals.

According to the methods of performing the work, the angle grinder, like the entire power tool, is created for operation in one of two modes:

1. permanent work in construction conditions with overcoming maximum loads during a full work shift - professional models;
2. for single use with the organization of breaks at nominal loads - a household tool.

This is one of the important differences to consider when buying. It affects the cost of the grinder.

Professional Models

In order for the tool to work for a long time in extreme conditions and be at the same time convenient, manufacturers use all sorts of technical tricks. For example, to slightly reduce the dimensions of the motor and its weight for the stator and rotor windings, an isolated copper wire not the usual round section, but in the shape of a square.

Even the composition of the plastic for the case is selected in such a design that when heated to 140 ° C, it does not transfer heat to the operator's hands and at the same time does not lose its strength.

Expensive models of grinders have:

• vibration-protective inserts on the handles, preventing the development of occupational diseases;
• quick-clamping nuts SDS, allowing you to install working bodies without using a special key;
• swivel rear handle;
• the function of turning the gearbox or the ability to rearrange the front handle in one of three positions;
• special design of bearings, providing balancing of the working body;
• long power cord with a protective layer of durable insulation;
• the ability to control the number of revolutions of the working circle and a number of other useful functions.

household tool

Bulgarians of this class are inferior in their characteristics to a professional tool. However, they are issued under strict technical standards, meet safety standards, allow you to work with breaks.

Device and principle of operation

After connecting the power cord to the mains voltage and turning on the start button, the rotor of the electric motor begins to rotate. The gear transmission at its end transmits the torque to the working circle.

When rotating under load, the disc material is subjected to significant loads and if the rules for handling it were violated during storage, it can shatter into pieces.

Automatic wheel balancing

Wear of the working surface does not always occur evenly. On the outside, due to impacts and uneven loads, small potholes are formed that create beats. This is most characteristically manifested on cutting wheels of large diameter.

Such a function facilitates the work of the operator, allows you to do it better. The presence of auto-balancing indicates the prestige of the grinder model.

Protection against accidental activation

When the mains voltage fails for various reasons and the grinder is re-powered, an unplanned engine start occurs, which causes injury or equipment damage. The manufacturers warned the occurrence of such an unpleasant situation by creating an appropriate blocking.

Motor protection against electrical overloads

For its implementation, control is used for:

1. current flowing in the motor circuit;
2. winding temperature;
3. or both of these options.

Such protection can only signal to the operator that the load is exceeded by lighting up the light or reduce the performance of the grinder by reducing the speed or completely stopping the engine.

Among workers who strive at any cost to quickly perform work at increased loads, this function causes irritation. But in general, it allows you to save the resource of the tool and consumable circles.

Motor overload protection in case of accidental jamming of the wheel

During an abrupt stop of the circle with the engine running, a strong mechanical shock is transmitted to the latter, which is also felt by a sharp jerk from the operator's hands. Different manufacturers use their own technical solutions for smoothing impact. Three options are common technical solution working on the basis of mechanics:

1. slip safety clutch;
2. centrifugal clutch;
3. spring construction SJS.

slip clutch

The design includes several disks that engage the driven gear with the spindle. They provide adjustable torque transmission force. When exceeding nominal value the rotor continues to rotate, and the working body stops.

The engine in this situation is under load, but it is less than during jamming.

Centrifugal clutch

The work is based on the transmission of torque due to the petals, providing traction from the action centrifugal forces. Torque is transmitted to the working body when the rotor rotates and is removed when it stops.

SJS function

A clutch made using this original technology is used in Makita angle grinders. It prevents the effect of shock due to the spring pressing the small bevel gear. This smooths out the push, and at the same time reduces vibration, ensures smooth running of the working body.

For some expensive models of angle grinders, engine protection during overloads is carried out by removing the voltage from the built-in electronic circuit.

Switch fixation

This useful feature designed to use the tool when it is stationary in the holding mechanism and the supply of the treated surface to the working body. But we do not recommend using it in order to remove your finger from the button and conveniently cut it.

If the disc jams in the material being processed, then it can shatter into pieces, and the grinder will jump out of your hands. The engine from the fixed switch will work. Try to stop him in this situation.

Dust protection

When cutting or grinding, a cloud forms around the circle smallest particles processed material. It penetrates through the slots of the housing, settles on bearings, brushes, a collector motor, changes the electrical resistance of current-carrying circuits up to the creation of a coil circuit. For dust control:

• fine-mesh nets or filters on vents;
• armored stator windings and rotor cord bandage;
• closed type bearings;
• windings filled with epoxy resins;
• case of increased tightness.

Automatic switch-off of brushes

The function works on expensive models, allows you to control the tension of the contact surfaces of the brushes to the collector plates of the rotor, and save the life of the engine.

For its implementation, a spring-loaded dielectric pin is introduced into the brush design. It controls the degree of wear of the carbon electrode and, with a critical decrease of more than 2/3 of the length, presses the brush contact from the collector.

The self-shutdown mechanism of the brushes also works when an overestimated potential is applied to the angle grinder when zero breaks, protecting the motor by breaking the current circuit.

Dust removal

Try chasing a concrete slab in indoors, and you will immediately appreciate the dust cloud that is generated during operation. A professional tool has a flange to which it is connected construction vacuum cleaner, which picks up debris directly from under the working body and discharges it into the dust collector through a hose.

The feature is very useful. But to perform single work around the house, such a grinder is quite expensive. However, you can purchase a special casing for this purpose.

Inner diameter has a built-in metal ring. It is the base for installation on the sleeve and its surface provides precise centering relative to the axis of rotation due to four protruding teeth.

The side surface of the ring serves to hold it on the surface of the circle. It is not a base surface that provides pressing the disk inside the flange, if only for the reason that cutting wheel may have a thickness of 1 mm, and the recess in the flange and nut is of the order of three.

The circle is pressed against the annular protrusion of the flange with its end surface due to the force of screwing the nut, and is held by the plane that creates the greatest moment of resistance - on the periphery.

On the side of the circle is a picture with technical characteristics. The inner ring, like the picture, can be applied on both sides or on one side. This marking is set by the manufacturer not for installing a disk, but for other purposes. However, some workers mistakenly believe that it is a reference point in the direction of rotation.

Where to direct the sparks

According to the laws of inertia, fragments fly from a rotating circle. Their high temperature can burn through the material of clothing, cause skin burns. If the circle jams in the part being cut off, then it can fall apart into parts that will fly in the same way. To protect the worker on the grinder, a metal casing is installed.

When working, the tool should always be positioned so that at any moment of the occurrence of a non-standard situation, the protective casing ensures its function as much as possible - it protects the human body from sparks and fragments.

Brush condition monitoring

Lifetime

The service life of carbon electrodes as reliable current leads is approximately 80÷120 hours of operation. After this period, wear occurs, they must be changed.

Signs of the formation of defects on the contacts are:

• the appearance of sparks forming a circular beam on the collector;
• a noticeable decrease in engine power;
• obvious development of the length of the carbon rods or the formation of chips on the surface of their fit.

Clamping force

Factory setting ensures optimal contact force between brush and commutator plates. If the brush assembly is worn out or incorrectly replaced, it may be disturbed in the direction of increasing or decreasing contact.

Increased pressure

Excessive pressure of the hard brush on the soft material of the commutator plate is created, leading to excessive heating of the engine parts.

Down pressure

There is an additional electrical resistance on the contacts, which does not provide a reliable current flow when switching the windings located on the rotor. A spark discharge appears that can develop into an arc that damages the brush assembly, collector, and motor.

Therefore, when replacing brushes, it is necessary to control their force, use original spare parts of the manufacturer.

Almost every craftsman who often works with metal knows the electrical circuit of an angle grinder. The grinder is a tool that is most often used for cutting metal. This tool is a source of increased danger, therefore, before each use, check the serviceability of the electrical and mechanical components of the structure.

The angle grinder, which in the post-Soviet territory is called the “Bulgarian”, was the dream of every home craftsman 3-4 decades ago. 30-40 years ago, this working tool was produced by one manufacturer, the Eltos-Bulgarian plant, located on the territory of Bulgaria in the city of Plovdiv. At the moment, manufacturers offer consumers various models and modifications of this tool, but the main components of the design have not changed much. Most of the structural elements on various models and modifications differ only in size.

The electrical component of the grinder design

For the entire period of its existence appearance instrument remained virtually unchanged. The grinder has an elongated body in which an electric drive and a gearbox are mounted. A handle is fixed on the side surface of the tool to hold the tool in the working position; additionally, to protect the master, a protective cover is fixed on the tool body, covering the working element.

The grinder, like any tool, can fail during operation. In most cases, troubleshooting requires simple repair working equipment, its electrical component.

In order to make repairs, you need to know the device not only of the mechanical part, but also the electrical circuit of the tool. For quality repair you should study the principle of the grinder. The electrical circuit of the angle grinder includes the following structural elements:

• anchor;
• collector;
• electric brushes;
• reducer;
• stator;
• start and lock button;
• power cable with a plug for connecting to a household network.

Each of the components is designed to perform certain functions in the electrical circuit, and a malfunction of any of them leads to a stop in the functioning of the device. For example, an armature is a rotating element of an electrical circuit. It provides the transmission of rotational motion to the grinding disc. In order for the tool to function properly, the armature must rotate at high speed. The higher the rotation speed of this structural element, the higher the power of the device.

Functions performed by the structural components of the angle grinder

The collector is an anchored platform to which all power and control cables are led. The task of the collector is to conduct the signals passing through the windings to the engine and the control unit. When removing the housing cover, the collector immediately catches the eye by the presence of polished plates, which are large in size.

Electric brushes in the design of the device are used to transmit electric current to the collector from power cable. In the process of operation, if the brushes are in a normal technical condition, then through the ventilation openings of the housing, a uniform glow is visible. If the glow in the process of turning on the device is not observed or has a pulsating character, then this is a sign of problems with this electrical component of the device.

The gearbox is one of critical components designs. Its purpose is to transfer the rotational energy from the rotating armature to the grinding disc, providing it rotary motion. The gearbox is responsible for the frequency and power of rotation of the working tool of the grinder.

The stator is a technically complex unit of the device design. The stator design includes windings, which, when interacting through magnetic field with armature windings set the latter in motion. The stator coils have a certain number of turns, calculated in accordance with the requirements of electrical engineering. If this unit fails, rewinding of the coils is required. This operation requires certain knowledge and skills. It is better to entrust the rewinding of the stator to a workshop specialist.

Schematic diagram of the grinder device

In the process of carrying out repairs, it is not enough to know the purpose of the main structural elements of the electrical circuit of the tool, you must also be able to read it. The electrical circuit of the angle grinder is not very complicated. However, even such a design in some cases during the repair can cause difficulties.

The electrical circuit of the grinder is arranged in a certain way. Two stator coils are connected in series through a cable to a household network with a voltage of 220 V. These coils are not electrically connected to each other. The switching on and off of these windings is carried out mechanically using a switch. This switch is mechanically connected to the start button. Each of these windings is connected through a switch contact to a corresponding graphite brush.

Further, the electrical circuit with the help of two windings connected in parallel to the graphite brushes goes to the rotor coils. The circuit closes at the collector terminals. The armature winding contains a large number of separate small windings, but only two are connected to graphite brushes.

Most often, the grinder fails precisely because of breakdowns of its electrical components and a break in the electrical circuit.

To diagnose and identify faults in the electrical circuit, a special device is used - a multimeter. This device may be required not only to test the performance of the grinder, but also any other electrical tool or device.

It is most convenient to start diagnosing from the electric current input section. The check is carried out in stages, checking and ringing each of the elements of the electrical circuit of the device.

Minor repair grinder

If, after pressing the start button, the tool does not start, it is likely that the cause of the breakdown is a small malfunction that can be fixed. on your own. Diagnosis is best done in order from simple to complex. Most often, the place of a break in the electrical circuit is the section from the power supply to the graphite brushes. During the repair process, remove the casing and test the circuit in the area where the electric current is supplied to the start button. If there is no current supply to the button terminals, then the supply cable should be replaced.

If the electric current is supplied to the start button, but is not transported further, then the tool breakage consists in the failure of the start button. If the button fails, it must be replaced. For this purpose, carefully disassemble the trigger and replace the start button. When connecting, Special attention turn to the terminals, as their incorrect connection can lead to burnout of the instrument windings.

Replacement of graphite brushes

The failure of graphite brushes is one of the most common breakdowns of an angle grinder.

The service life of this structural element of the tool is about 1.5-2 years. The brush replacement process does not represent special difficulties. To replace these structural elements, you will need to open the tool case. After opening the case with a screwdriver, the brush holders, which are fixed on the collector, are lifted and shifted.

Brushes should be replaced only with branded ones purchased in special stores. Upon purchase new brush it should be compared with the original, which is extracted from the instrument. New brush must completely, in all respects, coincide with the one extracted from the grinder. After installing new brushes, you should check the smoothness of its movement.

After installing and checking the smooth movement of the brush, it is fixed with a brush holder. After fixing the brush holder, the tool body is closed.

Replacing brushes is the only operation that should be carried out on your own during the repair process; it is better to entrust other types of repairs to specialists.

Schematic diagram of an angle grinder

Almost every craftsman who often works with metal knows the electrical circuit of an angle grinder. The grinder is a tool that is most often used for cutting metal. This tool is a source of increased danger, therefore, before each use, check the serviceability of the electrical and mechanical components of the structure.

Schematic diagram of an angle grinder.

The angle grinder, which in the post-Soviet territory is called the “Bulgarian”, was the dream of every home craftsman 3-4 decades ago. 30-40 years ago, this working tool was produced by one manufacturer, the Eltos-Bulgarian plant, located on the territory of Bulgaria in the city of Plovdiv. At the moment, manufacturers offer consumers various models and modifications of this tool, but the main components of the design have not changed much. Most of the structural elements on various models and modifications differ only in size.

The electrical component of the grinder design

For the entire period of its existence, the appearance of the instrument remained practically unchanged. The grinder has an elongated body in which an electric drive and a gearbox are mounted. A handle is fixed on the side surface of the tool to hold the tool in the working position; additionally, to protect the master, a protective cover is fixed on the tool body, covering the working element.

The device is an ordinary grinder.

The grinder, like any tool, can fail during operation. In most cases, to eliminate breakdowns, the simplest repair of working equipment, its electrical component, is required.

In order to make repairs, you need to know the device not only of the mechanical part, but also the electrical circuit of the tool. To carry out a quality repair, you should study the principle of operation of the angle grinder. The electrical circuit of the angle grinder includes the following structural elements:

• anchor;
• collector;
• electric brushes;
• reducer;
• stator;
• start and lock button;
• power cable with a plug for connecting to a household network.

Each of the components is designed to perform certain functions in the electrical circuit, and a malfunction of any of them leads to a stop in the functioning of the device. For example, an armature is a rotating element of an electrical circuit. It provides the transmission of rotational motion to the grinding disc. In order for the tool to function properly, the armature must rotate at high speed. The higher the rotation speed of this structural element, the higher the power of the device.

Functions performed by the structural components of the angle grinder

Anchor grinder device.

The collector is an anchored platform to which all power and control cables are led. The task of the collector is to conduct the signals passing through the windings to the engine and the control unit. When removing the housing cover, the collector immediately catches the eye by the presence of polished plates, which are large in size.

Electric brushes in the design of the device are used to transmit electric current to the collector from the power cable. In the process of operation, if the brushes are in a normal technical condition, then through the ventilation openings of the housing, a uniform glow is visible. If the glow in the process of turning on the device is not observed or has a pulsating character, then this is a sign of problems with this electrical component of the device.

The gearbox is one of the most important components of the design. Its purpose is to transfer the rotational energy from the rotating armature to the grinding disc, ensuring its rotational movement. The gearbox is responsible for the frequency and power of rotation of the working tool of the grinder.

The stator is a technically complex unit of the device design. The stator design includes windings, which, when interacting with the armature windings through a magnetic field, set the latter in motion. The stator coils have a certain number of turns, calculated in accordance with the requirements of electrical engineering. If this unit fails, rewinding of the coils is required. This operation requires certain knowledge and skills. It is better to entrust the rewinding of the stator to a workshop specialist.

Schematic diagram of the grinder device

The internal structure of the grinder.

In the process of carrying out repairs, it is not enough to know the purpose of the main structural elements of the electrical circuit of the tool, you must also be able to read it. The electrical circuit of the angle grinder is not very complicated. However, even such a design in some cases during the repair can cause difficulties.

The electrical circuit of the grinder is arranged in a certain way. Two stator coils are connected in series through a cable to a household network with a voltage of 220 V. These coils are not electrically connected to each other. The switching on and off of these windings is carried out mechanically using a switch. This switch is mechanically connected to the start button. Each of these windings is connected through a switch contact to a corresponding graphite brush.

Further, the electrical circuit with the help of two windings connected in parallel to the graphite brushes goes to the rotor coils. The circuit closes at the collector terminals. The armature winding includes a large number of separate small windings, but only two are connected to the graphite brushes.

Most often, the grinder fails precisely because of breakdowns of its electrical components and a break in the electrical circuit.

To diagnose and identify faults in the electrical circuit, a special device is used - a multimeter. This device may be required not only to test the performance of the grinder, but also any other electrical tool or device.

It is most convenient to start diagnosing from the electric current input section. The check is carried out in stages, checking and ringing each of the elements of the electrical circuit of the device.

Minor repair grinder

Causes of a malfunction of the grinder.

If, after pressing the start button, the tool does not start, it is likely that the cause of the breakdown is a small malfunction that can be fixed on your own. Diagnosis is best done in order from simple to complex. Most often, the place of a break in the electrical circuit is the section from the power supply to the graphite brushes. During the repair process, remove the casing and test the circuit in the area where the electric current is supplied to the start button. If there is no current supply to the button terminals, then the supply cable should be replaced.

If the electric current is supplied to the start button, but is not transported further, then the tool breakage consists in the failure of the start button. If the button fails, it must be replaced. For this purpose, carefully disassemble the trigger and replace the start button. When connecting, pay special attention to the terminals, as their incorrect connection can lead to burnout of the instrument windings.

Replacement of graphite brushes

The failure of graphite brushes is one of the most common breakdowns of an angle grinder.

The service life of this structural element of the tool is about 1.5-2 years. The process of replacing brushes is not particularly difficult. To replace these structural elements, you will need to open the tool case. After opening the case with a screwdriver, the brush holders, which are fixed on the collector, are lifted and shifted.

Brushes should be replaced only with branded ones purchased in special stores. When purchasing a new brush, it should be compared with the original, which is removed from the tool. The new brush should completely, in all respects, match the one removed from the grinder. After installing new brushes, you should check the smoothness of its movement.

After installing and checking the smooth movement of the brush, it is fixed with a brush holder. After fixing the brush holder, the tool body is closed.

Replacing brushes is the only operation that should be carried out on your own during the repair process; it is better to entrust other types of repairs to specialists.

Do-it-yourself grinder repair

As you know, nothing lasts forever and even the tools of branded manufacturers break, not to mention the so-called "consumer goods". And the grinder (angle grinder) is no exception. By the way, they began to call the angle grinder "Bulgarian" during the time of the Union, because then this tool was produced in Bulgaria and the first models were supplied from there. The grinder, as a tool, has become very widespread due to its versatility and ease of use. There are also many varieties and models of angle grinders, however, the principle of operation and the device are not fundamentally different. Therefore, having considered the device of the tool, possible malfunctions and repair methods, they can be applied to any model of the grinder.

Bulgarian device relatively simple. The basis of the tool is its body, inside which there is an electric motor, a starter and a gear transmission to the spindle, on which various nozzles are attached.

The case is made of strong impact-resistant plastic. Depending on the power, there are various dimensions and shape of the tool. Some models have a yaw rate control that is designed to optimal choice revolutions, for various types of work.
Another component can be a reducer. The reducer is designed to create optimal conditions transmission of rotation from the rotor of the electric motor to the cutting or grinding wheel. This reduces the number of revolutions on the output shaft of the gearbox. Properly selected rotation speed and circle diameter are the key to maximum effective work tool.

The button for replacing the working disk, when pressed, locks the disk in a certain position, preventing it from scrolling when removed.

The safety clutch serves as a limiter in the event of a sudden reactive torque. In another way, when the disc is jammed in the material, the grinder itself starts to rotate sharply, which can lead to injury to the worker. This clutch does not allow this rotation.

The electric motor normally consists of a stator and a rotor. The stator is located in the guide tides of the plastic body of the grinder. On the back of the stator there is a special device called a brush mechanism. It contains copper-graphite brushes. Brushes are needed to transmit voltage to the rotor through the collector assembly.

The rotor is located inside the stator and is fixed in the housing in bearing assemblies, which are inserted directly into the tool housing. The front bearing assembly is usually made in a metal plate, or this plate can be made of aluminum alloy.

The gearbox housing of the angle grinder is almost always made of aluminum alloy and has several threaded holes for attaching an additional handle. By screwing the handle into various holes, you can change the plane of location during operation.

The gearbox consists of two gears, with the help of which the direction of the output shaft is changed by 90 degrees and the rotation speed is reduced. The ratio of the number of teeth on the primary gear to the number of teeth on the secondary gear is called the gear ratio.

Typical malfunctions of angle grinders and diagnostic and repair methods

Bulgarian suddenly stopped working .
The first thing to do - disconnect physically from the network and manually rotate the disk. If the disk does not spin or spins very tightly, immediately disassemble the tool for visual inspection. If it spins easily, then the most likely thing is that electricity does not reach the brushes of the electric motor. That is, the problem lies either in the power plug, or in the wire itself, or in the Start button mechanism. It is enough to disassemble the case and “ring out” the cable with a conventional tester, or in some other way, for a break. After eliminating the break or replacing the wire, the grinder will work.

The wire and plug are guaranteed to be intact, but the tool still does not work.
It is necessary to disassemble the trigger, and it is desirable to mark the contacts to be removed - if they are subsequently connected incorrectly, the winding may burn out or the armature may jam. It is not often possible to repair the trigger mechanism - it is easier and more reliable to replace the trigger button with any similar one with suitable power parameters. Such a button is not so expensive and you can buy it in any store of the corresponding profile.

The start button and the power wire are in working condition, the grinder does not work.
Check brushes and brush holders. There may be a break or complete wear of the brushes. The resource of these devices is usually limited to several years, of course, it all depends on the intensity of use. Repair break or replace brushes.

More serious malfunctions follow, respectively, and repair requires certain knowledge and skills.

- breakage or licking of gear teeth of the gearbox;
- jamming of bearings;
- failure of the armature or stator;
- failure of the control electronics;
- failure of the collector;
- deformation of the hull;

When determining the mechanical defects of the grinder, more attention should be paid to the condition of the plonitary (large gear), shank (gear on the shaft) and bushings. Uneven wear of the teeth or the shank of the shafts indicates the immediate replacement of worn parts.

Breaking out the spindle lock button.
The reason is just one careless movement, namely pressing (intentionally or accidentally) on the button when the disk is spinning. Sometimes breakdowns occur due to attempts to remove a jammed disk using a button. Many grinders on the spindle, where the disc is attached, have slots specifically for the usual open end wrench, look at your grinder, most likely you have one too. So, it's better to use them and an open-end wrench than a disk lock button.

Chipped gear teeth.
Usually occur due to jamming (in such a situation, a tool breakage is not the worst thing that can happen). A sign of a malfunction is a rumble in the gearbox. If the gear has lost two or three teeth, then the tool will not be able to cut.
In this case, it is necessary to change the gears in a pair and the gear itself and the bevel wheel. When you go to the store for gears, do not forget to write down the name of your grinder and its power.

Failure of the electric motor.
This often happens with tools that work in dust and are forced to rest in sand or on the ground: the sucked-in dust wears down the winding. However, you can ruin the motor without dust - by strong overloads, especially if the tool is low-power. Therefore, in small grinders, not only the anchor, but also the stator often burns out. Small angle grinders also have a breakdown of the electronic speed control unit. If you use a grinder to cut very dusty materials, in particular slate, a stocking put on the ventilation slots in the case helps to protect the instrument.

Bearings.
Another sore spot for angle grinders (as well as other twisting power tools). Few machines stand out for their strong immunities against dust, and the high speed implies rapid wear. In general, bearings are not the worst failure, they are easy to change. However, it is important to replace it on time, otherwise there is a high probability of a more serious breakdown, the repair of which is comparable to the purchase

stator
If, when turned on, the disk starts to gain momentum and accelerates too much, there is definitely a turn circuit on the stator winding. Stator repair is one of the most serious breakdowns and requires appropriate skills. If you are not confident in your abilities, then it is better to entrust it to professionals or use the services of a repair shop.

We begin repairing the stator of the grinder by cutting off the frontal parts of the winding, the remnants of which we take out. Next, we make a new winding using a template sandwiched between two large plates on an axis that can be inserted into an electric drill. The main thing is to achieve an identical number of turns made with the proper density and withstand the thickness of the wire. We insert two coils into the stator housing, draw conclusions from the same winding wire, insulating with flexible tubes of the appropriate diameter.

Reducer
In models with a power of up to 1100 W, spur gears mounted on an anchor are usually used, but angle grinders with more power, for example, by 1500 W, require helical gear wheels. Both variants have a conical shape, since the axis of the gearbox rod intersects with the armature shaft, and transmission is possible only by angular engagement of the teeth.
As a rule, the repair of the grinder gearbox consists only in the replacement of gears. If the disk gear is broken, then it will be very difficult to remove it for replacement; this assembly is best fixed in the gearbox.

speed controller
Almost everyone modern models drills, jigsaws, screwdrivers have a speed controller. But not all grinders (grinders) are equipped with such a mechanism. In principle, a regulator is not needed for cutting metal with a cutting stone, but it is simply not replaceable for grinding. The proposed circuit of a homemade regulator is very simple and reliable. There are not many parts and they are not expensive. If you already have an angle grinder without a regular speed controller, then you can easily improve it.

You can also assemble it separately in a box with a socket and use it as a carrier with a power regulator. And you can immediately assemble the regulator in the grinder case and bring out the resistor knob.

Rules for using the angle grinder and preventive maintenance

The power tool must not be allowed to work for a long time under load at a significantly reduced speed (this can be determined by ear) compared to idle speed, and even more so, the tool must not be clamped (blocked), otherwise it will burn out within a few seconds.

After working at low speeds, do not immediately turn off the power tool. To prevent local overheating, it is necessary that it work for some time (more than 1 min.).

It is important to strictly observe the terms for replacing (adding) lubricant and its quantity indicated in the operating instructions.

With increased noise during the operation of the grinder or with a deterioration in its performance, it is necessary to carry out a prof. service.

Prevention consists in the complete or partial disassembly of the tool, cleaning, lubrication and replacement (if necessary) of some parts.
Timely replacement of relatively cheap parts that wear out quickly will allow you to save more expensive durable components, which in the end will lead to savings in tool operation, eliminate premature repairs and greatly extend tool life.

Do-it-yourself grinder repair. Bulgarian device

After a certain period of use, the grinder is characterized by such breakdowns as the wear of graphite brushes, the burnout of the stator windings, and so on. Of course, the wear itself takes place in terms of mechanics. To fully familiarize yourself with the topic: “How to repair an angle grinder,” consider wiring diagram collector AC motor, since just such an electric motor is installed in the angle grinder.

AC commutator motor circuit

The diagram (Fig. 1) shows the electrical connections of the stator windings, rotor and graphite brushes. Graphite brushes in the electric motor are installed in brush holders. The brushes are in contact with the collector lamellas. One ends of the stator windings are connected to an external power source. The other ends of the stator windings are connected to graphite brushes, the electrical circuit is closed on the rotor windings.

The grinder speed controller is connected by wires to the collector motor circuit in series. The connection diagram of the speed controller should be indicated on the body of the controller itself, or in the manual for the grinder.

Bulgarian device

According to the arrangement of the grinder, everything is indicated in the figure and no explanation is required. With the help of the driven and driving bevel gears, rotation is transmitted from the electric motor to the gearbox shaft.

Collector motor malfunctions

Possible causes of breakdown of the electric motor of the angle grinder are as follows:

• rotor collector wear;
• wear of graphite brushes;
• burnout of the stator windings;
• burnout of the rotor windings;
• lack of contact connection of the ends of the stator windings with graphite brushes;
• mechanical damage to the cable wire at the base of the plug;
• mechanical damage to the wire along the length of the cable;
• capacitor failure,

as well as other possible causes associated with any break in the electrical circuit.

Checking the collector motor

The cause of a malfunction of the collector motor is detected by a measuring device, using the example of such devices as:

If out of stock measuring instrument, any gap can be determined with an indicator screwdriver.

So let's say that the burnout of the stator windings (Fig. 3) is usually caused as a result of a general overheating of the electric motor. AT this case the insulation of the wires in the stator winding is broken and the winding itself can close to the frame housing. To establish such a possible cause of the malfunction, one probe tip of the device is connected to the output end of the stator winding wire, the second probe tip is connected to the stator frame housing.

To check the rotor winding, the probes of the device must be connected to the lamellas (plates) of the collector (Fig. 4).

That's all for now. Follow the rubric.

tell me, please, the cross section of the wire of the stator winding of the angle grinder Kolner 580 wt. Number of turns 167

08/09/2014 at 13:38

Hello Damir. Here, in general, it is not necessary to carry out settlement calculations. You need to take a piece of wire from the stator winding of the grinder and measure the cross section copper wire with a caliper \ lathe measuring tool \ or with this piece of wire, contact the seller consultant when purchasing the wire. It is desirable that the rewinding of the stator of the electric motor is carried out by an appropriate specialist, since the resistance of the winding is also taken into account here.

06/14/2015 at 18:00

Hello fellow electricians!
Tell me, please, why the electric motor of the angle grinder can warm up when idling for 2-3 minutes after turning it on to a cold one after replacing the rotor.
Initially, when working with a diamond disc on a new angle grinder, they overheated it by stopping the disc at full rotation of the rotor. Dismantled, checked the rotor — open circuit on the collector (two black lamellae). No other items were checked. They put a new rotor - it began to warm up without load.

06/15/2015 at 06:26

Hello Pavel. I believe that with this malfunction, you will also need to inspect and check for resistance the stator winding of the grinder's electric motor. A possible reason for the rapid heating of the electric motor is the cause of an interturn short circuit in the winding, that is, the insulation is broken (covering the wires with varnish). When the rotor stops abruptly, a current is created in the electric motor circuit that exceeds the nominal value by several times. This is just my personal opinion and I would also like to know the opinion of my friends, participants in the correspondence.
Victor.

01/17/2016 at 00:33

Hello!
Please tell me - after replacing such an anchor of the perforator http://rotorua.com.ua/product/jakor-perforatora-einhell-858/, the perforator barrel began to rotate in the opposite direction. What could be the reasons? Defective anchor or some kind of discrepancy? thanks for the answer.

01/18/2016 at 05:32

Hello. Maybe you need to reverse? If, when switching the reverse, the barrel of the perforator continues to rotate in the other direction, try changing the wires going to the brush holders.

Comments are closed.

Do-it-yourself grinder repair

An angle grinder (grinder) is very popular in everyday life when carrying out various repair and construction work, so the device is often subjected to overloads and harsh operating conditions, which invariably leads to wear in the mechanism. Repair grinder in most cases, you can do it yourself.

What is produced in Bulgarian

In the grinder device, almost every component is subjected to loads, which can lead to a general failure of the device for various reasons:

1. The rotor is the most loaded part of the grinder, because. it is subjected to both electromagnetic and mechanical influences at the same time:

• Numerous windings of the armature (an integral part of the rotor) have a fairly thin wire with a protective varnish color, which is destroyed when the shaft is overheated or jammed. The wire burns out or short circuit between the coils. In such a situation, do-it-yourself repair of the grinder is carried out only by replacing the rotor.
• The collector on the rotor is a powerful group of contacts that are produced mechanically due to the friction of the brushes and burn due to sparking.
• Bearings are located on the rotor shaft, which are heavily loaded, which causes wear to the extent of their destruction. Therefore, if extraneous noise occurs during operation, do-it-yourself repair of the grinder with the replacement of bearings must be carried out immediately. At the same time, there is a transfer groove on the rotor shaft, which is also produced with a decrease or destruction of the “tooth” shape. Elimination of breakdown is carried out only by replacing the node.

1. The stator has several powerful electrical windings which are rarely damaged.
2. The mechanical transmission requires periodic cleaning and lubrication, and if increased gaps are found in the pair, it is necessary to replace them.
3. Electric brushes are made from graphite-based materials, which causes them to wear out faster. Replacing brushes is a fairly easy undertaking, and individual models of angle grinders can be repaired without disassembly, because. have direct access to the brushes.

Simple do-it-yourself repair

Do-it-yourself repair of an angle grinder in order to avoid electric shock must be carried out in accordance with the rules of electrical safety, therefore, in the absence of such knowledge, skills and abilities, it is recommended to contact professional craftsmen. Troubleshooting and repair should be carried out in a certain sequence:

• The tool does not turn on, while buzzing, as from a transformer, does not occur - indicates a malfunction in electrical circuit: the speed control button is corny burned out, there is no contact in the brushes due to their development, or one of the conductors is broken. Do-it-yourself repair of an angle grinder is carried out in a sequential check of all electrical elements to detect a gap: wire, button, contacts on brushes, motor windings.
• When you try to turn it on, the tool makes buzzing sounds without rotating the shaft - there are serious violations in the mechanical and electrical parts. It is necessary to check the free rotation of the shaft when the device is turned off, because it can be partially wedged, which does not allow the spinning of the rotor. If the motor shaft rotates easily by hand, and when turned on, it does not spin up, then there is a short circuit in the device. Do-it-yourself repair of an angle grinder comes down to complete disassembly and replacement of the rotor with brushes.
• High sparking in the area of ​​the brushes with the impossibility of bringing the motor shaft to full speed - increased production of brushes with weak contact. Immediate repair is needed, because. sparking causes increased heating of the device, and the resulting arc is able to pierce the electrical part of the grinder, which is unsafe.
• Detection of crunches, knocks, any strong vibrational manifestation with a properly working electric motor of the device indicates the development of a transmission mechanism or bearings. Breakage requires immediate total disassembly of the tool with a strict rejection of all worked out parts. Ignoring the urgency of repair leads to a complete failure of the grinder.

Rules for self-repair grinder

For safety reasons and the possibility of repairing the grinder with your own hands, you must adhere to a number of rules:

• Disassembly and assembly are carried out in the exact reverse order, and very often the identification of serious damage can make it impossible to quickly assemble the tool, so the sequence of operations and the location of all components must be recorded on paper or a photo.
• Disassembly of the tool is carried out only when completely disconnected from the mains. Experiments with connecting a disassembled device to a 220 V network are unacceptable, because. this can cause a short circuit with a striking arc.
• The basis of repairing an angle grinder with your own hands is the timely replacement of failing parts with similar ones. at the same time, "Kulibinsky" improvements are unacceptable.
• Bearings are replaced only with similar ones due to special removable and mounting devices that do not allow breaking working parts.
• The laying of a new lubricant must be standardized and using a suitable technical specifications lubricant. Excessive lubrication or the use of inappropriate lubrication leads to increased load with overheating.

For everyone who has been using the grinder for more than one year, it broke. At first, each master tried to repair the sparkling grinder on his own, hoping that it would work after replacing the brushes. Usually, after such an attempt, a broken tool remains lying on a shelf with burned-out windings. And a new grinder is bought to replace it.

Drills, screwdrivers, perforators, milling machines in without fail equipped with speed control. Some so-called calibration grinders are also equipped with a regulator, and ordinary grinders have only a power button.

Manufacturers do not deliberately complicate low-power angle grinders with additional circuits, because such a power tool should be cheap. It is clear, of course, that the service life of an inexpensive tool is always shorter than that of a more expensive professional one.

most a simple grinder can be upgraded so that the gearbox and armature winding wires will no longer be damaged. These troubles mainly occur during a sharp, in other words, shock start of the grinder.

All modernization consists only in assembling the electronic circuit and fixing it in the box. In a separate box, because there is very little space in the handle of the grinder.

A tested, working circuit is laid out below. It was originally intended to adjust the incandescence of lamps, that is, to work on an active load. Her main asset? simplicity.

1. The highlight of the device soft start, the schematic diagram of which you see, is the K1182PM1R chip. This microcircuit is highly specialized, of domestic production.
2. The acceleration time can be increased by choosing a larger capacitor C3. While this capacitor is being charged, the electric motor speeds up to maximum.
3. No need to replace the resistor R1 variable resistance. The 68 kΩ resistor is optimally matched for this circuit. With this setting, you can smoothly start the grinder with a power of 600 to 1500 watts.
4. If you are going to assemble a power regulator, then you need to replace the resistor R1 with a variable resistance. A resistance of 100 kΩ or more does not lower the output voltage. By short-circuiting the legs of the microcircuit, you can completely turn off the connected angle grinder.
5. By inserting a TS-122-25 semistor VS1 into the power circuit, that is, at 25A, you can smoothly start almost any grinder available for sale, with power from 600 to 2700 watts. And there is a large margin of power in case the grinder jams. To connect grinders with a power of up to 1500 W, imported seven-stores BT139, BT140 are enough. These less powerful electronic keys are cheaper.

The triac in the above circuit does not fully open, it cuts off about 15V of the mains voltage. Such a voltage drop does not affect the work of the grinder. But when the sevenstor is heated, the speed of the connected tool is greatly reduced. This problem is solved by installing a radiator.

This simple circuit has another drawback - its incompatibility with the speed controller installed in the tool.

The assembled circuit must be hidden in plastic boxes. The housing made of insulating material is important, because you need to protect yourself from mains voltage. You can buy a junction box at an electrical supply store.

A socket is screwed to the box and a cable with a plug is connected, which makes this design look like an extension cord.

If experience allows and there is a desire, you can assemble a more complex soft start circuit. The circuit diagram below is standard for the XS-12 module. This module is installed in the power tool at the factory.

If you need to change the speed of the connected electric motor, then the circuit becomes more complicated: a tuning resistor of 100 kOhm is installed, and a control resistor of 50 kOhm is installed. Or you can simply and roughly introduce a 470 kΩ variable between a 47 kΩ resistor and a diode.

In parallel with the capacitor C2, it is desirable to connect a resistor with a resistance of 1 MΩ (it is not shown in the diagram below).

The supply voltage of the LM358 chip is in the range from 5 to 35V. The voltage in the power circuit does not exceed 25V. Therefore, you can do without an additional zener diode DZ.

Whatever soft starter you build, never turn on the tool connected to it under load. Any soft start can be burned if you rush. Wait for the grinder to unwind, and then work.

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If you have an old angle grinder in your arsenal, do not rush to write it off. Using a simple electrical circuit, the device can be easily upgraded by adding a speed change function to it. Thanks to a simple regulator, which you can really assemble with your own hands in a few hours, the functionality of the device will increase significantly. By reducing the rotational speed, the grinder can be used as a grinding and grinding machine for various kinds materials. There are new opportunities for the use of additional nozzles and equipment.

Why grinder low speed?

The built-in disc speed control function allows you to delicately process materials such as plastic or wood. At low speeds, the comfort and safety of work is increased. This function is especially useful in electrical and radio installation practice, in car services and restoration workshops.

In addition, among professional users of power tools there is a strong opinion that the simpler the device is, the more reliable it is. And it is better to take the additional service “minced meat” outside the power unit. In this scenario, the repair of equipment is greatly simplified. Therefore, some companies specifically produce remote separate electronic regulators that connect to the power cord of the machine.

Speed ​​controller and soft start - what are you for?

In modern angle grinders, two important functions are used that increase the reliability and safety of the tool:

• speed controller - a device designed to change the number of engine revolutions in various modes work;
• soft start - a scheme that provides a slow increase in engine speed from zero to maximum when the device is turned on.

They are used in electromechanical tools, in the design of which a collector motor is used. They help to reduce the wear of the mechanical part of the unit during switching on. Reduce the load on the electrical elements of the mechanism, starting them into operation gradually.

As studies of the properties of materials have shown, the most intensive development of rubbing nodes occurs during a sharp transition from a state of rest to a mode of rapid movement. For example, one start of an internal combustion engine in a car is equivalent in terms of piston group wear to 700 km of run.

When the power is turned on, there is an abrupt transition from a state of rest to rotation of the disk at a speed of 2.5-10 thousand revolutions per minute. Those who have worked with an angle grinder are well aware of the feeling that the machine is simply “pulling out of their hands”. It is at this moment that the vast majority of breakdowns associated with the mechanical part of the unit occur.

The stator and rotor windings also experience no less load. The collector motor starts in short circuit mode, the electromotive force is already pushing the shaft forward, but the inertia still does not allow it to rotate. There is a jump in the starting current in the coils of the electric motor. And although they are structurally designed for such work, sooner or later there comes a moment (for example, during a power surge in the network) when the winding insulation cannot withstand and an interturn short circuit occurs.

When soft start circuits and changes in engine speed are included in the electrical circuit of the tool, all of the above problems automatically disappear. Among other things, the problem of the “failure” of voltage in the general network at the time of launch is solved. hand tool. And this means that the refrigerator, TV or computer will not be at risk of "burnout". And the safety circuit breakers on the meter will not work and turn off the current in the house or apartment.

The soft start circuit is used in angle grinders of medium and high price categories, the speed control unit is used mainly in professional angle grinder models.

Adjusting the speed allows you to process soft materials with a grinder, perform fine grinding and polishing - on high speed wood or paint will simply burn.

Additional wiring diagrams increase the cost of the tool, but increase the service life and level of safety during operation.

How to assemble a regulator circuit with your own hands

The simplest power regulator, suitable for a grinder, soldering iron or light bulb, is easy to assemble with your own hands.

Circuit diagram

In order to assemble the simplest speed controller for a grinder, you need to purchase the parts shown in this diagram.

circuit diagram speed controller

• R1 - resistor, with a resistance of 4.7 kOhm;
• VR1 - tuning resistor, 500 kOhm;
• C1 - capacitor 0.1 uF x 400 V;
• DIAC - triac (symmetric thyristor) DB3;
• TRIAC - triac BT-136/138.

Circuit operation

Trimmer resistor VR1 changes the charging time of capacitor C1. When voltage is applied to the circuit, at the first moment of time (the first half-cycle of the input sinusoid), the triacs DB3 and TRIAC are closed. The output voltage is zero. Capacitor C1 is charged, the voltage across it rises. At a certain point in time, set by the R1-VR1 chain, the voltage on the capacitor exceeds the opening threshold of the triac DB3, the triac opens. The voltage from the capacitor is transmitted to the control electrode of the TRIAC triac, which also opens. A current begins to flow through an open triac. At the beginning of the second half-cycle of the sinusoid, the triacs close until the capacitor C1 recharges in the opposite direction. Thus, the output is a pulse signal complex shape, the amplitude of which depends on the operating time of the circuit C1-VR1-R1.

Assembly order

The assembly of this circuit will not make it difficult even for a beginner radio amateur. Spare parts are available, you can buy them at any store. Including soldering from old boards. The order of assembly of the regulator on thyristors is as follows:

How to connect the device to the angle grinder, options

The connection of the regulator depends on which type of device is selected. If a simple circuit is used, it is enough to mount it in the mains power supply channel of the power tool.

Installing a homemade board

There are no ready-made recipes for installation. Everyone who decides to equip the angle grinder with a regulator has it according to their goals and tool model. Someone inserts the device into the handle of the holder, someone into a special additional box on the case.

In different models, the space inside the grinder body can be different. In some, there is enough free space to install the control unit. In others, you have to bring it to the surface and fix it in a different way. But the trick is that, as a rule, there is always a certain cavity in the back of the instrument. It is designed for air circulation and cooling.

Cavity at the back of the machine

Usually this is where the factory speed controller is located. A hand-made circuit can be placed in this space. To prevent the regulator from burning out, thyristors should be installed on a radiator.

Video: soft start plus and engine speed control

Features of mounting the finished block

When buying and installing a factory regulator inside a grinder, most often you have to modify the case - cut a hole in it to bring out the adjusting wheel. But this can adversely affect the rigidity of the casing. Therefore, it is preferable to install the device outside.

The adjusting wheel changes speed

The numbers on the adjusting wheel indicate the number of revolutions of the spindle. The value is not absolute, but conditional. "1" - minimum speed, "9" - maximum. The rest of the figures serve as a guide for adjustment. The location of the wheel on the body is different. For example, on the angle grinder Bosch PWS 1300-125 CE, Wortex AG 1213-1 E or Watt WWS-900, it is located at the base of the handle. In other models, such as Makita 9565 CVL, the adjusting wheel is located at the end of the casing.

The connection diagram of the regulator to the angle grinder is not complicated, but sometimes it is not so easy to run the cables to the button, which is located on the other end of the device case. The problem can be solved by selecting the optimal wire section or bringing it to the surface of the casing.

The regulator is connected according to the diagram

A good option is to install the regulator on the surface of the device or mount it to network cable. Not always everything works out on the first try, sometimes the device has to be tested, after which some adjustments must be made. And this is easier to do when access to its elements is open.

Important! If there is no experience with electrical circuits, it is more expedient to purchase a ready-made factory regulator or an angle grinder equipped with this function.

Power cord attachment

Device instruction manual

The basic rule when operating a grinder with a homemade speed controller is compliance with the regime of work and rest. The fact is that an engine running on a “regulated” voltage is especially hot. When grinding at low speeds, it is important to take frequent breaks so that the collector windings do not burn out.

It is also highly discouraged to turn on the tool if the speed control is set to a minimum - the reduced voltage will not be enough to scroll the rotor, the collector lamellas will remain in short circuit mode, the windings will start to overheat. Unscrew the variable resistor to the maximum, then, turning on the angle grinder, reduce the speed to the desired value.

Compliance correct order turning on and adjusting will allow you to operate the angle grinder for an unlimited time.

In addition, it should be understood that the adjustment of the speed of rotation on the angle grinder occurs according to the principle of a water tap. The device does not increase the number of revolutions, it can only lower them. It follows from this that if the maximum passport speed is 3000 rpm, then when the speed controller is connected, the angle grinder will work in a range lower than the maximum speed.

Attention! If the angle grinder already contains electronic circuits, for example, is already equipped with a speed controller, then the thyristor controller will not work. Internal circuits The device simply won't turn on.

Video: homemade angle grinder speed controller

Equipping the grinder with an engine speed control circuit will increase the efficiency of using the device. and expand its functional range. It will also save the technological resource of the grinding machine and increase its service life.