As Shakespeare said: "Nothing lasts forever under the moon." Household appliances, alas, are no exception. It happens that even the most reliable mechanism fails. And one must be prepared to meet this fact without panic, with firm confidence that there are no hopeless situations. How is the angle grinder arranged, what kind of malfunctions can be, how to check the motor armature, determine the cause of the breakdown and troubleshoot? Knowing the design of the main components of the power tool will allow the master to conduct diagnostics and repair of the angle grinder.
Features of the asynchronous motor angle grinder
In almost all electrical appliances used in everyday life, an asynchronous electric motor is used. An important advantage of this type of motor is that when the load on it changes, the speed does not change. This means that if, for example, you cut a stone for a long time and without stopping a household angle grinder, there will be no noticeable external signs of engine overload. The speed of rotation of the disk will be constant, the sound is monophonic. Only the temperature will change, but this may not be noticed if the hands are wearing gloves.
With an inattentive attitude, an advantage can turn into a disadvantage. Asynchronous motors are very sensitive to overheating, a significant excess of the operating temperature entails a melting of insulation on the rotor windings. At first, the motor will work intermittently, and then. when an inter-turn short circuit occurs. the engine will stop completely. It is necessary to overheat the engine several times with an angle grinder and, most likely, the anchor will melt. In addition, contacts connecting the wires of the primary winding to the collector are soldered from high temperature, which leads to an interruption in the supply of electric current.
How to determine the malfunction of an anchor angle grinder
Signs of an anchor breakdown in an angle grinder are: increased sparking of brushes on the motor manifold, vibration of the motor at low speeds, rotation of the working shaft in different directions. If such symptoms are present, work with the tool should be stopped. this is dangerous. Suspicions are easy to verify with simple tests.
Visual inspection from the outside
Troubleshooting should begin with a visual inspection of the angle grinder:
- Carry out a general inspection of the tool.
- Pay attention to the integrity of the power cord, the presence of voltage in the outlet.
- Using a voltage indicator, make sure that current flows to the engine manifold and start button.
Inspection of the device from the inside
If everything is in order with power, but the angle grinder does not work, you will have to open the case to gain access to the motor. As a rule, disassembly is not difficult. But you need to adhere to simple rules that will avoid troubles during the reverse assembly:
- Be sure to unplug the appliance before disassembling.
- Remove the working disk and the protective cover from the spindle.
- Open the case in a well-lit place, on a clean table surface.
- Remember the location of all parts and assemblies before disassembling. It is recommended to sketch or photograph the internal structure of the device.
- Fold the screws and fastening screws in a separate place so as not to get lost.
Inspecting the motor is best done under bright light, so that all the small details are clearly visible. The anchor should rotate freely around its axis, properly working bearings should not make a sound during operation. There should be no traces of melted wiring at the anchor, the circuit windings must be intact, without breaks. You can smell the rotor. During interturn closure, the insulating varnish burns and emits a stable specific odor. But for such a diagnosis, some experience is needed.
If a visual examination does not give obvious results, it is recommended to continue the examination with a multimeter. Having set the mode switching toggle switch to the ohmmeter position (range 200 Ohms), it is necessary to “ring” two adjacent anchor lamellas with two probes. If the resistance on all turns is the same, it means that the windings are working. If on some pairs the tester shows a different resistance or an open circuit, there is a malfunction in this coil.
Rupture of the wiring may occur between the winding and the core. It is necessary to carefully examine the junction of the coils with the collector lamellas in the lower part of the armature, visually check the soldering of contacts.
Checking contacts with a light bulb
If there is no tester, you can get out of the situation with a simple 12 volt bulb. Power can be any, optimally 30–40 watts. The voltage from the battery 12 volts must be fed to the plug angle grinder, inserting a light bulb into the gap of one wire. With a working anchor, if you rotate the spindle by hand, the bulb should light up without changing the brightness. If the glow changes, this is a sure sign of an inter-turn short circuit.
Video: How to Assemble a Button on an Angle Grinder
If the light does not light, then this may indicate the following:
- Hanging of brushes in a non-working position is possible. The retaining spring worked.
- There was a break in the supply circuit.
- A short circuit or rupture has occurred in the stator winding.
There are other diagnostic methods, but they require more sophisticated equipment, which is usually not used at home. An experienced master will determine the failure with a high degree of accuracy using a “punch” or a simple transformer with a cut toroidal core and one primary winding.
In what cases can you save the anchor and restore it with your own hands
If damage to the armature is established with guaranteed accuracy, the part must be removed from the electric motor. The motor must be disassembled with special care, after removing the brushes and disconnecting the power terminals. The rotor is removed along with the thrust bearings and the cooling wheel of the motor, they form a whole with it.
If most of the wiring is damaged in the anchor and the balance is disturbed as a result of overheating, it is better to replace it entirely. An imbalance is indicated by increased vibration and an uneven hum during the operation of the mechanism.
How to rewind an anchor. step by step instructions
If the balancing of the armature is not broken, and the problem is only in damaged windings, then such an armature can be restored independently by rewinding the coils. Rewinding a rotor at home requires a lot of patience and accuracy.
The master must have skills in working with a soldering iron and devices for diagnosing electrical circuits. If you are unsure of your abilities, it is better to take the engine for repair to the workshop or replace the entire anchor yourself.
For independent rewinding of the anchor you will need:
- wire for a new winding. A copper core with a diameter exactly matching the old conductor is used;
- dielectric paper to isolate the winding from the core;
- varnish for pouring coils;
- soldering iron with tin-lead solder and rosin.
Before rewinding, it is important to count the number of turns of wire in the winding and wind the same amount of new conductor onto the coils.
The rewinding process consists of the following steps:
- Dismantling of old windings. They must be carefully removed without damaging the metal body of the anchor. If any burrs or damage are found on the case, they must be ironed or sanded. Sometimes, to completely clean the body of toxins, masters prefer to burn it with a burner.
- Preparing the collector for connecting a new wire. There is no need to remove the collector. It is necessary to inspect the lamellas and measure the contact resistance with a megger or multimeter with respect to the housing. It should be no more than 0.25 megohms.
- Removing old wiring to the collector. Carefully remove the remnants of the wires, cut the grooves in the part of the contacts. Subsequently, the ends of the wires of the coils will be inserted into the grooves.
- Installation of sleeves for an anchor. The sleeves are made of dielectric material with a thickness of 0.3 mm, for example, electrical cardboard. Cut a certain number of sleeves and insert into the grooves of the peeled anchor.
- Rewind reels. The end of the new conductor is attached to the end of the lamella and wound in successive circular motions, counterclockwise. This installation is called “right installation”. Winding Repeat for all coils. Pull the wires near the collector with a thick thread of cotton fabric (nylon is prohibited, since it melts when heated).
- Checking the quality of the winding. At the end of laying all the windings, check with a multimeter for the absence of inter-turn short circuits and possible breaks.
- Finishing Finish the finished coil with varnish or epoxy to fasten the winding. In the factory, the impregnation is dried in special ovens. At home, this can be done in the oven. As an option. apply quick-drying varnishes for impregnation, applying a coating in several layers.
Replacing the anchor yourself at home
Practice shows that if it is decided to replace the anchor with an angle grinder, then it is best to change it together with the thrust bearings and the cooling wheel of the engine.
To replace you will need:
- New anchor angle grinder. Must fit your model. Interchange with other models is not allowed.
- Screwdrivers, wrenches.
- Soft brush and rags for cleaning the mechanism.
How to remove the anchor
Replacing the anchor begins with the disassembly of the angle grinder. The following steps are taken:
- The brush nodes are twisted with a screwdriver on both sides. Brushes are removed.
Video: replacing bearings with an angle grinder
How to anchor in place
To reinstall the new anchor, the angle grinder should take a new part, and then assemble the tool in the reverse order. The sequence of actions is as follows:
- A fixation disk is mounted on the armature shaft.
- The bearing is mounted by pressing.
- The small gear is put on and fixed by a lock ring.
- The anchor is inserted into the gear housing, the docking holes are combined.
- The gearbox mounting bolts are tightened.
- An anchor with a reducer is inserted into the body of an angle grinder and fixed.
- Brushes are deposited in place, closed with lids.
After performing these steps, the angle grinder is ready for use. Replacement of the anchor made.
Video: how to check the angle grinder
Ancient Sufi wisdom says: “The person who is able to get out of a difficult situation with dignity is smart. But wise is he who does not fall into such a situation. ” Observing the rules for operating household appliances, preventing the motor from overheating, you can avoid breakdowns and troubles in the work of an angle grinder. Keeping the instrument clean and dry will prevent its mechanisms from contaminating and oxidizing current-carrying elements. Timely maintenance of the tool is guaranteed to relieve unpleasant surprises during operation.