What burns more often in the angle grinder.Signs of rotor combustion

As Shakespeare said: “Nothing lasts forever under the moon”. Household appliances, alas, are no exception. It happens that even the most reliable mechanism malfunctions. And you must be prepared to face this fact without panic, with the firm belief that there is no such thing as a dead end. How is the angle grinder designed, what are the possible malfunctions, how to check the motor armature, determine the cause of failure and fix the problem? Knowing the device of the main nodes of the power tool will allow the master with his own hands to diagnose and repair the angle grinder.

Factors that cause the stator to malfunction:

Signs by which you can understand that the stator is defective:

  • The smell of burning insulation appears.
  • The body overheats.
  • Smoke appears.
  • Shaft rotation slows down or stops.
  • The shaft unwinds spontaneously, the tool sharply gathers maximum speed.

The winding wires are covered with a protective layer of insulating varnish. When it overheats, it burns up and destroys. It causes the coils to short-circuit. The lacquer emits a peculiar odour. Shorting just one of the wires completely puts the angle grinder out of commission.

Rules to avoid overheating of the angle grinder motor:

  • Do not switch the machine off immediately after working at lower speeds, but after about one minute.
  • When working under load at reduced speeds, take frequent breaks.

You can often avoid replacing a faulty stator by rewinding its winding. Rewinding a damaged stator coil of an angle grinder can be done with your own hands, but it is still recommended to entrust this work to a specialist.

Why is the rotor the most common malfunctioning tool??

During operation, the rotor receives the greatest loads, namely:

If used incorrectly or for too long, the breakdown of the electric appliance may lie exactly in the armature, also called the rotor, which may need to be repaired or completely replaced. But before you can be sure of the malfunction of this particular part, you must verify that it has indeed malfunctioned.

Rotor malfunctions

In the case of an optimum utilization the rotor will not wear out. Routine maintenance with replacement of brushes as they wear out. But over time, with heavy loads, the stator gets hot and soars. The most common mechanical failure is bearing wear or misalignment.

The angle grinder will work, but the plates will wear out quickly and the motor will eventually break. To avoid damage, the tool must be checked and normal service conditions must be maintained.

Moisture on metal causes rust to form. Increases friction force, requires more current to operate. Significant heating of contact areas, solder, strong sparks.

Possible causes

Factors that cause stator failure:

Signs by which you can tell if the stator is malfunctioning:

  • The smell of burning insulation appears.
  • The housing overheats.
  • Smoke is produced.
  • The shaft rotation slows down or stops.
  • Spontaneous shaft unwinding, tool rushes at maximum speed.

Winding wires are covered with a protective layer of insulating varnish. Overheating causes the housing to overheat and disintegrate. This causes a short circuit on the coils. The lacquer emits a peculiar odor when you do this. Short-circuiting just one of the wires completely destroys the angle grinder.

Rules to help avoid overheating the motor of the angle grinder:

  • Turn off the device after working at lower speeds, not immediately, but after about one minute.
  • Take frequent breaks when working under load at reduced speed.

It is often possible to avoid replacing a faulty stator by rewinding it. Rewinding of a damaged angle grinder stator coil can be done with your own hands, but it is still recommended to entrust this work to a specialist.

Angle grinder has been known to have a problem

The angle grinder is a fairly unpretentious tool, t. к. is designed for heavy loads and dusty environments. The main problems in its operation in most cases are associated with improper use, as well as failure to comply with the timing of maintenance and scheduled repairs. The following malfunctions are most common:

  • the angle grinder does not turn on. The most common cause of this phenomenon is a wire breakage in the power cable or a faulty switch. And for angle grinders with electronic controls, failure of the speed control or the soft starter.
  • the angle grinder works at low rpm. As a rule, it is caused by an inter-turn short circuit in the rotor windings or a malfunction of the electronics.
  • The angle grinder is very hot. Often this occurs due to violation of the ratio of recommended work cycles and breaks. or the heat can be caused by poor cooling of the motor due to dust build up inside the housing.
  • The angle grinder sparks. In this case, the main causes are wear of the carbon brushes or deterioration of the motor collector. Brushes also spark if the collector plates are dirty or oxidized.
  • The angle grinder is emitting smoke. This usually occurs if there is too much use and the air cooling ducts are filled with dust. Short circuits in the rotor or stator windings may also be the cause of the tool smoking.
  • The angle grinder has a buzzing sound, but doesn’t rotate. This usually occurs if the gearwheels jam or the bearings fail.
  • The spindle lock knob is broken. This is caused by dust entering the collector, which wears down the plunger.
  • Bearing damage. Bearing failure most often occurs after prolonged use and work with shock loads.
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Another fairly common failure of power tools is jamming of the clamping nut.

Preparing a motor armature for inspection

After the armature has been removed from the housing, it is advisable to prepare it for diagnostics. The procedure is to thoroughly clean the graphite residue from the collector lamellae. If this is not done, further testing may not yield the desired results.

You can remove the plaque with a rag and alcohol. If there is not plaque on the blades, but rather a thick layer of carbon deposits, they can be removed with a fine grit emery cloth. Make sure you don’t leave any visible scratches on the collector from the abrasive. This will impair the contact between the lamellae and the brushes and accelerate their wear.

How to Check a Power Armature at Home

Diagnosis of the electrical part of the angle grinder

As mentioned above, more often than not, the angle grinder refuses to work due to breakdowns in the electrical part of the unit. To properly diagnose electrical circuits of the tool, electrician repairmen use a special device. a tester.

If you have pressed the start button of the machine, and it does not work, then in 90% of cases the cause of failure is not so serious that you can not repair the angle grinder with your own hands.

Experts advise adhering to the basic rule of power tool repair: move from simple to complex.

The first thing to do is to check the electrical cable and the plug at its end. If it is collapsible, unscrew it and check that the contacts are secure. Otherwise, you will have to disassemble the angle grinder (remove the hood of the machine) and “test” the cable with a tester, and make sure that the current approaches the contacts of the “Start” button. If the instrument shows a breakage, the cable should be replaced with a new one.

The situation when the current comes to the button, but does not go further (when the position is on), indicates a faulty switch. There is no way to repair the button. It must be replaced by a new one, but first mark the contacts to be removed so that you can connect them correctly in the future. Improperly wired contacts can burn out the motor winding.

If the check shows that both the cable and the start button are intact, but there is no current flow to the brushes, it is necessary to clean the brush holder contact pads. If this procedure is unsuccessful, it is recommended that the brushes be replaced. If the brushes are OK and are supplied with current, the rotor and stator must be checked for shorts or interruptions.

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Checking the Motor Armature

The motor rotor can have the following problems: Inter-turn short circuits and broken wires on the lamella contacts. You can check the angle grinder armature with a multimeter: put the instrument in resistance mode, set the value to 200 ohms and use the feeler gauges to measure the resistance between two adjacent blades. Check all blade pairs in this manner. If the resistance values are the same, then the rotor winding has no damage. If other resistance values are detected during the test and an open circuit is detected, this coil is defective. You may need to repair the angle grinder armature.

Usually the breakage of the conductors occurs at the connection to the winding. Examine the places where the coils are connected to the lamellae, make sure that the contacts are securely soldered.

If you do not have a measuring device, then you can check the rotor, using a 12 V light bulb and a battery for this purpose. The power should be between 30-40W. Checking is done as follows: supply voltage of 12 V from the battery to the plug of the angle grinder, connect a light bulb in the gap of one wire, start rotating the spindle angle grinder. If the winding is intact, the light bulb will burn evenly, without flickering. If there is an inter-turn short circuit, the bulb’s coil will change its degree of glow. In this case, the repair of the angle grinder armature with your own hands will be difficult, since the winding scheme of the armature is quite complicated, and the process itself requires special equipment and knowledge. It is therefore recommended that this operation be entrusted to professionals. But the best way out is to replace the armature on the angle grinder with a new one.

If the light bulb does not illuminate when testing the rotor, this indicates a break in the stator or a short in the stator windings, or a problem with the electric brushes.

Checking the stator of the electric motor

To check the stator of angle grinder, use, as in the previous case, a multimeter. The values need to be set to 20-200 ohms and do the following. Touch the stator winding with one probe and the housing with the other. If the instrument shows resistance, it means that there is a breakdown on the ground. Touch the contacts of one winding with your feeler and then touch the contacts of the other winding. If the resistance is the same, then the coils are good. If one winding has an open circuit, then the stator needs to be rewound or replaced with a new one.

Rewinding stator at home, without special knowledge, skills and equipment, will be problematic. It is better to contact a professional rewinder.

One at a time

Stage I

Use a wooden hammer or pickaxe to disassemble the stator. Remove the stator from the stator housing by tapping on it. By the way, to get the stator, you need from the body of the mechanical part.

Remember to disconnect the stator leads from the terminals going out around the collector. One end is attached to the brush holder and the other end to the wire that supplies 220V power.

It’s time to split it into two halves.

Step II

Both halves of the stator are glued together with a thin layer of glue. To separate one from the other, hit the stator core with a mallet. If you received the stator that can not be disassembled, then the dismantling of the wire is done by cutting all the turns from one end with wire cutters. Having cut, disassembled, take out the wire and measure the wire diameter and the number of turns. To measure the diameter of the wire use only a micrometer. Preheat wire by burning it on a match flame, wipe off the carbon deposits and after cooling down, measure.

Most often the coils are impregnated with an insulating varnish that prevents the wires from separating.

Using an industrial hair dryer, heat the coils until they disintegrate into individual wires. You can also heat impregnated wires in a gas stove over a burner.

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Disassembling stator, be sure to measure. We need to measure the wire diameter, the number of turns in one coil, the percentage of filling the stator slot, the material from which the wires are made. It is recommended that only copper wire be wound.

Coils wound on a template before inserting them into the stator

The wires are classified according to their cross-section. If you measure the diameter of the wire, recalculate its cross-sectional area by the formula S =ηr ², where r = ½d.

And now in layman’s terms: The cross section is 3.14 times half the diameter squared.

What is all this fuss about. If it turns out that you have wire of another diameter, you can’t do without calculations. If there is a thin wire, you can wind in 23 wires, the main thing that their total cross-section was not less than the initial one.

If you have a wire of slightly larger diameter, you can wind them, provided that the filling of the grooves of the old drive was incomplete.

Winding option for a non-disassembled stator

For winding of stator coils you should prepare wire of passing diameter, electric cardboard or presspan, adhesive tape, heat shrinkable tube of required diameter.

If you have a non-disassembled stator you need to make sleeves from press-spun material, cutting them to the width of the stator.

The blanks are cut from presspaper of the same width as the stator and the same length as the length of the inner groove. By the way, you need to add 2 mm on each side to the width of the stator. After cutting out the pieces, seal the edges with a wide Scotch tape. 50mm wide duct tape is adequate for the Makita stator.

Glue one side of the workpiece to a strip of duct tape, cut. On the second strip of duct tape, glue the blanks with the same side, but with the other edge. Your task is to cover the edges of the blanks from tearing during winding.

Making strips fixture

To facilitate the process of winding by hand, make simple devices, which are strips of soft metal up to 0.8 mm thick. It can be galvanized steel, copper, aluminum, or z. The strips are z.It can be made of galvanized steel, copper, aluminum, or shaped strips 10 mm wide and 70 mm long.

On the smaller hook of the device put the heat shrink tube and heat over the flame, crimp the tip of the plate.

Fix the plates with some masking tape on the stator body.

Winding process

Wire is prepared, fixture plates are fixed, data on the number of turns are at hand. Go to!

We put the stator on our lap, take the end of wire, put red color shrink sleeve on it (it designates the beginning of winding), fix the sleeve on the outside of stator and start winding. By the way, the color of the tube can be any, you just need to choose a different color for the beginning and end of the winding.

The winding process is the thumb feed of the wire in the slot, putting the wire behind the hook of the fixture plate, pulling the wire out and putting it behind the hook of the plate from the other side.Most importantly. watch the number of winded turns. The winding process is repeated for the second coil.

You can see it all very clearly in the video below.

All! The stator is wound. It is necessary to carefully tie the windings, make the armor.

Process of armoring stator windings

Armoring is the process of strapping the stator coils to protect them from being destroyed in the process. At high revolutions all parts are affected by various vibrations, which leads to destruction of winding integrity, their friction against each other and insulation failure.

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