How to check the serviceability of the anchor angle grinder

How to check an anchor if you don’t have special tools?

In the absence of a multimeter, you can check the armature contacts using a simple 12-volt light bulb. Having inserted it into the break of one of the wires, voltage must be applied to the plug of the angle grinder from a 12 Volt battery. With the simultaneous rotation of the spindle by hand, the light should burn brightly without dying out. This result indicates that the anchor is working properly. The changing glow indicates a short interturn circuit. If the light does not light up at all, the following breakdowns can be assumed:

You can also check the performance of parts in other ways, but they require complex equipment or measuring instruments that are not available or are little used in everyday life.

How to check the anchor and determine the cause of the tool breakage yourself?

Vibration and heating of an angle grinder during operation most often indicates the presence of a mechanical breakdown. On examination, you can find uneven wear of the brushes and their burning. Only a specialist with special skills and technical devices can diagnose a breakdown of the electrical system when checking the armature. The main reasons for the failure of the tool in this case are:

• damage to the armature winding;
• the presence of a short circuit in the turns;
• broken resistance between core and winding.

In order to check the anchor of the angle grinder, it is necessary to disassemble the power tool and access directly to the part itself. Disassembly should be done carefully so as not to damage other parts. Fold the mounting screws and screws carefully so as not to lose. The surface of the table on which you disassemble the angle grinder must be clean, the room lighting must be sufficient so that all the details can be clearly seen. In general, disassembly is not a difficult process, but it is worth preparing. After completing it, you can start checking. The main common defects of anchors of a power tool can be determined using a multimeter in resistance mode.

In which case, to check the anchor, you should definitely contact the specialists?

In order to check the armature for the presence of an interturn short circuit, a special measuring device is needed, which is a special bracket with a coil. But this is already the work of professional craftsmen. To detect such a breakdown by checking the anchor, they can only in a service center or a power tool repair shop. A qualified technician will identify the fault with high accuracy using a punch or the simplest transformer with a split toroidal core and one primary winding. Using the method described above, you can check the serviceability of the electrical parts of the drill.

Anchor check examples

Anchors of professional tools and equipment of medium power can fail. Below we present to your attention a specific example of checking the armature of a Makita GA 9050 angle grinder. The power tool is equipped with a powerful 2000-watt collector motor. To check the performance of the anchor, the Makita GA 9050 angle grinder should be diagnosed directly with the contact group of the part. Before that, you need to turn on the multimeter and set the measurement mode to 200 Ohm. If you have an analog digital meter, it is better to use it than a digital one. After setting the multimeter, you can proceed directly to checking the armature.

Resistance is measured between each plate. Multimeter probes are placed on each lamella so that the groove between them is located exactly in the middle. If the part is in good condition, the resistance between each of the lamellas should be the same. The discrepancy between the indicators most likely indicates a break in contact. Of course, at home, such a malfunction cannot be detected. If you notice a break in the winding outside when checking the armature, you can try to solder it yourself. Sometimes it will save the day, and the angle grinder will serve you for a while. The absence of indicators when examining the plates during the check of the anchor for operability indicates their breakage.

Sometimes a malfunction can be noticed visually. In working order, all plates of the armature contact group must be flat and smooth. In the cases described, the part cannot be repaired and must be replaced. Directly together with the armature, the engine brushes should be changed. A new part can cost a lot of money, but buying it is cheaper than purchasing a tool.

If, after walking along the contact circle, checking the anchor, you find that the resistance is the same between all the plates, its indicators do not “jump” and there are no visible breaks, you must carry out the following check. The measurement mode must be set to 200 kΩ. If your meter does not contain such a scale, it can be set to 20 kΩ. One probe of the multimeter is fixed to ground, while the other must touch any of the plates. Normally, when checking the armature, the contacts should not “ring”. If you do not observe such a reaction, then your anchor will not short to mass. Most likely, the part is serviceable or the presence of an interturn short circuit is possible.

How to check an anchor angle grinder: expert recommendations

Despite the quality and the manufacturer’s stated warranty, any tool is subject to wear and tear, especially during intensive use. You are unlikely to be able to repair an angle grinder at home, but you can diagnose the cause of its breakdown yourself. Most often, the armature is subject to wear on such a tool. Its breakdown can be both mechanical and caused by the failure of units and constituent elements of the electrical system. In this article we will try to figure out in detail how to check the anchor angle grinder yourself? To determine a mechanical failure, a visual inspection must be carried out; it does not require special skills. Otherwise, you should contact the professionals.

When you shouldn’t check the anchor yourself?

Without experience or skills, you should not open the angle grinder yourself. It is also not recommended to disassemble it without special tools. This could damage the device. If you recently purchased your power tool and it is out of order, you should contact the point of sale and show the warranty card to the manager along with the angle grinder. Disassembling a power tool under warranty at home is strictly prohibited. Otherwise, after such a check of the armature, you cannot count on the device to be repaired at the representative offices of the company from which it was purchased.

Fit the new bearing into the gear housing from the rotor side. Screw on the plate that caused the impeller to break. Insert the gear inside the housing and thread the nut so that it fits into the grooves of the gear. Put the impeller on the new anchor, insert the anchor into the gearbox housing. Tighten the nut.

Anchor device angle grinder

The motor armature of the angle grinder is a conductive winding and a magnetic circuit into which the rotation shaft is pressed. It has a pinion at one end and a manifold with lamellas at the other. The magnetic core consists of grooves and soft plates, varnished to isolate from each other.

Angle grinder anchor diagram

In the grooves, according to a special scheme, two conductors of the armature winding are laid. Each conductor is half a turn, the ends of which are connected in pairs on lamellas. The beginning of the first turn and the end of the last are in the same groove, so they are closed on one lamella.

Visual inspection from outside

Troubleshooting should start 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 the voltage indicator, make sure that current is flowing to the motor manifold and the start button.

In what cases can you save the anchor and restore it yourself?

If the damage to the armature is established with guaranteed accuracy, the part must be removed from the electric motor. Disassembly of the motor must be done with special care, after removing the brushes and disconnecting the power terminals.
The rotor is removed together with the support bearings and the impeller for cooling the motor, they form a single whole with it.

If most of the wiring in the armature is damaged and the balance is disturbed as a result of overheating, it is better to replace it entirely. Increased vibration and uneven hum when the mechanism is operating indicates a balance imbalance.

Replacing the anchor yourself at home

Practice shows that if it is decided to replace the armature of an angle grinder, then it is best to change it together with the support bearings and the engine cooling impeller.

Replacement will require:

• New anchor angle grinder. Must match your model. Interchange with other models. not allowed.
• Screwdrivers, wrenches.
• Soft brush and cloth for cleaning the mechanism.

Checking power circuits

When repairing a failed electrical equipment, sometimes it does not come to repairing the collector motor. it turns out that the extension cord socket is faulty, the power cord is broken, the connection terminal is unscrewed, or the switch is stuck. Should check
the presence of voltage at the nodes of the supply circuit of the collector electric motor for 220V, starting from the plug, ending with the connection terminal block.

Ring the power cord and power button

Since in collector electric motors, the comparison of electromagnetic fields occurs due to the constant switching of the rotor windings (collector brushes), the mechanical reason for the loss of electrical contact in the collector is the most common. The principle of operation of collector motors is described in the previous article, and below will be given some tips for repairing and replacing the rotor (armature) contacts.

Rotor (armature) of the collector motor

A variety of self-contained power tools, kitchen appliances, and children’s toys often use a brushed DC motor.
. These electric motors are powered by a constant voltage supplied from batteries, rectifiers, or controllers. The presence of voltage does not always indicate the operability of the power source (the battery may be planted), therefore, you should also check the collector current and the entire circuit when the collector motor is turned on.

Low-power brushed DC motor with control controller

If the electric drive of the equipment has stopped rotating, first of all, you should check the supply of voltage to the input contacts of the collector motor when it is turned on.

Collector repair and maintenance

The engine manifold consists of contact plates. lamellas
connected to the terminals of the armature windings. The large operating current of the collector, and the formation of reactive emf of the switching windings due to electromagnetic induction, leads to increased sparking when the brushes and lamellas contact. Strong sparking leads to burnout of the lamellas, due to which they become covered with pores and cavities. The deterioration of the surface quality of the lamellas leads to even greater sparking and accelerates their wear in an avalanche-like progression.

Collector contamination

The primary cause of collector wear is contamination of the lamellas with graphite chips from washable brushes. The gaps between the lamellas are designed to insulate them, but the graphite dust entering the gaps is a current conductor, which degrades the characteristics of the collector motor and leads to the formation of the so-called circular spark. If, during the operation of the electric motor, the spark seems to be drawn from the brushes around the circumference of the collector, then its lamellas are dirty, and they need to be cleaned.

Circular spark in the manifold

The collector lamellas are cleaned with an eraser, sponge, or fine sandpaper, cleaning the gaps with an awl. If the contamination is severe, a file can be used, but care must be taken not to distort the geometry of the collector circumference by uneven cutting. Another reason for collector fouling is corrosion of the lamella material with the formation of oxide layers, which also need to be cleaned.

Cleaning the manifold with a sponge

Carbide Tipped Cutting Disc

If, after cleaning the lamellas, deep cavities from corrosion or sparking are found, then the collector is repaired by applying copper to the plates by welding or electroplating to seal flaws. Since it is very difficult to give the correct shape to the collector with a file, it is turned on a lathe. In some cases, if it is possible to purchase a new collector, they replace it, but in this case, painstaking work will have to be done to connect the numerous conclusions of the armature winding.

Manifold groove on a lathe

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