Malfunctions of grinder brushes and their elimination
The angle grinder is a high-speed electric tool equipped with a collector motor. In this engine, the current is supplied to the armature - the inner rotating part. Such feeding is carried out by a sliding method, and the only way to make contact of the power source with the moving part is with graphite "brushes". They are "fuses" against overvoltage and are the first to fail.
A sign of their obvious malfunction is strong arcing with the release of sparks through the ventilation grilles, accompanied by a characteristic sound.
What is it?
These components are made by mixing carbon black with graphite and other binding components - hardeners. This mixture is a good conductor of electric current.
Rectangular brushes are widely used. They may differ in terms of length and width, depending on the specific electrical appliance in which they are installed.
A copper wire without a winding is mounted in the "body" of each brush, to the free edge of which a plate of an individual configuration is soldered. The wire is inside a spring, which rests on one edge against the brush, and the other against this plate. The spring has a free pressing action and the brush fits snugly against the collector as it rotates.
In the process, the brushes are erased due to constant friction. This creates the need for their planned replacement. For this, the manufacturer supplies the power tool with a spare set of brushes.
In other situations, you can observe the appearance of sparks in the area of \ u200b \ u200bthe location of the brushes. This fact is accompanied by the characteristic sparking sound and the smell of burnt graphite. If the brushes sparkle on the grinder, this is a sign of a malfunction of its nodes.... In this case, it is necessary to diagnose the device.
The essence of the problem
The sparking of the brushes makes it impossible for the power tool to operate at full power. Since they are a connecting link in an electrical circuit, disruption of their operation leads to interruptions in the supply of current. This negatively affects the motor winding and reduces its service life.
Sometimes the fault can be found in the brushes themselves. They burn out quickly due to cracks, chips, scratches, overheating. Replacing the old brush set will solve the problem. If the reason for the sparking is not in the brushes, then the new ones burn in the same way.
Causes
There may be several reasons why the brushes on the grinder sparkle and wear out strongly:
- malfunction or increased wear of the brushes themselves;
- violation of the contact density between them and the collector plates;
- deterioration of the clamping action of the brush spring;
- breakdown between collector lamellas;
- axial runout of the armature due to bearing wear;
- short circuit in the armature winding;
- introducing structural damage to the mechanism during repair.
The above reasons are the result of improper operation of the grinder or poor assembly of its components.
In order to avoid the appearance of sparks in the area of the brushes, you should follow the rules for the safe use of angle grinders.
- Do not turn on in case of high humidity, pronounced voltage drops in the network, dirt in the brush block, contamination of the air duct grilles in the housing.
- Avoid overheating of the engine, load that slows down the rotation of the mechanism at the time of operation.
- Do not use a low-power grinder to cut "heavy" materials.
How do I fix the problem?
Remove old brushes and replace with identical ones. New kits are available at most hardware stores or electrical outlets. When choosing a replacement, it is worth considering the density parameters of the graphite substance and the design features of a particular grinder. The composition and density of the brushes differ depending on the technical characteristics of the angle grinder. If these parameters do not match, the new brushes will also spark and burn.
Examine the collector for mechanical damage. If dust, dirt, sand gets on it at the time of work, scratches, dents, chips may form. Assess their degree, if any.
For minor damage, the collector lamellas can be turned with sandpaper or on a lathe. The groove must be very accurate, as any inaccuracies will lead to a greater deterioration in the performance of the brushes.
Sandpaper groove
The armature shaft is fixed in the chuck of any torque mechanism (lathe, drill). Rotation starts, the abrasive is applied to the collector. Forceful pressing and the use of coarse-grained sandpaper are excluded. The minimum grit value is 1000 P.
Using a multimeter, detect the presence of a breakdown in the armature winding. Set resistance test mode. Apply one probe to the lamella and the other to the contact of the corresponding winding track. The absence of an open circuit will be indicated by an audible signal. If there is no signal, this trace is broken. You will need to replace the armature or rewind its winding.
Determine the presence of runout in the bearings. If it is found, replace the bearings and measure with a micrometer the diameter of the armature shaft edges at the points of its abutment to the assembly units.
Prevention
The problem of sparking of grinder brushes can be prevented by taking preventive measures:
- follow the operating rules;
- regularly change the lubricant in the gearbox and bearing sections, reducing the mechanical and thermal loads (the factory grease must be changed before starting any work);
- timely replace bearings, while maintaining the structural integrity of the armature shaft;
- install a new set of brushes before the old ones start to spark.
If you notice that the brushes sparkle and burn, you should immediately check the tool or contact a specialist. The lack of timely diagnostics of angle grinders leads to the fact that the sparkling brush block eventually breaks the entire power tool.
You will learn how to replace faulty brushes in a grinder in the next video.
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