Why the brushes on the engine collector are arcing. Causes of arcing under the collector brushes. Methods of eliminating arcing.
It is difficult to imagine an arsenal of home without such a popular power tool, as an angle grinder angle grinder or angle grinder (popular name). The angle grinder has gained its popularity due to its versatility, as this tool can be used for cutting, grinding, sawing, polishing, deburring, grinding and other works. And it is possible to process absolutely any materials. During the operation of the tool there are various failures, and one of the most common is the sparking of brushes on the angle grinder. Not many people know why the brushes on the angle grinder spark, so let’s look into this question, as well as why they burn out and how they are replaced.
Before you figure out the causes of sparking brushes on the angle grinder, you need to understand their purpose. Collector brushes are used not only in the design of angle grinders, but also in the device of all modern power tools. drills, peorators, jigsaws and others. In the construction of angle grinder and other power tools 2 brushes are used, which have a simple design. This design is based on the following elements:
- The main part. has a rectangular shape, and is made of carbon or graphite
- The contact is a strand of wire of an appropriate diameter through which electrical current flows. The contact connects the wire to the graphite part
- The spring is the mechanism that holds the main part against the collector. There may be no spring on the element, and this indicates that such a brush is designed for installation in power tools, where brush holders have a built-in clamping mechanism in the form of a curved plate
Devices are designed to transmit electrical current to the rotor of the power tool. The voltage drawn from the stator is applied to the rotor, which is reproduced by the carbon brushes and the collector. The supply of current to the collector ensures its rotation. As the rotor rotates, the devices make contact with the collector (copper lamellas. armature winding leads), thus ensuring the continuous flow of electric current.
These devices wear out as they are used, so they are a consumable item. The service life of a brush is not only dependent on the service life of the power tool, but also on the materials from which the brushes are made. Brush wear is not only mechanically affected by friction, but also thermally. Electric current flowing through a conductor heats the conductor. The greater the value of the current, the higher the heating temperature. When current flows through the graphite brushes, they also heat up. The higher the load on the power tool, the higher the current and therefore the higher the temperature, which negatively affects the integrity of the consumables.
This is interesting!There is no difference between the brushes for the respective power tools (apart from the fixing method), because they are selected solely according to such parameter as the size of the main part.
Option 1. Quick access system for brushes.
This option is the easiest. But it can be realized only in those grinders, which are equipped with special quick-access brush compartments. They are usually located on the side of the tool. To change the brush you only need to unscrew the brush compartment lid, pull out the old worn out brush and put a new one in its place. It’s very simple. And this procedure only takes a couple of minutes. The main thing is that the brushes fit the model of the angle grinder.
If the manufacturer has not equipped the tool with a system of quick replacement of brushes, you have to dismantle the angle grinder to implement this procedure. First, you need to read the instructions to the tool and its diagram, if they are available in the kit. Usually the body of the angle grinder consists of two parts, fastened together. After you have taken the body apart, you must remove the old brush from the brush holder and replace it with a new one. Make sure the brush holder holds the brush firmly against the collector. Try to use only original brushes that are suitable for your specific tool model. But if you can not buy one and you can not find an analogue, you can adjust the brush to the size you need. It is done quite simply. by means of a fine needle file. Take your time when adjusting, be gentle with the brush. The main thing is that it did not end up being smaller in size than the original.
Separately, it should be noted that the replacement of brushes on the angle grinder is not complicated at all. However, if you are going to do this, make sure that your angle grinder is no longer under warranty. Simply put, usually manufacturers are against any unauthorized introductions to their products. There are special service centers for such maintenance. If you break the warranty agreement by penetrating into the tool, in the end the manufacturer simply refuses to provide free service or to replace the tool. In short, there are different occasions. Every manufacturer has its own rules, so before you disassemble your angle grinder, we recommend that you carefully read the warranty card of the tool.
How to replace brushes on an angle grinder
Very often the manufacturer of angle grinders has its products with a spare pair of brushes (graphite contacts, which transmit the electric current to the rotating rotor).
Does this part really wear out so intensely that it is the only thing to be added? If the tool is used from time to time, then the brushes will outlive the owner. But if you exploit the angle grinder every day, then, indeed, their wear will be substantial. And the day will come when a few centimeters graphite rod will wear down to a thin plate. If you let the brushes wear down to extremes, they must not damage the contacts of the rotor. The brushes should be checked periodically after dozens of hours of use.
Warning! Before replacing the brushes, as with any penetration into the machine, you must remove the mains plug from the socket.
Due to the design diversity of angle grinders, the replacement of graphite contacts in each tool model can have its own specific characteristics.
The most elementary way, without disassembling the housing
Some manufacturers have been very clever about replacing brushes. There are screwed plugs in the housing of the machine. And the whole process of checking or “repairing” takes two minutes (for both graphite contacts):
- Unscrew plug with screwdriver.
- Use a thin screwdriver to pry open the brush cap and remove the brush.
- If the brush has lost 70% to 80% of its length compared to the new one, it is worth replacing it. Otherwise you have to replace the old graphite contact with the same side as before it was removed in order to avoid the lapping process. After all, brushes wear unevenly because they are in contact with the rotating cylindrical surface.
- Screw in the cap as far as it will go. Warning! The plug can also be screwed in upside down. That’s why you should make sure there is a slot on top for the screwdriver. Otherwise, it would be difficult to unscrew it the next time.
- Repeat all the steps with the brush on the back side of the angle grinder body.
This is the easiest way to change brushes on an angle grinder without having to disassemble the housing. You can therefore take this into account when you buy a new tool.
angle grinder without back handle
For grinders that do not have a back handle, replace the brushes in the following sequence:
- Unscrew the self-tapping screw from the end of the angle grinder.
- Pull off the cylindrical brush guard.
- Pull the cover off the contact block.
- Use a thin screwdriver to pry off the brush cap and pull out the graphite rod.
- Insert the new brush, close the contact block with the cover.
- Repeat with the other brush.
- Slide the guard onto the angle grinder and secure it with the self-tapping screw.
There is often another way to attach the brushes. In this case, the sequence of operations will be as follows:
- Remove the cover by first unscrewing the self-tapping screw.
- Release the brush from the belt tension spring by prying it loose with a screwdriver.
- Remove the brush from the guide block by prying it out with a screwdriver.
- Remove the brush contact from the connector. Also by prying with a screwdriver.
- Connect the contact of the new graphite rod to the connector, insert the brush into the guide block and press down with the spring.
- Repeat all the steps with the second brush, close the housing with the cover and screw it on with a self-tapping screw.
These are the two most common ways to replace the graphite contacts. Although other grinder designs are not ruled out.
angle grinder with a backhandle
Angle grinders that have a back handle allow you to get to the brushes in a slightly different, simpler way:
- Near the handle you should find a small repair window, closed by a plastic plate, which is fixed with a self-tapping screw.
- It is necessary to unscrew the self-tapping screw, pick up the plastic plate in the groove with a screwdriver, take it out of the housing, opening the repair window.
- The following steps for replacing brushes are the same as for low power grinders: release the belt spring (1), release the plug (2), pull the brush out of the guide block by the wire.
- Then insert a new brush, connect the plugs, secure the graphite rod with a tape spring, cover the repair window with plastic and screw the self-tapping screw.
- Repeat all the steps with the second brush on the opposite side of the housing.
It is quite possible that there may be other ways to replace the graphite brushes, due to the design features of the grinder.
Structurally, angle grinders differ from each other, so the method of replacing brushes may differ slightly from the basic ways described above. But there are still some common features:
- The brushes are located near the back handle or the part of the body that is designed to hold the tool.
- The most common designs of graphite brushes: with and without spring.
The first type of design suggests a simplified method of replacement, because it has both a wire, a contact plate, and a pressure spring.
Springless brushes require a little more laborious process of replacement, because the fixing spring is attached to the body and it is more rigid, and the wire is attached in a separate place with a plug.
How to replace the brushes on the angle grinder Link to main publication
Repair angle grinder with their own hands: how to disassemble the angle grinder, check the brushes, replace the stator and other video
Angle grinders in Soviet times were made in Bulgaria. That’s why the angle grinder and became known as an angle grinder. At the present time, many companies for the production of angle grinder of various models. But the main elements are the same. After familiarizing yourself with the device, possible breakdowns and diagnostics of the tool, you will be able to repair an angle grinder of any modification with your own hands.
Design and function of the angle grinder
angle grinder is designed for grinding and cutting various materials.
angle grinder consists of the following elements:
- Flat gearbox housing made of aluminum alloy better dissipates heat.
- Carbon brushes.
- Handle fixing.
- Electronic soft start system. Prevents jerking when switching on and reduces stress on motor.
- Quick-detachable safety guard.
- Ball bearings.
- Electric motor.
- Angle grinder switch.
Basic malfunctions, their causes, and diagnosis
- Burns, sparks and jerks. Reasons: armature winding insulation damage, worn brushes, collector, clogged brush holders. Angle grinder sparks and jerks even after brushes are replaced if brush holders are clogged.
- Clattering sound. Brushes or intercircuit in either winding.
- Crunching sound. Check electrical circuits Check bearings.
- Mechanical hum and a loud thumping noise. Gearbox malfunction.
- The angle grinder stops working, does not turn on. If the wheel turns hard or does not turn by hand, it is the gearbox that is at fault. If it rotates easily, check the electric circuits. If circuits are working, check motor and brushes.
- Spindle lock button is broken. The reason for this is that it is pressed while the disc is turning or the disc is jammed.
- The angle grinder works intermittently. Check motor for interturn short circuit.
- Vibrates. The cause is in the mechanics. Check bearings, rotor shaft and gearbox.
- Is warm? If it gets hot in the motor area, it is caused by worn brushes or short-circuited windings. If the gear housing is hot, the lubricant has dried out or the gears are worn.
- No or little power output. The cause is in the electronics or motor. Check control board of softstarter and speed controller, brushes and collector.
- Smoke. The cause is overheated. Check motor windings for melting.
- Buzzing and doesn’t turn. Check motor bearings and gearbox.
How to disassemble and reassemble the angle grinder
The angle grinder must be disassembled to troubleshoot the problem.
Remove the nut holding the work disk. Bracing of the work disk
Open the screws on the protective housing.
Unscrew the bolts of the angle grinder body and those with which the body is attached to the gearbox.
Remove the upper part of the rear housing. Unscrew the bolts securing the cord. Remove wires and button from their grooves. In some models, for example in DWT, the rear case can not be dismantled into parts, but it can be removed as a whole.
Unscrew the gear bolts located around the shroud attachment.
To remove the armature from the aluminum housing, unscrew the nut located in the gear housing.
Reassemble the tool in the reverse order.
Clamping nut can not be unscrewed
During operation, the disc can be so tightened with the nut that it begins to crumble. It is not possible to unscrew the nut with a wrench. And you don’t want to do that, because you could break the angle grinder. Break the disc down to the nut first. Then find a metal plate slightly thinner than the work disk. Use it to grind off the rest of the disk under the nut. It can be unscrewed easily with a wrench or your hands. To avoid this problem, put a washer under the nut.
How to remove a very tight nut
Cover can not be removed
Some grinders, such as Bosh, do not have a hood bolted on, but a snap-on hood. To remove it, rotate the shroud cutout perpendicular to the angle grinder. To put on, twist until it clicks.
Checking the Stator
- Inter-turn fault. Set resistance mode to 200 ohms. Connect the probes of the instrument to the ends of the same winding. One indicates a breakage, and zero indicates a short circuit between the coils. If it reads more than 1.5 ohms then check the second winding. Both windings should have approximately the same resistance.
- Ground fault or short circuit of the winding to the metal stator housing. Set the multimeter to maximum resistance mode. Connect one probe to the end of the winding and the other probe to the metal housing of the stator. One indicates no breakdown.
Checking the armature
First visually inspect the manifold and winding. There may be visible damage: black marks, bent winding turns, raised, worn or burned collector plates. After the inspection proceed to check with the tester.
Set the resistance to 200 Ohm. Connect the feeler probes to the two adjacent collector plates. If the resistance is the same between all the adjacent plates then the winding is serviceable. If resistance is less than 1 ohm and very close to zero, there is a short circuit between the coils. If the resistance is two or more times the average value, there is a winding breakage. Diagnose armature inter-turn fault
Ground fault detection is done when there is no winding breakage. Set the maximum resistance on the scale of the instrument. Depending on the tester it can be from 2 megohms to 200 megohms. Connect one feeler gauge to the shaft and the other to each plate in turn. In the absence of malfunctions, the resistance should be zero. Do the same with the rotor. Connect one probe to the iron body of the rotor and move the other probe through the plates.
Checking the power button
Insert one probe into the output of the button and the other into the opposite input.
Press the button. A beep indicates that this part of the button is working properly.
Do the same with the other in and out of the button.
How to test the start button
Checking the power cord
Connect one probe to the plug and the other to the button inputs. There should be a beep in one of the two positions. Repeat the same procedure for the other end of the plug.
Option 2. Replace brushes directly in angle grinder body.
If the manufacturer does not have a quick-brush system, you need to take the angle grinder apart to use this procedure. To begin, read the instruction manual of the tool and its diagram, if they are included in the set. Usually the body of angle grinder consists of two parts, fastened together. After the housing is disassembled, the old brush must be removed from the brush holder and a new brush must be installed in its place. Make sure the brush holder holds the brush securely against the collector. Try to use only original brushes that are suitable for your specific tool model. But if you can’t afford to buy one and you can’t find an analogue, you can adjust it to the size you need. This is done quite simply. with a fine file. Take your time when making the adjustment and be careful when brushing. The main thing is that it must not end up being smaller in size than the original one.
Separately, it should be noted that replacing the brushes on the angle grinder is not a complicated procedure. However, if you are going to perform this procedure, make sure that your angle grinder is no longer under warranty. Simply put, it is common for manufacturers to be against any unauthorized introduction to their products. There are special service centers for such service. If you violate the warranty agreement by penetrating into the tool, then the manufacturer as a result simply refuses to provide free service or to replace the tool. In short, there are different cases. Every manufacturer has its own rules, so before you disassemble the angle grinder, we recommend to read carefully the warranty card of the tool.
To date, among the owners of country houses is very popular fences made of metal. Before you build a fence of corrugated boarding.
In the interior of any room, curtains play no small role: they not only protect the occupants from the bright sun or dust, but also decorate our lives.
Graphite brushes (carbon brushes, EG brushes)
|Mark||Hardness||Electrical resistivity, μOhm||Friction coefficient, not more||Current density, А/cm2, not more||Pressure on the brush, kPa||Linear speed, m/s, not more|
EG61A EG61 UK
EG841 EG84 UMK
Brush replacement on angle grinder
Angle grinder is one of the most popular home appliances. At some point the brushes start to wear out and need to be replaced. A sure sign of wear of brushes is a violation of the sound of the electric motor angle grinder. Also, if you look closely, you can see a sheaf of sparks and smell something bad through the ventilation grills. If the brushes show the first signs of wear, they must be replaced immediately. Delaying the moment of replacement, you risk damaging the collector, which is tantamount to buying a new anchor for the angle grinder.
So, first of all, you need to determine the technical feasibility of replacing the brushes.
Some models on the sides of the angle grinder have two small covers that are held on two screws. You just need to unscrew them and replace the burned brushes.
In most models, in order to replace the brushes, the angle grinder needs to be disassembled. Below we look at the explanatory photos of disassembly of a small angle grinder and read the instructions on how to replace the brushes.
Look closely at the handle of the power tool and look for the mounting screws. In our case, the handle of the angle grinder consists of two parts, but there are models where the handle is simply pulled to the side of the power cord. After disassembling the handle, we look for the location of brushes, which are in special brush holders.
The construction of brush holders may be different, but in any of them the brush must be disconnected from the general electrical circuit of the angle grinder. To do this, remove the tips and study the design of the brush holder. In some cases you can just pull out the brush. In the angle grinder we are considering, the brush holder is hinged, and after this procedure we insert the brush.
Not all of us have the opportunity to find a suitable size brushes, but the artifice is cunning. If you can not find the native brushes then take more or less similar to them, most importantly that they were slightly larger. Use a file to bring them to the right size, the main thing is not in a hurry, so as not to cut off unnecessary. If the brushes have different tips, then cut the leash from the old brush and screw it on the new one.
After all these manipulations we assemble the angle grinder in the reverse order.
On a side note: If you have already disassembled your angle grinder then blow it out with a compressor from dust, also look at what state the collector armature. When working with heavily worn brushes on the collector may cause scratches, which can be repaired with zero sandpaper.