Why are the brushes on an angle grinder sparking?. Manifold device prophylaxis
Why are the motor collector brushes sparking? Causes of arcing under the collector brushes. Solutions for eliminating arcing.
It is difficult to imagine an arsenal of home masters without such a popular power tool as an angle grinder angle grinder or angle grinder (popular name). Angle grinder has received its popularity at the expense of versatility, because this tool can be used for cutting, grinding, sawing, polishing, grinding and other works. And you can work with absolutely any material. During the operation of the tool there are different failures, and one of the most common is the sparking of brushes on the angle grinder. Why do the brushes spark on the angle grinder, not many people know, so let’s look into this issue, as well as find out 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 construction of all modern power tools. drills, torches, jigsaws and others. In the construction of angle grinder and other power tools is used 2 brushes, which have a simple design. This design is based on the following elements:
- The main part is rectangular in shape and made of carbon or graphite
- The contact is a wire strand of the appropriate diameter through which the electric 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 the electric 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 current flow to the collector allows the collector to rotate. As the rotor rotates, the devices make contact with the collector (copper lamellas. armature winding leads), thus ensuring the continuous flow of electric current.
During use, the devices wear and tear, so they are classified as consumables. the brushes’ service life is not only affected by the service life of the power tool, but also by the materials of which the brushes are made. Brush wear is not only a mechanical effect caused by friction, but also a thermal one. Electric current flowing through a wire causes wire heating. The higher the amount of 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 increased temperature, which adversely affects the integrity of the consumables.
This is interesting!There is no difference between the brushes for the respective power tools (except for the method of attachment), because they are chosen solely by such a parameter as the size of the main part.
What to do if the drill sparks
Wholesale production of hand grinders was launched in the USSR in the year of. Today no production facility can do without this tool. However, any tool will break down at some point, but many parts can be repaired in domestic conditions. The most common malfunction that you can try to repair is the breakage of stator coils. It occurs mainly due to high overloads. Rewinding the stator of an angle grinder with their own hands is quite possible today. However, such work requires a certain experience and relevant knowledge. When the voltage rises, the spark force increases in leaps and bounds.
Brushes on angle grinder and other power tools are made from different materials, but the main ones are. carbon and graphite. It is this material that has a low coefficient of friction and also has a high abrasion resistance. To improve contact, different additives are added to the graphite or carbon in the composition of the brushes. Depending on the impurities used, the following types of brushes are distinguished:
The composition of the main part affects not only durability or wear, but also such parameter as the signs of arcing. The extent of brush arcing depends on the composition of the brushes. When buying them, you need to pay attention to the composition, and not to buy equipment of unknown origin and of dubious quality.
This is interesting!There is a ceramic tip in the construction of the brushes, which performs one of the important tasks. When the graphite layer is abraded to the limit, the tip starts to contact the copper lamellae of the collector. Ceramics do not conduct electricity, so if the brushes wear out, the angle grinder will work intermittently or will not turn on at all until the devices are replaced.
Safety precautions when working with a vacuum cleaner motor
Household apparatus is not regarded as safe. A vacuum cleaner is a high-risk tool for the person who repairs it.
- Conduct all disassembly only with visible disconnection. the plug is off and away from the socket.
- When the motor is removed from the case, turning it on with the impeller will produce a moment of inertia, a violent jerk in the opposite direction. Before testing, the stator must be clamped in a vise or secured to the machine with a rigid insulator. Test only two people so that the current can be turned off instantly.
- A collector motor with no load at all will break down in seconds. The assembly cannot be started at all without the impeller. You can check for sparking with the impeller and a rigid closure of 80% of the incoming air flow.
These requirements must be adhered to so as not to cause current, mechanical injury, or make mischief.
Why is an angle grinder hot??
The motor becomes overheated in the following cases
- Incorrect operating mode. Excessive strain causes the motor windings to burn out.
- Breaking of the armature bearings. The result is that the motor can no longer work properly and overheats as a result.
- Clogged air ducts allowing air to flow to the motor and thus acting as a coolant.
- Windings of the stator and rotor windings are shorted.
The gearbox of the angle grinder overheats due to a lack of lubricant or insufficient lubrication.
Causes of arcing
It is important from a practical point of view that switching should take place without causing any significant arcing at the brush contact surfaces, because strong arcing spoils the collector and brush surfaces and makes continuous operation of the machine impossible. Brush arcing can be categorized as mechanical or electromagnetic
Brush arcing can be subdivided into mechanical and electromagnetic causes.
Mechanical causes of arcing are usually caused by a faulty contact between the brush and the collector. Such irregularities are caused by: 1) uneven surface of the collector, 2) poor grinding of brushes to the collector, 3) collector breakage if it exceeds 0.2. 0.3 mm, 4) protrusion of individual collector plates, 5) mica protrusion between the collector plates, 6) brushes jamming in brush holders (tight fit), 7) brushes vibration (slackness of slip-ring assemblies, bad balancing of machine, too loose position of brushes in brush holders with clearance over 0.2. 0.3 mm, too big distance between brush holder cage and collector. more than 2. 3 mm, etc.). Sparking can also be caused by uneven brush spring tension, asymmetrical breakdown of brush fingers and brushes on the circumference and other mechanical causes.
The electromagnetic causes of brush arcing are related to the nature of electromagnetic processes in the commutated sections
Ensuring that these processes occur in a sufficiently favorable manner is an important task in the construction of DC machines, especially large machines
Diagnosing malfunctions of angle grinders
Signs of improper operation of the angle grinder to the sensitive ear and keen eye appear long before the actual failure of the tool. Before it finally breaks down, the angle grinder usually begins to signal distress. It could be:
- increased vibration of the housing during operation;
- Excessive sparking of the collector brushes;
- Dull humming of the motor during startup;
- Cracking of the gearbox with broken teeth or gears that have dried up without lubrication;
- jamming of the rotor shaft bearings or their piercing creaking during acceleration;
- A specific smell or even smoke coming from the body of the angle grinder.
To save the angle grinder from a major and expensive repair, you should pay attention to the technical condition of the tool and respond to changes in its operation in a timely manner.
If the angle grinder has the first symptoms of improper operation, it is necessary to urgently diagnose the device and find the cause of the malfunction. There are two main systems to check: electrical and mechanical.
Checking the electrical part
The electrical part of the angle grinder consists of:
The electric motor, in turn, is divided into two main parts. the stator and the rotor (or anchor).
The task of the master is to check all these systems one by one and find the causes of malfunction. A multimeter or a tester is needed for this.
Universal tester for diagnosing electrical parts of the angle grinder
Checking power circuits
The first thing to check is the integrity of the power cord. Many mishaps can occur just because there are damages in the cable and the power supply of the device is uneven. The cord must be perfectly intact, with no signs of damage. During operation, it should not heat or spark at the bends and connections to the socket or angle grinder. If at least one of these conditions is not met, the cord should be repaired or replaced.
Using a tester switched to voltmeter mode, check the input voltage to the angle grinder, it should correspond to the specifications: 220 В. In the ammeter mode, measure the current consumption. it should not exceed the value of 6 A.
Checking the starter and control box
Next you should test the start button and the electronic control box. The switching contact block may be oxidized or clogged. If the unit is equipped with a soft starter, the drive should be brought up to speed gradually, without sudden increase in speed. Using a multimeter, make sure that the voltage is transferred to the electrical circuit when you turn on the button.
If during the operation of the angle grinder was noticed that the brushes in contact with the collector spark excessively, or the disk rotates unevenly, changing the number of revolutions per minute, then it is likely that the stator or armature windings are involved. Since the stator is less susceptible to overloading. it only creates the magnetic field, most attention should be paid to the rotor of the electric motor.
Diagnosing the rotor. how to “sound” the armature with a tester?
To make sure that the rotor is in good condition, you need to “test” it with a tester.
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With the multimeter toggle switch in the 200 ohm position, measure in series the resistance of the windings on the two adjacent armature lamellae. If the resistance is the same everywhere, then the armature is intact and functional. If the tester shows a different value on any of the pairs of lamellae, there is an inter-twist fault. Anchor to be repaired or replaced.
Diagnose rotor functioning of the angle grinder
Interturn faults tend to occur when the tool overheats during operation. The winding insulation is melting and this causes adjacent turns consisting of copper wire to come into contact. If the resistance is identical across the two adjacent armature blades then the armature is intact and functional If the resistance is identical across the two armature blades then the armature is in good working order.
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Diagnosis of motor stator
If the armature appears to be OK, then the stator should be tested with the same procedure, measuring the armature resistance. An inter-turn short circuit in the stator is characterized by spikes in the angle grinder’s RPM when it is turned on. The engine suddenly begins to revolve at an increased speed.
The insulation defect in the stator windings can be repaired or replaced. Repair usually consists of rewinding the copper wire.
A specially made template is used to rewind the stator coils. As a rule, it is made of plywood. The size of the template is determined with a reserve of 10 mm for each frontal part. To prevent the wire from jumping off the plywood during winding, on the sides of the plywood are attached cheeks.
Rewinding is made at home if you have the necessary tools and equipment. It is important to choose a copper conductor with a cross section that exactly matches the original. The number of winding turns must also not be changed.
Checking the mechanical part of the machine
- locking button fixing the spindle;
- of the working tool flange mount;
- bearings of the rotary shaft of the rotor.
To determine faults in the mechanical part of the angle grinder, it is necessary to open the gear case, which is made of aluminum alloy. Generally, the gear cover is secured with four screws, which must be unscrewed to gain access to the gear set.
Inspecting the Geareducer Gears
Inspection of the gear train is to determine that the gears are firmly mounted, that there is sufficient lubricant, and that the teeth are intact.
Planetary pair of spur gears
Checking the locking button
The spindle lock button is a spring-loaded steel rod that prevents the operating shaft from rotating. Button is used when changing cutting blades. Spindle lock pin failures usually occur when the disc is jammed or the motor is running with the button depressed.
Degree of sparking
Commutation quality, according to GOST 183-74 (Table 1), is estimated by the degree of sparking (commutation class) under the running down edge of the brush, ie under the edge from which the collector plates are coming out at their rotation. Arcing degree 1, 1¼ and 1½ and are permitted for all operating conditions.
Arcing degree (switching class) of electrical machines
Weak spot sparking under a small part of the brush
No blackening of the manifold and no carbon deposits on the brushes
How to disassemble the gearbox
When repairing the mechanical part of an angle grinder, first separate the gearbox from the drive by undoing the four bolts and disengaging the drive and idler gears. For internal inspection and repair of components, the lower part of the gearbox which is also bolted to the main body must be removed. Next, the gearbox is disassembled separately, separating the bearings, pinion and flange one by one from the shaft.
How to remove gear wheels
the angle grinder drive pinion is generally tightened on the shaft and secured with a nut, and the idler pin is secured with a dowel pin and a split washer. The video below shows how to do the repair, including disassembling the Geareducer, removing the top bearing, and replacing the idler pinion. The video is in English, but it is very clear, so you can watch it silently.
If the angle of the brushes is not correct in relation to the stator, sparks may also occur. The correct position is when both brushes are in exactly the same line through the rotation axis of the collector. Over time, constant vibration can cause the brush holder mount to become loose or even mechanically damaged. Carefully inspect the surfaces of the assemblies. Cracked, chipped or corroded parts must be replaced.
Each manufacturer introduces design features to their product line, and therefore different types of vacuum cleaners have a different type of brush attachment. However, in general, all models have the same device, and the brush holder is usually screwed with two screws and allows you to make adjustments.