In principle, common stepping motors can be divided into two types: reactive stepping motor and hybrid stepping motor. The reactive stepping motor can be disassembled, while the hybrid stepping motor must not be disassembled. Once disassembled, it will be a tragedy. The torque of the light ones will be doubled, and the heavy ones will be completely decorated. The mixed type mainly uses strong magnetic aluminum nickel cobalt material, which is high temperature resistant and does not demagnetize at high temperature. It is charged to saturated state during production. If it is disassembled, the magnetic circuit will no longer be closed, and the magnetic core will weaken. Special magnetizing equipment is required, which can not be solved by ordinary people. If neodymium iron boron material is used, it is not a big problem to disassemble it.
The rotor of the permanent magnet hybrid stepping motor (common 1.8 ° and 0.72 °) cannot be taken out, or it will be demagnetized. Unless you have a magnetizer to re magnetize. Once upon a time, I heard that when repairing a mechanical meter, the NS pole should be short circuited with soft iron after the magnet is taken out, so that the excitation will not be lost. However, this operation of the stepping motor is still a bit troublesome, after all, it is more precise.
If it is necessary to disassemble it, prepare a magnetic "short circuit" tool. In the same way, when disassembling the pointer multimeter, the magnetic circuit will be disassembled, resulting in a decrease in the magnetic density and the sensitivity of the meter head, resulting in a very large error. The magnetic "short circuit" method is also used to disassemble the multimeter. When the magnetic circuit must be disassembled, "magnetic short circuit" shall be carried out in advance, that is, the magnetic gap can be disassembled only when the soft iron material is laid on the two magnetic poles of the magnet to make the magnetic flux pass through the soft iron material without lowering. When installing it back, install the magnetic gap first, and then remove the "magnetic short circuit". However, sometimes "magnetic short circuit" is very difficult. For stepping motors, the inner diameter of the tool used for "magnetic short circuit" must be equal to the inner diameter of the motor stator, and only a few wire errors are allowed. It is difficult to process this tool even on a lathe.
The current permanent magnet hybrid stepping motor has small volume, large power, small magnetic circuit gap and only a few wires. It needs to prepare a magnetic "short circuit" device to fill the magnetic circuit gap, such as an iron cylinder with the same inner diameter as the stator (which can be loosely matched with the rotor gap). It is not a thin-walled iron cylinder with a wall thickness of at least 8-10mm. It is not to insert the ultra-thin iron cylinder into the gap, but to lean the cylinder end against the stator, make the cylinder and stator roughly concentric, and then move the rotor from the stator to the iron cylinder along the axial direction.
For the motor with a printed rotor once disassembled, a magnetizing coil is wound on the internal magnetic steel. Even demagnetization, if the torque margin of the motor itself is large, it will not affect the use. However, if the multimeter is used for accurate measurement, the error is obviously too large. All components using permanent magnetic materials, such as loudspeakers, pointer multimeter, permanent magnet motors... Unless absolutely necessary, do not disassemble the magnetic circuit, otherwise, "magnetism is weakened" and cannot be recovered.
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