Working principle and maintenance method of permanent magnet stepper motor

1.A brief introduction to permanent magnet stepper motor

Permanent magnet stepper motor (PM stepper motor), also known as PM stepper motor, is a motor that uses the interaction between permanent magnet and electromagnetic coil to achieve stepping motion. Its core feature is that permanent magnet steel is used as the rotor material, and the stator is processed into claw-type tooth poles by stamping, usually using radial multi-pole magnetized permanent magnet steel. This design makes permanent magnet stepper motors have the advantages of low cost, simple structure and high reliability.

2.Working principle of permanent magnet stepper motor

The working principle of permanent magnet stepper motor is based on electromagnetic interaction. When the stepper motor driver receives the control pulse and direction signal, the internal logic circuit controls the winding to be energized in a certain sequence. For example, for a two-phase stepper motor, when both phase windings are energized and excited, the motor output shaft will be stationary and locked in position. If the current of one of the phase windings changes, the motor will rotate one step in a given direction. By changing the direction of the winding current in sequence, the motor can achieve continuous step rotation.

3.Performance advantages of permanent magnet stepper motors

1.High precision: The torque and position control accuracy of permanent magnet stepper motors are very high, and the rotation angle can be accurately controlled to achieve high-precision positioning and motion control. This makes it perform well in applications that require high-precision positioning, such as precision machining equipment, automated production lines, etc.

2.High reliability: Since the mechanical structure and control circuit of permanent magnet stepper motors are relatively simple, and there are no wearing parts such as brushes and commutation mechanisms, they have high reliability and stability and can operate stably for a long time. This is very important for equipment that requires long-term stable operation, such as industrial robots, automation equipment, etc.

3.No noise and pollution: Permanent magnet stepper motors do not generate noise or pollutants caused by friction and wear because they have no mechanical contact parts, so they are very suitable for applications with high environmental requirements. This is a significant advantage for equipment that requires a quiet operating environment, such as medical equipment, precision instruments, etc.

4.Controllable speed and acceleration: The speed and acceleration of permanent magnet stepper motors can be precisely controlled by the controller, and have broad application prospects. This is very useful for applications that require precise control of movement speed and acceleration, such as CNC machine tools, automated production lines, etc.

4.Maintenance methods for permanent magnet stepper motors

‌1.Keep the motor clean‌: Regularly remove dust from the surface of the stepper motor, use organic solvents that do not cause corrosion to clean it, ensure that the motor surface is clean, and avoid dust affecting the motor's aesthetics and heat dissipation effect‌.

‌2.Check the bearing wear‌: Regularly check the bearing wear and replace the severely worn bearings in time. Ensure that the bearings have an appropriate amount of lubricating oil to reduce friction and wear‌.

‌3.Check the wiring and screw looseness‌: Regularly check whether the motor wiring is loose, and tighten the loose screws in time. Ensure that the electrical and mechanical components inside the motor are firmly connected to avoid abnormalities caused by looseness‌.

‌4.Monitor the motor temperature‌: When the stepper motor is running, it is necessary to monitor whether its temperature is moderate. Avoid running the motor in a high temperature environment, ensure that the motor runs in a suitable application environment, and avoid the impact of high temperature on the motor‌.

‌5.Avoid overload operation‌: Reasonably control the power supply voltage and current to avoid damage to the motor caused by overload operation. Ensure that the motor runs under the specified load to avoid shortening the service life due to overload.

‌6.Check the insulation performance‌: Regularly check the insulation performance of the motor to prevent safety hazards such as leakage. Ensure the dryness of the motor windings to avoid the influence of humid environment on the motor insulation material.

‌7.Abnormal situation handling‌: If the stepper motor makes abnormal noise or other abnormal conditions during operation, it should be stopped and checked immediately. The inspection content may include whether the coupling, pulley, fastening screws, etc. are loose, and whether the slider, slide rail, positioning sensor and line connection are normal. If an abnormality is found, it should be handled in time and the equipment should be restored to normal operation.

‌Reasons for abnormal noises in Worm Gearbox

1.Definition of Worm Gearbox

Worm Gearbox is a power transmission mechanism that uses a gear speed converter to reduce the number of revolutions of the motor to the required number of revolutions and obtain a larger torque. It is widely used in the transmission systems of various machines, such as vehicles, heavy machinery, processing machinery, automated production equipment, and home appliances. ‌

2.Working principle of Worm Gearbox

Worm Gearbox achieves speed reduction and torque increase through the meshing of the worm and worm wheel. The worm is a cylinder with spiral teeth, and the worm wheel is a spiral gear. When the worm rotates, its spiral teeth mesh with the spiral teeth of the worm wheel, thereby achieving the effect of speed reduction and torque increase.

3.Main components and functions of Worm Gearbox

1.Worm gear: This is the core transmission component of the reducer, and its main function is to transmit motion and power between two staggered axes. The worm is usually made of a harder material (such as alloy steel) to improve wear resistance, while the worm wheel is made of a softer material (such as cast iron or specially configured wear-resistant nickel bronze) to reduce friction and improve transmission efficiency.

‌2.Shaft and bearings: The main functions of bearings and shafts are power transmission, operation and efficiency. The parts on the shaft are axially fixed by shaft shoulders, sleeves and bearing caps. Deep groove ball bearings are usually used to bear radial loads and small axial loads. When the axial load is large, angular contact ball bearings, tapered roller bearings or a combination of deep groove ball bearings and thrust bearings are used.

‌3.Housing: The housing is an important component of the reducer and the base of the transmission parts. It should have sufficient strength and rigidity. It is usually made of gray cast iron. For reducers with heavy loads or impact loads, cast steel housings can also be used. The housing is made horizontally split along the axis, and the upper housing cover and the lower housing are bolted together.

‌4.Accessories‌: including oil cap/breather, end cap, oil seal, drain plug, oil mark cap/oil mark, etc. These accessories play an important role in lubrication, sealing, oil drainage, and oil quantity observation in the operation of the reducer. ‌

4.Reasons for abnormal noise in Worm Gearbox ‌

1.Worm gear wear: After long-term use, the worm gear and worm gear may wear, resulting in poor meshing and noise. The degree of wear can be detected by visual inspection or using measuring tools. If the wear is severe, a new worm gear and worm gear need to be replaced. ‌

2.Bearing damage or poor lubrication: Bearing fatigue or insufficient lubrication can cause metal peeling on the bearing surface and produce abnormal noise. Ensure that the bearing is well lubricated, add or replace lubricating oil if necessary, and if the bearing is severely damaged, a new bearing needs to be replaced. 

‌3.Improper use of lubricating oil: Insufficient lubrication or use of the wrong lubricating oil will increase friction, resulting in noise. Check the oil level and oil quality to ensure that the lubricating oil is sufficient and of good quality. If the lubricating oil is deteriorated or contaminated, a new lubricating oil needs to be replaced. ‌ 

‌4.Improper installation‌: Unsteady installation of the Worm Gearbox or loose connections can cause vibration and noise. Make sure the Worm Gearbox is firmly installed and well-aligned to avoid vibration and noise caused by misalignment.

‌5.Overload‌: Worm Gearbox running at a load exceeding the rated load can cause overheating and increased noise. Check the load conditions to ensure that it is running within the normal range.

‌6.Mechanical failure‌: Some mechanical failures such as severely worn gears and loose connection parts can also cause noise in the Worm Gearbox. Perform a comprehensive inspection and repair or replace the faulty parts.

‌7.Foreign matter intrusion‌: When the Worm Gearbox is running, foreign matter such as dust and accumulated water in the surrounding environment may enter the reducer, causing poor meshing of the worm gear and noise. Make sure the environment around the Worm Gearbox is clean to prevent foreign matter from entering.

‌8.Design and manufacturing defects‌: Gear processing errors, unreasonable tooth shape design, etc. can cause poor meshing and noise. Choose a reliable quality reducer brand and model to avoid design and manufacturing defects.

Source:https://plaza.rakuten.co.jp/stepperonline/diary/202502100000/