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HomeNewsVibration and noise reduction measures in the process of motor manufacturing, testing and use

Vibration and noise reduction measures in the process of motor manufacturing, testing and use

Vibration and noise reduction during motor test and use

After the motor is manufactured, if the vibration and noise are unqualified during the factory test or use, the cause must be found out and necessary treatment measures must be taken until the vibration and noise are qualified.

1. Diagnosis of the cause of vibration and noise
When the motor exhibits excessive vibration and noise during the factory test, the cause must first be diagnosed, and the vibration and noise spectrum test, waterfall chart, structural modal test and other methods are used to analyze the characteristics of various excitation frequencies to find out the strong vibration. Vibration source of noise or structural modal cause. Regarding the diagnosis of vibration and noise, the previous series of articles have been detailed, so I will not repeat it here.

2. Vibration and noise reduction measures during testing and use
First of all, we must first pour some cold water here. The vibration and noise of the motor are mainly determined by the design and manufacturing. Once the motor is manufactured, if you want to improve its vibration and noise performance during the test and use, it is mostly It's hard and hard. In other words, we must put the main energy to suppress motor vibration and noise in the motor design and manufacturing process. Once the motor is manufactured, the measures to fix the problem are often very limited, unless the motor has faults and obvious manufacturing quality problems. .
In the control of vibration and noise, there are four types of measures: "elimination", "reduction", "absorption" and "isolation". The so-called "elimination" refers to the treatment from the vibration source, which is the most thorough and effective method; "reduction" refers to the increase of damping on the parts or parts that cause strong vibration, and the energy of vibration and noise is reduced. Vibration noise; "absorption" is to attach a subsystem to the controlled object to reduce the response of the controlled object to a specific frequency excitation; "isolation" refers to the string between the excitation source and the controlled object Add an elastic component subsystem to reduce the response of the controlled object to the excitation source. In practice, it is not simply to take a certain measure, usually a combination of measures, such as installing rubber shock absorbers on the bottom of the motor, which is a kind of vibration isolation effect and damping vibration reduction effect. The sound insulation cover is a kind of effect that not only isolates noise radiation, but also consumes noise energy through the damping material inside. These measures are simple to say but difficult to do. Usually, vibration damping and vibration absorption are mainly considered in the design stage. After the motor is manufactured, the excitation source and structural mode have been solidified, and the measures that can be taken can only be limited. The vibration is reduced and isolated. Practice shows that the following simple methods are often very effective in improving vibration and noise during the test and use of the motor, which can double the result with half the effort.
① Good alignment and installation
The quality of alignment and installation is closely related to vibration. Good alignment and installation are effective measures to reduce mechanical vibration. During testing and use, the alignment accuracy and installation level and verticality should be improved as much as possible. The arrangement of the installed fasteners should be as symmetrical as possible, the tightening torque should be uniform, and the tightening sequence should be symmetrical.
② Repeat installation and tightening
During use, if the vibration and noise of the system at the initial stage of the new installation is good, and abnormal vibration and noise occurs after a period of use, after troubleshooting the motor short circuit, partial open circuit, open welding or cracks in the structure, it is often due to installation and tightening. If caused, tightening should be performed again. Under normal circumstances, due to uneven installation stress distribution and other reasons for newly installed equipment, after a period of operation, with the release and aging of the stress, there will be local looseness or poor coordination. The treatment method is to ensure safety. , During operation or after a period of operation and shutdown, immediately loosen part of the fasteners and then tighten them again. Especially when the bearing has abnormal vibration and noise, loosen the fastening bolts of the inner and outer cover of the bearing when the motor is rotating, and let the motor run adaptively for a period of time in the rotating state, and then tighten it again, the abnormal vibration and noise will disappear.
③ On-site dynamic balance of the whole machine
In the motor manufacturing process, only the rotor itself is dynamically balanced. After the system is formed, the original dynamic balance state occurs due to changes in the system shaft system, heat generation during operation, and uneven deformation. Therefore, after the system is installed and operated for a period of time, the overall on-site dynamic balance of the entire system shaft system can improve the overall vibration and noise performance of the equipment.
④ Adjust the parameters of the shock absorber
In the design of system vibration reduction and noise reduction, shock absorbers are often installed under the installation feet of the equipment to reduce vibration and vibration. However, in design, shock absorbers are usually selected based on simulation calculation and theoretical calculation results. In practice, Due to the simulation calculation error and the dispersion of the shock absorber parameters, the shock absorber parameters may not be the best. At this time, you can test by replacing the shock absorber with different parameters to choose the best damping effect. The shock absorber.
⑤ Adjust the overall installation rigidity
If there is local resonance after the system is installed, the resonance can be avoided by changing the rigidity of the installation structure. Specifically, it can be realized by temporarily increasing the installation of fastening ribs, changing the fastening position, and improving the installation base.
⑥ Sound insulation measures
In the last resort, the only way to install sound insulation panels or sound insulation covers to reduce local and overall noise.

Vibration and noise reduction measures in the motor manufacturing process

Manufacturing is an important part of product realization. No matter how good the design is, it requires good craftsmanship, careful construction and strict quality management to become a realistic product. The manufacturing process is the process of turning the design into the actual product. The actual performance of the motor is related to many factors such as the manufacturing process, processing and assembly accuracy, and manufacturing dispersion. Among them, vibration and noise are more related to various factors in the manufacturing process. Close, the degree of influence is more random and irregular, and this influence is difficult to accurately and quantitatively calculate through simulation and other analytical methods. Only rely on strict process discipline and inspection, meticulous operation and strict quality management procedures in the manufacturing process to ensure. The measures that are conducive to vibration and noise reduction in the manufacturing process mainly include:

1. Ensure structural rigidity
In addition to the design guarantee, the structural rigidity is also related to the manufacturing process. The most critical is the quality of the core stack, assembly quality, insulation treatment quality and welding quality. Insufficient stacking of iron cores, inadequate assembly of fasteners during assembly, poor interference fit accuracy, poor insulation immersion and baking quality, and poor welding quality will affect the overall structural rigidity of the motor. The structural rigidity of the motor is not the greater or the smaller the better, but depends on the closeness of the natural frequency of the structure to the excitation frequency, but overall, the high structural rigidity is beneficial to reduce vibration.

2. Ensure the symmetry of the magnetic circuit
The asymmetry of the magnetic circuit has a great influence on electromagnetic vibration and noise. The reasons for the asymmetry of the magnetic circuit are in addition to design factors (such as meeting the splicing conditions of the fan-shaped pieces, etc.). The manufacturing process is mainly in core manufacturing, magnetic pole assembly and final assembly In the process. This requires strict control during manufacturing and assembly. Even if the silicon steel sheet used in the core is non-oriented silicon steel sheet, there will be more or less anisotropy of magnetic permeability and uneven thickness. In order to reduce the influence of these factors, it should be Each punch is rotated at a certain angle, the so-called rotary punching process, which usually uses a rotary punching process that rotates 120º per punch. The punching equipment and tooling ensure automatic turning of the sheet. If conditions do not permit, at least manual turning shall be used And about 90º staggered rotating film. In addition, the overall dipping paint of the iron core is also an effective way to increase the stiffness and damping of the iron core and reduce vibration and noise. In the processing and assembly of magnetic poles, the consistency of magnetic pole shape and installation accuracy should be strictly controlled. Ensure the symmetry of the air gap during final assembly.

3. Improve the cleanliness of the production process and the tightness of the housing
Cleaning in the production process cannot be ignored for vibration and noise reduction, especially the cleanliness of bearing assembly and lubricating oil and grease seriously affect the bearing noise of the motor, and the bearing noise caused by the unclean lubricating oil and grease is often random. It is difficult to accurately diagnose the cause, so it can only be controlled during the production process. In addition to improving the protection level of the motor, the enclosure seal also plays a vital role in noise radiation. The cover on the enclosure, the gaps between the assembly parts, and the small holes and plugs in the enclosure must be strictly sealed. , Otherwise it will cause the "small hole radiation effect" of noise.

4. Improve rotor dynamic balance accuracy
The rotor is in poor dynamic balance, and when it rotates, it will produce mechanical excitation force, which will cause vibration, and the vibration frequency caused by it is double the frequency. Taking into account the technological advancement and economic rationality, the national standard (equivalent to the adoption of international standards) divides the rotor balance accuracy levels into 11 levels, each with an increment of 2.5 times, from the highest requirement G0.4 The G4000 with the lowest requirements is G0.4, G1, G2.5, G6.3, G16, G40, G100, G250, G630, G1600, G4000. For ordinary motor rotors, the dynamic balance accuracy requirements are G6.3; for higher motor rotors, the dynamic balance accuracy requirements are G2.5; for special requirements (such as tape recorders and record players, CD, DVD drives, For the small motor rotor driven by the grinder, the dynamic balance accuracy requirement should reach G1; for the spindle motor of the precision grinder and the rotor driving the gyroscope, the dynamic balance accuracy should reach G0.4.
The so-called balance accuracy G refers to the product of the maximum allowable eccentricity e of the rotor (or the unbalance rate per unit mass of the rotor) and the maximum rotational angular velocity ω of the rotor. The unit is millimeters per second (mm/s), namely:
G=e•ω/1000=(m•r/M)•n/9550 ⑴
Where: m is the maximum allowable residual unbalance (g); r is the radius of the correction balance ring (mm); M is the mass of the rotor (kg); n is the maximum operating speed of the rotor (rpm); e=m• r/M is the allowable eccentricity of the rotor (μm or g•mm/kg), also known as the allowable unbalance rate per unit mass of the rotor (degrees).
The balance accuracy is an index to measure the quality of the rotor dynamic balance. When the balance accuracy grade G is specified in the design, the maximum residual imbalance (g) allowed by the dynamic balance correction is calculated by the following formula (2):
m=9550•M•G/(n•r) ⑵
As the dynamic balance correction is usually carried out on two balance rings, the maximum imbalance calculated according to formula ⑵ should be divided by 2 to obtain the maximum residual imbalance (g) on each balance ring.

5. Improve processing and assembly accuracy
The machining accuracy and assembly accuracy of parts are closely related to vibration and noise, especially related to the concentricity of stator and rotor and the machining accuracy and assembly accuracy of bearing-related parts. The non-concentric stator and rotor will generate additional mechanical excitation force, thereby generating mechanical noise; it will also affect the distribution of the air gap magnetic field, thereby affecting the electromagnetic force wave and electromagnetic noise; in addition, the non-concentric stator and rotor will also affect the assembly accuracy of the bearing , Thereby affecting bearing noise. The characteristic of the mechanical excitation force caused by the non-concentricity of the stator and rotor is that the mechanical excitation force contains a strong double rotation frequency. The dimensions and shape tolerances of the main components that affect the concentricity of the stator and rotor and the bearing assembly include:
① The dimensional accuracy and roundness of the cylindrical surface of the core gear of the frame.
② The dimensional accuracy, roundness, concentricity and perpendicularity of the stop at both ends of the machine base and the cylindrical surface of the iron core gear. Usually the center line of the cylindrical surface of the core gear is used as the reference to control the radial jump and end jump of the stop of the machine seat.
③ The dimensional accuracy, roundness, perpendicularity of the end face of the end cover and the frame, the concentricity and parallelism of the end cover and the bearing chamber, the dimensional accuracy, roundness and roughness of the bearing chamber, the end face of the bearing chamber The verticality.
④ The dimensional accuracy, roundness and concentricity of the three circles of the stator and rotor cores, and the perpendicularity of the core end faces.
⑤ The dimensional accuracy, roundness, and roughness of the cylindrical surface of the shaft core gear; the dimensional accuracy, roundness, and roughness of the cylindrical surface of the bearing gear; the dimensional accuracy of the distance between the two bearing gears.
⑥ The dimensional accuracy and end jump and radial jump of the bearing cap; the deviation of the length and elastic coefficient of the preloaded spring.
The above dimensional accuracy and geometric tolerances must be guaranteed in strict accordance with the design drawings.

6. Increase structural damping
Increasing the damping of the structure can effectively reduce the amplitude, especially the amplitude at resonance. In the manufacturing process, the most critical part to increase structural damping is the insulation treatment process. Generally, there are two insulation treatment processes used in motors, one is insulation dipping treatment; the other is insulation casting treatment. Since the insulation treatment is a special process, no matter what kind of insulation treatment measures, it must be confirmed in a special process before the formal process is finalized to determine the best process parameters. Once the process parameters are determined, the insulation treatment should be performed during the formal production. The process is strictly implemented in accordance with the determined process. In addition to insulation treatment, applying noise-reducing damping paint on fans, casings, etc. is also an effective means to reduce air noise.

Shenzhen Maintex Intelligent Control Co., Ltd.
Business Type:Manufacturer
Product Range:DC Motor , AC Motor , Stepper Motor
Products/Service:Stepper Motor , Brushless motor , Dc motor , treadmill used motor , Brushed Dc Motor , Fuji motor
Certificate:ISO14001 , ISO/TS16949 , ISO9001 , RoHS
Company Address:Zhengde Science Park, No. 8, Pingdi Street, Longgang District, Shenzhen, Guangdong, China

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