Many problems may occur due to improper operation or poor maintenance of the balancing machine in use; Sometimes our technical after-sales personnel go to the customer's site and find that the problems that need to be solved are not difficult, mainly because there is no one who is familiar with the operation of the balancing machine. It's not enough to know the basic operation of the balancing machine. The operator must know the daily maintenance of the balancing machine, the correct operation of the machine and the precautions during operation.
1. Most measuring systems of dynamic balancing machines have the function of "self inspection", which can detect whether the measuring system itself is normal. The operation keys corresponding to the "self check" function may be marked as "self check" or "test". When the balancing machine is normal, the user can fix various set support conditions (support mode and a, B, C and two radii, etc.), then make the measuring system enter the "self inspection" state, and record the display reading corresponding to the "self inspection" state under this support condition. When the operator thinks that there is a problem with the measuring system, he can restore the measuring system to the "self inspection" state under the corresponding original set support conditions, and then check whether the display reading of the measuring system is normal.
2. The angle of the unbalance displayed by the dynamic balancing machine is generally 180 degrees or 0 degrees. Firstly, confirm that the balancing machine operates normally and the rotor still has a certain residual unbalance (even two unbalance values of different phases can be added to the rotor on the two counterweight surfaces). In the case of normal rotation measurement of the rotor, unplug the plug of No. 1 sensor line and check whether the displayed value of the instrument changes. If there is obvious change, it proves that the sensor wire and sensor are normal. If there is no change, there is a problem with this sensor wire or sensor. Plug in the No. 1 plug, and then unplug the No. 2 sensor line plug. In the same way, you can judge whether the No. 2 sensor line and the sensor are normal. The user can find a professional to repair the faulty sensor line or sensor by comparing another sensor line and sensor.
3. When the residual unbalance of the dynamic balancing machine is large, the fault is not obvious. However, when the residual unbalance is small and the balancing machine is started for measurement once, the angle showing the unbalance value always changes. Sometimes the angle changes within a certain range, and sometimes the angle changes within a 360 degree range.
① In order to reduce the interference of the same frequency, double frequency and frequency division, the diameter of the workpiece support shaft should avoid being the same as or close to the outer diameter of the support roller or its integral multiple to avoid interference. For example, if the outer diameter of the roller is 101 mm, it is better to avoid using the shaft diameter support in the range of 91 ~ 111, 46 ~ 55, 32 ~ 36 mm.
② Strictly check the stability of the rotor assembly part. If a process shaft is used, the fit between the shaft and the hole shall be emphatically checked.
③ Check the state of the contact between the rotor shaft (process shaft) and the roller. If the shaft diameter is rough, the knife marks are obvious or the roller surface is damaged, it will cause instability in small signal.
④ Check the state of the contact between the roller and the rotor shaft (process shaft). If the continuous smooth outer surface on the contact surface of the roller has been damaged, it will also cause instability in small signal. When there are obvious scars on the contact surface of the roller, the display of the balance is very unstable.
⑤ Clean the contact surface between the roller and the rotor shaft (process shaft) in the shutdown state, and add appropriate lubricating oil.
⑥ Carefully calculate whether your balance accuracy is too high.
4. When the residual unbalance of the dynamic balancing machine is large, the fault is not obvious. However, when the residual unbalance is small and the measurement is restarted after each balancing, the angle showing the unbalance value always changes in a manner of approximately 180 degrees.
① Too much balance is provided.
② Strictly check the stability of the rotor assembly part. If the process shaft is used, the clearance, Ovality and taper error of the fitting shaft and the hole shall be strictly checked, especially the ovality and taper error.
After the inspection and maintenance are completed according to the above methods, if the fault still exists, the balancing machine can be inspected according to the four point inspection method of dynamic balancing machine described below. In general, the user can use the real rotor according to this. If necessary, the user can record the following process and all data, and then provide them to the manufacturer of the balancing machine. The manufacturer can judge more than 90% of the faults according to this record.
1. Firstly, balance the rotor to the highest possible accuracy, and then prepare a removable counterweight that is 30-50 times greater than the residual unbalance of the rotor (the following process is as follows: the weight of the counterweight is 100g, and the residual unbalance of the rotor should be less than 2-3 g). The connection and loading form of the rotor and the balancing machine are unchanged, and the following test process is directly entered.
2. Check whether various settings of the dynamic balancing machine are normal.
3. Add a removable counterweight of known weight to 45 degrees around the designated counterweight circle on either side of the rotor (hereinafter, it is assumed that the counterweight weighs 100g). Start the dynamic balancing machine, and the indication value of the corresponding surface of the balancing machine should be 40-50 degrees and 90-110g (according to 90% weight removal rate).
4. After shutdown, remove the counterweight and install it on the same surface of the rotor at an angle of 135 degrees. Start the balancing machine, and the indication value of the corresponding surface of the balancing machine should be 130-140 ° and 90-110g (according to 90% weight removal rate).
5. After shutdown, remove the counterweight and install it on the same surface of the rotor at an angle of 225 degrees. Start the balancing machine, and the indication value of the corresponding surface of the balancing machine should be 220-230 degrees and 90-110g (at 90% weight removal rate).
6. After shutdown, remove the counterweight and install it on the same surface of the rotor at an angle of 315 degrees. Start the balancing machine, and the indication value of the corresponding surface of the balancing machine should be 310-320 ° and 90-110g (at 90% weight removal rate).
7. In the same process, install the counterweight block at four angles around the designated counterweight circle on the other side of the rotor for inspection.
8. If the dynamic balancing machine can meet the above requirements, it is considered that there is no fault in the balancing machine.
9. If the dynamic balancing machine can approximately meet the above requirements, it is considered that the balancing machine has slight inaccurate calibration. This problem will generally cause a decrease in operation efficiency without causing a large operation error.
If the dynamic balancing machine has slight inaccurate calibration, the user can eliminate it according to the contents in the supporting instructions of the balancing machine, or notify the manufacturer to handle it.
10. If the dynamic balancing machine does not meet the above requirements, and the error is very large, the user should notify the manufacturer for treatment.
11. Under special circumstances, when users have doubts about the accuracy or quality of the balancing machine, they can also conduct four point fault diagnosis for the balancing machine.
Sometimes, the user may find that the rotor has reached the balance accuracy on the balancing machine. Through the above methods, it is considered that the balancing machine is normal, but the rotor still vibrates to a certain extent during the actual installation and operation. At this time, it is necessary to carefully analyze other technological reasons.
3、 Carefully analyze the causes of vibration and correctly judge the true balance accuracy
There are many reasons for mechanical vibration, among which the vibration caused by the balance of rotating parts is the most direct. However, this does not mean that all vibration problems can be solved after the rotor is balanced on the balancing machine.
The unbalance of the rotor is caused by the deviation of the center of gravity of the rotor from the rotational geometric center line of the rotor. When the rotor rotates, the centrifugal force generated thereby rotates with the rotor, thereby exciting the rotor and the installation foundation of the rotor (such as bearing pedestal, machine base, chassis, vehicle body, etc.) to generate vibration.
Some process problems related to the balancing machine will be discussed below.
1. Process problems of dynamic balancing machine
When balancing with high accuracy, the influence of universal coupling, key and other relevant connecting parts shall be considered. If auxiliary mass such as cursor needs to be added in the balancing process of small rotor, its influence on the final balancing accuracy shall also be considered. When the unbalance caused by these relevant connecting pieces is close to or even greater than the rotor balancing accuracy required by the user, the unbalance displayed by the balancing machine is unreliable. For the balancing machine driven by universal coupling, the balance accuracy of universal coupling shall also be checked regularly.
When the process shaft is used for balance, the circular runout of the process shaft shall not be greater than the rotor balance accuracy index e (eccentricity), otherwise, the high-precision balance of turning 1800 must be carried out. Or discard the process shaft.
In addition, the structure of the process shaft and the actual installation shaft of the rotor shall be made as consistent or similar as possible to ensure that the mass distribution is consistent with the actual installation state.
2. Process problems of rotor
The user of dynamic balancing machine shall try to use the real installation state of the rotor for balancing and ensure its rigidity.
When the process shaft is used for balancing, there will be errors between the process shaft and the actual installation shaft of the rotor, such as the different installation methods of the rotor on the process shaft and the actual shaft, the keyway structure, and the runout of the process shaft and the actual shaft. These factors will cause changes in the unbalance.
When the process shaft is used for balancing, the dimensional accuracy and form and position tolerance accuracy of the rotor mounting hole must be guaranteed, such as large fitting clearance, hole ellipse or taper error, and low roughness are absolutely not allowed.
In addition, the rigidity of the rotor must be guaranteed. If there are other similar structures such as sliding splines, movable blocks and swing cutter blocks inside the rotor, such a rotor will never achieve the ideal balance accuracy.
3. Process problems of actual installation of rotor
The rotor has reached the required balance accuracy on the balancing machine. During the actual installation and operation of the rotor, if some factors are not seriously considered in the actual installation process, the balance accuracy will change and even cause a certain degree of vibration.
The first is the runout of the actual installed shaft, which is very important. Because of the unbalance of the rotor, the center of gravity of the rotor deviates from the rotational geometric center line of the rotor. When the rotor rotates, the centrifugal force generated thereby rotates with the rotor, thereby exciting the rotor and the installation foundation of the rotor to generate vibration. The balanced rotor is installed on the actual installation shaft with eccentricity, which will naturally lead to the vibration of the rotor and the machine.
In addition, other parts coaxial with the rotor will also cause vibration of the rotor and the machine, such as belt pulley, coupling, motor rotor, etc. their balance accuracy will also participate in the vibration of the machine together with the rotor.
During the after-sales service, our technical personnel found that some users of balancing machines did not pay attention to the early manufacturing quality of their products during the production process, but completely relied on the dynamic balancing process for the operation performance of their rotors. This is very serious.
For example, the process of dynamic balancing process is not considered in product design;
The basic parts of the product (such as brackets) are shoddy and even have serious defects;
The external end face runout of the rotor of the fan or other welded structure is too large;
The mass distribution of the cast rotor is uneven and the error is too large;
The accuracy and roughness of the mounting hole of the rotor are too low;
There are serious non rigid factors in the internal structure of the rotor (such as missing welding, loose rivets, etc.);
The roughness and accuracy of the process shaft are too low;
The accuracy and roughness of the actual mounting shaft of the rotor are too low,
All these factors will lead to the decrease of balance accuracy or even the failure of balance.
In addition, the dynamic balancing machine belongs to the instrument type testing machine product. Savage operation of the balancing machine (such as welding and sanding on the balancing machine) will also directly affect the performance and life of the balancing machine, resulting in balance failure. Please pay attention.
Reprint statement: This article was originally edited by Shenman balancing machine factory at www.shshenman.com, and cannot be reprinted without permission!
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