The balancing machine may encounter many problems during use due to improper operation or inadequate maintenance; 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 personnel familiar with the operation of the balancing machine present. Merely knowing the basic operation of a balancing machine is not enough. The operator also needs to understand the daily maintenance of the balancing machine, the correct operation of turning on and off the machine, and the precautions during operation.
1、 Fault diagnosis and analysis of common abnormal phenomena in balancing machines.
1. Most measuring systems of dynamic balancing machines have a "self check" function, which can detect whether the measuring system itself is normal. The operation buttons corresponding to the "self-test" function may be labeled as "self-test" or "TEST", etc. Users can fix various set support conditions (support method, a, b, c, and two radii, etc.) when the balancing machine is normal, and then put the measurement system into a "self check" state, recording the display reading of the "self check" state corresponding to this support condition. When the operator believes that there is a problem with the measurement system, they can restore the measurement system to the "self check" state under the corresponding original support conditions, and then check whether the display reading of the measurement system is normal.
2. The angle of imbalance displayed by the dynamic balancing machine is always approximately 180 degrees or 0 degrees apart. Firstly, confirm that the balancing machine is operating normally and that there is still some residual imbalance in the rotor (even two different phases of imbalance can be added to the rotor on each of the two balancing surfaces). With the rotor rotating normally, unplug the No.1 sensor wire plug and check if there is any change in the instrument display value. If there is a significant change, it proves that the sensor wire and sensor are functioning properly. If there is no change, it indicates that there is a problem with the sensor wire or sensor. Insert the first plug and then unplug the second sensor wire plug. The same method can be used to determine whether the second sensor wire and sensor are normal. Users can seek professional assistance to repair faulty sensor wires or sensors by comparing them with another sensor wire.
3. When the residual unbalance of the dynamic balancing machine is large, the fault is not obvious. But when the residual unbalance is small, the angle at which the unbalance value is displayed always changes when starting the balancing machine for measurement. Sometimes the angle changes within a certain range, and sometimes the angle changes within a 360 degree range.
① To reduce interference from the same frequency, multiple frequency, and frequency division, the diameter of the workpiece support shaft should avoid being the same or close to the outer diameter of the support roller or its integer multiples or fractions to avoid interference. For example, if the outer diameter of the roller is 101 millimeters, it is best to avoid using shaft diameter supports within the range of 91-111, 46-55, and 32-36 millimeters.
② Strictly inspect the stability of the rotor assembly part. If using a process shaft, special attention should be paid to checking the fit between the shaft and the hole.
③ Check the condition of the contact between the rotor shaft (process shaft) and the roller. If the shaft diameter is rough, the blade pattern is obvious, or the roller surface is damaged, it will cause instability during small signal.
④ Check the condition 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 can also cause instability during small signals. When there are obvious scratches on the contact surface of the roller, the display of balance is very unstable.
⑤ Clean the contact surface between the roller and the rotor shaft (process shaft) while parked, and add an appropriate amount of lubricating oil.
⑥ Carefully calculate whether your requirement for balance accuracy is too high.
4. When the residual unbalance of the dynamic balancing machine is large, the fault is not obvious. But when the residual unbalance is small, the angle displaying the unbalance value always changes by approximately 180 degrees each time the measurement is restarted after balancing.
① The balance quantity provided is too high.
② Strictly inspect the stability of the rotor assembly part. If using a process shaft, it is important to strictly inspect the clearance, ellipticity, and taper errors between the mating shaft and the hole, especially the ellipticity and taper errors.
2、 Four point method for fault diagnosis
After the above methods of testing and maintenance are completed, if the fault still exists, the dynamic balancing machine can be inspected using the four point inspection method described below. In general, users can use physical rotors based on this. If necessary, users can record the following process and all data, and provide them to the manufacturer of the balancing machine. The manufacturer can determine more than 90% of the faults based on this record.
1. Firstly, balance the rotor to the highest possible precision, and then prepare a detachable counterweight that is 30-50 times greater than the residual unbalance of the rotor (the following process is as follows: use a counterweight weighing 100 grams, and the residual unbalance of the rotor should be less than 2-3 grams). The connection and loading form between the rotor and the balancing machine remain unchanged, and proceed directly to the following experimental process.
2. Check whether the various settings of the dynamic balancing machine are normal.
3. Add a known weight detachable counterweight at a 45 degree angle around the designated weight circle on either side of the rotor (assuming the counterweight weighs 100 grams). Start the dynamic balancing machine, and the corresponding surface indication value of the balancing machine should be between 40-50 degrees and 90-110 grams (at a weight removal rate of 90%).
4. After shutdown, remove the counterweight and install it on the same circumference of the rotor at a 135 degree angle. Start the balancing machine, and the corresponding surface indication value of the balancing machine should be between 130-140 degrees and 90-110 grams (at a weight removal rate of 90%).
5. After stopping the machine, remove the counterweight and install it at a 225 degree angle around the same circumference of the rotor. Start the balancing machine, and the corresponding surface indication value of the balancing machine should be between 220-230 degrees and 90-110 grams (at a weight removal rate of 90%).
6. After stopping the machine, remove the counterweight and install it at a 315 degree angle around the same circumference of the rotor. Start the balancing machine, and the corresponding surface indication value of the balancing machine should be between 310-320 degrees and 90-110 grams (at a weight removal rate of 90%).
7. During the same process, install this counterweight block at four angles around the designated weight 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 are no faults in the balancing machine.
9. If the dynamic balancing machine can approximately meet the above requirements, it is considered that there is a slight calibration inaccuracy problem with the balancing machine. This issue generally leads to a decrease in operational efficiency without causing major operational errors.
If there is a slight inaccurate calibration problem with the dynamic balancing machine, the user can rule it out according to the content in the matching manual of the balancing machine, or notify the manufacturer for handling.
10. If the dynamic balancing machine cannot meet the above requirements and the error is very large, the user should notify the manufacturer for handling.
11. In special circumstances, when users have doubts about the accuracy or quality of the balancing machine, they can also perform a four point fault diagnosis on the balancing machine.
Sometimes users may find that the rotor has reached the balance accuracy on the balancing machine. Through the above methods, it is believed that the balancing machine is also functioning normally. However, when the rotor is actually installed and operated, there is still a certain degree of vibration. At this time, it is necessary to carefully analyze other process related reasons.
3、 Carefully analyze the causes of vibration and correctly determine the true balance accuracy
There are many reasons that can cause mechanical vibration, among which the vibration caused by the balance problem of rotating components is the most direct. But this does not mean that after the rotor is balanced on the balancing machine, all vibration problems can be solved.
The problem of rotor imbalance is due to the center of gravity of the rotor deviating from the geometric center line of rotation of the rotor. The centrifugal force generated by the rotation of the rotor rotates together with the rotor, thereby exciting the vibration of the rotor and its installation foundation (such as bearing seat, machine base, chassis, vehicle body, etc.).
The following will discuss some process issues related to balancing machines.
1. Process issues of the dynamic balancing machine itself
When achieving high-precision balancing, the influence of related connecting components such as universal couplings and keys should be considered. The balancing process of the small rotor requires the addition of auxiliary masses such as a cursor, and its impact on the final balancing accuracy also needs to be considered. When the unbalance caused by these related connectors approaches or even exceeds the rotor balancing accuracy required by the user, the unbalance displayed by the balancing machine is unreliable. For balancing machines driven by universal couplings, the balance accuracy of the universal couplings should also be checked regularly.
When using a process shaft for balancing, the circular runout of the process shaft cannot exceed the rotor balancing accuracy index e (eccentricity), otherwise it must be flipped 1800 for high-precision balancing. Or scrap the process shaft.
In addition, the structure of the process shaft and the actual installation shaft of the rotor should be made as consistent or similar as possible to ensure that their quality distribution is consistent with the actual installation state.
2. Process issues with rotors
Users of dynamic balancing machines should try to use the actual installation state of the rotor for balancing and ensure its rigidity.
When using a process shaft for balancing, there may be errors between the process shaft and the actual installation shaft of the rotor, such as different installation methods of the rotor on the process shaft and the actual shaft, keyway structures, and runout of the process shaft and the actual shaft, all of which can cause changes in the amount of imbalance.
When using a process shaft for balancing, it is necessary to ensure the dimensional accuracy and positional tolerance accuracy of the rotor mounting holes, such as large fitting clearances, elliptical or tapered hole errors, and low roughness, which are absolutely not allowed.
In addition, the rigidity of the rotor must be ensured. If there are sliding splines, movable blocks, swinging blade blocks, and other similar structures inside the rotor, such a rotor will never achieve ideal balance accuracy.
3. Process issues related to the actual installation of rotors
The rotor has already achieved the required balance accuracy on the balancing machine. During the actual installation and operation of the rotor, if some factors are not carefully considered during the actual installation process, it will still cause changes in the balance accuracy and even cause a certain degree of vibration.
Firstly, the runout of the actual installation shaft is a crucial factor. Because of the imbalance problem of the rotor, which is caused by the center of gravity of the rotor deviating from the geometric center line of rotation of the rotor. The centrifugal force generated by the rotation of the rotor rotates together with the rotor, thereby exciting the vibration of the rotor and its installation foundation. However, installing a balanced rotor on an actual installation shaft with eccentricity will naturally cause vibration of the rotor and the machine.
In addition, other components coaxial with the rotor can also cause vibration of the rotor and machine, such as pulleys, couplings, motor rotors, etc. Their balance accuracy will also participate in the vibration of the machine together with the rotor.
4. Other issues
Our technical personnel found during after-sales service that some balancing machine users did not pay attention to the early manufacturing quality of their products during the production process, and completely relied on the dynamic balancing process for the operation performance of their rotors, which is very careless.
For example, the processability of the dynamic balancing process is not considered in product design;
The basic components of the product, such as brackets, are cut corners and even have serious defects;
The outer end face of the fan rotor or other welded structure rotor has excessive jumping;
The quality distribution of the cast rotor is uneven and the error is too large;
The installation hole accuracy and roughness of the rotor are too low;
There are serious non rigid factors in the internal structure of the rotor, such as welding leaks, loose rivets, etc;
The roughness and accuracy of the process axis are too low;
The actual installation accuracy and roughness of the rotor shaft are too low, etc,
All these factors can lead to a decrease in balance accuracy or even balance failure.
In addition, the dynamic balancing machine belongs to the category of instrument testing machine products. The rough operation of the balancing machine (such as welding, sanding, etc. on the balancing machine) can also directly affect the performance and service life of the balancing machine, leading to balancing failure. Be extremely careful.
1、 Fault diagnosis and analysis of common abnormal phenomena in balancing machines.
1. Most measuring systems of dynamic balancing machines have a "self check" function, which can detect whether the measuring system itself is normal. The operation buttons corresponding to the "self-test" function may be labeled as "self-test" or "TEST", etc. Users can fix various set support conditions (support method, a, b, c, and two radii, etc.) when the balancing machine is normal, and then put the measurement system into a "self check" state, recording the display reading of the "self check" state corresponding to this support condition. When the operator believes that there is a problem with the measurement system, they can restore the measurement system to the "self check" state under the corresponding original support conditions, and then check whether the display reading of the measurement system is normal.
2. The angle of imbalance displayed by the dynamic balancing machine is always approximately 180 degrees or 0 degrees apart. Firstly, confirm that the balancing machine is operating normally and that there is still some residual imbalance in the rotor (even two different phases of imbalance can be added to the rotor on each of the two balancing surfaces). With the rotor rotating normally, unplug the No.1 sensor wire plug and check if there is any change in the instrument display value. If there is a significant change, it proves that the sensor wire and sensor are functioning properly. If there is no change, it indicates that there is a problem with the sensor wire or sensor. Insert the first plug and then unplug the second sensor wire plug. The same method can be used to determine whether the second sensor wire and sensor are normal. Users can seek professional assistance to repair faulty sensor wires or sensors by comparing them with another sensor wire.
3. When the residual unbalance of the dynamic balancing machine is large, the fault is not obvious. But when the residual unbalance is small, the angle at which the unbalance value is displayed always changes when starting the balancing machine for measurement. Sometimes the angle changes within a certain range, and sometimes the angle changes within a 360 degree range.
① To reduce interference from the same frequency, multiple frequency, and frequency division, the diameter of the workpiece support shaft should avoid being the same or close to the outer diameter of the support roller or its integer multiples or fractions to avoid interference. For example, if the outer diameter of the roller is 101 millimeters, it is best to avoid using shaft diameter supports within the range of 91-111, 46-55, and 32-36 millimeters.
② Strictly inspect the stability of the rotor assembly part. If using a process shaft, special attention should be paid to checking the fit between the shaft and the hole.
③ Check the condition of the contact between the rotor shaft (process shaft) and the roller. If the shaft diameter is rough, the blade pattern is obvious, or the roller surface is damaged, it will cause instability during small signal.
④ Check the condition 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 can also cause instability during small signals. When there are obvious scratches on the contact surface of the roller, the display of balance is very unstable.
⑤ Clean the contact surface between the roller and the rotor shaft (process shaft) while parked, and add an appropriate amount of lubricating oil.
⑥ Carefully calculate whether your requirement for balance accuracy is too high.
4. When the residual unbalance of the dynamic balancing machine is large, the fault is not obvious. But when the residual unbalance is small, the angle displaying the unbalance value always changes by approximately 180 degrees each time the measurement is restarted after balancing.
① The balance quantity provided is too high.
② Strictly inspect the stability of the rotor assembly part. If using a process shaft, it is important to strictly inspect the clearance, ellipticity, and taper errors between the mating shaft and the hole, especially the ellipticity and taper errors.
2、 Four point method for fault diagnosis
After the above methods of testing and maintenance are completed, if the fault still exists, the dynamic balancing machine can be inspected using the four point inspection method described below. In general, users can use physical rotors based on this. If necessary, users can record the following process and all data, and provide them to the manufacturer of the balancing machine. The manufacturer can determine more than 90% of the faults based on this record.
1. Firstly, balance the rotor to the highest possible precision, and then prepare a detachable counterweight that is 30-50 times greater than the residual unbalance of the rotor (the following process is as follows: use a counterweight weighing 100 grams, and the residual unbalance of the rotor should be less than 2-3 grams). The connection and loading form between the rotor and the balancing machine remain unchanged, and proceed directly to the following experimental process.
2. Check whether the various settings of the dynamic balancing machine are normal.
3. Add a known weight detachable counterweight at a 45 degree angle around the designated weight circle on either side of the rotor (assuming the counterweight weighs 100 grams). Start the dynamic balancing machine, and the corresponding surface indication value of the balancing machine should be between 40-50 degrees and 90-110 grams (at a weight removal rate of 90%).
4. After shutdown, remove the counterweight and install it on the same circumference of the rotor at a 135 degree angle. Start the balancing machine, and the corresponding surface indication value of the balancing machine should be between 130-140 degrees and 90-110 grams (at a weight removal rate of 90%).
5. After stopping the machine, remove the counterweight and install it at a 225 degree angle around the same circumference of the rotor. Start the balancing machine, and the corresponding surface indication value of the balancing machine should be between 220-230 degrees and 90-110 grams (at a weight removal rate of 90%).
6. After stopping the machine, remove the counterweight and install it at a 315 degree angle around the same circumference of the rotor. Start the balancing machine, and the corresponding surface indication value of the balancing machine should be between 310-320 degrees and 90-110 grams (at a weight removal rate of 90%).
7. During the same process, install this counterweight block at four angles around the designated weight 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 are no faults in the balancing machine.
9. If the dynamic balancing machine can approximately meet the above requirements, it is considered that there is a slight calibration inaccuracy problem with the balancing machine. This issue generally leads to a decrease in operational efficiency without causing major operational errors.
If there is a slight inaccurate calibration problem with the dynamic balancing machine, the user can rule it out according to the content in the matching manual of the balancing machine, or notify the manufacturer for handling.
10. If the dynamic balancing machine cannot meet the above requirements and the error is very large, the user should notify the manufacturer for handling.
11. In special circumstances, when users have doubts about the accuracy or quality of the balancing machine, they can also perform a four point fault diagnosis on the balancing machine.
Sometimes users may find that the rotor has reached the balance accuracy on the balancing machine. Through the above methods, it is believed that the balancing machine is also functioning normally. However, when the rotor is actually installed and operated, there is still a certain degree of vibration. At this time, it is necessary to carefully analyze other process related reasons.
3、 Carefully analyze the causes of vibration and correctly determine the true balance accuracy
There are many reasons that can cause mechanical vibration, among which the vibration caused by the balance problem of rotating components is the most direct. But this does not mean that after the rotor is balanced on the balancing machine, all vibration problems can be solved.
The problem of rotor imbalance is due to the center of gravity of the rotor deviating from the geometric center line of rotation of the rotor. The centrifugal force generated by the rotation of the rotor rotates together with the rotor, thereby exciting the vibration of the rotor and its installation foundation (such as bearing seat, machine base, chassis, vehicle body, etc.).
The following will discuss some process issues related to balancing machines.
1. Process issues of the dynamic balancing machine itself
When achieving high-precision balancing, the influence of related connecting components such as universal couplings and keys should be considered. The balancing process of the small rotor requires the addition of auxiliary masses such as a cursor, and its impact on the final balancing accuracy also needs to be considered. When the unbalance caused by these related connectors approaches or even exceeds the rotor balancing accuracy required by the user, the unbalance displayed by the balancing machine is unreliable. For balancing machines driven by universal couplings, the balance accuracy of the universal couplings should also be checked regularly.
When using a process shaft for balancing, the circular runout of the process shaft cannot exceed the rotor balancing accuracy index e (eccentricity), otherwise it must be flipped 1800 for high-precision balancing. Or scrap the process shaft.
In addition, the structure of the process shaft and the actual installation shaft of the rotor should be made as consistent or similar as possible to ensure that their quality distribution is consistent with the actual installation state.
2. Process issues with rotors
Users of dynamic balancing machines should try to use the actual installation state of the rotor for balancing and ensure its rigidity.
When using a process shaft for balancing, there may be errors between the process shaft and the actual installation shaft of the rotor, such as different installation methods of the rotor on the process shaft and the actual shaft, keyway structures, and runout of the process shaft and the actual shaft, all of which can cause changes in the amount of imbalance.
When using a process shaft for balancing, it is necessary to ensure the dimensional accuracy and positional tolerance accuracy of the rotor mounting holes, such as large fitting clearances, elliptical or tapered hole errors, and low roughness, which are absolutely not allowed.
In addition, the rigidity of the rotor must be ensured. If there are sliding splines, movable blocks, swinging blade blocks, and other similar structures inside the rotor, such a rotor will never achieve ideal balance accuracy.
3. Process issues related to the actual installation of rotors
The rotor has already achieved the required balance accuracy on the balancing machine. During the actual installation and operation of the rotor, if some factors are not carefully considered during the actual installation process, it will still cause changes in the balance accuracy and even cause a certain degree of vibration.
Firstly, the runout of the actual installation shaft is a crucial factor. Because of the imbalance problem of the rotor, which is caused by the center of gravity of the rotor deviating from the geometric center line of rotation of the rotor. The centrifugal force generated by the rotation of the rotor rotates together with the rotor, thereby exciting the vibration of the rotor and its installation foundation. However, installing a balanced rotor on an actual installation shaft with eccentricity will naturally cause vibration of the rotor and the machine.
In addition, other components coaxial with the rotor can also cause vibration of the rotor and machine, such as pulleys, couplings, motor rotors, etc. Their balance accuracy will also participate in the vibration of the machine together with the rotor.
4. Other issues
Our technical personnel found during after-sales service that some balancing machine users did not pay attention to the early manufacturing quality of their products during the production process, and completely relied on the dynamic balancing process for the operation performance of their rotors, which is very careless.
For example, the processability of the dynamic balancing process is not considered in product design;
The basic components of the product, such as brackets, are cut corners and even have serious defects;
The outer end face of the fan rotor or other welded structure rotor has excessive jumping;
The quality distribution of the cast rotor is uneven and the error is too large;
The installation hole accuracy and roughness of the rotor are too low;
There are serious non rigid factors in the internal structure of the rotor, such as welding leaks, loose rivets, etc;
The roughness and accuracy of the process axis are too low;
The actual installation accuracy and roughness of the rotor shaft are too low, etc,
All these factors can lead to a decrease in balance accuracy or even balance failure.
In addition, the dynamic balancing machine belongs to the category of instrument testing machine products. The rough operation of the balancing machine (such as welding, sanding, etc. on the balancing machine) can also directly affect the performance and service life of the balancing machine, leading to balancing failure. Be extremely careful.
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