Grinding Wheel Dynamic Balancing Measuring Instrument
Product Introduction:
With the rapid development of modern industry, higher and higher requirements are put forward for the performance of rotating machinery. When the mass center of rotating equipment does not coincide with the rotation center due to various reasons, vibration will be caused by centrifugal force. This vibration seriously affects the accuracy of equipment use and shortens the life of support bearings. To eliminate this vibration, dynamic balancing technology must be used.
Aiming at the highest technology at home and abroad, large-scale integrated circuits and single-chip microcomputer technology are adopted. This instrument is multifunctional, can be used as a tachometer, and can also be used for vibration testing. It can be used for time domain analysis and frequency domain analysis. In particular, it has all the functions for measuring dynamic balance.
Simple operation, human-computer interaction, menu prompts, measurement data can be locked and maintained at any time. The VT dynamic balancing instrument is compact in structure and light in weight. The keyboard and display screen are on the panel, and the input and output sockets and various control switches are all placed on the panel. It can perform on-site dynamic balancing of various rotating machinery as a whole. It is equivalent to a movable dynamic balancing machine. It is exquisitely designed and easy to carry. The entire instrument is packed in a portable instrument box. In addition to the general dynamic balancing function, the PHY series also has special designs for the whole machine dynamic balancing of horizontal spiral centrifuges and disc centrifuges, increasing anti-interference ability, and can conveniently measure the vibration of compound drum bodies with differential speed and perform on-site dynamic balancing of the whole machine.
3.1, Why choose the trial weight method first for dynamic balance measurement
This instrument is a portable on-site dynamic balancing instrument. Since the size of the equipment rotor is not fixed, the installation positions of the vibration sensor and the speed sensor are also not fixed. Therefore, the basic design principle of the instrument is to find the unbalanced point of the rotor by adding weights. Specifically, for single-plane measurement, two vibration measurement steps are required: one is the original vibration measurement, and the other is the vibration measurement after adding weights, to find the position of the unbalanced point. For two-plane measurement, three vibration measurement steps are required: one original vibration measurement, and the other two are the vibration measurement after adding trial weights on plane A and plane B respectively, to find the position of the unbalanced point and see the effect of dynamic balancing.
3.2, Why can the influence coefficient method save the step of adding trial weights
For the first equipment rotor (new rotor), a set of influence coefficients must be obtained through the trial weight method. For the second equipment rotor (old rotor), under the condition that the shape, size, and structure of the new and old rotors are the same, and the sensor installation position remains unchanged, the influence coefficients can be input for dynamic balancing, saving the step of adding trial weights. After one vibration measurement, the unbalanced point position can be found.
3.3, How does the instrument convert the vibration measurement vector value into the unbalance vector value
The vibration amplitude measured by the instrument has two units: one is the vibration velocity value expressed in mm/s, and the other is the vibration displacement value expressed in microns (um). The two units are selected by the "+1" key. Generally, users use microns: 1mm = 1000 microns. The phase angle of vibration only indicates the phase difference between the output signals of the vibration sensor and the speed sensor. Then the instrument requires input of the trial weight (in grams) and the position of the trial weight (in degrees). Through the change of the vibration vector before and after adding the trial weight, the instrument can convert the vibration vector value (microns and phase angle) into the unbalance vector (grams and angle). From the screen, you can see M=xxg, ФM =xx°. That is, the weight and angle of the unbalanced point, which is the most concerned set of data for users.
3.4, Why is there no dynamic balance accuracy index in the technical parameters in the manual
We only produce dynamic balancing measuring instruments. The measured objects are equipment rotors provided by users, which may be imported, domestic, or even self-made. The accuracy of various equipment rotors is different and varies greatly, so we cannot formulate a unified balancing accuracy standard. The measurement accuracy of dynamic balancing depends on the accuracy level of the equipment supporting the rotor operation. The higher the accuracy level of the equipment, the higher the measurement accuracy of dynamic balancing. The technical index in the manual is unbalance reduction rate > 85%. This means that if the original residual unbalance of the equipment rotor is 10g (grams), through on-site dynamic balancing operation, 8.5 grams can be removed, and the residual unbalance can reach about 1.5g (grams). This index is also an average. For rotating equipment rotors with high precision and low interference, this index can be fully achieved. For rotating equipment rotors with poor precision and large interference, this index may not be achieved.
3.5, Why do the amplitude and phase angle of vibration sometimes change constantly
In vibration signal measurement, unstable vibration values and phase angles are common phenomena. The vibration caused by unbalance is a periodic and regular sine wave, and the sine wave signal is very stable. However, the vibration of on-site equipment is very complex, generally mixed-frequency vibration, including various vibration signals. Only when the unbalanced vibration component accounts for more than 80% of the total mixed-frequency vibration, the amplitude and phase angle of the vibration signal are relatively stable. If the amplitude of the vibrating equipment has a 10% fluctuation and the phase angle changes within 10 degrees, the vibration signal is considered stable. If the unbalanced vibration component only accounts for less than 50% of the total mixed-frequency vibration, the amplitude and phase angle of the vibration signal become unstable. At this time, it is necessary to find ways to find the source of the interfering vibration signal. How to find the vibration fault of the equipment rotor can use the "FFT analysis" function in the "signal analysis" of this instrument to perform spectrum analysis on the vibration signal, and analyze the various frequency components causing vibration through the spectral lines.
On-site processing methods for unstable vibration signal amplitude and phase angle include: ① Install the vibration sensor as close as possible to the bearing seat of the equipment rotor. ② Select the narrow band in the menu for bandwidth selection. ③ When the vibration amplitude is very small, the measurement can be performed by expanding the instrument's amplification factor. ④ If the bottom feet of the equipment rotor are not fixed, fix them properly. Use rubber pads for vibration isolation.
There is a phenomenon that needs to be explained: during the dynamic balancing process, the unbalance value changes from large to small, and the vibration value and phase angle of the vibration measurement change from stable to unstable. This is a normal phenomenon, indicating that the measurement accuracy of the instrument has been reached.
