In a number of cases, for balancing of various rotors, relatively simple stands are created, which allow to provide qualitative balancing of rotor mechanisms of various purposes with minimal costs. Below there are several such stands made on the basis of a flat plate (or frame) mounted on the cylindrical compression springs. These springs are usually selected so that the frequency of natural vibrations of the plate with the balanced mechanism installed on it was 2 – 3 times lower than the rotor frequency of this mechanism during balancing.
Figure 1. shows a photograph of a balancing stand for abrasive wheels
Fig 1 photo of the stand for balancing
The stand consists of the following main units:
-plate 1, mounted on 4 cylindrical springs 2;
-Electric motor 3, the rotor of which is simultaneously a spindle, on which a mandrel 4, used for installation and fastening of an abrasive wheel on a spindle, is installed.
The principal feature of this stand is the presence of an impulse sensor 5 of the motor rotor rotation angle, which is used as part of the measuring system of the stand (“Balanset”) to determine the angular position of the place of removal of the abrasive wheel of the corrective mass.
Figure 2. shows a photo of the stand used for balancing of vacuum pumps.
Figure 2 stand used for balancing of vacuum pumps
This stand is also based on the plate 1 mounted on cylindrical springs 2. The vacuum pump 3, which has its own electric drive and the speed of which can vary within a wide range from 0 to 60000 rpm, is installed on the plate 1.
On the pump body there are vibration sensors 4, by means of which the pump vibration is measured in two different height sections. To synchronize the vibration measurement process with the rotor rotation angle of the pump the laser phase angle sensor 5 is used on the stand.
At the seeming primitiveness of the design of such stands it allows to achieve a very high quality of pump impeller balancing. For example, at subcritical speeds the residual unbalance of the pump rotor satisfies the requirements of the tolerance set for the balancing class G0.16 according to ISO 1940-1-2007 Mechanical vibration. Balance quality requirements for rotors in a constant (rigid) state. Part 1. Specification and verification of balance tolerances
Achievable in the process of balancing residual vibration of the pump body at speeds up to 8000 rpm does not exceed 0.01 mm/sec. Balancing stands made according to the above described scheme are also effective for balancing other mechanisms, e.g. fans.
Examples of stands designed for balancing of fans are shown in figures 3 and 4.
figures 3 and 4
stands designed for balancing of fans
The quality of fans balancing achieved on such stands is quite high. So, according to the data of the specialists of one of the customers, on the stand designed by them according to our recommendations (see fig. 3) during the balancing of fans the residual vibration level equal to 0.8 mm/s was reached. This is more than three times better than the tolerance limit set for fans of category BV5 according to ISO 31350-2007 “Vibration. Industrial Fans. Requirements for produced vibration and quality of balancing”.
Stand for balancing impellers.
Similar data obtained by us from the fan manufacturing plant show that with similar benches used in the serial production of duct fans, the residual vibration was stable, not exceeding 0.1 mm/s.