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Analysis on Vibration of Rolling rolls Grinder

Desicription:

This paper main writes what is the vibration produced in the grinding process, what is the reason for it, and what are the ways to eliminate this vibration.

Title: Analysis on Vibration of Rolling rolls Grinder

Keyword: Rolling rolls, Rolling rolls grinder, an effective way to eliminate vibration

Vibration generated in the grinding process is generally a harmful phenomenon that disrupts normal grinding. When the grinding speed is high and the amount of metal grinding is large, strong vibrations often occur. Due to the unreasonable structure of the equipment, the grinding wheel drive motor is installed on a small carriage, and the vibration generated by the motor transmits the vibration source to the grinding wheel through the small carriage. In the grinding process, the lateral feed movement of the small carriage transmits vibration to the grinding roller through the grinding wheel, and the roller feeds back the vibration to the small carriage system, which further intensifies the vibration of the entire system. The vibration generated by the processing system during the grinding process directly affects the quality and productivity of the roll surface. If the vibration is not eliminated and suppressed in time during the semi-finishing and fine grinding processes, the straight wave vibration pattern must be mapped on the roll surface.

 

The vibration source of the rolling rolls grinder mainly comes from the following aspects:

(1) The grinding wheel drive motor is unbalanced and generates vibration, which is the main factor.

(2) The grinding wheel is not in dynamic and static balance and vibrates when rotating.

(3) The length or tightness of the driving V-belt is inconsistent to cause vibration.

(4) Unbalanced grinding force, vibration caused by uneven metal grinding layer thickness.

(5) The lubrication effect of the support neck support shoe is not good, or it will vibrate when it is in a dot or line shape.

 

The effective way to eliminate vibration

There are three types of vibrations. To eliminate vibrations generated in the grinding process, you need to start with the grinder, grinding wheel, and workpiece. The grinding test is used to study the vibration of the processing system or the grinding machine. At the same time, the grinding process can be controlled by changing the process parameters that have an impact on the grinding process (such as the amount of grinding), thereby limiting the generation of vibration.

 

Ways to eliminate forced vibration

The most effective way to eliminate forced vibration is to find the external interference force (vibration source) and remove it. If it cannot be removed, isolation can be used. The grinding wheel drive motor is installed on a small carriage. Although a rubber pad is installed at the bottom of the motor base (to increase damping), there is no damping at the connection between the bottom plate and the upper cover of the small carriage, In this way, because the damping is too small, the vibration is not eliminated, and it is still transmitted to the small carriage. The improved measure is to install rubber pads on the bottom plate and the upper cover of the small carriage to finely balance the motor. Replace the drive motor belt to ensure that its tightness is appropriate and the length is consistent. In addition, the dynamic and static balance of the grinding wheel is adjusted to eliminate the centrifugal force generated during high-speed rotation.

 

Ways to eliminate self-excited vibration

⑴Reasonable selection of parameters related to the grinding process

The feasible method in production is to determine the grinding amount through experiments. You can first test the grinding according to the initially selected grinding amount, and then check, adjust the grinding amount according to this, until the final determination is made. In practice, observe the vibration of the grinding wheel when idling as follows: when the linear velocity V of the grinding wheel is in the range of 5-15m/s, the vibration is very slight; when V is in the range of 15-25m/s, the vibration is obvious, but it is still relatively stable; When V is in the range of 25-30m/s, the vibration is aggravated; when V=35m/s, the vibration is severe. Therefore, when grinding the support roller, according to the idling characteristics of the grinding wheel, it is necessary to choose medium and low-speed grinding as much as possible to avoid self-excited vibration. Usually, the effect is better when the 18-20m/s is selected.

As for the walking speed of the large carriage, the amplitude generally decreases as the speed increases. When the speed is lower than 300mm/min, the amplitude increases. Therefore, under the condition that the processing roughness requirements permit, select the appropriate feed rate, and it is appropriate to select 400-500mm/min for semi-finish grinding and fine grinding. And the speed adjustment is adjusted when approaching the end of the reversing point. Otherwise, the speed will change suddenly when commutation, which will easily cause creeping vibration. The operator generally selects 10-14r/min when the workpiece speed is in semi-finishing and fine grinding. According to observations in practice, using a lower number of revolutions is more prone to horizontal lines. The solution is to do the opposite. Properly increase the number of revolutions of the workpiece during semi-finishing and fine grinding. When n>18rpm/min, the occurrence of horizontal lines can be effectively avoided.

 

⑵In the process of semi-finishing and fine grinding, the use of coolant with a higher concentration of fine grinding fluid will have a better vibration damping effect.

⑶Use a suitable grinding wheel to improve vibration resistance. There are currently three main forms of grinding wheel bond: ceramic, resin, and rubber. In terms of anti-vibration performance, the rubber-bonded grinding wheel has the most obvious anti-vibration effect. The “Saint-Gobain” grinding wheel that has been tried is 23A60-LB24 (750×100×305). Its bonding agent is thermosetting rubber, and its anti-vibration performance is significantly better than that of the usual ceramic grinding wheels. ⑷Improve the positioning accuracy of the support roller

Rolling-rolls

The positioning part of the support roller is two tapered surfaces. If the two support neck frames do not coincide with the center of the grinder, the support roller will produce axial movement and radial runout during the rotation. Therefore, it should be carefully calibrated to improve the positioning accuracy. In addition, it should be noted that the corner screws of the neck bracket should be tightened after the alignment is completed. If the positioning is not accurate, the roundness and coaxiality will be out of tolerance during the grinding process, which will cause unstable operation of the rolling mill, uneven thickness of the rolled plate and strip, wave bending, Concave, and concave edges not only seriously affect product quality, but also reduce the life of roller bearings and other parts. Therefore, the control and detection of the coaxiality between the roll body and the roll diameter and the roundness of the roll body are a problem that cannot be ignored. In addition, manual glycerin lubrication is used for the lubrication of the neck frame support shoe, and the lubrication effect is not good. According to this phenomenon, storage oil grooves can be opened on the bottom and side shells of the neck frame to make the lubrication continuous and the oil film uniform, thereby ensuring the support roller rotate smoothly. . In the process of semi-finish grinding and fine grinding, because the roll is often stopped to measure the roll, when the workpiece is restarted after the measurement, the torque of the instant start will change the dynamic balance previously established, so it is better to measure the roll at a low speed during fine grinding. The method of not stopping. Or use a slow and uniform start when restarting to prevent impact and ensure that the dynamic balance does not change. Moreover, the semi-finishing grinding continues to grind for 2-3 passes, and then the fine grinding can obtain a stable grinding surface.

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