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Although stainless steel vibrating screens rely on the vibration force provided by a vibration motor to perform screening and filtration, with proper design and structural considerations, they should not experience excessive vibrations. This kind of violent vibration over time can seriously impact the lifespan of both the components and the main body of the vibrating screen. High-quality stainless steel vibrating screens typically feature a "smooth, vibration-free" operation with no significant resonance or aftershocks. However, if you notice sudden, intense vibrations, it is important not to overlook this issue, as it could be caused by problems in one or more of the following five areas:
If the issue stems from the exciter, the first step is to increase the weight of the eccentric block to adjust the amplitude. For vibration motors, the amplitude can be adjusted by modifying the angle of the eccentric blocks at both ends of the shaft to change the excitation force: a smaller angle increases the excitation force and amplitude, while a larger angle decreases them. For eccentric shaft-type exciters, the weight on the flywheel and pulley can be adjusted to increase or decrease the amplitude of the vibrating screen.
The centrifugal force generated by the eccentric weights during operation can cause the eccentric shaft to bend, leading to misalignment between the inner and outer rings of the bearing. This eccentricity, along with its corresponding resonant frequencies, can cause vibrations at specific frequencies, which, in turn, result in high-frequency vibrations. When the excitation frequency is close to the resonant frequency of the bearing or the screen box, a resonance phenomenon may occur, intensifying the vibrations. Moreover, the centrifugal inertial forces produced by the eccentricity can cause bending vibrations, and if the rotational speed approaches the critical value, bending resonance may occur.
Tests have shown that excessive radial clearance—either too small or too large—can lead to significant vibrations in the bearing system. When the radial clearance is too small, high-frequency vibrations occur, while excessive clearance causes low-frequency vibrations. Larger radial clearance lowers the natural radial frequency of the bearing’s elastic system, making it prone to resonance, resulting in significant low-frequency vibrations. This is because the impact points between the rolling elements and raceways generate large accelerations. In the early stages of impact, high-frequency compression waves are created and transmitted into the metal; in the later stages, mechanical vibrations are produced at a lower frequency than the compression wave frequency.
Excessive excitation forces in the stainless steel vibrating screen can subject the bearings to very high radial forces, leading to intense vibrations. Higher bearing precision results in lower vibration levels. The waviness on the rolling surfaces of the bearing, especially the rolling elements, has a significant impact on vibration. The gap between the rolling elements, cages, and the inner and outer raceways contributes to vibration as well, as the self-rotation frequency of the rolling elements is high, and their simultaneous contact with the inner and outer raceways intensifies vibrations. Typically, the ratio of vibration amplitude between the rolling elements, cages, and raceways is approximately 4:3:1. Therefore, reducing bearing vibration should begin with improving the surface processing precision of the rolling elements.
Bearings are a primary source of difficult-to-control vibration in stainless steel vibrating screens. The large excitation forces required for the operation of the vibrating screen subject the bearings to significant radial forces, causing the bearing system to undergo elastic vibrations. Poor lubrication can lead to excessive friction, causing the temperature of the bearings to rise rapidly. As the temperature increases, the radial clearance decreases, leading to even more friction and a further rise in temperature. This cycle accelerates wear and tear on the bearings and the overall system, significantly increasing vibration.
The fit between the outer race and the support hole can impact how vibrations are transmitted in the vibrating screen. If the fit is too tight, it can force the raceways to deform, increasing shape errors and consequently amplifying vibrations. A loose fit can lead to the formation of an oil film in the gap, which may dampen the vibration transmission. Additionally, when there is a significant difference in material properties between the outer race and the bearing housing, and if rubber damping rings are used, they can help reduce vibration transmission.
As shown in the analysis above, intense vibrations in a stainless steel vibrating screen are not normal. When such vibrations occur, it is essential to address the issue promptly to prevent further damage and avoid disruptions in the production process. Ensuring that all components are properly maintained and that the vibration parameters are correctly set will help extend the lifespan of your vibrating screen and maintain smooth operation.
