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What Is A Vibration Isolator, How To Choose The Right Vibration Isolator

What Is A Vibration Isolator, How To Choose The Right Vibration Isolator

October 24 , 2023 0

Vibration isolators are usually used in automated production environments, and the main role of vibration isolators is to reduce the friction generated by the equipment during operation and the noise generated by the equipment during operation. This article will mainly explain the definition of vibration isolators, as well as the common types of vibration isolators, how to choose the appropriate vibration isolators

Definition OF Vibration Isolators

Vibration isolators can fundamentally control vibration phenomena. In general, large equipment needs power when working, in the state of power, there will be friction between the various parts, as long as the friction appears, then the vibration will also appear, as long as the vibration appears, then the noise will inevitably appear, this is the principle of sound. However, since the use of this product, it can fundamentally reduce the vibration, so the noise will naturally disappear

What Are The Applications OF Vibration Isolators

Although the application range of vibration isolators is wide, but it is basically used in the field of industry, the industrial field includes all aspects, such as CNC machine tools, ordinary machines, water pumps, etc., these devices are widely used, and there will always be a lot of noise in the application process, which seriously affects people's work efficiency, since having this product, The noise is suppressed.
The role of the vibration isolator is reflected in aspects, at the beginning, the performance of this product is not particularly outstanding, after long-term development, this product is more and more ideal in terms of functionality, has been supported by more and more people, and this product is also more broad in the application field, very to meet the requirements of people on performance.

Common Types OF Vibration Isolators

Spring Isolator

In vibration isolation engineering, steel spring vibration isolator has the advantages of stable performance, strong bearing capacity, long life, strong anti-environmental pollution ability, reliable calculation, low natural frequency, and is widely used in vibration isolation, and there are fixed products. The commonly used steel cylinder coil spring isolator. Steel spring vibration isolators are widely used, from a variety of precision instrument vibration isolation to tens of tons of forging hammer, hundreds of tons of railway track vibration isolation, and even the isolation of the entire building, steel spring vibration isolators can achieve satisfactory results.

The biggest advantage of the steel spring vibration isolator is the low natural frequency, usually its frequency range can be 2~6Hz, so its vibration isolation effect is very good (especially low frequency band), and it is more effective for equipment with low speed rotation (speed less than 800rpm).

Another outstanding advantage of the steel spring vibration isolator is that it can be calculated very accurately, and there is a good linear relationship between the compression and the load in the load range, so it can be accurately calculated to obtain the compression and natural frequency of the vibration isolation system.

The disadvantage of the steel spring vibration isolator is that the damping is very small, usually the self-damping ratio is about 0.001~0.05, therefore, it will produce violent vibration through the natural frequency region, and it should be used at the same time with the damper.

In addition, the steel spring also has the problem of high-frequency failure, according to the principle of internal mass resonance, when the excitation frequency is greater than a certain value, the vibration propagates in the form of elastic wave, and the vibration isolation effect cannot be obtained.

Air Spring Isolator

The air spring is a sealed container into the compressed air, using the compressibility of the gas to reflect the spring action. The air spring has low stiffness, high load capacity and adjustable damping. The natural frequency of the vibration isolation system can be as low as 1Hz, which is mainly used in automotive, urban rail, railway vehicles and other industries. The commonly used air spring device consists of a spring body, an additional air chamber and a height controller.

Rubber Vibration Isolator

Rubber vibration isolators and rubber vibration isolators are widely used in vibration isolation, and their main advantages are:

The shape and size can be freely selected, the manufacturing is relatively simple, and the stiffness of 3 mutual vertical directions can be selected according to the need; By changing the rubber hardness and the internal and external structure of the isolator, the performance of the isolator can be greatly changed to meet the requirements of various stiffness.

It can make the natural frequency of the vibration isolation system reach a low level, usually up to 10~15Hz, and has high damping, which has a good effect on the absorption of high-frequency vibration energy, and usually does not need to install damping vibration isolators.

There is no high-frequency failure phenomenon, and the rubber vibration isolator can significantly reduce the high-frequency structural noise (also known as solid noise), which can usually reduce the structural noise in the 100-3200Hz frequency band by about 20dB.

The deformation is relatively large under tensile, compressive, shear and torsional forces.

Compared with metal spring isolators, its main disadvantages are:

Its natural frequency is difficult to reach below 5Hz, so it is not suitable for low-speed equipment. Its ability to resist environmental pollution and temperature change is weak, easy to be affected by sunlight, humidity, ozone and other environmental effects, and its life is short. In addition, under the action of long-term load, creep will occur, and large strains cannot be accepted for a long time. Rubber vibration isolators generally have a life of 3 to 5 years.

How To Choose A Vibration Isolator

The classical method of vibration isolator design is to assume that the whole system is a single degree of freedom (SDOF system). The stiffness of this single-degree-of-freedom system is provided by the elastomer of the isolator because its stiffness is much smaller than that of other physical structures. At the same time, the mass of the system is generally the smaller one of the vibration source devices and vibration sensitive structures. Let's just go back to the two examples: in the case of the engine bracket, the mass of the car engine is much smaller than that of the car bracket and chassis, so let's take the engine as the mass of this single degree of freedom system. In the case of the building, the mass of the building will be much less than the mass of the ground soil, so the building will be the mass of this single degree of freedom system. When we know the stiffness and mass of the system, we can easily calculate the natural frequency of the system.
One of the most important design criteria for a vibration isolator is that its natural frequency needs to be well below the minimum excitation frequency of the vibration source device, as is usually the case. In this case, increasing damping will reduce the performance of the isolator. So why are most dividers still designed with some kind of damping? This is because when the car engine is started, the speed of the engine is always from zero to the rated speed. In this process, the mode corresponding to the natural frequency of the isolator system is always excited, which will cause a certain impact on the frame, we can see that at the natural frequency of the system, increasing the isolator damping by 1.5 times will reduce the vibration transmission rate (at least five times). At high frequencies, the isolator transmission increases only a limited amount. Therefore, in the design of the vibration isolator, we still need to ensure a certain damping
From this single degree of freedom vibration isolation curve 9, we can see that when the natural frequency of the isolator system is much less than the excitation frequency, the effect of the isolator will be improved. In theory, we need to choose the softest isolator. However, in practical applications, vibration isolators have an important limitation. That's the maximum static load. How does static load affect the performance of isolators? We can look at it in the following two ways. First, when the static load is too large, the isolator is overly squeezed, and the vibration source device may be directly in contact with other components. Because the stiffness generated by the contact is much higher than the stiffness of the isolation dew, the isolator will be bypassed and the vibration can be transferred directly to the vibration-sensitive structure through metal contact. Secondly, the stiffness of the isolator is not completely linear, especially for rubber isolators. When the isolator is over-squeezed, the deformation of the rubber geometry will significantly increase the stiffness of the rubber, and the natural frequency of the system will be unexpectedly increased. This is also fatal to isolator design.