Vibration is generated by all kinds of machinery, particularly equipment with rotating movements. If solidly mounted, these generated motions are transmitted directly to the foundations causing irritating noise in the surroundings of the machine installation. Noise may also occur in areas some distance away, transmitted through the structure. This is normally referred to as structure-bore noise (structural noise). In addition to noise, the creation of vibration can cause serious problems to sensitive machinery. The human body, too, can be adversely affected and this manifests itself in reduced working capacity, tiredness, and headaches caused by both high and low frequencies/extremely low frequencies with considerable movement cause motion sickness and seasickness.
Combating the problem
The harmful effects of noise can eliminated by:
- Minimizing both imbalance in the machine and the machine’s natural vibrations by applying greater accuracy in manufacture, optimum design of engine balance, etc.
- Vibration-isolating the machine to prevent transmission of vibrations.
- Vibration-isolating the machine to prevent the effect of outside interference.
- Sound-insulating the machine with suitable sound insulation and absorbing material to combat airborne noise.
A cost effective cure
The manufacturing costs related the accurate balancing of machines are very high and can rise quickly with increased inner balancing. As vibration isolation of the entire machine may still have to be considered, anti-vibration mountings are cost-effective by reducing the need for intensive balancing.
Rubber spring to the rescue
Vibration isolation is based on installing machinery on springs or resilient material of known stiffness and damping. The most commonly used spring materials are rubber and steel. Another alternative is air springs. However, the properties of rubber make it particularly suitable as a spring material as it has:
- A high load bearing capacity with an ability to accommodate overload conditions with the catastrophic failures associated with steel and other materials.
- The ability to carry complex loading’s more easily and economically than alternative solutions. By bonding rubber to a rigid material, a product can be created to accommodate movement with no sliding or rotating surfaces that require lubrication. This allows operation in many harsh environment with substantially reduced maintenance requirements.
Components can be designed to integrate with the space limitations of the application and provide control in all six modes of freedom. Steel springs are normally used in the form of coil springs or leaf springs. Although steel springs permit relatively high deflections, the provide very little damping. Consequently, excessive movement occurs when passing through the resonance range. Often special devices are installed in order to limit deflections. To allow their properties to be utilized in a satisfactory way, Trelleborg Industrial AVS rubber mountings are available in various hardness grades and polymer types.
Trelleborg Industrial Anti-Vibration Solutions are the world leader in rubber to mental bonded anti-vibration devices. To find out more about how our solutions can help you, contact a member of our team today.