Anti vibration mounting for machines
1/1/2015
When choosing the most appropriate anti vibration mounting, various factors must be taken into account such as the level of vibration produced, the available space to arrange the isolators, the weight the isolators will support and the surrounding conditions. Once considered, we can select the most appropriate type of anti vibration mounting for our requirements. Below you will find descriptions of the three types:
• Elastomeric, a natural synthetic rubber. This type can be moulded to specified shapes and rigidities. With regard to its nature and quality, it is able to withstand large deformations and then return to its original state without occurring any damage. It has an exceptional extendibility and great deformability; as a result, it can be used in extreme elongations.
Natural rubber elastomers provide more favourable mechanic properties for isolation since they offer low energy dissipation which allow their transmit ability to be lower than other synthetic rubbers. Their excellent mechanical properties allow them to achieve stable solutions over time. In terms of limitations, the natural rubber deteriorates under the influence of oils and elevated ambient temperatures. Optimisation of the elastomer mix increases its resistance to UV rays and the Ozone.Silicone rubber is one of the most expensive elastomers on the market, but it presents notable stable properties and provides an effective isolation within a wide temperature range.Most of the elastomeric isolators should not be subjected to major deformations for long periods of time. An isolator with a great static deflection can temporarily perform satisfactorily, but an overload propitiates permanent deformations equal to the breaking of polymeric bonds.• Plastic isolators are less costly and offer exceptional uniformity. Materials most frequently used are polyethylene and styrene. The main disadvantage of these isolators is that they have poor mechanical properties, which is to say that they offer an inferior capacity to resist loads or forces and likewise excessive creep, and permanent deformation. Microcellular polyurethanes exist which can greatly alleviate these problems. For such elastomers, it is essential that their load deflection curve be “S” shaped, which is to say, a linear section, followed by a degressive one then finally a progressive section.• Metal springs. These are normally used in applications which require significant static deflexions. These isolators are used when it is necessary to achieve very low natural frequencies and require stability in deflexion over time. A disadvantage of metal springs is that in order to obtain low energy dissipation, it is necessary to attach spring systems which greatly raise the cost of the solution.
The anti-vibration isolator most frequently used is made from an elastomer, being the most popular natural rubber, since the devices are capable of withstanding great deformations and then reverting to their original state practically damage free. The anti vibration mounting from rubber-metal parts offers us the best characteristics, as well as the best profits. There are a range of forms and sizes of rubber-metal isolators which exist in the market, but we have to choose the one which adapts itself to our needs.
To determine which one achieves this, before installing an isolator to reduce vibration, it is advisable to carry out a theoretical anti-vibration calculation in conjunction with avibration measurement which establish the best solution in each case. This is the only way that we are able to provide the perfect anti vibrational mounting for our problem, and thus satisfactorily reduce the undesired effects resulting from vibration.
