Vibration isolation on industrial machinery

There is a wide variety of industrial machinery where several types of antivibration mounts can be used. In order to have a correct criteria for the selection of the ideal antivibration mount for each case, we must take into account several considerations in order to reach a correct vibration isolation and stability of the machine.
Considerations:

• A. Available input data on the application: 6 or 1 degree of freedom calculations for vibration isolation estimation.
• B. Available positions for the Antivibration mounts and their impact on the natural frequencies of the system and overall stability.
• C. Temperature.
• D. Type of work and exposure to shock and vibration spectra to be isolated.
• E. Structural limitations of the machine.
• F. Vibration Measurements.

A.- Available input data on the application: 6 or 1 degree of freedom calculation calculations for vibration isolation estimation

Industrial machines can be installed on platforms where several elastic steps are present. Wheels or frames depending on their construction have their own elasticity. This elasticity will affect the natural frequencies of the system. In theory, in order to have precise vibration isolation calculation we should take all the elastic steps in consideration.

Since this level of input data is hardly achievable, simplified mathematical models can be used to provide us a good guidance value. Calculations that take into consideration the suspended element as a solid and take into account the 6 degrees of freedom are AMC-MECANOCAUCHO®'s preference. This kind of vibration isolation calculation will be able to provide us the 6 natural frequencies of the system and the eigenvectors of the suspended system. In the image below we show an example of the calculation.

In order to allow AMC-MECANOCAUCHO® applications engineers to perform this type of vibration isolation calculations, here you will find a link to the questionnaire: Click on this link to download the questionnaire.

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This questionnaire allows us to introduce easily the position of the antivibration mountings, centre of gravity and moments of inertia. The below image shows the graphical visualization of the questionnaire.

Once this questionnaire is completed, please address it to AMC-MECANOCAUCHO® engineers and such type of calculation will be done and the results will be explained to you.

B.- Available positions for the Antivibration mounts and their impact on the natural frequencies of the system and overall stability

The position of the antivibration mountings determines the vibration modes of the suspended element. An even load distribution of all the antivibration mountings is advisable. One easy way of obtaining this is by installing the antivibration mounts equidistant to the COG (center of gravity).

Antivibration mounts at the COG level provide more stable solutions and avoid over movement of the suspended elements, particularly on machines highly excentric. Since this is not possible in the majority of the cases, antivibration mounts at different height levels crossing the centre of gravity can be of great help for stability and longevity purposes.

Nevertheless even if this feature cannot be achieved, AMC-MECANOCAUCHO® applications engineers will be able to study the limitations of the application and propose positions where the best vibration isolation and stability can be achieved.
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C.- Temperature

On cases where temperature is high, the limitations of the elastic element must be considered and a correct selection of the compound has to be done. The dynamic forces can also build heat on the mount that is why when the application exceeds 60 C a correct selection on the compound must be done. AMC-MECANOCAUCHO® applications engineers can calculate and test in the laboratory antivibration mounts in order to reproduce such conditions and verify the resistance of the antivibration mount.
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D.-Type of work and exposure to shock and vibration spectra to be isolated

Industrial machinery has different utilities and therefore a different type of work. Some machines are exposed to transient shocks either coming from the road or coming from the tool they are using. In these kind of cases the frequency is generally low, therefore low stiffness antivibration mounts are preferred. This fact allows the mount to reach low natural frequencies of the system and reduce the acceleration reaching to the machine. Low natural frequency is achieved through low stiffness antivibration mounts. Soft antivibration mounts can lead to unstable suspended elements. In order to add stability to the system antivibration mountings with damping systems allow suspended element to stabilize faster the as shown on the graphic below.

Antivibration mountings such as AMC-MECANOCAUCHO® Hydraulic mount and AMC MECANOCAUCHO® hydraulic cone mounts have this damping feature.

The image below shows the section of the hydraulic mount and the speed of the liquid transfer from chamber to chamber in colors. The energy dissipation is done through the liquid transfer. These products can be tuned to the stiffness and damping to suit each application. AMC-MECANOCAUCHO® applications engineers can calculate and select the optimum properties of the antivibration mount for your application.

Other industrial machinery may produce a fixed vibration frequency. This frequency can differ on each type of machine. Therefore the natural frequency of the suspended element will have to be studied and tuned in order to achieve a good stability and vibration isolation level. For this purpose AMC-MECANOCAUCHO applications engineers will be able to help and give you recommendations.
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E.- Structural limitations of frame

The issue of vehicle interior noise is becoming increasingly important as secondary characteristics such as vibration and sound levels are replacing primary ones such as reliability in vehicle purchasing decisions. Interior noise can come from many different sources, but a common one the booming. These phenomena can be generally described as a low frequency (less than 200 Hz) acoustic resonance that is driven by the structure. Structural inputs usually come from either the power train or structural response from road inputs.

In these cases, antivibration mounts can mask the problem but they will not be able to resolve the problem as the origin of it is structural. A correctly selected antivibration mount will be able to attenuate the vibration arriving to the cab, reducing the boom effect. Rubber compound with low dynamic stiffening properties are especially interesting for these cases. For this purpose AMC-MECANOCAUCHO applications engineers will be able to help and give you advice.
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F.- Vibration measurements

The previous considerations have taken into account theoretical aspects of the cabin. Empirical results on vibration isolation on cabs can be only understood by making analysis when making vibration measurements. Understanding this data and contrasting it against the theoretical calculations can allow us to progress and find better solutions for the customer. AMC-MECANOCAUCHO® provides a full service of engineering and vibration measurements in industrial machinery. Should you be interested on this topic do not hesitate to contact our applications engineers. They will be able to help and give you input.
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