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Problems with oscillation, vibration or knocking?


Vibration isolation aims to position a machine so that no impermissible vibrations or impacts occur in the surrounding area. Theoretically, the machine must be mounted flexibly enough to ensure that it moves virtually freely under the influence of the mass forces that occur when it is operated. The use of an elastic spring system between the machine and the floor can yield an extremely good level of isolation. However, with over-critical suspension, the spring system must have a resonant frequency that is considerably lower than the interference frequency.

The diagram below enables simple calculation of the spring deflection required to achieve the desired degree of isolation. However, lasting alteration of the interference frequency is only possible if springs remain elastic in the long term. Only materials that cannot be compressed or compacted (materials that are not displaced under constant dynamic loads) can ensure the specified degree of efficiency.



This diagram is obviously only valid for machines with constant output. Flexible machine suspension is not without risks. Not all machines can cope with selfmotion and therefore require cushioning for isolation purposes. Many machines also require a degree of stability that cannot be achieved using soft springs. Numerous other options are available to the user, such as reflection damping or so-called subcritical suspension. The importance of the location of the machine should not be underestimated. The resonant frequency of the floor can be a decisive factor for isolation. The difference between a machine location on the first floor and a machine location on solid foundations at ground level is enormous. Yet other results can be achieved with foundation isolation. Ask us for advice - we are happy to find a satisfactory solution for your needs.

This diagram is based on the mathematical relationship:

n = interference frequency (rpm)
fst = static spring deflection (mm)

Resonance occurs if the resonant f requency and interference frequency are the same. Vibrations build up in the system and damage can occur.

Example: A die cutting machine runs at 1,600 strokes per minute. 80% of the vibrations need to be isolated from the building. To the left of the diagram (interference frequency = 1,600 rpm), move downwards to the diagonal 80% transmission line. When you reach the point of intersection, move vertically downwards to determine a required spring deflection of 2 mm.