Deflection behaviour of isolation pads
Using vibration isolation pads with high-precision machines requires precise knowledge of the deflection behaviour of the isolation pads.
A prognosis of the compression values allows a suitable time for re-leveling the machine to be defined that depends on the required level fidelity. This permits a perfect operation of the precision machine to be ensured, even after several years.
A static load deflects an isolation pad by a certain amount. The deflection is the sum of elastic and plastic deformation of the anti vibration pad. The isolation pad rebounds by the elastic component when the load is removed.
In contrast to the elastic component, the plastic component is a function of the time the load is applied to the isolation pad. All materials that are exposed to a permanent load deform or are relieved plastically as a function of time. With anti vibration pads, this aftereffect, which is called "creeping", is not linear. With a constant load, it decreases proportionally to the time logarithm. (See diagram)
During the development of the AirLoc isolation pads, we attached great importance to keep the plastic deformation over time at the lowest level possible. For general applications without special requirements you can assume that at least 80% of the expected deflection are reached after 2 weeks. We therefore recommend that the machine is re-leveled after 2 weeks.
Besides many other parameters that are important for optimum isolation, we measure the deflection of AirLoc isolation plates in our own laboratory. The parameters of isolation pads for special applications of FEM analyses can thus be provided swiftly and easily.