GN 248 Leveling Feet Steel, with Vibration Damping

For correct selection of a standard part used for vibration damping, it is first necessary to understand the terms listed below:

The disturbing frequency is the frequency emitted by the machine, e.g. the number of strokes per minute, measured in Hertz, or the main shaft rotation speed, measured in revolutions per minute.

The static load in Newtons is the load that acts on a single vibration damping element. The total weight of a machine is divided by the number of damping elements. In an optimal arrangement, each element bears the same load.

The degree of isolation, given in percent, is the measure of the absorption of the disturbing frequency, i.e. the damping.

The compression or the spring travel is the maximum change in the height of the damping element in mm.

The calculated spring rate in Newtons/millimeter is the load that causes a height change of 1 mm.

Example with the following assumptions: Disturbing frequency = 50 Hz; load = 120 N; desired degree of isolation = 90 %

The selection of a suitable vibration damping element begins with determining the required compression. This can be taken from the y-axis of the diagram at the intersection of a vertical line at 50 Hz (x-axis) and the
characteristic curve of the desired degree of isolation of 90 %. The example values yield a compression of 1 mm.
With the compression determined in this way and the given static load, it is possible to calculate the required spring rate with the following formula:

Static load F [N] per damping element / Spring travel s [mm] = Spring rate [N/mm] => 120 N / 1mm = 120 N/mm

Based on the calculated spring rate and the desired shape, the appropriate damping element can then be selected. The respective spring rates are given in a table on the corresponding standard sheets. In making the selection, it is important to ensure that the spring rate at least satisfies the calculated value.
The example arrives at a vibration damping element with article number 148.3-46-M10-A-60-S and a spring rate of 138.3 N/mm.