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According to different spring combinations, with the compression and expansion of the disc spring group, the friction between the individual springs/between the spring and the guide element and the spring loaded part will increase. Therefore, for a given spring application condition, the theoretically calculated loading and unloading characteristic curves will deviate from the actual curve.
Bearing Preload Disc Springs
Friction of a single disc spring
The frictional force when the spring is compressed produces a moment that opposes the loading moment, thus increasing the compression force. When the spring returns, the frictional torque is in the same direction as the loading torque, thereby reducing the required holding force.
The actual coefficient of friction is related to factors such as the degree of polishing of the surface of the loaded part/the edge of the disc spring and the chamfer radius and the lubrication conditions.
Friction of superimposed combination disc spring group
When the superimposed combination spring group composed of N leaf springs is compressed, in addition to the friction generated by the edge of the spring at the loading position, the opposite radial friction will also be generated between the upper and lower contact surfaces of the spring. The N frictional moments generated by these frictional forces interact with the loading torque, so that the loading force of the spring assembly increases during the compression process, and the holding force decreases during the recovery process. The actual load deviation has nothing to do with spring deformation. The use of a thick disc spring (A series) will produce a greater damping effect. Experience has shown that the deviation of the load characteristic curve of the disc spring group increases with the increase of the number of combined springs in the spring group. This is due to the cumulative deviation of the geometric shape of a single spring (especially the deviation of the cone surface and the deviation of the free height) from the ideal state. If the spring moves or even rotates in the spring group, the load characteristic curve of the spring group will also change slightly. But in general, with the extension of time, the loading and unloading characteristic curve of the disc spring group will gradually stabilize. For safety reasons, even spring sets composed of single-leaf springs should be guided internally or externally. For disc spring groups with low friction design, the effect of friction is usually negligible.
Friction of inverse combination disc spring group
It can be considered that the inverse combination disc spring group adopts a low friction design. For example, the disc spring is designed with a special inner edge profile, which greatly reduces the friction between the spring assembly and the guide. This makes the individual springs of the spring group have a uniform amount of deformation, and the risk of premature fracture of the movable spring at the end of the spring group due to excessive stress is also reduced.
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