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Spring Compression Problems
- Jun 26, 2018 -

After the spring is formed, it is generally required to perform stress relief annealing or hairline treatment at a low temperature of 220 to 330°C, or according to the operating conditions of the spring and the properties of the selected material, quenching and tempering are required to increase the spring force. However, when the spring is heat treated, clamps should be used to prevent the ring from shrinking, and the shaft rods can be locked firmly during work. Others, such as removing the corners of the outer ends, radial burrs inside and outside, must not be ignored. In the case of springs with a tendency to bend, it is possible to use a ring of strips to apply friction on the tensioned spring several times longitudinally along the axis to partially harden the surface.

Spring is not in place, failure mode and cause

In practice, we often encounter springs that cannot push a moving object to a set position, which means that the calculated free length of the spring becomes shorter. The main reason is that there is no initial compression, that is, a manufactured spring is compressed to a higher or tighter height (if necessary) with a greater force, and cannot be restored after he is released. Free-length operation. The amount of shortening is called "initial compression." After repeating 3 to 6 compressions in general, the length is no longer shortened, ie the spring “positions”. After the initial compression, the spring is permanently deformed.


In practice, the compression spring should maintain its working length even if it is subjected to forces beyond the elastic limit of the material. Therefore, the length of the finished spring should be equal to the calculated length of the spring plus the initial compression amount, which can avoid the spring not being in place, so as to avoid dangerous stress when the spring coil is tight, resulting in abnormality of the spring indicating line and not being in place. In the heat treatment process, the finished product spring must be quenched and tempered. In particular, the workpiece must be placed horizontally (in the furnace) to prevent the spring from shortening due to its own weight.

The lack of spring force The spring requirement is that a certain spring force must be generated under the specified deformation. Once the load is removed, the spring is restored to free length and the moving part is smoothly moved to the set position. But sometimes it cannot be in place due to insufficient spring force.

Among them, there are technological factors. For example, in the process of stretching, the spring must overcome the friction generated between the ring and the ring, between the ring and the mandrel or the sleeve, and between the pairs of movements. Sometimes the frictional force can vary greatly (up to ±50 %), will lead to insufficient spring force, can not overcome the friction to the moving parts in place, resulting in spring failure. To this end, each process in the production process specification must be strictly implemented such as screening materials, spring forming, both ends grinding, removing edges and corners, heat treatment, correction adjustment, initial compression processing, and inspection refueling.

In addition, the spring force is also related to design factors, material selection factors, and the like. From the two main calculation formulas of the spring, that is, the deformation formula: λ=8PD32n/Gd4 and the stress formula τ=K8PD2/πd3, the spring force is greatly affected by the wire diameter, ring diameter, deformation, and number of turns, and the characteristics of the material, Ambient temperature, load characteristics and dynamic effects are closely related, and can all lead to abnormalities in the spring line and deflection line.

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