How to deal with compression springs failure?

How to deal with compression springs failure?

  After the spring is formed, it is usually subjected to low temperature stress relief annealing or blue treatment at 220-330°C or according to the working conditions of the spring and the characteristics of the selected raw materials. Quenching and tempering must be used to increase the spring force. However, clamps should be used during the heat treatment of the spring to prevent the ring from becoming smaller and locking with the shaft during operation. The rest should not be underestimated, such as removing the corners and corners of the two outer ends and burrs in the radial direction. In the case where the spring is easy to bend, the coil can be used to rub the tensioned spring on the tensioned spring several times along the longitudinal axis until the surface is partially hardened. Spring is not in place, failure mode and reason. In actual work, we often encounter situations where the spring cannot push the moving object to the set position, which means that the calculated free length of the spring becomes shorter.

  The main reason is that there is no initial compression treatment, that is, the manufactured spring is compressed to the compressed height or tight height (if necessary) with a lot of force, and cannot return to its original value after release. Free length operation. The amount of shortening is called the "initial compression amount". After repeated 3 to 6 compressions, the length is no longer shortened, that is, the spring is "positioned". After the initial compression, the spring is permanently deformed. prevention. In actual work, even if the force of compression springs exceeds the elastic limit of the material, it should be able to maintain its working length. Therefore, the length of the finished spring should be equal to the calculated spring length plus the initial compression force. This prevents the spring from being installed in place, so as to avoid dangerous stress when tightening the coil, which will cause the spring to deform. The indicator line is abnormal and not in place. In the heat treatment process of the finished spring, especially in the quenching and tempering process, the workpiece must be placed horizontally (horizontally) in the furnace to prevent the spring from becoming short due to its own weight and causing incomplete work. . Insufficient spring force requires the spring to produce a certain spring force under the specified deformation. After the load is removed, the spring returns to its free length and moves the movable part to the set position smoothly. But sometimes it cannot be installed in place due to insufficient spring force. Among them are process factors.

"For example, during the tensioning process of the spring, the friction between the ring and the ring, between the ring and the mandrel or sleeve, and between the moving pairs, and sometimes the friction range changes. Larger (maximum ±50%) will result in insufficient spring force and inability to overcome the frictional force of placing the moving parts in place, causing the spring to fail. To this end, each process in the production process specification must be strictly implemented, such as material screening, spring forming, flattening of both ends, edge and corner removal, heat treatment, correction and adjustment, initial compression treatment, inspection and oiling. In addition, the spring force is also related to design factors and material selection factors. From the two main calculation formulas of the spring, namely the deformation formula: λ = 8PD32n / Gd4 and the stress formula τ = K8PD2 / / dd3, it can be seen that the spring force is greatly affected by the steel wire diameter, ring diameter, deformation and number of turns. , It is closely related to the characteristics of the material, the environmental temperature, the load characteristics and the dynamic effect, all of these factors may cause the spring force and the deformation indicator line to be abnormal.