Coil springs can continuously provide greater restoring force in a small space, and can return mechanical parts to their original positions after one stroke is completed to prepare for the next stroke. It is currently widely used in cord retracting components such as garden tool starters and vacuum cleaners.
Coil spring manufacturing process
Coil spring is not only a process in spring manufacturing, but also an important process. The precision of coil spring production plays an extremely important role in the entire manufacturing process. It basically determines the geometric dimensions and characteristics of the spring as well as the utilization of materials.
Spring rolling equipment is generally divided into mandrel spring rolling machines and mandrelless spring rolling machines.
Coil springs can be made from single rollers and multi-roller continuous rollers. Single coil springs and oil-sealed springs are generally used in strip manufacturing. Continuous rolling means rolling a string of coil springs at a time and then cutting them into individual springs according to size.
In order to obtain the required dimensional accuracy after cold forming, when designing springs, spring process equipment and compiling process specifications, it is necessary to accurately grasp the rebound conditions of springs made of various materials during the forming process. There are many factors that affect springback, including the mechanical properties of the material, the winding ratio of the spring, and process equipment.
Rebound is directly proportional to the tensile strength fb of the material and inversely proportional to the elastic modulus e. The larger σ/e, the greater the rebound. When the mechanical properties of the material are unstable, the rebound is also unstable.
The larger the convolution ratio and pitch of the coil spring, the smaller the plastic deformation, the more unstable the internal stress, and the more difficult it is to control the accuracy of the diameter and pitch of the coil spring. Therefore, when winding springs with large winding ratios and pitches, special attention should be paid to the operation of each process. For example, the reversing speed should be slow, the rolled spring blank should be handled with care, and the movement should be as little as possible before stress relief annealing. For spring blanks with a large winding ratio, they are generally fixed after winding and then removed from the mandrel at the same time after stress relief annealing.