After the end face grinding of the spiral compression spring is completed, if the free height, perpendicularity, pitch, and outer diameter of the spring does not reach the deviation specified on the drawing, it is often necessary to correct the processing.
The calibration operation is currently in manual or semi-manual operation. Commonly used tools are: springs with a wire of 4mm or more, mostly hand-pull presses, splitters, punches, etc.; springs with a wire of 4mm or less are mostly used. Special tools, pliers, hammers, etc. for wedge-shaped blades. Correction processing is to use these tools to locally deform the spring to achieve the size required by the drawing.
1. Application of calibration process
1.1 Correction of outer diameter. In general, the coil spring can guarantee the deviation of the outer diameter, but when the winding ratio of the spring is too large and the spring outer diameter tolerance requirements are particularly strict (exceeding the requirements of the relevant spring standards), the outer diameter needs certain correction .
The commonly used correction tools are special pliers, special pressure plates and spindles.
1.2 Pitch and height correction. When the pitch is used as the main acceptance index and the free height of the spring cannot be guaranteed, the correction method can be used to adjust.
1.3 Verticality correction. In order to meet the requirements of high-precision verticality, and when grinding cannot be guaranteed, correction can be used to improve the accuracy of verticality.
2. Pros and cons of correction
The correction process is to use a certain tool to cause the spring to produce local plastic deformation to meet the requirements specified on the drawing. The correction has two sides: on the one hand, it improves the dimensional accuracy, and on the other hand, it often causes adverse effects on the performance of the spring, and even brings damage.
In order to reduce the influence of correction on spring performance, stress relief annealing treatment should be carried out after correction.
3. Ways to reduce correction
The calibration is labor-intensive, time-consuming, and increased manufacturing costs. Therefore, measures should be taken from the following aspects to reduce or eliminate the calibration process.
3.1 Under the premise of ensuring the main performance of the spring, try not to set too high requirements for the verticality, pitch uniformity and other indicators during the design.
3.2 Improve the uniformity and stability of the mechanical properties of spring materials, especially the fluctuation range of the tensile strength of spring materials should be as small as possible.
3.3 Improve the precision of coil springs. Make the helix angle, lap and pitch of both ends of the spring uniform, and the free height error is controlled within a certain range.
3.4 Improve the precision of the grinding spring. Make the verticality of the spring meet the requirements of the drawing as much as possible.