After the end face grinding, if the free height, perpendicularity, pitch and outside diameter of the spring do not meet the deviation specified in the pattern, the screw compression spring often needs to be corrected.
Calibration operations are generally manual or semi-manual.The commonly used tools are: the spring with the metal wire above 4mm, multi-purpose manual pressure machine, splitting machine, press and so on;For springs with wire under 4mm, special tools, pliers and hammers with wedge edge are often used.Calibration is to use these tools to make the spring locally plastic deformation to achieve the required size of the pattern.
1、 application of calibration process
1) outside diameter correction.In general, coil spring can guarantee the deviation of outer diameter, but when the spring winding ratio is too large and the spring outer diameter tolerance requirements are particularly strict (beyond the spring related standards), the outer diameter needs to be corrected.
Calibration tools are commonly used with special clamp, special pressure plate and mandrel, etc.
2) correction of pitch and height.When the pitch is used as the main indicator of acceptance and the spring free height cannot be guaranteed, the correction method can be adopted to adjust it.
3) correction of perpendicularity.In order to meet the requirement of high precision verticality, the verticality precision can be improved by adjusting the process under the condition of no guarantee during grinding.
2、the advantages and disadvantages of correction and the way to reduce correction. The correction process is to make the spring produce local plastic deformation through certain tools to meet the requirements specified in the pattern.This kind of work: the art has two sides: -- the aspect enhances the size accuracy, on the other hand often causes the bad influence to the spring performance, even brings the damage.
In order to reduce the influence of calibration on spring performance, stress relief annealing should be carried out after calibration.
Calibration of high labor intensity, labor hours, increased manufacturing costs.Therefore, measures should be taken in the following aspects to reduce or cancel the calibration process.
1) on the premise of ensuring the main performance of the spring, the design should try not to put too high requirements on the indicators such as verticality and pitch uniformity.
2) improve the uniformity and stability of mechanical properties of spring materials, especially the fluctuation range of tensile strength of spring materials should be as small as possible.
3) improve the precision of coil spring.The spiral Angle and coils of the spring's two ends are uniform and the pitch is uniform, and the error of free height is controlled within a certain range.
4) improve the precision of the grinding spring.Make the vertical degree of the spring as far as possible to meet the requirements of the pattern.