Effect of Back Tension on Free Height of Helical Compression Springs

Despite increasing demand for high dimensional accuracy of helical compression springs for the compact design products in recent years, influencing factors on the dimensional accuracy of helical compression springs have not been clarified thoroughly yet. The characteristics of material (the loop uniformity) and the shape and position of coiling tools (feed rollers and coiling pins) as factors influencing the dimensional accuracy of helical compression springs have been studied by the research and study committee for compression coil forming. However, the effect of back tension, which is the tensile force working in the opposite direction of wire feed, on the dimensional accuracy of helical compression springs has not been clarified yet because quantitative measurement of back tension is difficult to accomplish. In this paper, we conducted an experimental investigation on back tension and estimated its effect on the accuracy of free height of helical compression springs. As the result of the experiments, it is clarified that back tension has direct effects upon the accuracy of free height of helical compression springs.