Patent ID: 8438733
Filing Date: 2013-05-14
Classification: B21F,C21D,G01B,Y10T

Abstract:
1. A method of manufacturing a coil spring using a helicoid reduction mill, comprising the steps of: supplying a coil spring material linearly unrolled by a pre-straightener to a surface treatment machine and then shot-blasting or scarfing its outer surface to surface-treat the coil spring material; primarily heating the surface-treated coil spring material to a predetermined temperature using a first heater; sequentially supplying the primarily-heated coil spring material between upper and lower rollers of a plurality of helicoid reduction mills and then pressurizing it in a stepwise fashion so as to reduce a cross-section of the coil spring material such that the coil spring material has the same diameter as that of a coil spring to be manufactured; measuring the diameter of the coil spring material using a diameter measuring machine, measuring the length of the coil spring material using a length measuring machine and then cutting the coil spring material to a desired size; secondarily heating the cut coil spring material to a predetermined temperature using a second heater such that a temperature drop of the coil spring material cooled through the cross-section reducing process and the coiling spring material cutting process is compensated for; forming the secondarily heated coil spring material into a coil spring using a coiling machine; and oil-quenching and then tempering the formed coil spring.