Provided is a method of manufacturing a spring for inspecting the stress distribution of the spring under load. The method for manufacturing a spring (1) includes the steps of applying a load to the spring (1), measuring the stress of the spring (1) under the load, and releasing the load applied to the spring (1), the measuring the stress of the spring (1) being made by measuring the stress on the surface of the active part of the spring (1) using X-ray diffraction with the cos ? method, and the method further including the step of determining whether the magnitude of the stress of the spring (1) meets a criterion.

Provided is a method of manufacturing a spring for inspecting the stress distribution of the spring under load. The method for manufacturing a spring (1) includes the steps of applying a load to the spring (1), measuring the stress of the spring (1) under the load, and releasing the load applied to the spring (1), the measuring the stress of the spring (1) being made by measuring the stress on the surface of the active part of the spring (1) using X-ray diffraction with the cos ? method, and the method further including the step of determining whether the magnitude of the stress of the spring (1) meets a criterion.

A coiling machine includes feed rollers for moving a wire, a wire guide, a first forming roller, a second forming roller, a pitch tool, a cutting mechanism, and a support mechanism for supporting the wire. The cutting mechanism includes a cutting rotor. The wire coming out of the wire guide is formed into a helical shape by the first forming roller, the second forming roller and the pitch tool. After one coil spring of a predetermined length is formed, the wire is cut by moving the cutting rotor in the radial direction of the wire. The cutting rotor cuts the wire supported by the support mechanism in the radial direction of the wire between the second forming roller and the pitch tool.

A coiling machine includes feed rollers for moving a wire, a wire guide, a first forming roller, a second forming roller, a pitch tool, a cutting mechanism, and a support mechanism for supporting the wire. The cutting mechanism includes a cutting rotor. The wire coming out of the wire guide is formed into a helical shape by the first forming roller, the second forming roller and the pitch tool. After one coil spring of a predetermined length is formed, the wire is cut by moving the cutting rotor in the radial direction of the wire. The cutting rotor cuts the wire supported by the support mechanism in the radial direction of the wire between the second forming roller and the pitch tool.

A method is provided for verifying operative parameters of a selecting device of a machine for forming springs, configured for subdividing the springs formed by a spring forming device of a spring forming machine in at least one first group corresponding to springs having dimensional parameters falling into predefined tolerance values, and a second group corresponding to springs having dimensional parameters varying from the predefined tolerance values.

A method is provided for verifying operative parameters of a selecting device of a machine for forming springs, configured for subdividing the springs formed by a spring forming device of a spring forming machine in at least one first group corresponding to springs having dimensional parameters falling into predefined tolerance values, and a second group corresponding to springs having dimensional parameters varying from the predefined tolerance values.

A servo-rotating all-function tool module is provided for use with a spring forming machine and includes an axle rotating tool module and a servo transmission module assembly. The axle rotating tool module is mounted to the axle and includes an axle slide base and a tool, so that the axle slide base is acted upon by a force to slide along the axle, the tool is caused to press downward or return upward. The servo transmission module assembly is mounted to the spring forming machine to provide a driving force for causing the axle slide base to slide along the axle. Since the tool module is mounted to an axle mounted to a front wall board of the spring forming machine, the direction in which the tool approaches a wire can be varied by rotating the axle in order to conduct operations of bending at different angles and twisting/looping.

A servo-rotating all-function tool module is provided for use with a spring forming machine and includes an axle rotating tool module and a servo transmission module assembly. The axle rotating tool module is mounted to the axle and includes an axle slide base and a tool, so that the axle slide base is acted upon by a force to slide along the axle, the tool is caused to press downward or return upward. The servo transmission module assembly is mounted to the spring forming machine to provide a driving force for causing the axle slide base to slide along the axle. Since the tool module is mounted to an axle mounted to a front wall board of the spring forming machine, the direction in which the tool approaches a wire can be varied by rotating the axle in order to conduct operations of bending at different angles and twisting/looping.

A steel wire for a spring is formed of a steel containing from 0.5% by mass to 0.8% by mass of carbon, from 1.0% by mass to 2.5% by mass of silicon, from 0.2% by mass to 1.0% by mass of manganese, and from 0.5% by mass to 2.5% by mass of chromium, the balance being iron and incidental impurities. The steel has a tempered martensite structure. The hardness of a surface region that is a region within 10 m from an outer surface is from more than 0 HV to 50 HV higher than the hardness of a region other than the surface region.

A compression coil spring having high durability can be provided by using an inexpensive wire material. The present invention provides a compression coil spring formed by using a steel wire material, the steel wire material made of C: 0.45 to 0.85 mass %, Si: 0.15 to 2.5 mass %, Mn: 0.3 to 1.0 mass %, Fe and inevitable impurities as a remainder, and a circle-equivalent diameter of 1.5 to 9.0 mm, wherein hardness of a freely selected cross-section of the wire material is 570 to 700 HV, and at an inner diameter side of the coil spring, unloaded compressive residual stress at a depth of 0.2 mm from a surface in an approximate maximal main stress direction in a case in which compressive load is loaded on the spring is 200 MPa or more, and unloaded compressive residual stress at a depth of 0.4 mm from surface is 100 MPa or more.