The manufacture of spiral tension springs and torsion springs is currently performed by a small number of manufacturers in the introduction of foreign CNC CNC spring forming machines for automatic forming and stretching of various types of tensile and torsion springs. The vast majority of manufacturing plants still use traditional processing methods to manufacture them. Now they are briefly introduced.
1, spiral tension spring. The process is basically the same as the helical compression spring. The only difference is the processing of the hook and loop at the end. The forming method of the tension spring is as follows:
1) In the same way as the helical compression spring, after stress forming and annealing after winding, hook and ring processing is performed, except for specially shaped hook and loop or spiral tension springs requiring high initial tensile force. Outside the roll, most of the springs are rolled by an automatic coiler.
2) Use a straight-end coil spring machine. It is a vertical centered coil spring machine with a vertical axis. After stressing, stress relief annealing is performed, and then hook and loop processing is performed. Spiral extension springs have many end structures and many processing methods. Commonly used are: small springs use pliers-type special tools or special process equipment for manual processing; common spiral tension springs are processed with hooks or molds by manual or automatic operation methods; long arm hooks are stretched The spring, usually the length required to leave the hook when winding, or the number of turns required for processing after rolling, straighten the ends with a straightening tool, and then use a special tool to bend the hook and loop. The stress relief annealing process specification is as described previously. After the spring roll is prepared, stress relief annealing is performed first, and then cutting and hooking and ring machining are performed. After the hook and loop processing is completed, a stress relief annealing of 1 to 2 times is generally performed. In order to prevent the relative angles of the two hooks from changing, it is necessary to make the temperature of the hook and loop after the stress relief annealing is 20-30°C lower than that after the coil is finished. Spiral extension springs are generally not subjected to shot blasting and forced drawing.
2. Helical torsion springs. The process is basically the same as the spiral compression and tension springs, and the difference is also the end processing. In the case of small-volume production and the torsion arms are relatively complicated, most of them are formed manually or semi-automatically with a mandrel coil spring method, and then the torsion arms are processed according to the pattern requirements with a fixture. In mass production, it can be rolled on straight-to-tail coil spring machines and special machines for torsion springs. The twist arm can't be finished according to drawings, and then processes and fixtures can be used to process. According to the characteristics of spiral torsion springs, the following two points should also be taken into consideration when designing and manufacturing:
1) The torsion arm of the helical torsion spring end should be bent once during manufacture to avoid machining defects and correct shaping. A second stress relief annealing should be performed after the twist arm is finished;
2) The current spiral torsion springs are mostly dense rings, so that a similar compression force is generated between the spring coils, which is equivalent to the initial tension of the tension springs. When loading and unloading, friction occurs and hysteresis occurs. This tendency increases when the load is the same as the direction of rotation or when the number of turns increases; it also causes difficulty in the surface treatment process. Therefore, when designing and forming, there should be a slight gap between the spring coils. In mass production, under conditions, the manufacturer can use hydraulic and pneumatic methods to process the spiral tension, torsion spring deployment, bending, and hooking.