Helical torsion spring. The process is basically the same as that of spiral compression and tension spring, but the difference is also the end processing. In the case of small batch production and complicated torsion arm, most of them are formed by manual or semi-automatic mandrel coiling spring method, and then the torsion arm is processed according to the drawing requirements with the fixture. In mass production, it can be rolled on the straight tail spring coiling machine and the special machine for torsion spring. If the torsion arm can not be completed according to the drawing, it can be processed with tooling and fixture according to the division of labor. According to the characteristics of spiral torsion spring, the following two points should be paid attention to in design and manufacture
1) The torsion arm at the end of spiral torsion spring should be bent once during manufacturing to avoid machining and correction. The second stress relief annealing should be carried out after the torsion arm is processed;
2) At present, most of the spiral torsion springs are dense rings, so there is a similar pressing force between the spring coils which is equivalent to the initial tension of the tension spring. When the load and the rotation direction are the same or the number of turns increases, this tendency increases. In addition, it also brings difficulties to the surface treatment process. Therefore, in the design and forming, a little gap should be left between the coils. In mass production, under the condition of conditions, the manufacturer can use hydraulic and pneumatic methods to process the spiral drawing, torsion spring expansion, bending, hook and other processes.