1. Initial tension: When the tension spring is rolled into shape, the spring coils will generate compression force between each other. When a tensile external load acts on the spring, if the tensile force generated by the load does not reach this force, the spring will not deform. When the compressive force is reached or exceeded, the spring will begin to deform. The tensile load corresponding to this compressive force is the initial tensile force F0.
2. The load-bearing capacity of springs with initial tension is much higher than that of springs without initial tension.
3. For the tension springs that do not require initial tension, the valve spring company will have more or less gaps between the rings. When the number of turns of the spring is large, these gaps will affect the theoretical value of the free length of the spring, and it is necessary to negotiate with the customer.
4. The formula for calculating the winding ratio and stiffness is the same as the compression spring.
5. The total deformation of the extension spring of the spring manufacturer is the sum of the deformation produced by the effective number of turns and the deformation produced by the hooks at both ends. For semi-circular shackles, it is equivalent to 0.1 turns; for full-circle shackles, it is equivalent to 0.25 to 0.5 turns.
6. The spring with initial tension must be made of steel wire in quenched state.
7. Tension springs with small material diameters, many effective turns, and relatively large springs are not easy to guarantee the quality during electroplating.