Thread Content
First, what is the effective number of turns of a spring? The number of turns from one end to the other of the compression spring is called the total number of turns Nt. Among the total number of turns, the spiral portion that acts as a spring, while maintaining a constant pitch per turn, is referred to as the effective number of turns Na. The spiral part that does not function as a spring is called the support ring Nia. The calculation formula is: the effective number of turns of the spring, Na = total number of turns Nt – support turns Nia. The specific value is determined based on the structure. For conventional compression springs, the effective number of turns Na is equal to the total number of turns Nt minus the number of support turns Nia. For conventional tension springs and torsion springs, the effective number of turns Na is equal to the total number of turns Nt (all turns contribute to the tensioning or twisting action). In simple terms, to determine the effective number of turns in a compression spring, one subtracts from the total number of turns the number of turns that would not deform even under upper or lower pressure; generally, this means subtracting 1 turn from the top and 1 turn from the bottom. The effective number of turns for torsion springs and tension springs is the total number of turns. However, in most cases, it is difficult to establish a clear boundary between the support rings and the active rings, and visual inspection is the only option. To ensure that the spring force meets the requirements specified in the drawings, manufacturers often adjust the number of effective turns. The effective number of turns is generally monitored as a reference parameter. As an example, take the standard part CIM010ZA 02S from the Lisi Skylark spring series. As shown in the diagram, this spring has a total of 7.5 turns; subtracting the 2 turns that do not deform under upper and lower contact, the effective number of turns for this spring is 5.5