Various advantages of changing the spring spacing of CNC spring machines

Manufacturers have discovered many advantages in changing the spring spacing capability of CNC spring machines. For example, conical springs (and other types of variable diameter springs) can be deflected at a linear rate. Variable pitch can also be used to prevent the coil from fully closing in "soft" springs or springs with low spring stiffness. Both tension and compression springs can sometimes benefit from containing several rows of closed coils, which still allows flexibility but prevents entanglement.

Another technical advantage is the ability to prevent spring surge. When the natural frequency of the spring corresponds to the frequency of the applied force, spring surge occurs, causing the spring to swing back and forth (similar to the bending motion when tightly held at both ends). Spring surge can shorten the lifespan of the spring and in some cases may lead to immediate failure. By changing the spring spacing, manufacturers can prevent spring surge in high-frequency applications such as valves and automation.

If both the coil diameter and wire diameter are constant, springs with larger spacing (greater distance between adjacent coils) require greater force to deflect. In a variable pitch spring, the lower pitch coil deflects first, requiring less force. As the applied force increases, the coil with a higher pitch begins to deflect, and the observed spring stiffness also increases.