Official Answer
Answer
Hysteresis in wave springs is the difference in load at a given height between the compression stroke and the return stroke. It is primarily caused by friction between the spring and the piloting surface (bore or shaft) and internal molecular friction. In a Multi-Turn Crest-to-Crest spring, friction also occurs at the contact points between waves. To minimize hysteresis for precision sensors or control valves, we use dry-film lubricants (like $MoS_2$), ensure high-quality surface finishes on mating components ($Ra < 32 \mu in$), and optimize the number of waves $N$ to reduce the radial expansion force. A low-friction installation ensures that the spring responds instantly to small changes in displacement.
