How does permanent set occur in wave springs and how can it be mitigated during the manufacturing process?

Permanent set, or 'taking a set,' occurs when the spring is compressed to a height where the internal stresses exceed the material's elastic limit, leading to plastic deformation and loss of free height. To mitigate this, manufacturers often perform a 'preset' or 'remove set' operation during production. The spring is compressed to its solid height (or a height lower than the minimum work height). This induces beneficial residual stresses in the direction of the load, effectively increasing the apparent yield strength for subsequent cycles. This process ensures the spring remains stable at the design work height.