Official Answer
Answer
Stacking separate wave springs in 'Series' (crest-to-crest) reduces the spring rate: $\frac{1}{k_{total}} = \sum \frac{1}{k_i}$, effectively doubling the deflection for the same load. Stacking in 'Parallel' (nested/nested) increases the spring rate: $k_{total} = \sum k_i$, doubling the load for the same deflection. In assembly, series-stacked springs must be keyed or guided (e.g., using a rod through the center) to prevent buckling, as the slenderness ratio $L/D$ increases. Parallel-stacked springs (separate springs placed inside one another) are rarely used; instead, a single continuous 'Nested' spring is preferred to prevent inter-turn interference.
