Official Answer
Answer
Stacking wave springs in series (Crest-to-Crest) without shims is standard, but stacking them in parallel (Nested) or 'flat-to-flat' without proper alignment leads to wave peaking. If waves do not align perfectly, the load distribution becomes non-uniform, causing localized high-stress points $\sigma_{peak} = K_{stress} \sigma_{calc}$. This can lead to premature fatigue failure. In series stacking, if the waves of one spring slip into the valleys of another, the spring rate doubles while the deflection halves, effectively changing the system from a spring to a solid washer, which can cause catastrophic assembly failure.
