Official Answer
Answer
'Shingling' occurs in multi-turn wave springs when the waves of adjacent turns slide over one another instead of remaining crest-to-crest. This usually happens because the spring is not properly guided by a shaft or bore, or because the radial wall $b$ is too thin relative to the wave height. Once shingling occurs, the spring rate doubles or triples instantly, and the spring can no longer reach its design work height. Diagnosis is easy: the spring will appear 'telescoped' or tilted upon disassembly. The fix involves increasing the radial wall or improving the guidance tolerances.
