Official Answer
Answer
Compression to 'solid height' occurs when all waves are flattened and the turns of the spring are in direct contact. This condition should be avoided during normal operation because the spring rate $k$ becomes infinite. If a wave spring is accidentally compressed to solid (e.g., during an over-travel event), the stresses at the crests can exceed the ultimate tensile strength of the material, leading to immediate fracture or severe permanent set. Troubleshooting these failures often reveals 'flattened' crests or crack initiation sites at the most compressed points. Design-wise, a 'positive stop' should be engineered into the housing to ensure the spring never reaches more than $80\%$ of its available deflection.
