Official Answer
Answer
In applications where the ratio of free height to mean diameter ($H_f/D_m$) exceeds 1.5, the wave spring is prone to lateral buckling under load. A centering plate or an internal guide rod is used to provide lateral stability. The physics is similar to the buckling of a slender column; the critical buckling load $P_{cr}$ is a function of the spring's lateral stiffness. Using a guide ensures that the deflection remains purely axial, preventing the spring from contacting the bore walls and generating abrasive wear or frictional hysteresis.
