What are the critical considerations for shimming wave springs to achieve a precise preload in a ball bearing assembly?

Shimming is used to compensate for the tolerance stack-up of the housing, shaft, and bearing width. The required shim thickness $t_{shim}$ is calculated as $t_{shim} = \delta_{target} - (L_{gap} - H_{free})$, where $\delta_{target}$ is the deflection needed for the desired preload $P$. In high-precision electric motors, an error of 0.05 mm in shimming can result in a 10 percent deviation in preload, leading to either excessive bearing noise (too loose) or premature wear (too tight). Using hardened steel shims is recommended to prevent 'pounding' or deformation of the shim itself under dynamic loads.