Discuss the use of 'Shim Plates' to adjust the preload of a wave spring in an assembly.

In many assemblies, the tolerance stack-up of the housing and the retained components can be larger than the desired deflection range of the wave spring. Shim plates (thin, flat washers) are used to adjust the working height $H_w$. If the measured load $P$ is too low, a shim is added to further compress the spring. The relationship is $P_{new} = k(f + t_{shim})$. This is common in high-precision optical mounts where a specific 'feel' or 'torque' is required. Shims also provide a hardened wear surface, preventing the spring from digging into soft housing materials during cycling.