How do shim ends on a Crest-to-Crest wave spring improve the interface with mating components?

Shim ends provide a 360-degree flat contact surface, unlike plain ends which only contact the mating part at the wave peaks. This distribution of load reduces the contact pressure $P_c = Force / Area$ on the mating components, which is vital when the mating part is made of a softer material like aluminum or plastic. Shim ends also eliminate the 'wave peak' indentation that can occur over time, ensuring a stable work height and preventing the spring from 'digging in' and creating wear debris (fretting) in precision assemblies.