Which component of a self-winding movement is sometimes made of ceramic?

The component of a self-winding movement that is sometimes made of ceramic is the ball bearing of the rotor. In self-winding watches, the rotor is a part of the movement that spins as the wearer moves their wrist, allowing the winding of the mainspring. Ball bearings are crucial in this mechanism because they reduce friction and wear, enhancing the efficiency and longevity of the movement.

Ceramic is often chosen for these ball bearings due to its high strength, lightweight nature, and excellent wear resistance. This allows the rotor to operate smoothly and quietly, which is important for maintaining the accuracy and functionality of the watch. Ceramic ball bearings provide a significant advantage over traditional metal bearings, especially in the context of high-performance and luxury watches.

The other components mentioned—balance wheel, escapement, and mainspring—do not typically utilize ceramic materials. The balance wheel is primarily made of metals or alloys that can be finely adjusted for precise timekeeping. The escapement is usually made from metal parts to ensure reliability, and the mainspring is traditionally crafted from an alloy designed for optimal energy storage and release.