Damper Overfill Chamber to Increase Functional Robustness Regarding Variance in Parts and Processes

A damper mechanism for a drug delivery device comprising a frame member, a damper member operably coupled to a drive assembly of the drug delivery device, a damper fluid chamber formed between at least a portion of the frame member and the damper member, and a damper fluid disposed within the damper fluid chamber. The frame member and the damper member rotate relative to each other, and the damper fluid exerts an opposing force on at least one of the frame member and the damper member. The damper fluid chamber includes a main section and an overfill section. The overfill section receives excess damper fluid from the main section to reduce an effect a variation in fill level in the damper fluid chamber has on the opposing force exerted on at least one of the frame member or the damper member.