When ID choices fight the assembly line

On a recent med device line build, the industrial design spec used a perfectly symmetrical cap in uniform matte gray. Beautiful on paper, but on the floor it doubled orientation errors and slowed pick verification. Operators started adding Sharpie marks just to keep pace.

We mocked up a slight asymmetry with a micro key and a contrasting inner ring. Added a small tactile notch you can feel through gloves. Orientation errors dropped 70% in pilot, and takt recovered without adding inspection. Our work instructions got shorter because the part began to self-explain.

Lesson for me: early ID and manufacturing reviews pay back fast. Small affordances beat more training. What subtle design tweaks have you used to make assembly foolproof without changing the look? Any go-to cues that pass regulatory scrutiny and still respect the design intent?