Repeatability
Repeatability (ISO 9283, e.g. plus/minus 0.02 mm) is how precisely a robot returns to a taught point. It is the key accuracy spec to verify on used robots.
Repeatability (ISO 9283) is the closeness of agreement between positions the robot reaches when commanded to return to the same taught point repeatedly. It is expressed as a value such as ±0.02 mm and is the most quoted accuracy figure for industrial robots.
Repeatability is not the same as absolute accuracy: a robot can be highly repeatable yet still differ from the commanded coordinate. Repeatability matters for taught, point-to-point work (spot welding, pick-and-place); absolute accuracy matters for offline-programmed paths.
Repeatability degrades as bearings, gears, and cables wear, so it is a core checkpoint when buying used robots. A reputable refurbishment includes a repeatability test against the original spec — The Robot Portal flags refurbished units and their condition.