When assemblers talk about the Japanese concept of poka-yoke (pronounced POH-kah YOH-kay), or mistake-proofing, the first thing that comes to mind is often manual assembly. Error-proofing lore is replete with simple solutions to vexing quality control problems, like adding a simple feature to a part so it becomes obvious if it hasn't been placed in a fixture the right way.
However, there is also a high-tech approach to error proofing. Electric fastening tools, servo-driven presses, sensors and process-monitoring software not only make it possible to control process parameters-they also serve to wave a red flag when an assembly isn't done right.