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Yazaki Poka Yoke Idea Generator
Step 1 – Customer / Business Impact was observed as field warranty returns of charging inlets showing burnt contacts and melted housing within 18 months of vehicle delivery, leading to a 3,200 PPM warranty claim rate and a Tier-1 supplier penalty notice from the OEM. This happened because the system allowed inlets with below-minimum contact plating thickness to be shipped to the OEM assembly line to continue while the production process drifted on plating bath chemistry across the night shift. The issue was not detected at the in-process plating thickness X-ray fluorescence (XRF) check at the plating line (first missed check) because the XRF gauge was calibrated only at shift start and drifted by 8% across an 8-hour shift, while the operator sampled only 1 part in 500 instead of the specified 1 in 100. It was also not detected at the end-of-line electrical resistance test on the finished inlet (second missed check) because the EOL test measures resistance at 25°C on a single mating cycle, which cannot detect thin plating — the failure only manifests after thermal cycling and 2,000+ mating cycles in field use. The failure at the source was a plating thickness of 1.8 µm against a specification of 2.5 µm minimum, producing higher contact resistance, localised heating above 90°C under 400 A load, and accelerated plating wear. This exists because the root cause in the system is the absence of a real-time, automated, in-line plating thickness verification with auto-reject — the current control relies on human sampling discipline and a gauge that drifts faster than its calibration interval.
Step 2 (Trade-off) – If we do rely on operator-sampled XRF gauging at the plating line and a single-cycle resistance test at end-of-line to verify contact plating thickness, then we keep plating throughput at 1,200 parts per hour and avoid the capital cost of an automated in-line gauge on every plating rack, but thin-plated contacts below the 2.5 µm specification are escaping to the OEM and causing field warranty failures at 3,200 PPM after 18 months of customer use.