Two design problems identified in consumer product recalls: Degradation over extended use and scarce FR-coupling

One hundred recalls of consumer products, e.g., home electronics, in the Japanese market identified two design problems; aging degradation causing failure to meet functional requirements (FR) over extended use and scarce FR-coupling failure that affect meeting other FRs. The former was found in 22% of the recalls with products used over 10 years. The designer could not foresee the long-term degradation in plastic or insulator. The latter contributed to 66% with an extremely low failure rate of less than 0.01% of all production. Rare design error affected by secondary FRs like cooling or friction is another hard-to-notice factor for designers.