Process Capability: The Heat Coil

摘要

During 1926, one of my assignments concerned the heat coil, a tiny circuit breaker Hawthorne made by the millions. The sensing element was a wire wound coil A circuit overload would overheat that coil and cause the circuit to open. The inspectors regularly scrapped about 10 percent of the finished product because electrical resistance was out of specification limits. The local production supervisor and I became a team trying to reduce that waste. The wire from which the coils were made was bought from outside suppliers and came in reels, each having enough wire to make several hundred coils. I measured many reels of the supplied wire and found the electrical resistance was very uniform within any reel, but the reel-to-reel variation was considerable.