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Details of the automobile manufacturing example mentioned here

When asked for more explanation, the reader wrote:

"We produced steering u-joints and u-joint/ shaft assemblies for several major automakers. . . The automaker produces the design, and farms out quite a bit of work to suppliers. These suppliers farm out some of the work to sub-suppliers and so on.
. . .the design had a tubular, splined shaft that was attached to a u-joint. Think of your steering wheel. It is attached to a telescoping shaft (tort liability created this back in the 20's), and this shaft is attached to a u-joint, which is attached to another shaft, which is attached to a gearbox, which is attached to the rods that turn the wheels. Of course, in cars today, there is the power steering mechanism involved also. Because the car flexes, the u-joints are necessary. The point is this: The steering wheel is directly controlling the wheels, and if any component in that chain were to fail, the driver would not be able to control the steering, often with disastrous results. In this design, at the point the tubular shaft was attached to the u-joint there was, as I mentioned before, a double safety. The joint was to be both peened and welded. Both the peen and the weld were individually strong enough to last, by themselves, the life of the car. Here, the design was good, but in initial manufacturing, a mistake occurred.

"This particular operation was performed on a rotary table machine. The operator would load the shaft and the u-joint into the machine, and unload a completed part at the same time. He would push the button, and the machine would press the shaft into the u-joint for proper location. This press fit was for location purposes only, and was not part of any plans for safety at that connection. Then, the operator would cycle the machine again, and the pressed together assembly would rotate to the next station, where a hydraulic ram would peen the u-joint and the shaft together. The operator would cycle the machine again, and at the next rotary station, the same connection would be welded, completing the double-safety called for in the design. Each cycle, the operator is loading new components and unloading completed assemblies.

"At the beginning of the production, we were having problems with the rotary table machine for a variety of reasons. I don't have time to delve into them at the moment. Basically, the machine was not running smoothly, and the operator would constantly have to stop the machine, manually reset items, perform operations a second time, and so on. Think of a high-school grad, well-meaning, but paid not much, having to deal with loading, unloading, reloading, resetting many hundreds of parts per shift. This was right at the beginning of production, and things hadn't been smoothed out. What happened was that a shaft/ u-joint assembly left our factory with no peen, no weld, but with a press fit. The press fit was strong enough to handle any manual stimulation. The defect wasn't noticed at our customer, and not noticed at the assembly plant.

"In Israel, a customer bought a new car, and when he drove it off the lot, he noticed the engine light was on, so he drove it back into the dealership. The mechanic put it on the rack, and noticed that he was turning the steering wheel, but the tires weren't moving. The dealer knew some bad kind of manufacturing mistake had been made. . . [The customer was given a loaner car] The unrelated failure that caused the engine light to come on was fortuitous.

"By the time the customer in Israel had bought the car, ~250,000 of these parts had been made. Our statistical process control didn't give us any idea how many parts could have this defect.

"What the manufacturer did was immediately ground all the new cars in production, transportation, and on dealer's lots. No one was allowed to drive the cars until a mechanic confirmed the presence of the weld (the peen could not be seen without removing the part, and because the weld itself was strong enough, this was seen as a proper action). A "silent" recall was issued where the dealers and certified auto repair places were informed to check for presence of weld, but not inform the customer.

"For days, there were about 50 of us working on the problem. We tested assemblies with only a press fit. Virtually all failed at less than 50 cycles, but one outlier lasted more than 100. Keep in mind that the welded/ peened ones lasted millions of cycles (more than the life of the car). The determination was made that if there were any other such parts out there, we would have known about it by now, or if one had just been sold, that we would find out quickly. We also determined that if there were others, there couldn't be very many, and almost certainly, there weren't others. Inspections of the vehicles turned up no other examples. 100% inspection of the parts leaving our factory was ordered, which was expensive, and other improvements were made.

"So, here, there is a massive response to a potential problem, [without anyone having] actually been injured. I dealt with other things in automotive, and I can tell you that safety issues are taken very, very seriously. It is not perfect, by any means, but it is a far cry better than medicine."