I'm sure you've heard of the cases of Dell laptops catching on fire and the resulting recall.
Sony, the manufacturer of the batteries, offered this explanation:
“It's a number you can count on two hands,” [Sony spokesperon Rick] Clancy said, adding that it is inconsequential “when you look at it by Six Sigma standards.” Six Sigma is a measure of engineering quality that ensures a process will not produce more than 3.4 defects per million opportunities.
Ugh. The goal is not to “only” have 3.4 defects per million, especially when the failure mode could result in such severe consequences. Do you want the guy sitting next to you in 13F to have his laptop suddenly catch fire? I don't! The goal for quality should be ZERO defects. I guess this is a difference between Toyota (the zero defects goal) and other Japanese companies (they all aren't like Toyota). When it's YOUR laptop that catches fire, you don't care that yours was a rare and limited case. It's not “inconsequential” to you.
Now is Toyota perfect? No, they've had plenty of recalls this year. But, I wouldn't expect them to say “it's OK, it's only a few vehicles.” Toyota seems to really apologize for quality problems when they occur.
That's why one of the lean principles is “Continuous improvement in the pursuit of perfection.” If you reach “Six Sigma” quality levels, don't stop! Keep improving, the goal really is zero defects, not 3.4 per million.
The Sony/Dell fires are caused by what has been described as a manufacturing defect.
The defect was caused by a short circuit that happens when microscopic metal particles break through the lithium ion cell wall and contact a battery anode, said Sony spokesman Rick Clancy.
“You try to eliminate that in the manufacturing process, but to eliminate them 100 percent is very difficult. Usually when you have a short circuit, it might lead to a battery powering down so you'd have a dead battery, but other times it could lead to incidents including flaming,” Clancy said
The chances of a short circuit depend on the design of each PC, such as whether the battery cells are aligned in parallel or perpendicular, and their proximity to heat sources like the processor and power supply. But ultimately, the odds are against the engineers, since any given particle can create a short, just as any given sperm can make a baby.
I'm not sure how good this Sony spokesperson is, considering this analogy he drew, seems somewhat unprofessional:
“It's kind of like impregnating someone. It only takes one, so the more of them there are, the more likely that you'll impregnate someone,” said Clancy.
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