The Takata airbag inflator problem illustrates a fine dilemma: quality standards across the auto industry are good, those for safety-critical devices are exceptional. The higher the standards, the more difficult it is to spot, much less address, potential problems. If there are only a handful of "incidents" reflected in accident or warranty reports, it requires luck to spot a correlation. Such reports aren't necessarily high in quality. So even when there does appear to be a potential issue, small numbers and limited information make tracing the root cause(s) challenging and potentially impossible.
In Takata's case, they have made over 100 million inflators of the type associated with 5 known fatalities and a handful of additional injuries when the inflators generated shrapnel. Likely they went off with a "bang" not a "whoosh", but there are few data points, and the "bang" aspect destroys evidence. This is the veritable a once in a million occurrence. Is the problem systematic? If so, why? Until that is known, a recall is pointless. Indeed, the lower standards of a dealership service bay – we're talking about millions of airbags being replaced – could readily create more problems than the original one-in-a-million defect.
Now I've sat through engineering presentations on design and manufacturing issues and looked at shop-floor process controls for many types of safety-critical parts, including airbags. Screws are torqued in, with digital records for each. Everything is bar coded, for full traceability. Mistakes still happen; machines get out of adjustment. But if each part is barcoded and scanned at each step, with a "check" (poke-yoke device) after each stage and frequent zeroing in of machines, you can tell when a part came off a misaligned machine, or is missing a screw. A scanner reads the code of each part on each new machine; anything with a barcode associated with a bad reading shuts down the machine, and it takes a supervisor to turn it back on. The part won't be accepted by subsequent machines, so even if somehow it's placed back on the rack, it should never make it to the end of the production process. In the worst case scenario a misaligned machine isn't discovered immediately, but once it is, all the barcodes since the last alignment are flagged to prevent possibly defective parts from getting shipped. Customers get computer files of each check for each part, tied to machine data, shift, machine operator and so on. Those records are retained for at least 15 years.
While production is being ramped up, it's not odd to test multiple parts after machines are turned on from the weekend, with another check following each shift change during the week. Testing is done whenever there's a new batch of plastic or steel. Hence it can take months for a part to be brought to full production – and that's subsequent to design validation, prototype testing and then running parts off the actual production line in pre-production runs.
Car companies like to double-source, so there can be a second plant, up and running. That provides negotiating power. It also provides backup in case of a mechanical failure that takes more than a few hours to resolve, or a batch of substandard materials that make an entire batch of parts suspect. No one is willing to deliberately pay for significant excess capacity, however, so turning out millions of replacement parts requires adding new lines. Even at an existing supplier that replicates the existing setup, the new machinery still has to be broken in and readjusted, and for safety-critical parts the ramp-up is gradual. No one wants to introduce new sources of error into the system. And at least some reports suggest that as much as anything, it may be overall sloppy production controls at Takata that are at fault, rather than one core issue; see the following Automotive News story that draws on Reuters.
In a major recall a car company is thus stuck: in the short run it has to get the replacement parts from the same firm that shipped defective parts.
So back to airbag specifics.
- Actual problems are exceedingly rare.
Globally there are tens of millions of Takata airbags on the road, with virtually every car company as a customer; to date something approaching 20 million have been recalled, including vehicles assembled by at least 10 companies: Honda, Toyota, Mazda, Subaru, Mitsubishi, Nissan, Chrysler, Ford, General Motors and BMW. In the US alone there are over 300,000 airbag deployment per year, or on the order of 2 per 1,000 cars on the road per year (many trucks and older cars among the 250 million registered vehicles in the US – including my 1988 Chevy pickup – don't have airbags). So using US numbers as a base, with Takata having produced over over 100 million airbags of the sort facing recalls, and cars on the road for 10 years, around the world 2 million have deployed. Of those, to date there are 5 known fatalities and several more injuries. There are additional reports of fragmenting inflators in scrapped vehicles, as at least in Japan airbags have to be detonated before a car is sent to a shredder. (I've watched that being done…)
- The cause is as yet unknown. According to a non-Takata airbag engineer I know, there are multiple failure modes that could generate the same shrapnel outcome. For example, it could be the propellant, or it could by the metal cylinder, or it could be only when there is a combination of stronger than normal propellant and weaker than normal steel tubes. Which failure mode(s) are leading to the observed problems? Small numbers mean (i) this analysis is intrinsically very challenging. It is complicated by (ii) the evidence going up in smoke when an airbag inflator explodes and (iii) other evidence going up in smoke because documents in Japan were sent to the incinerator.
The concentration of incidents in very high humidity locales suggests deterioration of the ammonium nitrate "propellant" due to hydration, which could cause the sheets of material — which go "whoosh" – to crumble. Particles have more combustible surface area so generate more bang; clumps can concentrate the force in one part of the cylindrical propellant container and create a local shock wave that ruptures it. Disconcertingly, there are Takata incidents reported from areas not known for high humidity.
So is humidity really the issue? I have given the interior of my car an unintentional steam bath or two, but it's not the sort of thing you record carefully on your warranty card. It could still be a humidity issue. But…there could be two different problems, or one systematic problem and the random one-in-a-million manufacturing defect that escapes all the checks, or all random problems some of which just happened to be clustered geographically.
- This uncertainty is not a trivial issue. So in hopes of pinning down what is really going on, 10 automakers who use Takata airbags got together in Detroit a week ago Friday. This meeting was in effect a gathering of the global car company airbag engineering community. (Needless to say, in light of the continuing supplier price fixing scandal, this closed-door meeting of direct competitors sought and got clearance from the Department of Justice, under the proviso that it was limited to engineers discussing technical issues.) NHTSA is forcing recalls; carmakers aren't yet convinced that merely replacing old inflators with newer and drier ones will fix the problem(s).
- If the actual problem is not systematic, then a recall is much ado about nothing, an expensive gesture that will cost lots of money but that will save no lives if the same one-in-a-million bad inflator ratio doesn't change. Indeed, as a perennial pessimist I fear a rush to increase production will introduce new sources of defects, while making the monitoring of quality compliance more challenging. The bottom line could be a higher number of (idiosyncratic) random defective airbag inflators, not fewer.
- Again, car companies can't simply substitute inflators made by other companies for a Takata inflator — they would have to design a product that matched the gas generation profile needed for the Takata airbag, verify their method of manufacturing produced parts that actually worked to design, test prototypes with the Takata airbag to make sure there was no unforeseen interaction (vent angles or orientation slightly different, lots of subtle interactions). Then they would have to set up a production facility, run off a lot of parts coming through the actual production process on the machines and tooling with the inspection processes that would be actually be used (rather than the prototype build process), and have these tested and retested. This is necessary because the bag portion is very, very specific (the exact grade of material and how it is folded are all very carefully specified, tested and then monitored during production for exact replication). It would be very hard to do this in under 6 months, and production does not ramp up from nil to full overnight.
It would be impossible to do this in 6 months across all of Takata's airbag-inflator-vehicle combinations, because each would need to be tested separately. Engineers can work 16 hour days for a while, but not for month after month. There isn't excess engineering and testing capacity just waiting for a recall to come along, and car companies want their engineers to continue working on new vehicles, they don't want to stop everything under development to re-engineer an old (perhaps decade-old) product.
- As far as I can tell Takata is the only inflator manufacturer that did not start out as a rocket engine or munitions company. Instead Takata was a cut-and-sew fabric operation that built its pyrotechnic capabilities from scratch. That adds to the suspicion of a systematic albeit very rare propellant problem, because explosives are tricky. (For the perspective of someone with experience in the defense industry, see this post on the NBR Japan Forum.) But again, the number of incidents remains very small and there is essentially no ability to cull the necessary information from incident reports or (when they were kept) piles of shrapnel.
- For reference, manufacturers of inflators include Autoliv (the other really big player), TRW, Key Safety Systems, Daicel and (making only inflators) ARC. Innovation continues in this area; Autoliv for example has an inflator that burns hydrogen gas to form water vapor. Over the next few years Takata may bleed business to rivals. Recalls may thrust them into some version of bankruptcy. However, Takata is a big enough player that for the time being car companies have nowhere else to go besides back to Takata.
- A car going 30 miles per hour is traveling 44 feet per second. If you hit a tree, the worst sort of accident, and are sitting 5 feet behind your car's bumper, the airbag has 5/44 = 110 milliseconds to do its thing. Your airbag sensor needs to detect a sudden deceleration within 20 milliseconds, has to start the propellant igniting in another 2-3 milliseconds, and the airbag (some are over 20 gallons = 70 liters!) must inflate into the proper shape in another 60 or so milliseconds.
Airbags ignite with the bang comparable to a fair-sized firecracker. Those who complain of airbag burns after an accident – not that such burns aren't real, I've been at accident scenes – should be made to go to their local gym and have a boxer hit their face with a steering wheel to see what they missed. That airbags can be made to work, yet seldom cause serious injury, is to me pretty amazing.
- The numbers are clear: you are much safer in a car with a potentially defective Takata airbag than a car without any airbag. In the US alone, NHTSA estimates front airbags save over 1,000 lives a year, and lessen serious injuries by many times that number. Even if the inflator did spin off shrapnel, the chance you will be seriously hurt by that is lower. Afraid of projectiles hitting you? Consider the alternative: if you don't have an airbag, your head is the projectile, hitting first and then slowing down the rest of your body. That story never has a good ending, and frequently has a fatal one.
- Always wear a seatbelt. It alone makes a big difference, and gives the airbag precious extra milliseconds to do its thing. All the people I personally know who perished in car accidents were sans seatbelt. Others in the same cars but belted walked away.
Back to the quality-safety dilemma. If you need to find a needle in a haystack, to make sure one of your cattle doesn't ingest it, good luck. If you need to find a single needle in each of a field of haystacks, better luck. If you need to then reassemble all the haystacks exactly as they were, with a harmless needle look-alike in place, best of luck. You'd better be really, really sure that the while doing all this work you don't introduce more debris into the hay, that your cows still get milked and fed on schedule – and that your house doesn't burn down while you're panicking in your hunt for needles.
So … with the information at hand, I'm not yet convinced the Takata recall isn't doing more harm than good. (Caution: bad double negative, re-read slowly.)
Ralph Nader did help move the industry to produce safer cars, with real benefits. To me it feels like we've now reached the point of returns diminished past the point of usefulness.
The post Editorial: Takata and the Dilemma of High Quality appeared first on The Truth About Cars.
from The Truth About Cars http://ift.tt/Jh8LjA
Put the internet to work for you.
No comments:
Post a Comment