A great example of sticking to the problem and following the trail until total problem resolution is achieved. All I can say is I wish more engineers and companies practiced this kind of dogged determination to get to the truth. Kudos to you and your design team.
David, I agree with Beth. It took a lot of attention to detail to find the change you mentioned. It is interesting to note that the environment was such that even a "small" material change could cause a failure. Good work!
Yes, Naperlou, this is a good example of attention to detail. Something as simple as wire insulation made difference between sensors that worked and sensors that failed. This is excellent Sherlock sleuthing.
This story provides a good example of how a secondary effect (insulation change) caused a tertiary effect (shorted contacts). New engineers must keep these types of problems in mind when they look for the root cause of a defect. That cause isn't always obvious. Nice work.
The interesting aspect of this is that the change was made, not just for cost reduction reasons, but for reliability purposes, as well. It makes me wonder if the original PTFE insulation had a problem, too. Was this a case of replacing something that wasn't working well with something that was even worse? Or was it a case of, "If it ain't broke, don't fix it?"
Thanks for your insightful comment Charles. In this case the change was made for the right reasons (reliability; cost was a secondary benefit) by the system engineering folks, but it had an impact on a sub-system (the sensor) - an unintended consequence. Lesson learned - evaluate everything that might be affected by a change, not just how it affects "your own stuff."
The moisture absorption of polyamide is often overlooked in design. We manufacture a polyamide product that is used on average two years before discard. Consumers that were keeping the product over the two year mark complained of premature breakage of the product (non-safety related). Investigation showed that the PA absorbed enough moisture to push out the plasitcizer on the product making it brittle. As there was no other material available, we opted to put use by dates on the product to guide the consumer to when the products life was ending.
It appears that on many occasions "epoxy" material is not suited for many kinds of electrical applications. I am aware of some antennas that don't work right when they are insulated with epoxy material, although one would think that they should. Moisture leaching out salts to short circuit a connector is a long way to go, though. It took good troubleshooting skills to find that problem.
The first Tacoma Narrows Bridge was a Washington State suspension bridge that opened in 1940 and spanned the Tacoma Narrows strait of Puget Sound between Tacoma and the Kitsap Peninsula. It opened to traffic on July 1, 1940, and dramatically collapsed into Puget Sound on November 7, just four months after it opened.
Noting that we now live in an era of “confusion and ill-conceived stuff,” Ammunition design studio founder Robert Brunner, speaking at Gigaom Roadmap, said that by adding connectivity to everything and its mother, we aren't necessarily doing ourselves any favors, with many ‘things’ just fine in their unconnected state.
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