The conductivity of carbon black can easily be overlooked with material. It is a relative natural assumptin to figure that plastic is non-conductive. The addition of any color typically adds a certain amount of carbon that increases its conductivity.
"sufficient perseverance must occur to resolve all the root causes" is huge! Too many times processing engineers/design engineers/ etc...stop at almost good enough and fight quality for the rest of the time. I know this because I've done it. You just get tired of fighting it.
And I certainly understand your statement, "just because the problem didn’t totally go away doesn’t mean you didn’t fix a root-cause source of the problem." But...if I have several problems; in this instance, 3 and I fix 2, I have to ask myself, will everyone be ok with that? If not, I've often times had to come with a dollar vs time figure to show that I'm justified in continuing to try to solve the problem OR its not worth it to go on.
Good points, plasticmaster. This was a particularly strong Sherlock Ohms posting. The detail of the process outlined here reveals the complexity of tracking down problems and the difficulty of determining when you've reached the point of diminishing returns.
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