@Alex: When it comes to environmental stress cracking, there is not necessarily any advantage to making the plastic thicker or thinner. The key variables are stress and chemical exposure. If by making the plastic thicker, you can reduce the stress below the threshold, then it might be a solution. But often the threshold stress is so low that this is impractical. And if the internal stresses in the material are high enough, it doesn't matter what you do with the external stress.
Here is a good introduction to residual stress in plastics. At some risk of oversimplification, thin-wall sections are more likely to have flow-induced residual stresses, while thick-wall sections are more likely to have thermal-induced residual stresses. But either way, molded-in stresses can be significant.
I never realized the commonplace chemicals like oil and grease were precursors to stress cracking in plastics. Good to know. Also didn't realize there's some built-in prestress. It seems that, in consumer systems, the plastic always ends up cracking at some point. Is that because thin(ner) plastics are always prone to cracking (and on the other side of the design equation, making them thick enough to be more crack resistant doesn't comport with weight and cost requirements. Or are the thicker plastics just as stress-crack prone?)
Wal-Mart will hold its second Made in the USA Open Call July 7-8, at its headquarters in Bentonville, Ark. The event will be a repeat effort by the world’s biggest seller of consumer goods to increase the amount of US-made products it sells in Wal-Mart stores, in Sam’s Club members-only wholesale outlets, and on walmart.com.
From design feasibility, to development, to production, having the right information to make good decisions can ultimately keep a product from failing validation. The key is highly focused information that doesn’t come from conventional, statistics-based tests but from accelerated stress testing.
There’s a good chance that a few of the things mentioned here won't fully come to fruition in 2015 but rather much later down the line. However, as Malcolm X once said, "The future belongs to those who prepare for it today."
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.