Most engineers including myself understand that Bill. It was clear to me when Dan stated "it is the shape of the tool".
I am hoping someone can explain why this type of plastic forms micro cracks under these conditions, so all can understand.
Good pictures
Why don't you guys just mold these parts?
I understand if you mold first then cut, the cracks will not be as much an issue due to stress patterning. Would only be $1-2K for a simple mold like this, we make them all the time.
Even better we use this machine for small runs and REAL cheap tooling.
It has a high price new, in fact you could buy a real good full size used injection machine for same costs. But if you can find a used one it may just be your answer.
http://www.morganindustriesinc.com/index.htm