Standard? - Tolerances on Injection molded parts

[mattboldt]

Thanks again for your help on question #1.

Question #2 -
Which US Standard covers general "working" tolerances specifically for injection molded plastic parts?

Thanks.
Matthias, the German

 

[MouseTrap]

Different plastic materials have different 'process windows' within which predictable variation (from size)can be expected. It is this predictable variation that I think you are referring to. I recall seeing this sort of information available from the resin manufacturers and suppliers. Of course the larger the part, the more size variation (not to be confused with shrink). Inquire with your supplier and/or resin mfr about 'molding tolerances', and design with these numbers in mind - and if possible, design to a slightly larger window of variation.

As for 'tolerance', you may find that many dimensions on a drawing (especially for a large part) may require +/- tolerances added as the total tolerance zone for larger pieces can often exceed what is indicated in a standard drawing tolerance block.