Plastic shrink factor

[[Me...]]

good morning

a question someone has used this Din 16901 plastic tolerance to calculate the shrinkage of plastics
We are trying to reach the shrinkage factor of a plastic piece with a 72-hour study, we are trying to avoid that when arriving at 72 hours our pieces are out of dimension there is some way or someone has run into a similar case

Plastico.png

[[Ro...]]

I've never used this standard before, but i have in the past been a part if a team to figure out how to manufacture a part (several parts) that would be in tol after several machining ops and a couple 2ndary operations, and time, and shipping.
I think we got the most data out of just observing what the parts do over time and adjusting our "windage" to direct our aim point.
We also spent some time googling "Coefficient of linear expansion" and "Coefficient of volume expansion" and found that the tables & charts that pertained to our materials were pretty much dead on to what we were able to measure.
I know that doesn't really help you, but good luck.

[[Me...]]

thanks Roberto I will continue to look for information on this subject

[[No...]]

DIN 16901 is outdated and no longer valid. The replacement standard is DIN 16742.

DIN 16901 was "just" a tolerancing standard, which gave designers with little to no experience in plastic tolerancing some additional guidance as to which values are realistic and why. While the information it conatins about shrinkage are true, I wouldn't consider it a viable starting point to learn about this topic. Plastic shrinkage is a complex matter, influenced by many parameters. And shrinkage is not the only factor. Different sorts of plastic also accumulate a varying amount of moisture over time, which may - particularly after 72 hours - have much more influence on the dimensions than any remaining shrinkage.