I printed some interlocking parts which worked (reasonably) well when fresh. 6 months later, they had deformed in a systematic way. One parameter showed maybe 3% change, which was enough to matter when several objects were interlocked. These were Polylite PLA. If they absorbed water, would they change shape? Could they get warm enough to “recrystalize”, as I read that PLA has a crystalline and an amorphous component (have not figured out the details here). I am doing new parts in PETG. But since I don’t know for sure what happened with the first batch, I am fretful. Attempts to dry the PLA (1 week of 120F and dessicant) have not fixed the problem.
PLA deforms when it is under constant load.
That is normal.
Thanks. Deformation under load or “creep” is a separate problem, but one reason for my moving to PETG.
My question is about a small but consistent (across many identical parts) shape change over time and temperature and humidity. The odd thing is that it’s NOT a uniform (isotropic) swelling.