So I had a problem that when i print multiple prints sometimes they dont fit together perfectly, theres a bit of bleed. I found a neat trick where you can just wave the joint over a candle for a second or 2 and fit it together. The filament becomes slightly soft and when connected it hardens to fit a bit better. That bottle cap just wouldnt screw in but now it does.
Depends. I’ve definitely used boiling water with some tight fits. It’s only half the temperature of most common filament printing range.
100 °C is still above the glass transition temp of most plastics, so be careful.