We’ve all been taught the scientific method: Form a hypothesis, do some experiments, gather some data, and prove or disprove the hypothesis. But we don’t always do it. We will tweak our 3D prints a little bit and think we see an improvement (or not) and draw some conclusions without a lot of data. Not [Josef Prusa], though. His team printed 856 different parts from four different materials to generate data about how parts behaved when annealed. There’s a video to watch, below.
Annealing is the process of heating a part to cause its structure to reorganize. Of course, heated plastic has an annoying habit of deforming. However, it can also make the parts firmer and with less inner tension. Printed parts tend to have an amorphous molecular structure. That is to say, they have no organization at all. The temperature where the plastic becomes soft and able to reorganize is the glass transition temperature.
Common glass transition temperatures are 65C for PLA, 75C for PET or PETG, and 105C for ABS, in fact those are the minimum temperatures. Until the plastic melts, the temperature is technically a glass transition temperature. However, the hotter you get, the more likely the plastic is to warp, shrink or deform.
There’s a lot of data in the post about how different temperatures affect PLA, ABS, ASA, and PETG. They measured the change in dimensions, how much force it takes to break a part, and the resulting part’s tensile strength.
After reviewing the data, the post and the video talk about how you might do the same thing in a home electric oven. We had to wonder whether a convection oven would be better for eradicating hot spots.