If we look at a few of Bambu’s PLA pages, it looks like they all roughly agree on 55* for 8 hours when drying in a blast oven.
When we move onto the drying recommendations wiki it shows 50* for 8 hours. This page also makes no mention of the AMS 2 Pro or AMS HT. Are they considered a blast (forced air) drying oven?
Last but not least, using my H2D controls to use my AMS 2 Pro or AMS HT to dry a spool of PLA, the profile shows 45* for 12 hours.
It would be nice if there was some consistency and cleanup. I’d much rather dry at a slightly higher heat if it won’t take me 12 hours. Which is correct? Are they all correct in some way?
All are probably mostly correct but there could be other considerations. First, those filaments are different with different additives. Those affect the print conditions and probably also the drying. The drying instructions for the AMS2 or any drying technique could be limited by what settings are available. (Don’t know - don’t have an AMS2).
Also, if you dry at too high of temperature and too long, you could drive off plasticizers or other ingredients and change the properties, make the filament brittle, etc.
I’d go by the drying directions for the filament first as those are more likely to be correct and proper for the filament and then not exceed those parameters in specific dryers.
The only way to be certain filament is dry is to weigh it periodically during the drying process. The filament is dry when the weight stops dropping.
A clock is a poor substitute for a scale because you never know the initial moisture content or the rate of moisture loss. Drying on the basis of time will almost always under-dry or over-dry.
I don’t disagree with you, however it feels somewhat immaterial to what I’m reporting.
If Bambu wishes to continue being a mostly push-button user-friendly option, then I’d recommend they…
Add additional profiles to their built-in AMS 2 Pro / AMS HT for each style they sell, rather than one generic ‘PLA’ profile when they sell many of them.
Correct any existing profiles
Ensure the profiles match product documentation
Ensure product documentation matches their drying FAQ.
That’s a misconception though. It only means the filament has stopped drying when the weight stops changing - not that it’s dry. Caveat is drying conditions. The statement can be correct with certain key qualifiers.
I did the experiment when doing the dry air thing. I put a spool in a Sunlu S2 and monitored humidity and weight as a function of time. The weight gradually dropped but the deltas got smaller and smaller until the weight stopped changing. Turning on dry air caused the weight to start dropping again which means even though the spool weight had stopped changing, it wasn’t “dry”.
The best indicator of dry vs wet filament that I’ve found is simply putting it in a poly box with a hygrometer and reading the humidity after it quits changing. Not many have done it and there’s not much to compare with but with PLA I get good print results up to around 20% humidity in that test give or take. My dried spools always pull humidity below where my hygrometers bottom out (10%) at room temperature.
Also “dry” isn’t truly dry. There’s lots of literature on desiccants and how they behave. Filament is essentially a desiccant too and does the things purpose-built desiccants do. The point being there are curves that relate humidity to desiccant moisture content. Dive deeper and you can see it gets harder and harder to remove remaining water as the water content decreases. It’s diminishing returns. Filament always has some amount of water in it. The question is just how much.
