I’ve got an X1C and AMS (all very new; just a few weeks old now), and I’ve been trying to use Bambu PVA with PLA models.
I dried the PVA for the recommended time and managed to get one print out of it (though the AMS does sound like it’s struggling sometimes, and it’s very stringy). The next day I tried another print and it failed (stuck/unable to feed/retract).
The spools have been kept inside the closed AMS, with fresh desiccant.
I’ve spotted some mention that slots 2 and 3 in the AMS can have problems due to the PTFE tubes not being sufficiently straight (I have the PVA in slot 3).
You may try a different slot, but it seems to be a humidity problem from the description and BL info on PVA(see below).
The easiest way to confirm this is to redry and test the filament. BTW how did you dry the filament?
BL recommendation on PVA:
Drying conditions: 80 °C for 12 hrs. To achieve optimal printing performance, it is recommended further drying before use and after storage.
PVA is suitable for use with AMS and AMS lite in a dry state. If the filament becomes soft or sticky due to moisture, it must be dried again before use to prevent issues such as feeding failure, nozzle clogging, and low print quality.
Note: AMS does a good service of keeping the filament dry if loaded with a reasonable amount of desiccant and kept closed. How are the AMS desiccant and humidity levels? Installing a hygrometer within is helpful, as the sensor response is faster.
I dried the filament at just under 80C for about 16 hours before I got the single print out of it. The next day a print failed.
I don’t have a reading of the exact humidity levels inside the AMS, but it was full of new desiccant, and kept closed. Kinda worrying if every print is going to need extensive drying beforehand.
I would expect that a dry AMS would keep a (dry) PVA slightly longer. Yet, PVA is highly hygroscopic, so it may not be enough.
Having a system that allows filament drying at 80ºC is excellent. I asked as most of the standard equipment (as mine) runs below 70ºC, which permits a maximum of 65ºC of air bulk temperature, hindering the drying process.
The most straightforward way to verify if drying solves the problem is to dry and retest.
I never thought about it, but you are correct in worrying. You will want to run it from the AMS as support material, so you may need to maximise the desiccant content. If you didn’t do it, you can find many containers in MakerWorld specifically designed to be filled with silica beads and fit into the AMS. Additionally, ensure that all the filaments within the AMS are dry.
Last, I would dry the PVA after printing (before storage) and store it properly in an airtight or “vacuum” sealed container with silica and a hygrometer. These containers can be expensive unless you do it yourself (e.g. Filament Drying Recommendations | Bambu Lab Wiki).
No idea what’s wrong with the original spool; but I cleaned the edges with IPA just in case it’d somehow gotten oily (still didn’t make a difference though).
Try inserting PVA filament into slot 4 and see if it helps improve print quality. To avoid moisture problems, it is recommended to dry the PVA for 12 hours before use.
I think I’ve spent more time drying the PVA than printing with it (so I’m hoping it is dry enough). I’ve had it running in slot 1 on the AMS (no reason other than I’d just put a different spool in slot 4) and (with the PLA printed spool holder) I’ve not had any more problems with the filament feeding. It does cause a lot of stringing though. So bad in fact that it triggered a spaghetti warning during a print, and then clogged up the waste chute.
Fortunately the print was ultimately OK, but the stringing is a bit of a problem.
Pre- and post-processing are often the most time-consuming tasks.
It seems to be the classic issue of low-weight.
As the spool gets empty, the reduced mass affects the sliding in the AMS.
If you close the AMS, it will help. But, most importantly, add some weight (not much!) to the spool. I usually have a desiccant fitted into the spool, but a quick solution is a couple of batteries with some tape covering it to avoid falling into the AMS.
Suggestion: Dry a little more, and carry tests on small prints to avoid filament and time waste.
Ironically, the problems I had were with the new (full) spool; with one of the 3D printed desiccant holders fitted to the middle. Having unwound probably half the filament onto a PLA printed spool (and moved the desiccant holder across) I’ve had no problems with slipping; even though that spool would be lighter.
It did occur to me that adding a low friction pad/slider to the inside of the AMS lid might prevent spools from slipping/jumping. A spring loaded bearing would be better but there’s not really the room for that.
The print did complete in the end, and has worked well - so the main outstanding issue is the huge amount of stringing of the PVA filament.
EDIT: A bit of searching indicates moisture is the likely reason for the stringing, so I guess it’s back into the oven with it. I have a proper dryer on the way so that’ll be a better tool for ensuring the PVA is “just right” before every print.
I’m glad that is “solved”.
Be aware that most dryers don’t work above 70ºC (setpoint); this doesn’t mean you can’t dry PVA, only that it may take significantly longer.
