I put in a near full spool of Sunlu PLA Matte that was stored in a vac bag for a month or so and it failed to print. All I got was a few strands before I shut it down. I tried to manually purge the hotend at 220c to clean it out but that didn’t work. I then manually cut the filament and the blade stuck, I had to manually pull the handle back.
I removed the PTFE tube from the extruder and found the filament end looked like it was gnawed a bit but was cut.
I then tried to pull back the filament to it’s spool in the AMS but it appears to be jammed in the AMS.
Many people jump straight to “moisture” without confirming that moisture was actually a factor. There is no baseline weight, no post-drying weight, and no measured moisture loss. Without those data points, moisture remains a theory, not a conclusion. The only practical way to confirm or rule it out is to weigh the filament before and after drying.
A vacuum bag with desiccant does not prove anything either. Desiccant only works when there is enough capacity, enough exposed surface area, and a truly airtight environment. Most consumer vacuum bags leak slowly, and desiccant that has not been regenerated is useless. None of that demonstrates that moisture was present, and none of it proves that moisture was removed.
Your symptoms can just as easily point to a different root cause. Matte PLA, especially Sunlu’s matte line, is known for brittleness and inconsistent filament integrity. A brittle section can snap under cutter load, leave a deformed plug, and produce exactly the “gnawed” end you found. That is a mechanical problem in the filament, not a moisture profile.
Until someone provides measured weight loss before and after drying, moisture remains an unproven assumption.
Rule #1 of troubleshooting: change only one variable at a time.
Start with the simplest test setup:
Remove the AMS from the equation and feed the spool using the external spool option.
Run a first-layer test to see how the filament behaves coming straight out of the nozzle. If it cannot produce a smooth sheet, you have a flow issue independent of the AMS.
If moisture is still on your list of possibilities, verify it empirically. As noted above, the only reliable method without lab equipment is weighing the filament before and after drying. Drying with desiccant is pointless for this purpose because desiccant only maintains ambient moisture levels. It cannot force moisture out of the polymer. Heat is required for that.
For reference, here is a comparison I use from time to time. This is Bambu’s discontinued golden silk PLA. Straight out of the factory sealed vacuum bag, it still showed moisture. After drying it on a heated bed inside a box, it lost over 5g of weight. That is one teaspoon of water.
I’ll let you guess which sample came straight out of the sealed bag.
