As the title says, filament is breaking at the exit side of the H2 buffer Not a big issue as it has happened maybe five times now. I disconnect the tube exiting the buffer and pull the filament back to the spool and I have a broken section of filament about 100mm long.
Anyone else?
Is this happening when you are printing a large job and one nozzle is idle for a long time?
If so, this might be triggered by the many motions of the tool head while the filament sits idle in the PTFE tube. The constant motion triggers a break in sharper bends.
I had this 2 times since I have the H2C… so once per 6 weeks - not a big deal.
But it never happened with 1 year of X1C, so it was a new experience.
I’ve had brittle filaments do this if they were idle for a 10+ hour print, the filament would also be brittle from that point to the head, so I figured it was just heat over time, motion (large circular prints) and being static inside the tube since it wasnt used anymore. It would always be that first print that puts text on the plate for 1 or 2 layers too, I just started putting that spool in the same side as the next layer just to get it unloaded and the problem stopped.
ABS-GF, PETG-CF, PC, PA6-GF have all done this to me at least once. I’ll get the filament failed to extract at the end of the job. I did have one break off inside the extruder and it drove me crazy for a few minutes trying to find where it was stuck since it wasnt in the nozzle or the inlet.
Third print job in a row with that nozzle, three different filaments. So no it can not be idle filament.
What makes filament brittle?
What filament is breaking? Filament can get brittle for various reasons but some are natively brittle and all that flexing on the tubes is going to cause cracks and breaks in filament if its sitting the printer at the head idle (like a support/seldom used color) for a while. Not to mention retracting and feeing the same sections over and over and over on high change prints.
If it’s normally not brittle, it being too wet will do that. If you bend the filament right off the spool, will it break (far too easy)? If so, it needs dried.
You should be able to get a 180 degree sharp bend out of most filament in my experience. Wet filament is usually the problem in my experience. If it breaks, cut back until it doesn’t, or throw it in the dryer for a few hours.
Both PC and PETG, nothing idle with my printer…
Perhaps it’s not clear what I mean by idle. You can have a long print job and filament loaded in both nozzles, and they will not be unloaded until the job completes. Say you have white letters and a black print that is large. The white filament is on left and black is on right. The left would be idle while the black was printing since it doesn’t unload. Thats all I was getting at, and this exact scenario has happened to me. Thats when it broke at the buffer exit.
Only single color prints, only the right nozzle, all under 3.5 hours, only Black PC or Gray PETG …
Must happen loading or unloading the filament.
Does your filament feel brittle just before or after the broken piece?
It cant happen during loading if your 3.5hrs into the print job.
Older machines are known to have slightly shorter PTFE tubes that cause the buffer to make clicking sounds when printing close to the front of the printer. At that location there is quite a sharp bend in the tube, that might snap your filament.
But itis most likely brittle due to moisture.
Drying a roll too short only dries the circumference and not the core of the roll. So you should feel brittle filament near the crack.
I have seen something similar with an old brittle pink PLA spool. Something had clearly happened to that spool over time, and it had basically become good only for collecting dust.
It could still print, but the filament would randomly break anywhere in the path — from the AMS 2 Pro, through the buffer, or further along the PTFE path. So in your case, I would not rule out a bad or brittle spool, especially if it only happens with that specific filament.
One thing to watch out for is that small broken pieces can also end up inside the extruder or somewhere in the filament path. That may not cause a problem immediately, but sooner or later you may need to clean that section out.
I would first try the same print/path with another spool that you know is good. If the problem disappears, I would replace that spool and move on. If it happens with other filaments too, then I would start checking for debris, rough edges, or resistance in the PTFE path around the buffer.
I also have a faulty AMS 2 Pro that sometimes pulls the filament so hard that it breaks regardless of filament type, so excessive pulling force from the feeding system can also be part of the problem.