Please help me understand how the feeding mechanics work, from the spool to the extruder, especially with the AMS. This applies to both X1C and A1 Mini.
If I understand correctly, the filament is continuously pushed into the extruder by the spool rolling.
If that’s the case, then as soon as the spool becomes empty but a print is still going with filament still in the tube, nothing is pushing the filament, and the print should stop. This is not true.
If that’s not the case and there’s a sucking mechanic in either the extruder or the entrance into the printer, broken filament should not be a problem, because the broken part will just be sucked in, used to print, and the rest of the spool continuing to be used. This is also not true.
Yesterday I was running a very small print with barely enough filament on my A1 mini, using external spool holder. The print successfully finished, no visible filament in the tube, but the screen keeps detecting filament in the extruder.
I tried to heat up the nozzle, manually extrude, but nothing came out. I changed the tube from external spool to ams and tried to print from AMS, but it kept telling me to remove filament from external spool. I had to take the extruder apart, removed leftover filament from the nozzle and the extruder.
What might have happened here? Also if I do not want to waste any filament and not get stuffs stuck again, is my only option to pick a print that requires more filament than what is left, and feed another spool after it runs out?
In both printers the extruder pulls filament and extrudes it through the hot end. From an external spool the filament is simply pulled from it by the extruder. When using an AMS (X/P series), it and the AMS buffer work in conjunction together to supply filament to the extruder. Basically, the AMS buffer stores a small amount of filament for the extruder to pull from. Think of it as a tiny external spool. When this “Buffer” is used up it signals the AMS to pull filament from the spool being used to refill the buffer (ie tiny external spool). the AMS lite functions slightly differently as the buffer is much closer to the print head.
The small piece of filament still in the extruder that you had to clean out was triggering the printer to think that it still had filament loaded. When using the external spool holder to print from you need to have enough filament to manual retract it, otherwise you will have either disassemble the extruder to pull it out or heat up the nozzle and extrude it out.
I actually did heat up nozzle and try to extrude, all done on the control on the touch screen, but nothing came out. Any idea why that might have been?
Your explanation for the pulling makes sense. How does this buffer work in the case of a spool running out, but filament is still in the PTFE tube? Does it signal the printer to just pull and not wait for the buffer? If that’s the case I can see a potential problem in multicolor print, where a spool runs out mid way, filament still in the tube, but a color change happens, nothing pulling the filament back
On the A1 Mini, the filament sensor is just under the filament hub on top of the extruder.
So you shouldn’t have any left over filament in the tube unless the filament snapped (I’ve had this happen once).
A small piece of filament was above the extruder but still in the sensor. As @lion7718 mentioned filament does break especially when PLA has moisture in it.
Yup this can happen but it isn’t a common occurrence. In general when printing lots of colours in a model, it’s best to not use small spools.