Auto loading filament for use in the auxiliary nozzle can easily go awry and present you with a tricky situation.
The filament load appears to proceed normally, but there is no extrusion from the nozzle. The “check extrusion” message puts one in a cycle of retries that make no progress. A careful look at the feed tube within the printer leading directly to the print head shows that filament has not reached the nozzle. Yet, the control panel indicator shows that the filament is loaded. Repeated attempts only feed the filament a few millimeters at a time, stopping far short of the print head. Withdrawing the filament and reloading produces the exact same result every time.
Initially, I suspected that there was a malfunction with the Bowden feeder. Disconnecting the downstream feed tube from it showed the filament only advancing about 30mm from where it exits the Bowden extruder and then stopping, but indicating that the filament was loaded, even though this was impossible. Each additional control panel commanded feed simply replicated my initial observation when the feed tube was attached - only a few millimetres at a time. Very puzzling. So, the filament is registering as being loaded when it enters the Bowden extruder not when it is in the nozzle. The feed tube appeared clear as the filament last used had been unloaded as per standard practise - done previously many times! Clearly, I needed to look further for the actual problem.
Removing the feed tube from the print head solved the mystery. The filament, in this case Support for ABS, had snapped within the confines of the print head cover with the downstream filament firmly embedded in the nozzle itself, not visible unless the cover was removed. As such, this would constitute a clog, in that it is too small to be mechanically advanced for further extrusion. The filament was removed by clearing the heated nozzle with the nozzle needle. Once this was done, the filament made it all the way down the feed tube into the nozzle and extruded correctly straight away.
So, things to take away:
- The filament loaded indicator is activated when the filament reaches the Bowden extruder
- Any residual filament in the print head that cannot be properly mechanically advanced for extrusion on its own or reversed out, will somehow prevent new filament from being pushed down the feed tube to the nozzle, giving the impression that the Bowden extruder is faulty.
- There is no indication of a fault condition under these circumstances, nor any applicable diagnostic tool that I could find to help
- No description of such a situation came up in any search or through the use of AI tools that would normally dig something of this nature up for consideration
- The extra mechanical sophistication of the X2D filament feeder can throw you. If such a thing happened in my P1S, I would have deduced a clog within a minute
- Be careful with brittle filaments. If there is a hint of a clog, they can easy break off as they are mechanically being reversed out the nozzle
- You can easily burn a couple of hours fiddling around, fault finding, disassembling various uninvolved printer components or otherwise engaging yourself in a wild goose chase without this knowledge.