When loading filament, the toolhead is not always moved to the rear of the printer, causing jamming. The feed tube/boden is at an extreme angle, allowing the filament to catch on internal edges of the toolhead, preventing further auto-insertion. The current solution is to pull the feed tub toward the front of the printer to remove stress, and allow the filament to be fed straight into the toolhead, relieving the jam. If the toolhead is moved to the rear, this stress is removed automatically. I also worry a bit about the amount of strain there is on the tube socket/connection. When at the front of the printer, the release collar is tilted significantly from the pressure. Adding another strain relief would be helpful.
Sounds like something isn’t assembled correctly. Pictures?
Is this a new printer and first print(s)? Is so I’d redo the initial setup procedure with manually moving the head around with the belt screws loosened in case it’s binding and then do a calibration again just like when new out of the box…plus make sure you’re on the newest (or more recent firmware update). If you’ve been using it a while, how many hours and start a ticket.
To expand on my previous post:
Why would the feed tube* be “at an extreme angle”? That doesn’t sound right, and a picture is worth a thousand words (as they say). I presume the extreme angle is because the tubes and cables are incorrectly constrained in some way and are under tension when the print head is at its extremes of travel. This should not be the case.
* For information: not “Bowden”. In 3D printing, a Bowden tube is where the extruder isn’t fitted at the tool-head and has to push the filament along a close-fitting tube, relying on that pressure alone to deliver (and regulate) filament into the nozzle. This is only effective if the tube can be short; any room for deflection of the filament within the tube (or stretch of the tube itself) gets magnified by the length, and deflection amounts to errors in the feed and retraction, resulting in poor print quality.
The term comes from bicycle brake cables, where the hand-grip brake levers deliver force to the brake callipers through a cable sliding within a sheath, although this is generally by tension rather than compression. The U1 has a tool-head extruder, so the tube is just a feed tube (albeit that the auto-feeder units confuse matters!) and it doesn’t need to be such a snug fit to the filament so there is less friction.
The boden tubes are different lengths are you sure you have them in the correct place?
this angle at full extension is the issue. And it’s completely unnecessary. When feeding, the head should be further back. I’m guessing roughly at about 150mm from rear. At that point the tube is vertical at the toolhead, and prevents most insertion jams. When at the front of chassis, around 250mm +, the filament comes in at an angle and catches most times on internal geometry. I have to pull the feed tube vertical to resolve.
I’m also seeing the extruder tensioner gear getting kicked off the filament, causing the extruder to fail while printing. In this failure mode, it refuses to re-engage. Actuating it repeatedly will sometimes slow it to snap back into place, but not always. The first time it occurred I was convinced something had broken internally and fully disassembled the head looking for debris. Found nothing. I then found I could recreate the issue on the bare extruder. Forcing the gears back together fixes it temporarily. I don’t know if this affects my other toolheads (this is slot 3). Either there is a major design flaw, or my toolhead is defective.
In my U1 from January 2026, all four feeders are the same length!!!
It looke like the entry grommet or whatever it is is tilted. Is it not secure or broken?
Yea, it’s tilted, but that’s to be expected. These tubes are stiff and not pliable. There really should be some kind of strain relief, just like the chassis connection has. Maybe I’ll print some up and test it. Another solution would be to use longer tubes, but they are already pretty long.
BTW, for anyone else… yes the tubes are rotated correctly for the notches to go as deep into the head as possible.
The question remains why nobody else has this problem. If it was a design defect, there would be many more instances.
On the 2nd toolhead on my U1 it would often fail to load filaments. It didn’t occur on the other toolheads.
I understand exactly what Danlor is describing, I’ve seen it and wondered about it too. As mentioned, the toolhead is moved to the front (door side) and the feeding tube is at a more extreme angle when it is nearer the front.
My diagnosis was same as Danlor’s, thinking it is the more extreme angle, yet it doesn’t happen on all of the toolheads. My thought then moved to the extruder gears and adjustment with the extruder tensiion wheel/lever. My workaround was to gently push in on the orange extruder lever as filament is loaded into the extruder gears for that toolhead. That fixes it.
My more permanent fix was to adjust that exteruder lever using it’s tension screw. Loosening that Extruder Lever Tension gear a little bit allows for a cleaner and more open path into the extruder gears as filament is loaded.
Might also check or clean the extruder gears if there is filament gunk on the gears which could also cause those gears to slip against the material enough so as not to pull it in. But I’d experiment with that lever first (and then that tension screw) because it’s easier and doesn’t require opening the toolhead assembly.