Tight Bowden tube for feeding filament



  • So I have a CoreXY printer and I use a filament dry box. I run some 1.75mm bowden tube from the dry box to the print head. It's a direct drive extruder, so it's only pulling the filament through. The issue I have is that there is some serious resistance at the print head due to the friction from the bowden tube because of it's extreme length (over 1 meter). I've tried to use a larger diameter tube, but then I can't feed the filament all the way through due to it binding. Is there a better way to go about feeding my filament from the dry box to the print head? This is causing issue with a lot of prints across a wide range of materials.



  • what make is the bowden tube?
    have you tried the capricorn low friction tube?
    https://www.captubes.com/shop/#!/1-Meter-XS-Low-Friction-1-75mm-Bowden-Tubing/p/82190682/category=23214267



  • @surgikill said in Tight Bowden tube for feeding filament:

    I've tried to use a larger diameter tube, but then I can't feed the filament all the way through due to it binding.

    Is that with flexibles only? I recently switched from 2mm ID PTFE tube to 3mm ID PTFE tube for my filament tube (I have direct drive as well) because some of the more textured filaments would have a lot of resistance and some of the more brittle filaments would snap entirely. The 3mm ID tube seems to have solved it. But I've never been able to push a flexible filament all the way through it. It's close to 1 meter as well. For flexibles I had to just hang the roll above the printer.



  • @phaedrux Flexible and regular filaments like PETG and PLA. The diameter of my large tube is 4.25mm (I got it for free)

    @Veti I have the capricorn tube and it's even worse because it's such a tight diameter.



  • @surgikill Does it actually need to go through a tube from the dry box to the print head? I appreciate that it might pick up some moisture transiting between the two but while you are printing it won't be "out in the open" all that long I'd have thought, and there is no guarantee that the tube will keep it dry - unless that too is heated I guess. Just a thought.....



  • @deckingman It's more for routing it. I have an entire cable bundle that goes to the head, and the dry box is on the floor next to the printer (big dry box and printer). The bowden tube also acts as rigid reinforcement for the cable bundle. I could try elevating the dry box and just moving the filament direct to the print head with a few inches on each end so it doesn't pinch.



  • @surgikill said in Tight Bowden tube for feeding filament:

    @deckingman It's more for routing it. I have an entire cable bundle that goes to the head, and the dry box is on the floor next to the printer (big dry box and printer). The bowden tube also acts as rigid reinforcement for the cable bundle. I could try elevating the dry box and just moving the filament direct to the print head with a few inches on each end so it doesn't pinch.

    Yes, I know all about cable bundles. I have 5 extruders mounted on a second gantry above the print head, so that's 20 conductors without all the fans, heater, sensor, probe etc. ☺ Have you tried any really big tubing like garden hose for example? Difficult to imagine how filament could bind inside it but it could be PITA to thread it through if it isn't a straight path.



  • @deckingman I just elevated the dry box on a table and stuck a short piece of 2mm bowden on the dry box and another on the hot end. It seems to be working okay so far.



  • Did that solve your problem you were having with TPU?



  • @phaedrux Haven't checked TPU yet. PETG is printing better. I'll let you know in a little bit. For some reason my printer decided to ram all axes in the positive direction so my whole gantry crashed hard (luckily it seems okay) and my bed as well, but my z leadscrew couplers are completely destroyed.


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