Ptfe tube dilemma

Discussion in 'Build Help' started by cez, Feb 12, 2017.

  1. cez

    cez Well-Known Member

    Joined:
    Apr 4, 2016
    Messages:
    103
    Likes Received:
    19
    For all parts of my Dual Hybrid Titan v1.1 build I used 4mm external 2mm internal ptfe. I've just noticed a length of 4mm external 3mm internal ptfe tube was present in my kit. What's it for? Do I need to swap something over?
     
  2. mike01hu

    mike01hu Well-Known Member

    Joined:
    Apr 22, 2014
    Messages:
    954
    Likes Received:
    166
    The smaller internal diameter tube is for the hybrid side to reduce the hysteresis in retractions etc.
     
    cez likes this.
  3. cez

    cez Well-Known Member

    Joined:
    Apr 4, 2016
    Messages:
    103
    Likes Received:
    19
    I see, so the 3mm is solely for direct feed?
     
    mike01hu likes this.
  4. elmoret

    elmoret Administrator

    Joined:
    Mar 1, 2014
    Messages:
    571
    Likes Received:
    91
    3mm ID tubing is for running from a direct extruder to the filament spool.
     
  5. mike01hu

    mike01hu Well-Known Member

    Joined:
    Apr 22, 2014
    Messages:
    954
    Likes Received:
    166
    That's right Cez. The 3mm tube is just used as a guide, as there is no issue of hysteresis between the extruder and the hotend. By hysteresis I mean that when the extruder feeds filament, how quickly the filament flows from the nozzle; if it is instant then the hysteresis is low but if not then the hysteresis is higher. In the case of the hybrid, if the 3mm ID tube is used then there is space inside the tube for the filament to move sideways rather than ahead i.e. it kinks so there is more filament inside the tube and that has had to be supplied by the extruder before it can push filament through the hotend or pull it on retraction. For the non-Bowden setup the extruder is pushing into a much shorter tube i.e. the length of the hotend and no kinking takes place, so the filament flow from the nozzle is instant also it is puling the filament through the feed tube so that kinking is not an issue, hence the larger diameter tube; this larger tube also reduces the friction, making the extruder work less..
     
    cez likes this.
  6. Spoon Unit

    Spoon Unit Well-Known Member

    Joined:
    Sep 6, 2015
    Messages:
    1,095
    Likes Received:
    318
    I've just encountered an issue with mod the adds the short piece of tube to the top of the Titan and wondered if anyone else had the same issue. For clarity, it's the piece of tube marked with a red line in the pic.

    ApplicationFrameHost_2017-02-21_14-39-36.png

    Now, while this is a really nice tight fit into the top of the Titan, it's not prevented from moving downward. The tiny effect of each retraction is to hit the top of this short tube with a tiny hammer repeatedly. Eventually the tube will be pulled (or pushed (or both)) through yellow window and on downward to the hobbed bolt. My print was just killed by it reaching the hobbed bolt, which then leads to bits of PTFE certainly fouling the hobbed bolt and possible being pulled down in the melt area. It also ultimately reduces the grip on the filament and, for me, resulting in clicking and ultimately no filament being pulled down to the extruder.

    So first question. Has this happened to you or did you already do something to counter this outcome?

    At present, I'm considering printing a small clip (sort of Pi shaped) to go in the yellow window, thin enough edges to permit the filament to pass through, but enough to prevent any further motion of the tube downward. Even better would be a replacement part where that was already in the design.
     
  7. Miasmictruth

    Miasmictruth Well-Known Member

    Joined:
    Sep 4, 2015
    Messages:
    744
    Likes Received:
    105
    I havent had this issue but good point, it may be wise to file grooves into the PTFE tube and desing the clip to slide into those grooves. Or are you saying instead of pusing the ptfe all the way down the clip will slide around the filament.

    If we were to try and grip the tube, the grip could be at the top where there is more room.
     
  8. Spoon Unit

    Spoon Unit Well-Known Member

    Joined:
    Sep 6, 2015
    Messages:
    1,095
    Likes Received:
    318
    So far, this has turned into a full blown nightmare. After the first jam, I cleared, reset, jammed again. I then disassembled the x carriage to get to the PTFE tube between the Titan and the hot end. That looked a bit damaged, so replaced (ensure I re-chamfered the top). Rebuilt, reset, re-jammed. Horrible horrible jam.

    upload_2017-2-22_0-27-46.png

    The only thing I could think was that some small particle from that PTFE tube had made it's way into the nozzle. So I swapped the nozzle as a test. Now seems to be printing fine again, currently on about layer 5 after jamming repeatedly during layer 1 (pretty large print job). I'm now wondering how to fully clean out the old nozzle, given that it is a hardened steel type and probably undamaged really. I don't have a blowtorch to incinerate it ...
     
  9. mike01hu

    mike01hu Well-Known Member

    Joined:
    Apr 22, 2014
    Messages:
    954
    Likes Received:
    166
    That looks pretty disastrous! Have you tried the cold-pull cleaning method that is pretty successful at dragging bits from the hotend? It looks like a modified lever is needed with a moulded in feed tube but I may consider a short brass tube of the right size with a soldered ring around it to prevent the tube passing too far into the lever. So far I have not had that problem but I can appreciate how it can occur, particularly with lots of retraction taking place and I will inspect before each job until I effect a solution.
     
  10. Spoon Unit

    Spoon Unit Well-Known Member

    Joined:
    Sep 6, 2015
    Messages:
    1,095
    Likes Received:
    318
    It looks worse than it is I think. This is just the end result of a jam. The problem is invisible. I'm actually wondering whether my nozzle might have come slightly loose also - perhaps in combination with the heatbreak. I think small gaps in the filament path can also result in these jams. But the PTFE tube issue definitely needs a solution as it feels like it was the start of the problem.
     
  11. Ephemeris

    Ephemeris Well-Known Member

    Joined:
    Nov 25, 2015
    Messages:
    285
    Likes Received:
    178
    Ick! Here's a thought, How about a precision stainless steel stop at the end of the PTFE tube to make sure the tube cant go any further? Specifically a #1 washer :)

    [​IMG]
    As you can see its ID and OD are a good match for the 4 mm teflon tube. Its outer diameter is 3.96 mm and the inner diameter is 1.9 mm

    Will it fit? Will it stay between filament change outs? More thought would be required, but it's a possibility
     
  12. Spoon Unit

    Spoon Unit Well-Known Member

    Joined:
    Sep 6, 2015
    Messages:
    1,095
    Likes Received:
    318
    Well for me, filament changes don't result in the removal of the short piece of tube.
     
  13. Spoon Unit

    Spoon Unit Well-Known Member

    Joined:
    Sep 6, 2015
    Messages:
    1,095
    Likes Received:
    318

    Attached Files:

    W1EBR.Gene and Henry feldman like this.
  14. mike01hu

    mike01hu Well-Known Member

    Joined:
    Apr 22, 2014
    Messages:
    954
    Likes Received:
    166
  15. mike01hu

    mike01hu Well-Known Member

    Joined:
    Apr 22, 2014
    Messages:
    954
    Likes Received:
    166
    As promised, here is what I propose to use in place of the PTFE guide tube. It is made from brass and the small flange is to stop it twisting. The finished dimensions are not correct, as I have some measurements to do.

    https://cad.onshape.com/documents/b...731ff6505f24abd900/e/d2a841ae3c3d9b9c06ee3a19
     
    Spoon Unit likes this.
  16. Miasmictruth

    Miasmictruth Well-Known Member

    Joined:
    Sep 4, 2015
    Messages:
    744
    Likes Received:
    105
  17. mike01hu

    mike01hu Well-Known Member

    Joined:
    Apr 22, 2014
    Messages:
    954
    Likes Received:
    166
    It would be fairly simple to make. The brass or copper tube and strip is available from most model-making suppliers. The tube can be cut with a small hacksaw and a hole drilled in the strip then carefully bend it and solder it to the tube. the round taper at the bottom of the tube can be filed with a small round file. As to cost, I have no idea at the moment but it will be cheap.
     
    Miasmictruth likes this.
  18. Miasmictruth

    Miasmictruth Well-Known Member

    Joined:
    Sep 4, 2015
    Messages:
    744
    Likes Received:
    105
    Ah, what do you need to solder brass? I assume a regular soldering iron, but what kind of solder?
     
  19. mike01hu

    mike01hu Well-Known Member

    Joined:
    Apr 22, 2014
    Messages:
    954
    Likes Received:
    166
    I would use ordinary multicore solder as used for electronic soldering and ensure the parts are clean. You could glue the tube with epoxy if you are not happy with soldering.
     
  20. Miasmictruth

    Miasmictruth Well-Known Member

    Joined:
    Sep 4, 2015
    Messages:
    744
    Likes Received:
    105
    No issues using solder just have never done it with brass. Thanks for the info.
     

Share This Page