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  1. #1
    3D Printer God(dess)
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    Lightbulb Salvage - PC4M5 fitting +Bonus

    For all the great efforts accomplished by great people on the board, I feel the need to dive into one of the smaller aspects of our efforts.

    If you've been playing with these printers for a while along with the little tube fittings, you noticed one annoying thing...
    These cheap PC4M5 fittings have a very nasty way of failing. The start of the failure is a simple turning of the tube...
    The PTFE tubing is rasped by the biting teeth inside the fitting.
    The newly created groove catches the gripping metal washer and rips it apart as you try with all your might to remove the tube.
    Next thing you know the tube won't stay in the fitting and the print you were working on fails.

    Sound familiar?

    First tip I will post is that if the tube is already stuck in the fitting, don't yank it out! Instead, find a pair of slender tweezers or appropriate needle nose pliers and pop the black cap off the fitting.

    zero_start.PNG

    The effort you put into removing the cap is about the level of pressure the fitting is capable of holding. The reason you can thwart this effort is that you are inducing a small angle which makes the cap come out easier. Do know that doing this can cause wear on the lip that holds these together. Meaning, yes, you can overdo this operation and the fitting's cap will be useless after a few times. However, with the cap removed, you can now remove the gripping washer by cutting off the end of the tube. But if you failed, or have fittings that have failed already, keep reading.

    I haven't figures out the best way for the layperson to do this, but here goes:

    I use a lathe with a through-hole drill chuck to make this simple groove in my tubing. Teflon cuts very easily and I'm sure we'll get some ideas on how to do this with common tools and/or a printed widget.

    zero_groove.PNG
    The "top" of the groove, furthest from the end is ~7mm away. The groove is about 1.8mm wide.
    The depth is minimal, just enough to get a good edge.

    I had considered that I needed to put a c-tube in the groove (c-tube being a short tube with a groove along the edge). I did the following on a whim.

    Next I wrap the groove, neatly to start, with a 200mm length of bare copper wire 0.3mm in diameter. Direction doesn't matter but a reasonably tight wrap does.

    zero_wirewrap.PNG

    You can use different wire gauges and lengths but the outcome should be similar to this.

    ...put the black cap on from the other end of the tube...

    zero_stuff.PNG

    ...and stuff the fitting back together.

    It should look like this when you are done. Go ahead, pull-test the heck out of it. It isn't going anywhere. Worst case, the black cap will come out again. But that should be a whole lot more pressure than the printer will ever subject it to.

    zero_stuffed.PNG






    Now for the bonus: Go ahead... twist it... I dare you! There is nothing left inside to rasp the tubing. Nothing left to wear out! Nothing to sphincter down the tube's ID!

    The reason this works is that the fitting has rubber inside. This conforms well to the knot of copper wire that remains. The copper wrap cannot easily expand either since stretching one loop will likely reduce another loops diameter. Essentially the tube is trapped by filling the groove.

    Can you carve a groove good enough with a hobby knife? Tube cutter? File? Post here if you have a success that should be shared.

    - - - - - - - - - -

    BTW: I don't consider this a solution on the hot-end simply because I want to keep that end removable for filament changes.

    If you have figured out a way to keep both ends of the Bowden tube fixed while changing filament, this solution would be great.
    The only way I can consider this is to put on a spool and forget about it until it is empty.
    Then taking the nozzle apart for the next spool is no big deal as it becomes a rare event.

    Pulling a filament all the way backward through the tube with the "bulb" on the end just doesn't make sense as it most likely will get stuck and then you have to undo one of these. Again, lifting out the cap is a limited operation as the hold will weaken.

  2. #2
    Administrator bolsoncerrado's Avatar
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    Aint something like this

    https://www.thingiverse.com/thing:1620721

    be more.... KISS?

  3. #3
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    Hahaha... not quiet. That only works if you didn't break the gripper washer first.

    What I am after here is a fixed tube to the fitting that is capable of rotating without self-destruction.

  4. #4
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    what about E-Clips? Similar to the clip that bo suggested but this one is metal.

  5. #5
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    The clip that Bo suggested is to keep the fitting locked.

    An e-clip of the appropriate size should work also. But you still need a clean groove to keep the Teflon from tearing.

    The wire wrap idea kind of opens this up to more people. Everyone has spare power cords, right?

    In the past I tried just threading a nut onto the tubing.
    But with Teflon's cold-flow characteristics, the Teflon tends to work that 60 degree angle of the threads.
    And with pressure on the tube, this actually made for a smaller ID over time.
    Plus think about what happens when you rotate the tube is the nut is fixed?

  6. #6
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    I now have 2 tubes using this and on my last fitting, I put a very small dab of solder on it to prevent it from coming undone. The wire I used was tiny and wouldn't hold its form. This worked nice too. didn't heat the spot up very long at all, just to get the solder flowing. Yet again, Tommy you da man.

  7. #7
    3D Printer God(dess)
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    solder is a good idea. Teflon is perfectly capable of managing the small amount of heat transferred if you don't linger.
    You can also twist the two ends when done winding.

    Now I know what to do with all this fittings with the bad M6 threads... pull the caps for future use for worn caps

    - - - - - - - - - -

    Yesterday I had another fitting self destruct. Odd thing is that it was on a mod'd original hot-end.
    The grippers fell apart into about 5 pieces. This means it has been whittling on the grippers for quite some time.

    This was on a machine that had 2Kg tied to it and not touched until the spool was empty; all those Cyan colored pieces.
    I recently swapped it out for a different spool and trouble started within 10 printing hours of the replacement.

    I've been working on a better system that allows the ends to turn without the fear of wearing a groove in the tube.
    The groove is what catches the internal grippers of the fitting and rips them apart.
    What I never saw before is the self-destruction of a gripper during normal operation.

    So now I have a dedicated spool; looks a lot like a trimmed up stock spool; that now has both ends fixed.
    The intent is to just fill the stock spool and run it until its gone; then reload it by whatever means required.

    - - - - - - - - - -

    tease.PNG

    Finally found a use for that heavy tube in the stock 3DS cartridges.

    Still need a tool solution to making a sharp groove in the tubing.
    This is a very strong union using the same groove talked about before in this thread.

    You know where this is going, right?

    - - - - - - - - - -

    Tool:

    tool.PNG

    I was going at this backwards... this worked!

  8. Likes ztoddman1, bolsoncerrado liked this post
  9. #8
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    I'm digging it.

  10. #9
    3D Printer God(dess)
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    Here is a private viewing...

    https://youtu.be/KqJDFyE91vo

    Feel special... I don't normally narrate anything.

  11. #10
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    O

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    m

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    G!

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    Hook a brother up!! Beta tested a lot of your stuff flawlessly, awaiting a trial run with this gem!!! Btw- I watched it twice so 14 min gone!!

 

 

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