Extruder Skipping!!

Discussion in 'Tool heads & ToolChanger' started by Amr, Nov 27, 2019.

  1. Amr

    Amr Well-Known Member

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    3 of my Titans on the TC are acting strange, after a 1-2 hour print time the extruder starts skipping while printing PLA at 215 nozzel not clogged I triple checked what could be the reason for that or what Ideas you have for me to test to find the issue.

    another strange behavior if I pause a print and resume the extruder will skip steps immediately!
     
  2. Greg Holloway

    Greg Holloway Administrator
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    try setting standby temperatures to 150 or so and see if that helps.
     
  3. Amr

    Amr Well-Known Member

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    This happens in single material prints
     
  4. Greg Holloway

    Greg Holloway Administrator
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    how long is your retraction?
     
  5. Amr

    Amr Well-Known Member

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    i tried retractions from 2 to 5 mm with retraction speed of 40mm/s it some times go through the print if retractions are off but then the print is awful.
     
  6. Greg Holloway

    Greg Holloway Administrator
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    i run 5.5mm retraction at 100mms
     
  7. Jai Stanley

    Jai Stanley Well-Known Member

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    I have exactly the same problem....

    Print quality in general was awful (since getting the printer); much worse at speeds above 50mm/s. After tuning, retuning, then retuning again; the extrusion I would get inconsistant extrusion rates from print to print and even over a single first layer.

    After seeing a blog post (presumably by a user on here) I swapped from capricorn PTFE bowden tubing to no-name blue PTFE and a lot of problems went away, well a bit. Then came back as soon as I went from printing Polymaker PC max and PETG to a PLA (prototyping parts to save the more expensive materials).

    Next I swapped to an original Bond-tech extruder on one of my tools, which further improved results with the better materials, but PLA contiuned to be a problem.

    Next, I took the bowden tube out of the braided tube on the tool-feed and used a couple of velcro cable ties to tie it loosely next to the braided wiring, but not overly constrained by it. This made a difference again. Still not perfect. Once again I swapped the blue generic PTFE tube for some older even more generic white PTFE I had lying around and it got better yet again, now actually able to get a PLA print off (to an acceptable standard I mean).

    Where I am at the moment: I have purchased two 'left hand' bond-tech clones and modified them so they actually work. I will install those today (I have also ordered a right hand one, but that has to come from triangle-labs in china as they seem to be the only ones doing them) and let you know how it goes.

    One thing to note: I had reduced the current on the extruders from the standard 1680mA to 1000mA due to them getting extremely hot and me assuming they didn't need that much current with a 3:1 ratio. Wrong. They are now at 1500mA and this actually made the most significant improvement.

    In my oppinion: Bowden is crap. Particularly crap on the tool changer due to the long tube (and Titan extruders, but more on that in a minute); but other printers manage it I guess. This is my first bowden fed machine and I am not very impressed with the concept in general. With the rate plastic can practically be extruded/printed at, I would much rather have the additional gantry weight and improved extrusion control of direct drive and print slightly slower (acceleration wise anyway).

    Now: I fell I must piss and whinge about Titan extruders... They are crap. crap crap crap. Well made, and an improvement on the home made extruders of the past; but crap. I have had three bearing failures and one even torqued it's own bolt down so much that it shattered the cover! The gears seem pre-disposed to grind through filament the second you look away and they are an absolute penis to load in the machine. The bond-tech can be fed simply by pushing the filament into the tube whilst it is running. It grabs the material and feeds, EVERY time. It has far greater control and can push against the friction in the long bowden a LOT better. Also, much more consistant.

    I have just live chatted with customer service regarding the release of the Hermes tool-head release date but they only gave the standard 'we can't comment' replies. To be expected of course. At this point I'm close to driving down and buying Sanjay/Greg a coffee so I can actually chat to them!
     
  8. Jai Stanley

    Jai Stanley Well-Known Member

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    Interesting.. Is that with PLA? I found a g-code generator that increments the extrusion length and speed and found that for PLA 5mm at 30mm/s works the best. Higher than 35mm/s left gaps in the extrusion, which looks like it requires adding restart distance. If restart distance is added, blobs/seams become a problem!
     
  9. Jai Stanley

    Jai Stanley Well-Known Member

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    Also worth noting: I run copper heat blocks, titanium heat brakes, mixture of nozzle x and copper nozzles; rather than standard hot ends. I have had numerous (every print one day!) jams with PLA; and in 6 years of 3D printing have only had ONE before (on a CR-10; which I immediately upgraded with a direct drive Titan Aero, and never had another one). This is with the printer outside of the enclosure I use. With it in the enclosure I haven't had a jam with PC, ABS, ASA, Nylon or PETG. PLA is awful stuff. Practically no use to me other than for cosmetic parts (not interested) or for a cheap prototpye material (easy to print???!).
     
  10. Jai Stanley

    Jai Stanley Well-Known Member

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    God: I sound like a cranky old mayer.. Sorry, that's not the intention..

    Anyway heres a picture of the output from swapping from cheap blue (not capricorn, that was worse) PTFE to cheap white PTFE; same g-code:

    [​IMG]

    Here is a photo of the aforementioned retraction calibration g-code:

    [​IMG]

    the left corner is the origin, and as you move around the part the retraction increments by 0.5mm each step, the height increments 10mm/s every 5mm print height. You can't see it, but 5mm @ 30mm/s seems best for this material, this hot end, this printer, this alignment of the stars.
     
    #10 Jai Stanley, Nov 29, 2019
    Last edited: Dec 1, 2019
    Greg Holloway likes this.
  11. Andy Cohen

    Andy Cohen Well-Known Member

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    With PLA: 5mm @ 30mm/s is what I have set for retraction and it works fine for these Bowden/Titans. For the Nimble I have retraction set to 1mm @50. I've gotten clogs at a Bowden hotend, but they are rare. It's happened once with PLA and once with nGen. When it happens it is a major PAIN since the Titans have to be dismantled to get the back end of the filament for removal. ARG! Not what I would call maintainable! The Nimble stumbled on nGen too, but clearing the Zesty Nimble with it's clip-on idler took seconds. :)

    My TC is now working well enough in single tool mode for production work(which is not recommended for an "experimental" machine). Each tool is 100% reliable and I get print quality which is as good as my best machines. The Bowdens are not good for tool changing unless the object is larger so that all tool paths allow the Bowden to pressurize/depressurize the long length of filament in the tube. Nothing will over come that for a tiny tool path and a Bowden. Only a direct drive extruder will fix it. I don't care for use case limitations like that so the Bowdens gotta go. and... BTW... when I print with lots of tool changing everything I said above about how great it works gets revised. Lots of tool changing changes the game. But you must start with reliability for all 4 tools by themselves.

    Re: Amr's OP... I'd bet when you pause and then print the tip in the extruder is somehow getting distorted and going out of tolerance. Also... have you changed PLAs? 215c may be a bit high. I always start at 200c with a new spool and watch to see if it needs a change. Is it happening on the same object? If so, what slicer are you using?

    The problems described in Jai Stanley's post may be trickier to troubleshoot given how we all mod the TC. But my gut says... look at all your settings related to extrusion rate. When it pumps more plastic out faster then it should... even if it initially works OK... overtime it will clog. You may also need to slow it down. I print at 40mm/sec with these Bowdens which is half my usual printing speed. (The Nimble will easily do 80mm/sec... just sayin...)
     
  12. Amr

    Amr Well-Known Member

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    I switched to hemera on all 4 extruders my problems are behind me now :) Finishing a profile on Prusa Slicer and finalizing the 4 tool offsets to start working on multitool print profiles. will share once I have some thing solid
     
    cj.matthes likes this.

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