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TPU filament Project

Discussion in 'Projects' started by tkoco, Aug 3, 2019.

  1. tkoco

    tkoco Administrator
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    [Note: The goal of this project is to get the right combinations of parameters so that printing with TPU filament can be as easy as printing with PLA filament.]

    IMG_20190803_143710.jpg

    Yes, my C2 printer is so old that it is printing mushrooms:)

    That aside, can a model printed in TPU filament be lightly sanded?

    Update: NO! The flexibility of the TPU filament causes the surface to get worse with sanding.
     
    #1 tkoco, Aug 3, 2019
    Last edited: Aug 9, 2019
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I see no reason why not.
     
  3. tkoco

    tkoco Administrator
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    Starting a printing project which needs to be printed in TPU filament. First a big thank you to @Jerome Helbert for posting the TPU settings from his print jobs. I used his information as a basis for the settings for this project. Cura 4.2 settings to follow in the next posting.

    TPU print with lighting:

    IMG_20190803_161640.jpg

    TPU print without lighting:

    IMG_20190803_161502.jpg
     
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  4. tkoco

    tkoco Administrator
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    For those of you using Cura as your slicing software, I have posted the details on creating a TPU profile for Cura.
     

    Attached Files:

    #4 tkoco, Aug 3, 2019
    Last edited: Aug 3, 2019
  5. tkoco

    tkoco Administrator
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    Some more images of the model printed in TPU "Glow in the dark" Filament.

    IMG_20190803_174529.jpg

    IMG_20190803_174537.jpg
     
  6. tkoco

    tkoco Administrator
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    Some additional tips for printing with TPU filament.
    1. Any kinks in the filament will cause a printing failure. So sacrifice any leading filament which has been kinked during storage.
    2. The Teflon feed tube can be used for printing with TPU filament. You have to be patient while you push the filament into the spool end of the Teflon tube. Once the filament exits the extruder end of the tube, you can reseat the tube into the feed sensor and pull the TPU filament to get a few inches (or cm).
    3. When feeding the extruder via the Teflon tube, carefully hand feed the filament into the extruder. [Once you get TPU filament coming out of the nozzle, and it is 100% TPU filament, stop the filament wizard. Then seat the Teflon tube into the top of the extruder.] <- Wrong order of feeding. After the TPU filament is beyond the toothed gear of the extruder motor, take the time to properly seat the Teflon tube into the extruder BEFORE running the Filament Load wizard. Read the third posting below this one.
    4. Try not to pull or push the TPU filament any more than you have to. The filament is rubbery and will distort with excessive force.
     
    #6 tkoco, Aug 3, 2019
    Last edited: Aug 15, 2019
  7. tkoco

    tkoco Administrator
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    An observation from watching the TPU print jobs.

    Printing multiple models on the same bed (or possible a large model) seems to print better than a singular small model. I believe that the improvement in printing multiple models comes from the slicing software doing a better job with heat management. Thus allowing a slightly hotter material setting without running into the issue of laying molten filament on top of semi-soft filament (insufficiently cooled filament).

    The material settings (0.4 mm nozzle opening) which I use for my TPU printing are as follows:

    Default printing temperature -> 217 C
    Default build plate temperature -> 40 C
    Retraction distance -> 2 mm
    Retraction speed -> 30 mm/s
    Fan speed -> 0%


    The filament tends to ooze slightly while the hot-end is stationary. But I don't get any clogs and the filament layers bond well to each other. On PLA print jobs, I usually use raft adhesion. However, with TPU, skirt adhesion is all you will need (or desire for that matter). A generous 'tip of the hat' to @Jerome Helbert for pointing out this bit of information.

    And if you have problems with skirt adhesion, please revisit the bed leveling procedure in the Troubleshooting forum for the R2 printer.
     
    #7 tkoco, Aug 6, 2019
    Last edited: Aug 6, 2019
  8. tkoco

    tkoco Administrator
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    Tried a multiple model printing (20 parts) with TPU and ended badly. The nozzle was "air printing". Postmortem analysis found that only the 0.4mm channel of the nozzle was clogged.
    So I am going to try reducing the fan speed cooling from 20% to 10% and see if the multiple model printing can finish. I'll report back in this project.

    Update: Trying different combinations to see what will prevent the nozzle tip from clogging. I've set parameters back and now am trying 110% flow rate with a 1mm retraction at 215 C. Also reduced the part count from 20 to 8.

    Update 2: Increased flow to 115% and bumped the temperature to 222 C.

    Update 3: Restored all settings. See the next posting.
     
    #8 tkoco, Aug 7, 2019
    Last edited: Aug 8, 2019
  9. tkoco

    tkoco Administrator
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    The tip of the nozzle getting clogged is a symptom, not the actual cause of the problem. When you do a cold-pull of the filament you will get something like this image.

    filament.jpg

    The culprit is the Teflon tube not being 100% seated into the extruder. The TPU filament (and probably Ninjaflex filament) is so flexible that it is easy to think that you have seated the tube, when in reality, you haven't. So when you are loading the TPU filament into the extruder, take a few extra seconds to wiggle the tube around and make sure that the tube is truly seated in the extruder.
     
  10. tkoco

    tkoco Administrator
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    Update: was still getting "air-printing"on multiple model printing. So, I bumped the print temperature to 225C and disabled retraction. Those changes seem to be helpful (no air-printing on multiple model printing). Currently trying different retraction settings as the stringing is really bad without retraction. Of course, still checking for air-printing.
     
  11. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Yea, retraction on flexibles can be a bad thing.
    Not having retraction means you may have to deal with a bit more stringing :)
    Try slower retraction speeds and less of it.
     
  12. tkoco

    tkoco Administrator
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    I agree. So, I'm pursuing that line of thought. Hopefully there is a happy medium for those settings.
     
  13. tkoco

    tkoco Administrator
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    New update: I solved the problem of how to smooth out the stringing artifacts of printing with TPU.

    You will need:
    1. A good pair of leather gloves
    2. A hot air rework station like this one on Amazon.com : https://www.amazon.com/gp/product/B076Q8Q4LW
    3. A micro-cutter tool like this one on Amazon.com: https://www.amazon.com/Hakko-CHP-170-Micro-Cutter/dp/B00FZPDG1K
    The micro-cutter tool can be purchased at Hobby Lobby, Home Depot, Lowe's stores as well as online.

    Simple enough,
    • Cut off the strings as close to the model as possible. You will end up with some "nubs".
    • Set the temperature of the rework station to the high end temperature of the filament. Use a narrow nozzle cone and set the air flow to the half-way setting.
    • While wearing gloves, heat up the string nubs on the model and then press them into the model using your gloved hand. Let the model cool.
    Be careful to not overheat the model. You want to get the nubs warm enough to be "reworked" into the model. How long to heat? Depends on the size of the nub. Some experimentation may be necessary.
     
    #13 tkoco, Aug 15, 2019
    Last edited: Aug 15, 2019
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  14. tkoco

    tkoco Administrator
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    I considered the factors which might cause a TPU print to fail. I put in place 2 mods to assist with this issue. One was the friction between the filament spool and the printer's spool support. The second factor was the heating up of the extruder motor and the subsequent heating of the tooth gear which pulls / pushes the TPU filament. Both issues have been addressed. You can read the details of the mods in the R2 Mods and Upgrades area.
     
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  15. tkoco

    tkoco Administrator
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    Update: Making progress with the stringing issue without clogging the hot-end. The model on the left was printed after installing the two mods. Also reduced the printing temperature from 225 C to 222 C and enabled some retraction (nowhere near the retraction settings of PLA)

    stringing.jpg

    More updates to follow
     
  16. mark tomlinson

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    That left one in clean enough that a quick hit from a lighter will remove that fuzzyness :)
     

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