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  1. #1

    Unhappy Nozzle repeatedly clogging while printing Ninjaflex TPU

    Hello,

    I'm having a problem printing white NinjaFlex TPU on an Airwolf3D AXIOM Dual Direct Drive printer. I am trying to run some test prints of a face mask ear strap but am having problems with the nozzle clogging shortly after the print starts (within the first 5 or so minutes). What happens is the print will start printing the first layer without a problem, but after printing the brim and the outline of the part, the nozzle starts clogging as it prints the infill for the first layer. I used the recommended profile settings on the NinjaTek product page as a guide for the settings and am using Apex (Airwolf3D’s rebranded version of Cura) for the slicer with the standard TPU profile modified with the NinjaTek settings for speeds.

    So far, I have tried a deep clean of the nozzle (which was using ABS previously), and tightening the hobbled bolt in the direct drive hoping that would help. I also tried changing the Z offset from the table in case the nozzle was too close or far away from the bed. I have attached an image showing the part I tried to print, and a copy of the profile I used for the test print (you can still view the settings without having Apex). Can anyone give me some advice on what I can do to solve this issue?

    Thank you!
    Jason O
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  2. #2
    Ok, no idea about your printer but here is what I do with my Makergrear m2
    Had to replace the OEM extruder housing with one that had been modified for TPU open spaces were tightened up to keep the filament form getting jammed.
    Tension has to be very light or filament will squish and then get jammed
    Nozzle size must be .5mm or larger for good results.
    Speed must be 15mm no faster
    retraction must be no more than .4mm (direct drive)
    temp on my printer i 230 and cold bed (sticks too tight to polymide tape
    Nozzle is always cleaned with esun cleaning filament before changing material and a a couple feet wroth of thread is extruded to remove cleaner or the print will not adhere.
    Filament is mounted on a bearing supported gravity feed rig
    filament diameter in slicer is set to 1.65 and extrusion multiplier is bumped by .1 (most every filament I use has an extrusion multiplier of .93 on my machine assuming I set the actual diameter of the filament.
    Just printed some vibration dampers yesterday with no issue using the above but I use S3d to slice .
    My guess is your are probably printing way to fast.. start out at 10mms and work up 2 of 3mms ..
    Good luck

  3. #3
    Super Moderator curious aardvark's Avatar
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    you are printing too fast.

    For bog standard wet-noodle-style (it's a technical term) ninjaflex you need to be dow around 10mm/s max print speed and depending on the machine sometimes as low as 5mm/s.
    Also you need to be at to top end of the 'recommended' print temperature.
    And often 10-20c above it.

    what speeds are you using - I can't be arsed to download and unzip a profile - just tell us :-) It makes life easier all round.

    But sounds like - and looks like - classic trying to print flexible filament too fast.

    Okay I looked - 30mm/s - yeah right, you've got almost no chance of running ninjaflex at that speed.
    You'd need a combined extruder and heatbreak length of about 10mm to get away with that.

    Okay looked at some of the other settings - who wrote these ?
    5mm retraction, for flexible filament on a direct drive extruder ?
    knock that right down to 1
    Lower if you can get away with it.

    1.8mm retraction should work for pla on a direct drive - but for flexibles, as short as possible and slowly.

    And 230c printtemp for ninjaflex is too cool.
    Try it at 240, I think the last time I bothered witht he stuff I was running at around 250c before it worked well.

    Because it is so soft and stretchy, you want as little pushing and pulling as possible - hence the short retractions and low print speed. It needs to flow out of the nozzle with minumum back pressure.
    the retraction speed is fine. If you can get it to retract during the wipe period. No clue how you do that on cura.

    Also you should not need the bed heated at all.
    40c is neither here nor there anyway. So set that to off or 0c (depends on slicer).
    And you definitely shouldn't need a brim.

    Also get your print cooling fan on 100% after the first layer.

    But whoever wrote that profile was looking at a much firmer and less stretchy filament than original style ninjaflex.
    And they were probably using a bowden tube setup.

    The vast majoritiy of tpu on the market, are all harder and less stretchy. So that profile might work for one of those, but it ain't setup for ninjaflex, that's for sure.


    Okay it's a rep pro style printer.

    For the really soft and stretchy filament you ideally want a top loaded filament roll with as little friction as possible.
    Just the extruder pulling it from the reel will cause the filament to stretch - which in turn will bugger up the slicers calculations and effect the print.

    You don't need the enclosed print volume for flexibles. So you could take the top off the machine and rig up some sort of stand that would feed the filament directlydown into the extruder.

    It's what I need to do for my rep pro clone.
    Last edited by curious aardvark; 01-08-2021 at 11:23 AM.

  4. #4
    TPU needs a good filament drive that has no place for the filament to go but into the hot end, direct drive does not make it so..
    you should have a .5mm nozzle at the very smallest
    You can not tighten the tension screw too tight of the filament will become flat and jam in the extruder housing
    You can not use much if any retraction
    You must go slow 7-10mm second
    Temp should be at the low end of their scale
    If you used ABS you will need to clean that nozzle with cleaning filament first and flush it with a lot of TPU after.
    Feed rate to flush needs go be very very slow..
    Good luck,
    Oh and the most important thing.. filament must be gravity fed, in other words .. the drive can not be expected to pull the filament and make the real of filament move..

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