ColorFabb XT-CF20:bulge accumulates then drops on the print

Discussion in 'E3D-v6 and Lite6' started by 3Dmaker4U, Jun 1, 2015.

  1. 3Dmaker4U

    3Dmaker4U Member

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    I started some longer (8 hours) prints with ColorFabb XT-CF20 filament and I got some layer shifting now and then.
    I'm using v6 with stainless steel 0.4 mm nozzle.
    By analyzing the parts, I observed that there are come bulges attached to the parts, nearby the layer that started the shift.
    Moreover, the nozzle looked very dirty, having material all around.
    Initially I suspected material leaked around the thread for some reasons, but after dismantling the hotend and analyzing it, there was no evidence of that.
    I decided to be patient and observe the printing process as close as possible and I was surprised to find the following phenomenon.
    Material accumulates around the tip of the nozzle and slowly rise up around the nozzle. Seems that after a while (I do not intend to recreate the full experiment, just extrapolate the observations) it creates a bulge that fall on the print due to gravity. If the print is large enough so that the bulge will cool down until the nozzle returns to that area, it will obstruct the normal print path and the layers will shift.
    It's a peculiar behavior that I didn't meet with other filaments. I say an older topic related to the Taulman Bridge that reported a similar issue, but it was not reported as being solved or at least explained.
    It looks like that surface tension is responsible for it, perhaps "supported" by the nozzle profile and certain conditions (temperature?!). (see the accumulation on the right side of the nozzle tip in the picture).

    Any ideas?
     
  2. 3Dmaker4U

    3Dmaker4U Member

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    Re: ColorFabb XT-CF20:bulge accumulates then drops on the pr

    Dropping the temperature from 250C to 245 C has improved somehow the issue.
    Now the print may run for at least 2,5 hours without a significant bulge formation.
    I tend to believe that having the edges of the tip of the nose slightly filleted could solve the issue.
    This will be the next try.
     
  3. Sanjay

    Sanjay Administrator
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    Re: ColorFabb XT-CF20:bulge accumulates then drops on the pr

    We observe this as well, it's something that we see across all carbon fibre filled materials as well as glass fill and some other weird filaments with fillers.

    I don't have a clear solution for you - these filaments are new to market and weren't available at the time of the design. I would suggest using some sort of an integrated brush that you can clear the nozzle with using a quick G1 move on layer change or similar.

    We do actually have a very slight fillet on the edges of the tip, if you check it out under a microscope. Increasing the fillet by much results in inconsistent laydown of filament tracks, particularly on corners.
     
  4. 3Dmaker4U

    3Dmaker4U Member

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    Re: ColorFabb XT-CF20:bulge accumulates then drops on the pr

    Thanks, Sanjay!
    Good to know it happens :)
    While I believe you have experimented more, I still believe that you can slightly increase the diameter of the coned part of the nozzle, so that the flat part of the tip will maintain the area but the fillet will be a bit bigger. This will also improve the behavior in case of overhangs that curl up slightly and may be grabbed by the nozzle during non-printing travel.
     
  5. mr_clark1000

    mr_clark1000 Member

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    Re: ColorFabb XT-CF20:bulge accumulates then drops on the pr

    Hi, this is exactly the same issue I am having, it accumulates, and then causes blobs to form and drop in random places, sometimes causing the shifting of the piece.

    I think one of the issues is the "fluffyness" of the material once it is laid down, it catches ever so slightly on the nozzle and the nozzle being hot just collects it and melts it, until enough exists to cause the blob of death.

    The brushing solution might work, not sure how this would be integrated though?

    I will be trying my old ultimaker nozzle to see if the profile helps alleviate this problem - I think with the nozzle having a much longer V profile, it would take longer for the blob of doom to come to creation...

    I can report back later with my findings but I really need a solution to this! It seems that other people with different setups are successfully printing this material so maybe it's just the nozzle profile thats the problem here for this material?

    It would be good if we could come to a solution on this becuase it's doing my head in... the CF20 is a really nice material when it prints well, the surface finish and rigidity of it makes it suitable to finished products but the blob of desolation kills this dream of perfect prints off completely!
     
  6. 3Dmaker4U

    3Dmaker4U Member

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    Re: ColorFabb XT-CF20:bulge accumulates then drops on the pr

    Incidentally, I found today something that may help.
    When trying to use an extrusion width equal to the nozzle diameter (0.4 mm), there was no chance to print even a couple of perimeters of a 12 cm circle. Not even reducing the flow helped. I returned to 0.5 mm extrusion width and... ta-daaam, everything worked fine again. Seems that squeezing the extrusion under the flat area of the tip prevents the phenomenon. I suspect the extrusion curl up behind the nozzle, and not grabbed in front how I thought at the beginning.
    For the time being I didn't have prints longer that 3 hours (at a maximum speed of 60 mm/s), but the nozzle looks pretty clean when prints are ready. Next days, there will be some longer prints, so I can see if the nozzle will grab more material (hopefully not :)
    For reference, I'm using the 0.4 mm stainless steel nozzle @ 245 Celsius on BuildTak warmed up to 60 Celsius.
     
  7. mr_clark1000

    mr_clark1000 Member

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    Re: ColorFabb XT-CF20:bulge accumulates then drops on the pr

    Are you using Cura to slice? I guess the only way to force a wider extrusion width is to say it's a .5mm nozzle when in reality i'm using a .4 nozzle, or when I'm using the .5mm nozzle, say it's .6mm, as there is no dedicated field in Cura to say extrusion width.

    I will try this. I had a go with the ultimata nozzle that has more of the V shape and it didn't go well, there is still material pickup and the blob of doom forms...

    Something I thought might be a problem would be not using a cooling fan, as if you have a poke at the print whilst the head is in another area, with a bed temp of 70c, it is still very mushy and quite gooey... I think this might also be a problem as the gooey layer below is easily dragged and picked up by the head as it passes over.

    I am now printing a direction fan duct to see if some cooling of the previous layer will help by making it less liable for pickup.

    Might have a better idea later...
     
  8. 3Dmaker4U

    3Dmaker4U Member

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    Re: ColorFabb XT-CF20:bulge accumulates then drops on the pr

    No, not Cura. Either Slic3r or Simplify3D, depending on the print job. Don't remember about how Cura handles enlarged extrusion width, but there has to be a trick for this.
    I don't think fan cooling helps. Plain XT does not normally require cooling (actually it works rather worse than better). I'm not using fan at all, just slowing the speed for smaller layers.
    I did not experiment yet with layer height. I'm printing now at 0.2 mm and the silky look of the surface gives the appearance of 0.1 mm!
     
  9. mr_clark1000

    mr_clark1000 Member

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    Re: ColorFabb XT-CF20:bulge accumulates then drops on the pr

    thanks for heads up... I got into a bit of a rage last night with the machine and a perfect storm of failures resulted - 80 quids worth of parts from E3d later and I should be back up and running tomorrow - I think when this material prints well it's great but when it goes wrong it's not in an controlled and slow fashion like PLA and it doesn't happen straight away like ABS, it is just fine, fine, DEATH BLOB, destroyed...

    Suffice to say I have scars (probably life long scars to tell the kids about) from my episode of rage last night... it's weird, I've printed many different materials and this is a bit of a problem one for me - thing is I won't give up until it's sorted.

    I will try using 0.5 nozzle (0.4 real) in cura as that correlates to extrusion width. See what happens, but it's odd about the pickup. maybe tweaking extrusion a little more and slowing it down - it's a material that acts very oddly - liquidy but also gooey at high temps and does't do well being forced out quickly, perhaps real slow with lower extrusion factor.

    80% of a reel used in testing so far, with 4 or 5 high strength but not so perfect parts as a result, expensive experimentation. The reason I am pursuing this material so much is it ties in with my CNC'd carbon fibre sheets I'm using for this project and self taps with M3 Stainless bolts better than anything I have ever come across... I mean once it is threaded it's good for repeated insertion / extraction and feels like you are threading into a machined metal part, in line with my CNC'd and tapped alu frame parts - real nice feel to it. Gives it that machined feel to things which as a crossover from CNC'd rigid parts works really well in a suitable design.

    need to make it work!
     

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