Z Seam Gap 0,8mm Nozzle

Discussion in 'Volcano' started by Peter85, Aug 15, 2018.

  1. Peter85

    Peter85 Member

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    Hi all,

    I have some issues with my Titan Aero Volcano setup with. Currently i try optimize the quality of my printer. But I can´t figure out how to minimize the Z Seam gaps for my volcano. As you can see on the picture the z seam gap is quite huge around 1.40 mm.
    For slicing i use cura 3.4.1. For me it seems that my extruder always starts delayed on the outer perimeter.
    I tried many variations (coast, wipe, layer height; line width) but this are currently the best results for the seam.
    My setup is (for the picture):
    nozzle: 0.8 mm
    layer height: 0.6 mm
    wall thickness: 1.6 mm
    line width: 0.8 mm
    bowden: 1600 mm
    material: ABS
    print temperature: 230 C°
    rectration : 1.6 mm / 55 mm/s speed

    Any ideas for reasons? Many thanks in advance for your sulutions.

    Peter IMG_20180815_213204.jpg
     
  2. Spoon Unit

    Spoon Unit Well-Known Member

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    I was playing with the same issue using a 1mm volcano nozzle. I see similar results. Ultimately it's down to tuning retraction to get the best result you can manage, but I have a feeling that perfection will be a challenge to arrive at.

    You don't mention about what your extra-restart-distance is. I don't know Cura, but would be surprised if it's not there. This is a positive or negative value which, added to the retraction amount, determines how much material must be pushed to re-prime after the retraction+move.

    Not sure if that's clear, but that's where you'll need to start.
     
  3. Peter85

    Peter85 Member

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    Hi Spoon Unit,

    thx for your quick reply. I think i understood your advice. My next print is with 0.8 mm retraction.
    Cura does not offer an extra restart distance. It only offers a retraction extra prime amount (see pic blue box). But it is only for oozing problems and you can add only positive values. I´m trying now a further benchy with a 0.8mm retraction.
    Why do you think perfection is a challenge? Is it through the 0.8 mm nozzle to get good results of the benchy?
    I currently try to get better results with a 0.6 mm layer height for this nozzle. When i print a benchy with 0.4 mm layer height surface quality is much better and the gaps are smaller but schematic problem is the same :(.
    Unbenannt.png

    Do I need also adjust my jerk acceleration settings for my retraction?

    Regards Peter
     
  4. Spoon Unit

    Spoon Unit Well-Known Member

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    The retraction extra prime amount looks like the same thing I was thinking about. Interestingly, it looks like Cura wants that value specified in cubic mm.

    For the record, my current settings for the benchy print I posted elsewhere on the forum were 1.5mm retraction and 0.5mm extra restart. This means it retracts 1.5mm before the move, and primes 2mm on restart. I think I printed with only a single outline, but 2 outlines would have probably worked better as then the re-priming issue that we both displayed would be on the inner shell, assuming printing from inside to out. While looking around the internet for other input on retraction for volcanoes I did see someone else used 4mm for retraction and -0.4mm for extra reprime, meaning it would only reprime with 3.6mm. I'm guessing this was an attempt to counter the effect of the material oozing down the nozzle interior during the move.

    I'm not sure about your machine, but tuning retraction would be easiest if you can actually tune retraction while printing. I use Duet electronics which implement retraction in the firmware, which gives you the ability to alter all these retraction parameters on the fly during a print. By sitting next to the print and watching it closely, this should make learning the right retraction settings easier, but there are still so many permutations possible.
     
  5. Vik Sahota

    Vik Sahota New Member

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    Ah, its the same issue im dealing with at the moment. Im running titan, volcano & the 1.2 nozzle, 0.6mm layers and I see exactly the same, and more so than the 0.6 or 0.8 nozzles im sure. Retraction amount and speed, z lift, have some minor effect but not enough to resolve that gap, that I have found at least.
    Extra restart amount can help but not without side-effects.

    Here is what I figure - this large a filament diameter doesnt break and stay like we'd hope when retracting. Esp with PETG as Im running, and hot, its pretty hard to not string to some extent, and its emptying some filament from the nozzle. Trouble is, when the travel movement on retraction is large, the gap is large, when the travel is smaller, so is the gap. So getting a good setting for extra restart amount , only works for whichever length of retraction move you want to tune it for.

    I think it can be overcome but it would call for a variable restart amount, based on the distance of travel involved in that retraction. Then I can figure that multiplier which will give me several mm restart after moving all the way across my 500mm bed , and near 0 for very short hops.
    cant figure a way to do that via S3D as is.

    It would need for some post processing of the g code to tweak that on the particularly troublesome ones (others maybe out of sight). For one-off's that would be a pain but if you are going to run that print over and over, maybe worth the tweaking. Option b is to alter the design itself to cause the retractions away from areas of interest, or remove the need for retraction altogether. Ie just print a wall and drill the holes that were supposed to be printed. The end result would be cleaner after all.
    But the scaling restart distance would be the 'correct' fix for this i think.
     

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