"Dimples" appearing since upgrading to Titan

Discussion in 'Titan' started by Drahkan, Feb 25, 2017.

  1. Drahkan

    Drahkan Member

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    I recently upgraded my printer from a Mk8 with dying motor to a (non-Bowden) Titan with E3Dv6 using an 11Ncm 0.9-degree motor (calibrated e-steps are a whopping 1674!). (The old motor was a lot bigger and 1.8deg.) Although I'm still tweaking settings, I'm pretty much to the point where there's only one issue remaining: bizarre "dimples" at the end of each layer:

    [​IMG]
    (This is PET running at about 45mm/s and 243C, if that matters; note that I have not tried any other filaments yet since installing the Titan, but this never occurred with this or any other filaments prior to the upgrade.)

    The smaller motor seems to have enough power - I have yet to have any "clicking" or other indications of extrusion issues beyond this due to lack of torque. I've messed with all the LCD-changeable firmware settings I can think of (acceleration and jerk primarily; I admit that I'm not too knowledgeable in the firmware area), I'm using S3D and have tried every combination of settings imaginable, and no matter how awesome I get the overall print, I cannot get rid of these tiny little indents. Bolts have also been loosened enough that I seriously doubt they are the issue.

    I'm 99% sure the dimples are at the end of the nozzle movement, not the beginning (settings-changes affecting the start of the line pretty much universally make the whole print worse), and since S3D won't let you set coasting distances to negative values I can't kludge a fix that way (enabling coasting but at 0.0mm doesn't help; I even gave that a try).

    Everyone I know is stumped at this point, so now I'm moving on to those that I don't know. ;) I've spent at least 10 hours this point, probably double that, and am completely out of ideas. :( Hopefully someone here can help me solve this!

    Cheers!
     
  2. Kanedias

    Kanedias Well-Known Member

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    What are all your slicer settings? Too much retraction could look like that.
     
  3. Drahkan

    Drahkan Member

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    That's at 0.6mm. :( I've actually gone so far as to completely turn retraction off, and as expected it created blobs and other artifacts...without doing anything to fix these dimples.

    Here's the important(?) settings used on this print; I might have slightly modified them since printing this thing, but they were very close (and in any case these settings here appear to be optimal print settings with the exception of the dimpling.) -

    [​IMG]
     
  4. Spoon Unit

    Spoon Unit Well-Known Member

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    Random starting points .... = dimples.
     
  5. Drahkan

    Drahkan Member

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    If your other settings are correct, no. If I set it to optimized points, or to "closest to x/y coordinates", I end up with a really horrible vertical seam. That never happened with my old Mk8 extruder, nor does it happen on my other (cheap) printer. This specific dimpling is definitely post-Titan upgrade.
     
  6. Spoon Unit

    Spoon Unit Well-Known Member

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    I can only speak to my experience with the Bigbox. But logically, your shell will either start or end at some point on the outer surface. That will essentially be the end of the "tube" of material. It's got to be visible, it seems like a physical necessity. I prefer to group them into a seam, which can be sanded if required, or hidden depending on the model. I'd just love to understand if there's a way to completely hide these start or end points. I was hoping LIN_ADVANCE might auto control the extrusion to neatly peter out in order to minimise the effect, but haven't seen seccess with it. There is a feature, coast at end, you might want to play with, which is a un-smart version of one of the LIN_ADVANCE effects. Maybe other hardware you have was doing that for you, or maybe other slicers?

    I'd really like to see your prints that don't show this effect from other extruders or machines, or anyone's. I'd love to hold out hope that it's fixable.
     
  7. Kanedias

    Kanedias Well-Known Member

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    It's perhaps unlikely given your low retraction but are we sure it isn't being caused at the START of each layer, in which case extra restart distance might be the one to twiddle.

    I'm not sure how fully you can eliminate the zipper effect on a round object without vase mode it shouldn't be any worse with a Titan I'd have thought.
     
  8. Drahkan

    Drahkan Member

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    (Sorry, for whatever reason I'm not getting email alerts...or Gmail is filing them away into some strange corner of my folders. Anyway, that explains the lack of quicker replies...)

    I just spent a ridiculous amount of time trying to find pre-Titan prints that have areas of 100% "roundness" and, well...the only round objects I can find were printed right at the end of the Mk8's lifespan, when it was failing badly enough that the only way I could prevent huge gashes from appearing was to print extremely slowly and at unusually high temps. I didn't think about it until now, but they came out shiny as compared to the duller color I get now, so I'm now wondering if the slow+hot effectively "melted the dimples out"..? Now, I've got quite a few prints that are *almost* completely round, but they have at least one "corner" (even if it is beveled on the model) where I can't discount evidence of a seam. (It's too difficult to know for sure.) I could post pictures but since its not definitive I'm not sure if there's a point.

    As for my other printer, although I can print round test objects, apparently I haven't printed 100% round objects before as my settings go from Great to Crap the moment I print a completely circular object. I thought I could, and just tried doing so with a few different settings, but for whatever reason my normally-okay coast and retraction settings suddenly turn awful when dealing with a completely round layer. :(

    So...I'll post once I (re?)verify that extra restart causes issues rather than fixing the dimples, but otherwise I'm starting to think that you guys are right, dimples were probably always there, but the lesser quality of the prints "covered them up" as compared to the much-more-precise prints I'm getting from the Titan...o_O:confused:

    EDIT: Extra restart is definitely causing problems, so the dimple must be at the end of the line. So I guess I just spent a week trying to fix a problem that has always existed, but for whatever reason(s) I never realized it until post-Titan-upgrade. *SIGH*
     
  9. Tom De Bie

    Tom De Bie Well-Known Member

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    Change the settings as described
     

    Attached Files:

  10. Drahkan

    Drahkan Member

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    On my round test object, the only visible difference between your suggested changes, my original changes, or (as a 3rd test) completely disabling retraction, is that the changed or disabled retraction settings create blobs on the inside of the print. Although the changes might be a tiny bit better dimple-wise, the blobs that form on the inside appear to effect the outside layer in their own right, offsetting any benefits. :(
     
  11. majikthyze

    majikthyze Member

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    I've been fighting a similar battle over the last couple of weeks with my MakerFarm Pegasus and have landed at pretty much the same place. I upgraded to a Titan and noticed dimples / seams depending on the layer starting point, but eventually concluded they've always been there even with the original extruder. (Like you, I coincidentally started printing some round designs after getting the Titan.)
    I've bracketed all the retraction settings, and can definitely introduce new issues or make the seams worse with too much retraction, but the seams are still quite noticeable with the optimal settings. The seams on my cheaper Anet A8 are hardly noticeable at all and I've been scratching my head over it.
    I found this post when searching for LIN_ADVANCE, which is something I was about to start playing with...
     
  12. Spoon Unit

    Spoon Unit Well-Known Member

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    I started playing with the Wipe Nozzle feature and have definitely improved seams over what you would get without it. A short wipe distance (1mm) seems to be enough to just lay the end of the "pipe" of filament nicely in place. Wipe happens before any retraction, and there, having a minimum distance for retraction also helps to keep the nozzle wiped for the start of the next line.
     
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  13. majikthyze

    majikthyze Member

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    I tried wipe and did not help the issue I was seeing at all. The blob is deposited after that and the wipe doesn't dissipate it.
    I'm now using LIN_ADVANCE with K=50 on my Titan and it is working really well. Evidence:

    The image on the left is with LIN_ADVANCE, K=50. The image on the right is without LIN_ADVANCE>
     
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  14. Spoon Unit

    Spoon Unit Well-Known Member

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    Which firmware are you using for that? I've got Lin_ADVANCE on, but I have a feeling it's still not actually on.
     
  15. majikthyze

    majikthyze Member

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    I'm using the RCBugFix branch of the marlin firmware. I'm using the M905 command in my init script to set the various parameters -- e.g.:
    M905 K50 W0.4 H0.1 D1.75
     

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