Return of the Banding

Discussion in 'Calibration, Help, and Troubleshooting' started by PsyVision, Mar 3, 2016.

  1. PsyVision

    PsyVision Moderator
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    So I'm printing this F1 car at the moment.

    I have replaced the z-axis parts with the new ones and printed out the nose cone and then the front section. Last night I printed out the main body section and the z-banding has returned.

    The print profile is exactly the same, same filament. The only thing, previously I was set at an incorrect steps per mm, however, the prints were still fine. I re-calibrated my steps per mm last night and printed a test cube. Steps per mm went from ~270 to 315 and I have set the extrusion multiplier to 0.94. The test cube at 1 perimeter, 1 top and bottom, 100% infill came out perfectly sized, with no banding and no gaps top and bottom.

    In the image below the part of concern is on the right.

    Is this an (over) extrusion problem and not something mechanical? If so what should I do to resolve?

    20160303_124756.jpg
     
  2. Mike Kelly

    Mike Kelly Volunteer

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    Are the striations consistently spaced?

    I still don't understand how extrusion multiplier works in relation to esteps. Your esteps are also significantly higher than most of us have been getting.

    I believe extrusion multiplier does not affect retractions so a retraction may cause issues.
     
  3. PsyVision

    PsyVision Moderator
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    Thanks for the reply Mike.

    They are evenly spaced. My printer came with the 304 steps in the firmware. The grey PLA/PHA I have been using goes at 300.. Is a difference of 15 that much of a difference?

    I am printing a Marvin at the moment so will see how that comes out.

    If my test cube is really good then why would this be so different in the banding? I have re-done PID in case temperature fluctuations in the hot end and bed are affecting it.
     
  4. Mike Kelly

    Mike Kelly Volunteer

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    I feel like a test cube is a poor quality indicator. It's a relatively easy print and ignores a lot of print cases. Even a deprime test object will show more than a cube.

    I like the Make tests, the Z resonance is a good one (Printed a 12" one to test my Z)

    Their Rook is also good.
     
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  5. PsyVision

    PsyVision Moderator
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    Thanks, grabbed the z-resonance one to print next. Marvin had one bad part to it but was OK otherwise.
     
  6. PsyVision

    PsyVision Moderator
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    Resonance is underway, I havent set it printing using exactly the same settings (i.e. not change to vase mode or anything)
     
  7. UlrichKliegis

    UlrichKliegis Well-Known Member

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    The bands on the rounded surface look like a typical aliasing - there may by a multitude of reasons for that.
    Since the lines follow a certain pattern tied to their x / y position, a quantization error comes to mind. That can be a mismatch between the achievable and desired resolution, it could be the input geometry data (scaled up from a smaller scale?), original data (did they come from a 3D-scanner or where from?) - I don't believe it is the same reason as in the former z guide rail error. I also would look at the extrusion side as the last option.

    S3D offers the graphical simulation of your gcode. Load the gcode data you used for the print there and zoom in on the questionable region.
     
  8. PsyVision

    PsyVision Moderator
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    I should really update my own threads.

    Essentially I think this is down to over/under extrusion based on on-the-fly tuning I did during the Z tower print. I had some essentially perfect prints followed by some bad ones (banding) after a bad recalibration. I think I've solves it this morning with a number of tweaks. Will report back once I get home and check the print.
     

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