SOLVED Y axis issues

Discussion in 'Calibration, Help, and Troubleshooting' started by Sarah Nicholson, Jun 19, 2016.

  1. Sarah Nicholson

    Sarah Nicholson Well-Known Member

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    So although my BigBox is generally working well, while trying to fine tune my extrusion multiplier I noticed some very small artefacts in the Y axis, this manifests as very slightly misaligned bands at certain layers of the print. It's not axis shifting as such as it usually corrects itself within a few layers, just the walls are not perfectly aligned, and only in the Y axis. I've printed the same model in different parts of the bed and the same thing happens, and it's usually at a different height as well.

    I've double checked all the pulleys and belts are tight, the rods and bearings are greased, and the stepper voltage is set correctly, but it was still happening. So I decided to go through the whole Y axis commissioning steps again, and one thing is that my Y axis, even with everything slackened off, does not move as freely as it does in the video in the build manual. It feels evenly smooth with no binding or rough or lumpy spots, but there is definitely much more resistance to moving it manually than there appears to be in Greg's video. Any suggestions for other things I could check or ways to try to get it moving more freely?
     
  2. Old_Tafr

    Old_Tafr Well-Known Member

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    Did you slack (grub screws) off the pulley on the Y axis motor to see if the motor is causing some resistance?
     
  3. Sarah Nicholson

    Sarah Nicholson Well-Known Member

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    Yep, I unscrewed everything. I think I may have resolved it, although I'm not sure of exactly what I did that sorted it out. After an hour or so of slackening off screws and slowly gradually retightening while constantly checking the movement, I now seem to have it in a state where it moves reasonably freely with the motor pulley slackened off. Currently doing a test print and it looks much better.
     
  4. Sarah Nicholson

    Sarah Nicholson Well-Known Member

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    I'm going to tentatively mark this one down as solved, second print now in progress and looking good. I don't know if I had something out of square somewhere, one of the things I did was to slacken off quite a lot of the frame screws as well and then really systematically tighten them all up gradually in turn rather than one at a time, so perhaps that helped to true things up a bit.
     
  5. R Design

    R Design Well-Known Member

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    If you have stock bearings then there will always be a doubt....
     
  6. mike01hu

    mike01hu Well-Known Member

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    Sarah, you did exactly the right things as the Y axis is the most likely to suffer from misalignment due to differences in frame tolerances and minor distortions in the printed parts. The bushes are not so critical on this axis because of the direct belt drive provided that belt tension is adequate. In my case I found that slackening the frame screws slightly and doing the Y alignment and carriage clamp tightening first before going back to tightening the frame screws starting at the back and moving forward on both sides. It is also very important to recheck the rod clamps on each axis, particularly the X axis, after a few hours of running as I found they had loosened substantially due to the relaxation of the printed parts through natural normalisation and "bedding in" processes, something that happens in many engineering assemblies.
     
  7. Stian Indal Haugseth

    Stian Indal Haugseth Well-Known Member

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    @Sarah Nicholson, I would be interested in a photo of the bands if you have any. Nice to know what to look for.
     
  8. Sarah Nicholson

    Sarah Nicholson Well-Known Member

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    Sure, I'll post some up, probably tomorrow.
     
    Stian Indal Haugseth likes this.
  9. Sarah Nicholson

    Sarah Nicholson Well-Known Member

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    As promised, some pictures of the artefacts. Apologies for the not-great picture quality, these were taken with a mobile.

    The left and centre cubes in this pic show the issue, the right hand one was after recommissioning everything. For scale, these are 20mm² cubes.

    [​IMG]

    A close up of the affected side:

    [​IMG]

    From the side (you can see the other axis is fine and also how small the displacement is):

    [​IMG]

    Close up after recommissioning, looking much better:

    [​IMG]
     
  10. Henry feldman

    Henry feldman Well-Known Member

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    Still some regular ringing every 4 layers on that last one. Strange that it is so regular all the way up the item
     
  11. Sarah Nicholson

    Sarah Nicholson Well-Known Member

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    When viewed with the naked eye it actually looks very good. The problem seems to be more in the corners, this was printed with a pretty much out of the box S3D profile so there's probably some tweaking to be done there.
     
  12. Alex9779

    Alex9779 Moderator
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    It looks like a starting/ending point issue. Four corners, four layers, every layer a different corner is chosen as start and so end... Probably "Fastest printing speed" option...
     
  13. Sarah Nicholson

    Sarah Nicholson Well-Known Member

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    Was just about to post to say that on examining it with my 15x loupe I use for soldering, you can actually clearly see that it's the layer change point. I'm printing one with randomised start points now for comparison.
     
  14. Stian Indal Haugseth

    Stian Indal Haugseth Well-Known Member

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    That was very distinctive. Strange stuff.
     
  15. Sarah Nicholson

    Sarah Nicholson Well-Known Member

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    Yep it's odd, not seen this particular kind of issue before which is why it's useful to post pics. I'm still not really sure what could have been the cause given how small the displacement is and the slightly random nature of it. It's definitely not a slicing problem though but something mechanical.
     

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