Crooked frame / Y-axis

Discussion in 'Build Help' started by JesperJuul, Apr 25, 2016.

  1. JesperJuul

    JesperJuul Well-Known Member

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    Hi guys and motions system wizard @Greg Holloway,

    I worked all night yesterday trying to sort out why my frame is bending on y-axis movement.

    You can watch my problem here: https://youtu.be/UIe5JVBpS3E

    What i fund:
    - The linear rods look straight enough
    - The problem seams to located to the left side
    - Natural track of the y-axis seams (then removing bolt on the left rear y-axis bracket) to be offset a bit towards the center of the printer.

    Please someone tell me what is wrong, i´m going insane here!
     
  2. Rob Heinzonly

    Rob Heinzonly Well-Known Member

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    Did you tighten all the screws yet ? If you have, loosen them. Do not tighten the screws until the decommission chapter.
     
  3. PsyVision

    PsyVision Moderator
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    Did you have your frame loose and then tighten the X-axis, then put the carriage at the front of the printer and tighten the front of the frame, then move it to the back and tighten that (really poorly described) as in the manual? It looks as though there is a difference in the front/back that causes the movement.
     
  4. Stefan

    Stefan Well-Known Member

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    Maybe the left and right belts are not sync, I mean did you tighten the grub screws on the pulleys already.
    Or other way to ask do have the y-belts tensioned already? They should not have tension before the holders are aligned correctly.
     
  5. JesperJuul

    JesperJuul Well-Known Member

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    It does it even with all framescrews loose. As soon as i tighten the y-axis brackets to the frame i tightens up in the rear end.
     
  6. JesperJuul

    JesperJuul Well-Known Member

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    The belts have been loosen didn't make a difference.
     
  7. Old_Tafr

    Old_Tafr Well-Known Member

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    Maybe take the belts off and see if it happens then?

    Slackening off any tightened grub screws in the pulleys (back of frame left and right) would not do any harm either.

    Also you could measure between the two "Y" rods i.e. horizontally between the two to see if they are parallel.
    I have used a piece of wood with a round head screw in each end as a gauge. You can get a very precise change in length by turning the screws a very small amount. Bamboo is ideal.

    The exact measurement isn't critical you are simply comparing the distance at the front and rear of the frame.

    There is also somewhere a check on the distance of the "X" rods (the front one of the two) to the front of the frame, in essence to check that the frame is square and the "Y" rods are parallel and the "X" rods perpendicular to the Y rods.

    http://wiki.e3d-online.com/wiki/Printer_Commissioning

    search on "measure" it's the first hit. (note here it says " If you find it hard to adjust make sure the grubs on the pulleys are loose" )

    I suspect as others that it's something tightened up too soon in the build.

    You could also check with a set square if the frame is square, the back two corners would be ideal for this.
     
  8. Dr Jeep

    Dr Jeep Well-Known Member

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    I had a bit of this and found that it is actually possible to push the ends on to the X rods a bit too far and make the X assembly too short, by tweaking that (literally a screwdriver handle tap from the left hand side being fully pushed onto the rods, before tightening the X rod retaining screws) solved it.
     
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  9. Greg Holloway

    Greg Holloway Administrator
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    The rods are not parallel, but that won't be adjusted until the commissioning process.
     
  10. Irawan Tri Kusumo

    Irawan Tri Kusumo Well-Known Member

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    I have the same problem last time, and the problem as Greg said. The X Rods are not parallel.
     
  11. orcinus

    orcinus Well-Known Member

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    Just had the exact same issue and found a solution.
    It might not apply to everyone with the same symptom, but just in case *nothing* else helps, here's what it was in my case...

    It wasn't the rods themselves that were pushing the front of the frame apart and/or causing friction - it was the X axis idler assembly. Past the half of the Y axis, it was chafing against the lexan wall and spreading it apart when it reached the front. It was driving me crazy, because everything was fine with everything loosened, but the moment i'd start tightening the bolts, it'd go back the way it was, no matter what i did.

    Cause: the Y rod brackets on the rear were ever so slightly out of alignment with the Y rod brackets at the front, and no amount of commissioning, untightening, moving about and retightening would or could help, because tightening them would just shift them back the way they were. I assume the tolerance of the printed parts is to blame.

    Solution: i moved the carriage to the front, tightened everything *including* the X axis, then undid the rear brackets, moved everything back, PRESSED HARD on the sides at the back WHILE tightening. And then, everything was smooth and no chafing of the X idler bracket anymore. You might think it'd be easier to just shove something between the rear Y brackets and the printer walls, to keep them pushed closer (while tightening up the bolts), but that doesn't really work - it just pushes the printer case apart instead.

    PS: In my case, it wasn't that dramatic of an issue, it's just that i sometimes obsess over stupid things like that. I could push the X assembly along the Y rods just fine with my finger, but i could feel it tightening beyond the half-point, and if i shoved it, it wouldn't just fling all the way under its momentum like it did with everything undone. So i kept poking and prodding until i got it completely smooth.
     
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  12. orcinus

    orcinus Well-Known Member

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    Post-tweak and after tightening:



    And yes, all of my rods/bearings are that loud.
    I'm waiting for a replacement on one of the X bearings, it's gritty.
     
  13. kevclarx

    kevclarx Active Member

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    Thank you for this, fixed the issue for me. Just had to loosen the x-axis, then pull on the bars a tad and retighten.
     
  14. ldaponte

    ldaponte Well-Known Member

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    Same issue I ran into last night, exactly as you describe it here. Pulling out x-axis rods did not solve the issue - yet.
     
  15. Irawan Tri Kusumo

    Irawan Tri Kusumo Well-Known Member

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    @Idaponte, No, it has to be parallel and same "length". There are 2 X-Rods which connect the X-Ider and X-Motor Mount. The hole for the Rods on those 2 printed parts is so tight, you might not push them deep enough. So, the 2 X-Rods does not parallel and have the same length. I hope this will help, because it happened to me exactly same on the video.
     

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