Y-Axis belt is tight like a guitar string on one side and sloppy on the other
 
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READY.
(@ready)
New Member
Y-Axis belt is tight like a guitar string on one side and sloppy on the other

I'm having a weird problem with my Y-axis belt. It's seated properly in the carriage assembly from both ends, but the lower part that goes from motor to pulley is bowing. It's not parallel to the top one, and if you push down on one side, it's very tight, but the other is floppy and can bend around itself.

I'm thinking that it's not properly aligned in the X-axis, but the pulley tightener and motor mount doesn't have any way of moving it sideways.

Any tips?

Postato : 19/12/2017 6:26 pm
Enginman
(@enginman)
Trusted Member
Re: Y-Axis belt is tight like a guitar string on one side and sloppy on the other

Is the idler rotating freely? May have over tightened it. The drag would cause upper lower tension difference..

Postato : 19/12/2017 6:47 pm
READY.
(@ready)
New Member
Topic starter answered:
Re: Y-Axis belt is tight like a guitar string on one side and sloppy on the other

Good idea. I loosened it quite a bit, but it didn't make any difference.

Postato : 19/12/2017 7:19 pm
spark
(@spark)
Reputable Member
Re: Y-Axis belt is tight like a guitar string on one side and sloppy on the other

Belt tension should be equal if pulley is free of friction. There is almost no doubt you have a pulley issue. I'd check these things.

  • Is there excessive wear on either side of the belt?

  • Are either y-idler or y-stepper unaligned to bed's belt carrier when pushed fully toward respective part?

  • Is your printer's chassis heavily skewed resulting in issue above?

  • Did you over-tighten the idler pulley nut and screw as to cause unnecessary friction?

  • Are there any filament fragments jammed in Idler pulley?
  • Basically, the idler pulley should be totally free of friction, the belt should ride dead center on both idler pulley and motor gear at all times. Whatever you do to achieve this will equalize belt tension possibly improving printer performance and most definitely reducing stress on your Y-Stepper motor.

    MK2S kit owner since 8/15/2017

    Postato : 19/12/2017 7:55 pm
    Enginman
    (@enginman)
    Trusted Member
    Re: Y-Axis belt is tight like a guitar string on one side and sloppy on the other

    Is the lower part of the belt caught under the joiner instead of passing through it?

    Postato : 19/12/2017 8:04 pm
    spark
    (@spark)
    Reputable Member
    Re: Y-Axis belt is tight like a guitar string on one side and sloppy on the other

    @David
    Ah, right, stock design has a free pitch idler design. I've completely replaced with a fixed pitch, adjustable tension design so long ago I took this for granted. Good call.

    MK2S kit owner since 8/15/2017

    Postato : 19/12/2017 8:37 pm
    READY.
    (@ready)
    New Member
    Topic starter answered:
    Re: Y-Axis belt is tight like a guitar string on one side and sloppy on the other

    Good suggestions. I'm going to take it apart and check each one to make sure.

    Here's a few images and a video of the problem.
    https://drive.google.com/file/d/1Ervlkk-1ipxurKEQ3-Qy6qP-uHd0xkZ9/view?usp=sharing
    https://drive.google.com/file/d/1321d7UXuJbfJA5SNllmMqZwUvYYkEuy0/view?usp=sharing
    https://drive.google.com/file/d/1OQaw8fCWZAlb7noPc00jmzkHrCEDmClq/view?usp=sharing

    Postato : 19/12/2017 8:41 pm
    freshmas
    (@freshmas)
    Utenti
    Re: Y-Axis belt is tight like a guitar string on one side and sloppy on the other


    @David
    Ah, right, stock design has a free pitch idler design. I've completely replaced with a fixed pitch, adjustable tension design so long ago I took this for granted. Good call.

    Could you elaborate on this one? I have been considering alternatives to the stock mk3 idler design, as the belts do not want to ride in the center of their idlers, and there is no adjustability.

    Postato : 19/12/2017 8:51 pm
    spark
    (@spark)
    Reputable Member
    Re: Y-Axis belt is tight like a guitar string on one side and sloppy on the other

    My bad, hadn't realized this was MK3 thread. I've fixed this same issue on my MK2S so thought I'd try to help. But I do have access to a CAD model and your issue should be not possible. Also, there is no way to adjust belt alignment as mount positions for all parts involved are essentially fixed.
    What I can see from the CAD files is:

  • Tightening the belt with y-belt-idler too much on upper screw resulting in pitch upward loosing belt clearance beneath y-belt-holder part.

  • Belt is too deeply to too shallow in the retainer groove of the y-belt-holder part causing misalignment thus excessive rubbing on both idler pulley or motor gear
  • Bowing out as I don't own an MK3.

    MK2S kit owner since 8/15/2017

    Postato : 19/12/2017 9:14 pm
    Enginman
    (@enginman)
    Trusted Member
    Re: Y-Axis belt is tight like a guitar string on one side and sloppy on the other

    My second comment about the joiner was dumb. I flipped into X.... Sorry. The first pic sure looks like the pulley is pinched by the support. But you're there and I'm manning a keyboard in the ether...

    Postato : 19/12/2017 9:32 pm
    spark
    (@spark)
    Reputable Member
    Re: Y-Axis belt is tight like a guitar string on one side and sloppy on the other

    This might be really silly simple but linear alignment could be achieved...

  • Adjust belt depth in the bed holder so idler is centered.

  • Now, loosen the drive gear grub screws and adjust depth until belt is centered.

  • Tighten grub screws and test. Repeat adjustment as needed after the belt settles from repeated back and forth moves.
  • MK2S kit owner since 8/15/2017

    Postato : 19/12/2017 9:46 pm
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