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Big problem with OX 1000x1500

Discussion in 'CNC Mills/Routers' started by Faxe-IT, Jun 24, 2017.

  1. Faxe-IT

    Faxe-IT Well-Known
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    Hi all, I'm Fabio from Italy!
    I've just bought and assembled a 1000x1500 OX with 2.8A nema23 and double GT3 belt on X and Y axis.

    I will use Grbl with a pibot kit to control the router and I've set 1/16 step on the drivers.

    Now, I've got a big problem during the axis adjustment.

    I want to test the precision of X and Y axis, so I create a path of 5 squares of 20x20 to 100x100 sides. I'm using a 4mm mill with 800mm/min speed.

    Problem is that the real dimensions are not equal to the programmed one (see image below) but I don't know what to modify.
    If I just increase the step/mm ($100 and $101 parameters) I get the right dimensions for the little squares but the big squares have a big gap. If I decrease $100 and $101 the big squares are right but the small one are smaller than the programmed one. Someone please could help me? I'm trying to figure out how to solve this problem since the last 5 days
     

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  2. David the swarfer

    David the swarfer OpenBuilds Team
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  3. Faxe-IT

    Faxe-IT Well-Known
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  4. David the swarfer

    David the swarfer OpenBuilds Team
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    Tighten the grub screws on the pulleys. This is a common problem area that will cause backlash and prevent proper calibration.
     
  5. JustinTime

    JustinTime Master
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    And don't use 1/16 steppes, for crying out loud. It's a router not a 3d printer. Try 1/8, or even better try 1/4!
     
  6. Faxe-IT

    Faxe-IT Well-Known
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    Hi guys,
    I've checked all the screws and they're all tight.
    Today i've had a major problem on the x axis, i give g91 g01 x-300 f1500 command but at x-250 the motor stopped and don't move over, it makes a bad sound like it "slips" (don't know if it's the right term).
    The pulley did not move, I think that the motor was not good, I've pick it used from another guy.
    I've replaced the motor with a 1,4A nema23 but I've noticed that the gantry on the x axis is really hard to move manually even without the motor mounted on.
    Eccentric bolts are already on the minimum position, could it be a mechanical problem of the holes not in the right position that make the gantry hard to move, so the belt stretches and the motor lose steps for the excessive effort?

    Sorry for my bad English, I'm trying to do my best
     
  7. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Yes, the gantry should move freely without belts and motors attached. You note that eccentrics are at their widest, so there may be a problem with either your plates or your rails. Where did you get them from?
     
  8. Faxe-IT

    Faxe-IT Well-Known
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    Hi Rick, I've bought the entire kit from the official Italian openbuilds store.
     
  9. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Then you should get with them regarding resolution of the problem. Sometimes you can achieve acceptable results by slightly drilling out/oversizing the non eccentric holes and resetting the wheel screws to the widest point but it's really up to you as to how you wish to proceed.
     
  10. Faxe-IT

    Faxe-IT Well-Known
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    Yes in that case I'm thinking to oversize a bit the holes in the upper part of X axis plate, so I will gain some more space to set the eccentric on the bottom part
     
  11. Faxe

    Faxe New
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    Hi all!
    I've solved the problem with the hard movement of the gantry, i've drilled the upper holes on the x axis plates at the diameter of 5,8mm and now the x gantry moves freely, much better than before!
    now it's time to re set all the calibrations.
    Do you advise me to change the steppes from 1/16 to 1/8 as justin suggest? in that case, how could i calculate all the settings for GRBL?
     
  12. Faxe-IT

    Faxe-IT Well-Known
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    Done the calibration of X and Y axis following the tutorial, with 1/8 steppes, now I've less than 0,5mm gap on a distance of 500mm
     
    David the swarfer and Rick 2.0 like this.
  13. JustinTime

    JustinTime Master
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    That is a very good result, Faxe-IT. Nothing wrong with that. :thumbsup:
     
  14. Faxe-IT

    Faxe-IT Well-Known
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    little update:
    i've set the max rpm for the motors at 3500 (it was 7500), played a little with $100 and $101 and now on a distance of 500mm it stops exactly on the spot
     

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