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Losing 2 mm, when moving from x0 to x10 and returning to x0

Discussion in 'CNC Mills/Routers' started by Kent Alstrup, Mar 6, 2017.

  1. Kent Alstrup

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    Hi
    Im trying to figure this out, and i am running out of idea´s
    When moving from G1 X0 F10 To G1 X10 F10 And Again G1 X0 F10, im loosing 2 mm
    The opposit direction, spot on.
    I make no difference if i move 10, 100 or 1000 mm. the exact same 2 mm.
    I tried adjusting the pully on x, same with z, to make sure there is no issue with slack
    Using mach3 and polabs57cnc bob
    There is as far i can see, no issue with the hardware, due to same 2 mm, on returning form +,.
    Backlash don´t make any sense, when it´s only one direction causing the problem.
    I´m totaly out of idea´s!
     
  2. Mark Carew

    Mark Carew OpenBuilds Team
    Staff Member Moderator Resident Builder Project Maker Builder

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  3. Kent Alstrup

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    The issue is not calibration, it should be on both sides of X0 if calibration where the reason
    The 2 mm, would not be exact the same, when the machine is traveling 10, 100 and 1000 mm, if there was error in the calibration.
     
  4. Mark Carew

    Mark Carew OpenBuilds Team
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    Let me see if I understand correct, so when moving from x0 to x10 (your spot on) then when moving from the x10 back to x0 your always 2mm from 0 leaving you at 8mm.
    If this is the case, right, calibration would not be the cause.I would go back to your first guess at mechanical slippage. You may have already tried this but make sure one of your set screws is seated snug on the flat section of the motor shaft. If its not seated flat, and is off just a little, it can rock from side to side just slightly until it catches the angles on each side causing a small amount slippage that can be really hard to trouble shoot. It can also stick in one direction kick back out when the direction is reversed making it seem as if its working properly in one direction and not the other. A good way to see if there is any mechanical play would be to engage your motors so that they are locked and then push on the gantry back and forth to see if you feel any play in the system. Also try wiggling the pulleys as well with the motors locked to see as well. If you exhaust these methods it may help to look more into polabs57 board.
    pulleyslip.jpg
     
  5. Kent Alstrup

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    I found out what's wrong.
    My gantry was to tight. I loosened the gantry at much as possible, and it solved the problem.
     

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