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How to calibrate small gaps

I have drawn grids a few times on a wooden board or some sheets of paper a while back, and recently for a few days I have tried to fix the tension of two belts with following manuals, however, there are some small gaps still remaining between lines drawn on it, they are getting larger as the head approaches to the left down corner, so how can I say for that, they are bended or distorted a little, still I am almost pleased with its results, but if someone should know where to check for fixing it, I would try them all.



  • I would guess you either have a rail out of alignment or possibly a bent rail.

    First check that your X & Y rails are at exact right angles to each other, a large builders square might be useful, if not a sheet of paper would suffice, align it precisely on one axis then eyeball it against the other.

    If that looks OK then take the drive belts off the laser head and slide the head by hand to each limit, both vertically and horizontally and diagonally.
    Do it slowly with a gentle touch, you should feel no binding or stiffness as it moves.

    Let us know how you go
  • Daisuke,
    What feedrate are you using to create this?

    Can you try an experiment where you increase the tension of the bottom belt by 1 tooth and see whether this improves the result?
  • Thanks for reply, and I'll go along with the suggestions that you have, somehow work out the problem asap.

    I used the file to draw grids at default, leaving all parameters in it, showing that it is 1000mm/min :)
  • Please let me know if this improves the result. We had a customer recently with a similar problem who resolved it by increasing this belt tension.

    If this doesn't work we will try to emulate the problem on our machine to see what the possible cause could be.
  • Yay, I got a good result today:D The all gaps have been fixed correctly. I increased the tension of the first belt by 3 at last, and this made an over 8-9mm gap(5mm in manual) in the right side, however, that brought me the really good result after all. I tried 1 tooth at first, but it didn't work well.
  • I've got a similar problem, however I noticed increased friction on the left end of the rails for the laser unit (without the belts). Maybe for the last 3-4cm before the end stop.

    When drawing small circles (from a calibration macro) I notice the ends don't align near the left end of the drawing area; if drawn on the right side everything is fine... (G21;G91;M3 S96;G1 F300;G2 X-5 Y5 I0 J5;G2 X5 Y-5 I5 J0;M5)

    What can I do to solve the problem?

    Thanks in advance!
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