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Improving accuracy

Discussion in 'GENERAL Phlatprinter MKII Talk' started by Ringo Davis, Apr 28, 2014.

  1. Ringo Davis

    Ringo Davis Member

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    I did a test cut on my mkII. I drew a 6: square with a 3" circle in the middle. When I cut it out it starts in the middle of the square near the front of the machine. When it goes around the square and returns to the beginning it is off about 1/8" in the Direction the material moves. I don't think this would be calibration, more of a material slippage or missed steps problem. Is this common and is there a fix for it?
     
  2. rcav8r

    rcav8r Moderator Staff Member

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    I'm thinking missed steps if this is foam as it almost NEVER slips.
    Check for binding, skipping belt, voltage on the board (Actually adjusting the current), or try slowing the cut down to see if it improves.
     
  3. TigerPilot

    TigerPilot Well-Known Member

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    I don't know why you would exclude calibration. You didn't say what speed, or material, you were using but my experience is that most of the time it is calibration. If you were cutting MDF and/or at high speed then slippage is also a probable cause.
     
  4. Ringo Davis

    Ringo Davis Member

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    I just assumed that calibration would give me a 5.95X6 square instead of a 6X6 square, but not 6" in X+ and 5.95" in X-.
    I'm cutting dollar tree foam with the paper off just as a test. I'll be cutting blue foam.
    I slowed the feed rate from 100 to 80 and did not see a change. I then changed it to 30 and got the same result. So Now I'm thinking maybe backlash could be to blame. that would explain why different speeds different help. Is there a way to calibrate out backlash? does that sound like a correct assumption? I posted a pic of the cut. look at the horizontal cut on the bottom of the pic.
    Thanks
     

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  5. swarfer

    swarfer Moderator Staff Member

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    reduce your acceleration rate to half what it is now and test. you are mostly likely to lose steps during acceleration.
    if you still lose a little, reduce max speed by 10% as well.

    maybe disconnect the motor and rotate the axis by hand to see if it has any stiff spots.

    you will be able to feel blacklash if you push and pull on the foam. have you go infeed and outfeed tables? if the foam is curling down over the front/rear edge it may getting caught on an edge or just high friction, support it. plenty of plans for foam extension tables here on the phorum.
     
  6. Ringo Davis

    Ringo Davis Member

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    Acell was set to 80. I changed it to 40 and it looks like the error is gone. I cut several rectangles and could not see anything so I cut part of an ezfly. Looks good. Thanks, this is my first successful cut.
     

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  7. TigerPilot

    TigerPilot Well-Known Member

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    Cool showing, Ringo. Glad you go it up and running! :doubleup:
     
  8. foamlvr

    foamlvr Member

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    are you running inches per min, or mm ? if inches, 40 is still high on acceleration. Lower accel until you can hear it start slow and build up to speed. Even with accel set at 3 or 4 it will only take a second or 2 to reach top speed.
     

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