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4x2 ox

Discussion in 'CNC Mills/Routers' started by amcculla, Sep 28, 2014.

  1. amcculla

    amcculla New
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    Hi,

    Just finished building my 4x2. Took me a while to figure out wit=ring etc but have got there.
    I'm running Mach3.

    I can get it to cut squares etc fine but circles are miles out. I don't know where I am going wrong.

    I will post photos below shortly.

    Any tips would be greatly appreciated.
     
    #1 amcculla, Sep 28, 2014
    Last edited: Sep 28, 2014
  2. amcculla

    amcculla New
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    IMG_1824.JPG IMG_1825.JPG IMG_1822.JPG image.jpg
     
    #2 amcculla, Sep 28, 2014
    Last edited: Sep 28, 2014
  3. Tweakie

    Tweakie OpenBuilds Team
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    Generally flat spots on circular cut-outs are caused by back-lash (slack) in the system. From your photo the flat appears parallel with the Y axis - if this is the case then check your X axis - the most common cause is the pulley slipping on the stepper shaft (possibly a loose grub screw ?).

    Tweakie.
     
  4. amcculla

    amcculla New
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    That's what I thought but I have ground a flat spot on the shaft and thread locked the screws etc to make sure it isn't slipping.
     
  5. Dave Millard

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    Check your asymmetric bearings are not too tight. I was making great circles until I decided to tighten it all up a bit. This led to some very blobbish shapes. Slackening off back to where I was, got my circles back.
     
  6. amcculla

    amcculla New
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    Hoping someone could help point me in some direction. Ive attached a video below of the machine cutting a circle.
    Its almost as if its skipping steps.

    Do you think its the physical machine or cheap drivers and control board?

    Thanks Aaron

     
  7. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Start by checking for loose pulleys.
     
  8. amcculla

    amcculla New
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    They are all tight. I can't find any play in the machine.
     
  9. John Meikrantz

    John Meikrantz Veteran
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    What kind of controller are you using? I had a similar issue with xPro CNC Controller. One of the Y axis drivers would go into thermal shutdown. The other would keep working fine, and was strong enough to move the Y axis, so it wasn't immediately obvious that one of the motors was not working. Copper heat sinks fixed it for me.

    -- John
     
  10. amcculla

    amcculla New
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  11. Joe Santarsiero

    Joe Santarsiero OB addict
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    Mechanics I would look at first before assuming electrical:
    With power to the steppers is there any play in the x and y. when pushing by hand.
    stepper mounting bolts are all tight.
    eccentrics are set nicely against the extrusion.
    check belt tension near both sides of the pulleys.
    Are the belts and pulleys compatible.
    Belt ends aren't moving with direction change.
    does this happen the same all over the work area.
    work is fixated well to the spoilboard.
    good luck. keep us updated.
     
    #11 Joe Santarsiero, Apr 26, 2015
    Last edited: Apr 26, 2015
  12. amcculla

    amcculla New
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    Everything is tight. and no play.
    Work is screwed down to eliminate this.
    Every circle cut is identical to another (Not round)
    It almost looks like the motor skips a step now and again when moving. But not a belt slipping.
     
  13. Joe Santarsiero

    Joe Santarsiero OB addict
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    It does look like lost steps in both axis.
    Are you using shielded motor cable?
    Do you have separate drivers on the long axis?
    Which variant controller are you using?
    Post your M3 xml
     
    #13 Joe Santarsiero, Apr 26, 2015
    Last edited: Apr 26, 2015
  14. amcculla

    amcculla New
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    Having played about with the micro stepping its running better but still no difference to circles.
    Is it possible the hytech control board is complete rubbish??
    I have spare pibot driver boards and have swapped these out and it makes no difference.


     
  15. Joe Santarsiero

    Joe Santarsiero OB addict
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    Its probably the cheap tb6600 on those drivers. Up your pulse and direction widths! they need a 3.3 usec min. If 5 doesnt work then try circles in sureline mode and see if they get round.

    edit; clarity.
     
    #15 Joe Santarsiero, Apr 26, 2015
    Last edited: May 11, 2015
  16. amcculla

    amcculla New
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    Finaly got it sorted. Thanks to Joe and a few other tweaks.
    Just need to work out how to stop the burr on the edge of the cuts. Im using a 3mm single flute up cut. Should I try a down cut?

    Thanks everyone for your suggestions!

     
  17. Joe Santarsiero

    Joe Santarsiero OB addict
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    Glad you got it sorted. I reread my last post and it was pretty ambiguous. Must've been beer involved in that one.
     

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