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Thread: Can't Machine a Simple Circle with a Probotix Fireball

  1. #13
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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    and ID's and OD's are usually oversized. X or Y axis doesn't seem to matter.
    Now that IS strange.
    If cuts were undersized then you could be missing pulses, have backlash, or several other things, but OVER-sized?
    Just how much oversized?

    Cheer
    Roger



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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    Quote Originally Posted by RCaffin View Post
    and ID's and OD's are usually oversized. X or Y axis doesn't seem to matter.
    Now that IS strange.
    If cuts were undersized then you could be missing pulses, have backlash, or several other things, but OVER-sized?
    Just how much oversized?

    Cheer
    Roger
    Roger, there's no rhyme or reason in the dimensions being out of tolerance. In other words, no pattern. I'll program to cut a circle 1" in diameter. Doesn't matter if I cut full depth (1/8") or just 1/16", the X axis can vary between 0.015" to 0.050" over. Same as with the Y axis. Non concentric, and no matter how many I try, they're never consistent. Beats me. Really was a great little machine for my needs.



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    Registered Jim Dawson's Avatar
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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    Cutting oversize with varying result would indicate that extra pulses are being randomly introduced into the system. This would normally be caused by electrical noise or a bad connection between the computer and the ''box''. It could also be an internal bad connection to the breakout board or to the driver board inside the box. Maybe just a failing board. Or even a problem in the computer.

    Based on this new information I'm going to say that the power supply is probably OK, and that the motors are doing exactly what they're being told to do. Given that the problem seems common to both the X and Y axis, I might start at the computer. If you have another computer available, a good test would be to install it and see if the problem persists.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    Quote Originally Posted by Jim Dawson View Post
    Cutting oversize with varying result would indicate that extra pulses are being randomly introduced into the system. This would normally be caused by electrical noise or a bad connection between the computer and the ''box''. It could also be an internal bad connection to the breakout board or to the driver board inside the box. Maybe just a failing board. Or even a problem in the computer.

    Based on this new information I'm going to say that the power supply is probably OK, and that the motors are doing exactly what they're being told to do. Given that the problem seems common to both the X and Y axis, I might start at the computer. If you have another computer available, a good test would be to install it and see if the problem persists.
    OK, Jim, I wrestled my big PC into the work area and plugged it in. Ran several sample programs. A 1" line cuts at 1", whether X, Y, or diagonally. A 1" circle is 0.020" to 0.050" over on the ID. A 2" ring with a 1" center hole has 0.020" to 0.050" under on the OD, and same over size results as the 1" circle. So, I conclude that the older, more powerful PC doesn't have any effect vs. the newer CNC-dedicated PC.

    These would point directly to a bent cutter or seriously sloppy spindle (router). But that's not the case here. As mentioned before, the TIR on the spindle is less than 0.0005". The clamp holder for the router could be flexing, but that's some wild movement when I cut only 0.0625" at a pass.

    Reckon I'll tear it down when I get time and just try and find... something, anything, I don't know. Thanks for your suggestions.

    Last edited by JPX2000; 11-25-2018 at 07:44 PM.


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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    ''circle is 0.020" to 0.050" over'' That is what is strange, if the steps per unit were off and everything else is OK then the error would be consistent, not vary by 0.030. One thing I didn't ask; is the circle off 0.020 in one axis and 0.050 in the other axis or is it random?

    Will it cut a square that is on size in both axes? How about a square rotated 45° off axis?


    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    Quote Originally Posted by Jim Dawson View Post
    ''circle is 0.020" to 0.050" over'' That is what is strange, if the steps per unit were off and everything else is OK then the error would be consistent, not vary by 0.030. One thing I didn't ask; is the circle off 0.020 in one axis and 0.050 in the other axis or is it random?

    Will it cut a square that is on size in both axes? How about a square rotated 45° off axis?
    The offset, or overcut/undercut, is random. It won't cut an on-size square no matter what the orientation. I'm taking a deep look into some of the sub-settings. I still can't find any backlash, but the evidence points to just that very thing.



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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    Have you made any adjustments to backlash correction in the program settings?

    Sent from my LGL84VL using Tapatalk



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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    I'm running out of ideas. There is one other possibility that I can think of that is software related, Constant Velocity (G64) vs. Exact Stop (G61) This can effect some machines. Try using the opposite value.

    Failing any software related issues, I'm going to suggest a control problem, maybe a loose connection, bad solder joint, or just simply a failing board.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    Quote Originally Posted by Raydsm View Post
    Have you made any adjustments to backlash correction in the program settings?

    Sent from my LGL84VL using Tapatalk
    No, I haven't gone to the software settings yet. I checked for SPU adjustment, but it wasn't needed. I'm not really sure where to go or what to measure for software backlash correction.



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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    Quote Originally Posted by Jim Dawson View Post
    I'm running out of ideas. There is one other possibility that I can think of that is software related, Constant Velocity (G64) vs. Exact Stop (G61) This can effect some machines. Try using the opposite value.

    Failing any software related issues, I'm going to suggest a control problem, maybe a loose connection, bad solder joint, or just simply a failing board.
    OK, Jim, I'll give that a try. Do I edit that in the G-code or is there a setting for it?



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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    There should be a setting option when you post the code, or you could just hand edit the G code.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    My vote's on electrical interference. If the photo of the control box is yours, then it's clearly had a serious impact at some point - it might even just be that there's intermittent grounding somewhere in the box. I'd pull the case apart to make sure that there's nothing being shorted, and if it's got an internal metal liner to act as a faraday cage, then that's definitely been compromised by said imact.



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