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Just Built Ox CNC, but it is doing something strange?

Discussion in 'General Talk' started by CDUH, Jun 30, 2015.

  1. CDUH

    CDUH Well-Known
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    Just built an OX CNC and love working on it. I is doing something strange after switching to LinuxCNC. I have managed to get the everything tuned, but when it cuts the inside of a square it has this little jag in the corners. Any thoughts on the cause? The machine is cutting clockwise and the spindle is rotating clockwise. Attached is a picture of the issue.
    square.jpg
     
  2. Dave Millard

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    My machine does exactly the same thing when entering the wood. Does not do it on corner two, three or four. Very frustrating.
     
  3. Joe Santarsiero

    Joe Santarsiero OB addict
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    are you cutting full depth of pocket?
     
  4. Dave Millard

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    I get it when doing the pocket in single or multiple passes. Thought is might be runout on the spindle, but that does not make sense otherwise it would cut wider all along the pass.
     
  5. Joe Santarsiero

    Joe Santarsiero OB addict
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    It may be a cutter compensation issue. cutter compensation is a mode (modal) command. To switch to that mode a g1 linear move longer than the offset must be issued. This sounds like your issue Dave. You may be picking up your offset in the cut. check your code for this. If you are then it's a simple fix...program it to pick up the offset on the way to part home prior to the cut. If the error is through the full depth of pocket on multipass then it might be dropping comp and picking it up again though this is unlikely and is a CAM issue. Check the code for this too.
    With all the controller and CAM combinations it can be tough to diagnose certain issues that may be program specific if you don't use the same program. I think CDHU may be having an issue with motor acceleration through corners or a roll through corner issue. It could be the control or the cam program or a combination. Heck, its possible it's mechanical. I don't use linuxcnc or his cam prog. so it's tough to say.

    Good luck guys.

    Joe
     
  6. Joe Santarsiero

    Joe Santarsiero OB addict
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    Hey Justin. That picture is CDUHs and the post you quoted is Dave's. Dave says he does have a problem with corners 234.
     
  7. Knut Bøje

    Knut Bøje Well-Known
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    Have you tried same cut counterclockwise?
     
  8. CDUH

    CDUH Well-Known
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    I am cutting pockets to test the X and Y distance. Yes the jag is in the top left and bottom right. The cut is a pocket that spirals out of the center with the transition to the next step in the lower left corner. I was playing with it tonight and was watching the code and on thoughts two corners it looks like there is a jag in the code. I am using Vcarve Pro 8 with the LinuxCNC mm post processor. I was thinking of trying generic post processor to see if it made a difference. I am not sure if it makes a difference, but I have LinuxCNC controlling spindle speed. I will try the cut counter clockwise and let you know. Originally I was running GRBL and EASEL to drive the CNC, but now I am trying to make one of Brian Law's clocks so needed a little more control.
     
    Joe Santarsiero likes this.
  9. CDUH

    CDUH Well-Known
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    No I was cutting an 8mm deep pocket. Testing all the axis for accuracy.
     
  10. CDUH

    CDUH Well-Known
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    I tried adjusting speed and acceleration, but I did not see any change.
     
  11. Joe Santarsiero

    Joe Santarsiero OB addict
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    Maybe look into lead-in/lead-out settings or changing your cut strategy.
     
  12. David the swarfer

    David the swarfer OpenBuilds Team
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    please can you try a simple square with Gcode generated using Sketchup + Sketchucam.
    actually, let me give you some code to try....
    simple 50mm square, 10mm up and right from x0,y0. 6mm material, 3mm bit

    Code:
    %
    (Generated by SketchUcam V1.3b-64f6)
    (Bit diameter: 3.0mm)
    (Feed rate: 1000.0mm/min)
    (Plunge Feed rate: 750.0mm/min)
    (Material Thickness: 6.0mm)
    (Material length: 2500.0mm X width: 1200.0mm)
    (Overhead Gantry: true)
    (Optimization is ON)
    (www.PhlatBoyz.com)
    G90 G21 G49 G61 G17
    M3 S30000
    G00 Z5.000
    X8.500 Y8.500
    G01 Z-6.000 F750
    X61.500 F1000
    Y61.500
    X8.500
    Y8.500
    G00 Z5.000
    (EndPosition)
    X250.000 Y250.000 Z32.000
    M05
    M30
    %
     
  13. Joe Santarsiero

    Joe Santarsiero OB addict
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    Yeah. Dave's the swarfer is right CDUH. Check the machine and control software first. Then go on to v carve.
     
  14. Tracy Ranson

    Tracy Ranson Journeyman
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    Just a thought...I took a closer look at your picture and it appears that the same thing is actually showing up in all corners. I would check to see whether your machine is either out of square or needs to be calibated.
     

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