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  1. #1
    Hello,

    I need help with generating a part to an STL file. I had a colleague of mine generate it but it was not curved, but instead angled. We are using DeskCNC (Carkin) to run our CNC XYZ router table, but that's a whole another issue. It will accept DXF or STL files, but since this is a 3D part, I was told that STL might be a bit better.

    This is generally what we want to machine:

    However, the part we are trying to machine is a block that is 4" x 4" x 1/2" thick with a cylindrical shape cut out of it so it appears similar to this:




    Again, it is not 8" x 2", it is 4" x 4". The radius required is 5 17/32".


    So basically it's a block minus the cylindrical portion removed. I have tried several different CAD programs including FreeCAD, but could not getit to work. Call me a CAD dummy.

    I am attaching what I came up with for the STL file and resulting G-code (NC code).
    However, when I run this on our setup, the axes stall through DeskCNC. Maybe the
    rapid moves are stalling the motors? We have been able to cut simple parts with the
    same config, but then again this is a different type of G-Code file.

    Any hints or help are very appreciated.

    Thanks
    Mike
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Attached Files Attached Files

  2. #2
    Hello

    What cutting tools do you have and whats the material?

  3. #3
    I made this gcode for you, it's assuming you have a ball nosed end mill and you have already roughed it out(taken away the bulk of the waste). You need to edit the lines for the spindle speed if applicable(M03) and feedrate (G1 Z0.5 F11) for your machine. Also I assumed a 0.1 width of cut which maybe wrong for your cutter.
    Code:
    G20 G18
    M03
    G0 X0 Y-0.2 Z2
    G1 Z0.5 F11 
    G3 X4 R5.53125 
    G1 Y-0.1 
    G2 X0 R5.53125 
    G1 Y0 
    G3 X4 R5.53125 
    G1 Y0.1 
    G2 X0 R5.53125 
    G1 Y0.2 
    G3 X4 R5.53125 
    G1 Y0.3 
    G2 X0 R5.53125 
    G1 Y0.4 
    G3 X4 R5.53125 
    G1 Y0.5 
    G2 X0 R5.53125 
    G1 Y0.6 
    G3 X4 R5.53125 
    G1 Y0.7 
    G2 X0 R5.53125 
    G1 Y0.8 
    G3 X4 R5.53125 
    G1 Y0.9 
    G2 X0 R5.53125 
    G1 Y1 
    G3 X4 R5.53125 
    G1 Y1.1 
    G2 X0 R5.53125 
    G1 Y1.2 
    G3 X4 R5.53125 
    G1 Y1.3 
    G2 X0 R5.53125 
    G1 Y1.4 
    G3 X4 R5.53125 
    G1 Y1.5 
    G2 X0 R5.53125 
    G1 Y1.6 
    G3 X4 R5.53125 
    G1 Y1.7 
    G2 X0 R5.53125 
    G1 Y1.8 
    G3 X4 R5.53125 
    G1 Y1.9 
    G2 X0 R5.53125 
    G1 Y2 
    G3 X4 R5.53125 
    G1 Y2.1 
    G2 X0 R5.53125 
    G1 Y2.2 
    G3 X4 R5.53125 
    G1 Y2.3 
    G2 X0 R5.53125 
    G1 Y2.4 
    G3 X4 R5.53125 
    G1 Y2.5 
    G2 X0 R5.53125 
    G1 Y2.6 
    G3 X4 R5.53125 
    G1 Y2.7 
    G2 X0 R5.53125 
    G1 Y2.8 
    G3 X4 R5.53125 
    G1 Y2.9 
    G2 X0 R5.53125 
    G1 Y3 
    G3 X4 R5.53125 
    G1 Y3.1 
    G2 X0 R5.53125 
    G1 Y3.2 
    G3 X4 R5.53125 
    G1 Y3.3 
    G2 X0 R5.53125 
    G1 Y3.4 
    G3 X4 R5.53125 
    G1 Y3.5 
    G2 X0 R5.53125 
    G1 Y3.6 
    G3 X4 R5.53125 
    G1 Y3.7 
    G2 X0 R5.53125 
    G1 Y3.8 
    G3 X4 R5.53125 
    G1 Y3.9 
    G2 X0 R5.53125 
    G1 Y4 
    G3 X4 R5.53125 
    G1 Y4.1 
    G2 X0 R5.53125 
    G0 Z2
    M30
    Last edited by Rufe0; 20-11-2015 at 12:18 AM.

  4. #4
    So what do you want STL file or G-code file.?

    For G-code we will need more details like Cutter type and diameter, # of flutes, Material.

  5. #5
    Rufe0 he needs it concaved your code is convexed.

  6. #6
    Click image for larger version. 

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    There you go 4x4 saved as a STL let me know

  7. #7
    Quote Originally Posted by JAZZCNC View Post
    Rufe0 he needs it concaved your code is convexed.
    Also, by programming a ball-nose tool to trace an arc, it will not cut the same path, unless the tool radius is zero! This is due to the way the contact point on the tool moves - my quick diagram should make it obvious:

    Click image for larger version. 

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    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  8. #8
    Try it Old school and learn G-code from Master TP (terry parker).!!! https://www.machsupport.com/forum/in...?topic=24988.0

  9. #9
    RE: JAZZCNC

    It looks pretty concave to me, I guess if you had your machine set with the Z low at the top and high at the bottom then it would be, anyway it's a simple task to do file>replace the G2>G3 and vise versa.

    RE: Jonathan

    Yes I forgot to mention he would need a ball nose tool with radius less than 5 17/32.

    You could do it longitudinally with a normal endmill but you'd be massively wearing the tooth corners out and it would take practically a million passes to get smooth.
    The ideal way todo this would be with a fly cutter however you'd need a horizontal mill, unless you could fix the work piece vertically.

  10. #10
    Quote Originally Posted by Rufe0 View Post
    RE: Jonathan

    Yes I forgot to mention he would need a ball nose tool with radius less than 5 17/32.
    or equal to! But more seriously, that's not the point I was making - your code will be more accurate as the tool diameter tends to zero, so clearly you need to compensate the tool height as in my diagram.

    I'm not sure that the code Jazz has linked to does this either?
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

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