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Mach 3 post processor and tool path issues

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This topic contains 8 replies, has 5 voices, and was last updated by  Burr 9 months, 1 week ago.

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    I purchased BobCAD a few years ago to use as a CAM package, and have dabbled with it on and off every so often. I’m now at the point where I’d like to really start using it (as a CAM package), and I’ve gotten far enough along that I can now generate reasonable tool paths with it but I’m running into problems with the posted files not working as expected on the machine (an X2 running Mach 3).

    I’ve tried the “Mach 3 no ATC” post, along with the “BC 3X”, “Fanuc 0M” and “Fanuc 6M” posts, all resulting in the same few errors.

    The Fanuc and BC 3X post outputs start off with an error due to G00 and G28 being on the same line, which I fixed simply by editing the code and moving the G28 instruction to a new line.

    Regardless of the above, ALL the files I’ve tried end up with Mach 3 wanting to move the table in a series of arcs larger than the machine.

    I ran into a similar issue when I first started using MeshCAM, but it was a simple fix of just changing Mach3 to use “Incremental” vs “Absolute” for IJ.

    Thinking it was a similar issue here, I tried simply changing the Mach3 setting but found it had no effect. The reason being that the BobCAD gcode files were including a G91.1 in the gcode itself (which overrides the default in the controller).

    Given this discovery, I went into the posting settings for both the part and the “default” and set them to use “Absolute” vs “Post Setting”. Unfortunately, it seemed to have no effect, and I still noticed G91.1 codes being placed in the posted gcode.

    I then tried setting the part and “default” to both “Incremental” and gave it another shot. I figured that even if there might be a bug that forced the file to always have a G91.1 code while the actual measurements were in absolute, this should fix it. Still, however, I get nothing but those large arcs.

    Given the tool path preview in Mach3, it appears that it can interpret the intended tool path correctly — it just simply won’t follow it.

    Anyhow, with the large volume of “get a good post file” responses to these sorts of issues on the Mach3 forum, I thought I’d post here first.

    Attached is my bbcd file, as well as the BC 3x (“fanuc” file, with the added line break between G00 and G28) output and the Mach3NoATC output.




    I don’t see no attachments



    I didn’t see that until just now. Apparently one cannot upload .nc or .bbcd files to the support forum.

    That’s unfortunate…

    Upload Errors:

    PlungerDrillHoleJig.bbcd: Sorry, this file type is not permitted for security reasons. Sorry, this file type is not permitted for security reasons. Sorry, this file type is not permitted for security reasons.



    you have to .zip your files



    Zipped files attached.


    You must be logged in to view attached files.


    I had the same problem. I have forgotten what I did to fix it. But I think it was due to a bad font. I use MACH 3 as well and have many problems with it and bobcad-cam. Mostly with the post doing strange things.



    Ok so I figured out to get rid of the circles you have to do a few things.
    1st select the problem areas. (most likely a Fillet or a circle that had part of it deleted) Do a Explode witch brakes the curve into many parts.
    2nd do a erase dabbles.
    3rd Cleanup and optimize

    You should be good to go.

    Now by doing this you lose the ability to slow down the cutter in a arch. So make sure you have the travel speed set low enough for the whole cut, This makes the entire process take a lot longer but it works.

    P.S. I am using V26 not sure what you are using,

    • This reply was modified 2 years, 1 month ago by  Shane.


    I ran both of your files on my Mach 3 cnc emulator. I have mine set to incremental IJK for arc center. G91.1 is the setting for incremental arc center in Mach using absolute coordinates for programming.
    I see a couple issues with your programming. 1st, go to utilities and select extract edges from solid, select single, select the top of your solid, go to the Blank icon on your tool bar and hide the solid. The 2 day geometry will remain. Select the geometry for your pocket. You’re using adaptive pocket which is more for pockets with an open side such as in the graphics shown when that feature is selected. your step over is 30% which is not good, the width of the pocket is only .408 and you are using a .25 end mill. Change your step over to 50%. Use pocketing offset in with .010 tolerance for side allowance, then do a finish pass. If you are having issues, please contact Bobcad tech support.
    thank you,



    Open your BC_3x_Mill.MillPst and look at lines #222 and #511…

    This is where you change the code output type.

    But I’m not sure if that is your issue.

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