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  1. #1
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    Apr 2015
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    14

    5 Axis 3D toolpath display problem

    I've came across an issue that has me scratching my head; I built a 5 axis machine with the primary B axis parallel to the Y direction and the A axis as secondary rotating parallel to X. I Enabled the A and B rotation display on the Settings but I get weird results.

    For testing I started with a truncated cone and a swarf operation, the toolpath is a few depth cuts at fixed (more or less) Z heights going around the part, the sides of the cone are at an angle of about 15.5 degrees. The CAM simulation loos good, the GCode looks correct, the actual motion of the machine is good , but on the 3D display the toolpath looks, as best as I could set things up, like a Pringles potato chip.

    Top view, according to the GCode it should show circles, not an ellipse. This is with the tool at the 3 o'clock position, note the X, Y, B and A values, more or less X-2 Y0 B-15.5 and A0 approximately


    Now at the 12 o'clock, X0 Y2 B0 and A15.5, which means the XY motion is a 2mm radius circle and the tool is going around the vertical axis at a constant 15.5 degrees; so I don't know why it displays a vertically stretched toolpath.


    From the side it shows the toolpath curving up at the ends (again the actual machine motion is correct, the tool tip is kept at a constant Z height).


    Looking down the Y Axis it shows the double curvature of the toolpath as displayed.


    This is are the settings I'm using, the Rotation Offset of Z: -90 is the best result I could find, at 0 offset things look even more wrong.


    I've tried less uniform shapes and the toolpaths look even worse, this is supposed to be a more or less triangular part, with a hole cut out at the center with two 3 axis contour operations (those look correct) but the 5 axis swarf around the outside perimeter is displayed as a twisted mess to one side.


    What could be the issue? It's very confusing because, as I said, the actual motion of the machine is correct, so it looks as if the 3D display follows its own logic to represent the toolpath and I haven't figured out what settings are needed to make it work. I have to say that it's been difficult because the program tends to crash every time I try different 3D Interface settings.

  2. #2
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    Mar 2017
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    731

    Re: 5 Axis 3D toolpath display problem

    Software does not know how your machine is assembled, how axes are linked or chained. 3D display for rotational axes is just one (most simple) possibility.
    It is possible to show 3D representation of your machine with help of 3dObj file. With this you can accurately show machine model in motion.

    Can you send me your profile, gcode and screenshot of CAM to our support email and I'll check if there is anything I can do to improve this generic 3d display.

  3. #3
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    Re: 5 Axis 3D toolpath display problem

    I will prepare the files to send you ASAP.

    I was just tinkering with the machine, setting it up for a test run by first doing a surface measurement (which didn't work, more on that later) and that made me think, if TNG doesn't know how the machine is configured then I suppose the Warp function won't work, correct? Because it will only know, at best, the Z offset at the XY coordinates, not at the position of the tool tip when it is at an angle.

    This would make the issue much worse than I though because it means I can't use the machine for what I had in mind, cutting thin PVC sheets with beveled edges, small Z variations on the surface of the table, spoilboard and stock will create dimensional errors on the parts.

    As for the Surface measurement not working, it goes out of bounds; for example I set it to for a rectangle of X275 by Y350 with 25mm steps, it does the first row, from X0 Y0 to X275 Y0 correctly but the second one from X275 Y25 to X0 Y25 the machine keeps moving past the zero position and hits the limit switch. With other combination of values it even fails on the first row, it tries to continue moving on past the X distance set.
    By the way, I miss the previous version way of setting the grid for measuring, where I can set the XY dimensions and the number of samples, instead of having to pull a calculator to do the same.

  4. #4
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    Re: 5 Axis 3D toolpath display problem

    By the way, I don't understand what you mean by "It is possible to show 3D representation of your machine with help of 3dObj file" I don't see anywhere the option to load a 3dObj file into TNG.

  5. #5
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    Re: 5 Axis 3D toolpath display problem

    Check 3DObj profile in ProfileExamples".
    I'll include another one with stl files in next version.

  6. #6
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    Re: 5 Axis 3D toolpath display problem

    I loaded the profile and it seems to work, I suppose it works by automatically reading the 3dObj.txt file placed in the same zip file as the profile settings.
    Although the toolpath is still incorrect for 5 axis I guess that, if a 3D model of the machine is made it would at least show the position of the 3D tool in space, even if it doesn't match the toolpath displayed, not ideal but workable; the only problem would be that the tool length would need to be adjusted by changing the STL 3D mesh for the tool each time, right?

  7. #7
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    Mar 2017
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    Re: 5 Axis 3D toolpath display problem

    Toolpath shows location of tooltip in 3D space. When rotational axes are used it is assumed that rotation is around main axis. I reality this is not true and machine and workpiece coordinate systems differ.
    3D display shows toolpath in machine coordinate system and it does this correctly. You want to see toolpath in workpiece coordinate system.

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