Another Roland drag knife mount

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This topic contains 6 replies, has 4 voices, and was last updated by  Mark 7 months, 1 week ago.

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    Alexander Pruss

    I adapted the Roland-style drag knife holder mount that I had made for my 3D printer to work with the MPCNC. It has a plastic spring (ABS recommended, unless you want more tension) for pushing on the tension button at the top of the holder. I haven’t tested it yet with the MPCNC. Back when I used it with my 3D printer, I drove it with my [gcodeplot]( python script, which I’ve adapted to work with MPCNC.




    That looks pretty good, if you spring mount the body instead of the blade you can use the body to limit depth (for things like cutting vinyl and not cutting the backing) and the spring to control overall tension for different materials.


    Alexander Pruss

    Good point. I should experiment more.



    That software looks pretty cool. Do you have some images you can share of what it’s capable of?


    Alexander Pruss

    There are some pictures here:

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    Alexander Pruss

    If you’re interested in using the software, on my github I included two sample mpcnc configuration presets: mpcnc-10-10 and mpcnc-5-10-overcut1.

    python -c mpcnc-10-10 filename.svg > filename.gcode

    is for drawing. It generates gcode that assumes that the pen starts in the lower-left corner of the page, 10mm above the drawing position. (I prefer that to starting with the pen right on the page, so it doesn’t need to make a mark. One strategy I’ve used is to put some aluminum foil on the page, adjust the z position on top of the foil for good tension, lift 10mm in Repetier Host, remove foil, print.) It cross-hatches shaded areas by default. Cross-hatching density corresponds to how dark the color of the polygon is, and can be adjusted in the code. (I haven’t tried it, but one could presumably calibrate the density so that a marker shades blacks completely.)

    Coordinates are reset by the gcode to be 0,0,10 at the starting position.

    For cutting:

    python -c mpcnc-5-10-overcut1 filename.svg > filename.gcode

    This preset assumes the cutter starts in the lower-left corner of the page, 10mm above the cutting position, and turns off cross-hatching (!).

    Any text in the svg files needs to be converted to outlines in Inkscape. Also, if there are any overlapping polygon in the svg, hidden features in the lower polygon will also be drawn. (To get rid of overlapping polygons, you can use this version of the path ops extension in Inkscape with the Trim option: )

    I still need to learn how to use Estlcam. I find its UI intimidating.



    This is the one I want, for both a pen and the drag knife:

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