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drawing for more efficient cuts?

Discussion in 'SketchUcam Help' started by Yolande, Mar 8, 2016.

  1. Yolande

    Yolande New Member

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    Is there a way to draw an array with space for the cutting bit in between each piece so that cuts are not being repeated needlessly?
    I'm working with 3/16" plexiglass, using .015" multi-pass which gives about 12 passes. It's a very slow process but it gives me a good edge without melting the plexiglass.
    Lets say I want 20 rectangles 1/2" x 10" and I do need tabs. If I do outside cuts, the space between each shape is being cut twice. If I draw in such a way that I only use inside cuts, the tool goes back up after each pass, that's 11 times too many (seeing that 12 passes are needed for 100% cut).
    It takes about one to two hours of run time on the CNC each time I cut something.
    I would be very happy to reduce the cutting time.

    I can't begin to tell you how grateful I am about SketchUcam. It's a pleasure to work with, having it right there with sketchup.
     
    Yolande, Mar 8, 2016
    #1
  2. swarfer

    swarfer Moderator Staff Member

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    Hi
    I have just experimented a bit with various ideas and I think the best one is this:

    space your objects exactly bitdiameter apart (I used 3mm in my drawing)
    place an outside cut on every second object.
    add tabs. (I used Vtabs as they cut faster, make sure they are long enough! short vtabs can disappear when cut)

    create a copy of all your objects, without the cuts.
    add a construction line at top and bottom, 1.5mm away from the objects.
    draw a line on every alternate object so it can cut the end off.
    set those lines as 'centerline' cuts, 100% deep (or more).
    (this works best with an odd number of objects)

    set the safearea to only enclose one set of objects
    place it at the marker for file1 and generate gcode

    place the safearea at the second marker and generate gcode file2

    join the 2 files.
    if you select ramping ON then the short centerline cuts will be much faster.

    efficient.png
    btw you can probably feed much faster than you think in the plexi, so long as the chips are clearing properly the heat goes with them.
    do some test cuts and see what you can do.
    you can also rub the surface along the cut lines with a wax candle. this helps to prevent the chips sticking to the bit.

    https://www.plexiglas-shop.com/pdfs/en/311-1 Machining PLEXIGLAS®_en.pdf
    http://www.cnczone.com/forums/glass-plastic-and-stone/46102-cnc.html

    Let us know how it works out, please.
     

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    swarfer, Mar 9, 2016
    #2
    TigerPilot likes this.
  3. Yolande

    Yolande New Member

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    Hi Swarfer,

    I did as you suggested and it worked like a charm!
    I tried checking ramping but I ended up removing it because it was doing funny stuff (which I don't know how to describe)
    With depth passes at .015" It didn't matter really.
    I have experimented with a lot of different bits (and I broke quite a few in the process) and with different speeds but not having any cooling system I found the slow and steady gives me the best results.
    Thank you so much for taking the time to answer my problem. It's the kind of solution that I can reuse often.

    Yolande
     
    Yolande, Mar 9, 2016
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    swarfer likes this.

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