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Jan 14, 2021, 06:02 AM
Registered User
Thread OP
Help!

Cnc cutting planes


Hello, I have a little problem:

I have acquired a cnc mill and would like to cut out an airplane kit for a DeHavilland Beaver. The plans are in a pdf format.
My cnc software is CNCjs and only takes g-code files. I've taken the pdf and cut out the part with all the parts on it, that need cutting out.
My problem:
I need to turn this pdf file into a g-code file. This has proved quite difficult for me, due to the fact, that the converted g-code file doesn't show the parts, but only seemingly random rectangles, triangles and other shapes.

If you need any extra information, feel free to ask.

hugo s.
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Jan 14, 2021, 09:43 AM
Design Engineer
I'm not sure how familiar you are with programing a cnc machine so i'm gonna go in pretty basic here. G-code comes from telling the programing software what lines and such you want cut, how you want the cut run, and various other things (tooling offset, material properties for feeds and speeds, etc).

Essentially, you need to convert the pdf to a format that your cnc programing software can read and be able to select lines and shapes from. From there, you will pick your lines, tell the program what side of the line (or centered on line) you want to cut, the tool you're using, etc. You will then export the program file thru a post processor that converts what you've just done into the gcode your machine can recognize.
(I'm not sure how your setup works so this next bit might be a bit different. )
You will then do one of two things. Take the gcode file to the machine via usb stick or sd card, and select the file to run and run it. Or if your machine is connected to your computer, you might be able to control directly from the computer and you won't really handle the gcode file.
Looking at CNCjs, it looks like your cnc is controlled and operated directly from the computer, if i'm understanding it correctly.
And yes, when you look at a gcode file that the program has turned into a bunch of tool paths, you will see all the cutting movement as well as all the travel movement when the cutting head is traveling thru the air. All in all, this may end up looking like a spaghetti bowl of lines and nonsense.

The questions:

Does CNCjs allow a pdf to be used for selecting lines and shapes and such?

Are there tutorials on YT that could walk you thru the process better?

Final thoughts:

I set up a simple cnc a while back that uses the GRBL controller and Inkscape for the image processing. To make sure i had everything set up and running smoothly, I had it cut out a couple simple shapes to check everything. I would recommend this before you attempt to cut out anything more complex or with multiple pieces per program. Once you know for sure it can cut out a square, triangle, circle, etc, accurately then move on to a wing rib or a fuse former. Keep it simple at first so you can better know what you are looking at when you see the ready to run program file.

(credentials note: i'm a design engineer and have been in charge of programing several different cnc machines for various jobs. I'm not an expert by any means, but I know my way around them and the gcode the programs spit out.)

Good luck!
Jan 14, 2021, 12:10 PM
Registered User
Thread OP
Thanks a lot for your help, I'll definitely start out with some simple shapes at first, to see how it goes.


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