CNC workflow
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First things first, the workflow of a typical CNC job:
Everything starts in a CAD (Computer-Aided Design) program: this is where you will create the 2D or 3D objects to be machined. CAD software packages are usually able to import 2D and 3D features from a variety of file formats, and the most common/useful ones for CNC are "vector" formats.
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Carbide Create, the CAD program provided by Carbide 3D for the Shapeoko, can import SVG or DXF vector files (and the Pro version has additional capabilities) |
Once the object is designed, a CAM (Computer-Aided Manufacturing) module that is usually integrated in the CAD suite, is used to create toolpaths to cut the object out of a block of stock material (more on this later). Once all required toolpaths are created, the very last step in the CAM program is to generate one or several G-code files, containing instructions for the machine to move the cutter along these toolpaths.
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G-code format is a standard (originally ISO 6983-1 back in the 80s) so one would expect that a G-code file can be run on any CNC. Well almost, but not quite. Different CNCs support different subsets of the G-code instructions, as well as implement their own custom instructions. |
Since CAM programs are usually not bound to any specific CNC machine, they make use of a specific post-processor to generate the correct G-code for a given machine.
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In Carbide Create, there is a single G-code post-processor that gets executed behind the scenes, and it knows what Shapeoko model you have since there is a dedicated "Machine" parameter in the job setup. |
If needed, a G-code viewer can be used to double-check the generated toolpaths, if the CAM tool does not have a toolpath preview feature. CAMotics is a popular (and free) option.
Finally the instructions from the generated G-code files must be sent to the machine to produce the required movements of the router to cut through the material. This requires a G-code sender, that goes through the G-code file line by line and sends the instructions to the machine, or more precisely to the machine's controller, via a communication link (USB on the Shapeoko).
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Carbide Motion is Carbide 3D's G-code sender for the Shapeoko, but alternative senders can also be used |
The controller executes a piece of software that interprets incoming instructions, and translates them into specific movements of the X, Y, and Z motors. On the Shapeoko, this software is "GRBL", (pronounced "Gerbil"), an open source motion control software (see https://github.com/gnea/grbl )
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