InkScape is good for 2D (laser, plasma). It uses SVG files natively and can export many others.
I believe the Shapoko gcode generator uses dxf files, but I’m not really familiar with it, sorry. Perhaps others can comment.
Laser
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Lightburn can import SVGs.
RdWorks can import .ai (Adobe) or .dxf files. I used to convert svg to ai using Adobe Illustrator. Now I just use Lightburn and SVGs directly.
Plasma
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Uses dxf. You can export dxf from InkScape or Adobe Illustrator.
3D printers (FDM and resin)
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For 3D, you’ll need 3D modeling. TinkerCAD (web-based) is an easy intro. WYSIWYG, and it has primatives (squares, cones, cylinders, et al) which you can manipulate after placement.
If you like programming, consider writing scripts in OpenSCAD. This is good for parametric models and is the basis for Thingiverse’s Customizer. Downloading a Customizer model and reviewing the code is a good way to learn new tricks.
Fusion360 is another option for 3D, albeit with a lot more power and a correspondingly much harder learning curve. It’s a good gateway for CAD/CAM, too.
3D files have to be “sliced” to convert into the low level GCode used by the printers. STL is the input format most widely supported by slicers. OpenSCAD and TinkerCAD can both export STLs. Google Sketchup can export STLs with an optional plugin. Fusion360 supports STL generation as well.
Slicers
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The PolyPrinters use KissSlicer but other slicers can be used: some have better/different features. I’m not sure which slicer the resin printers use, but learning about placement of support, hollowing, and model orientation is worth some time spent within the slicer program.