Preparing files for CNC-milling has 2 steps: First you design your file in CAD-software and then you use CAM-software to generate the files that will run the machine (CAD stands for Computer Aided Design and CAM stands for Computer Aided Manufacturing). Below we'll talk about the CAD part of preparation. If you're looking for the CAM file preparation, have a look at CAM - Creating toolpaths for running the machine
The first thing to consider when preparing files for cnc-machining is whether you will be cutting a 2D file or a 3D file. In general 2D files have quicker production and quicker preparation time in CAD in comparison to 3D files (although there are exceptions). 2D files are often used for cutting out pieces out of flat plates that can be assembled afterwards or for engraving text or a logo, or both. 3D files are mostly used for making 3D shapes like sculptures, molds or landscapes for architecture models. It’s also used for mechanical parts, but those are a bit more complicated with our current setup at Fellesverkstedet.
Comparison of 3D vs 2D cutting. The red lines show the way the machine will run. 2D cutting effectively cuts in the spots which need to be cut using a flat milling bit. 3D cutting will result in a way less efficient running of the machine and the result will not look as clean. In this case it obviously makes more sense to do 2D cutting so only a 2D file is needed.