I couldn't find free directions online so I did my best job of reverse engineering and scaling (1/6) a 1790's French style Guillotine. Note that the blade in my version is real and therefore it is dangerous (see video). Although I'm only using it to cut carrots and other vegetables, it could potentially do some serious damage to your finger! If you want a safe version, I suggest printing the blade and not including the weights.
I uploaded 25 files. With that, I hope you are good with models. I haven't 3D printed the guillotine so I'm hoping for the best. I broke apart the individual files and created assemblies (base, table, etc.) which gives you options. The main concern I have is the sliding of the blade assembly. You might need to do a little bit of sanding to the groove to make it slide better. If needed, I can remodel the part with a larger groove - just let me know.
Build Instructions: https://www.instructables.com/id/Mini-Guillotine/