It is pretty easy to use a 3d printer as a pen plotter. You can easily print a pen holder that mounts to your print head. This one (https://www.thingiverse.com/thing:3139205) includes a retaining screw for different sized pens. I have also seen mods for CNCs that will click retractable sharpies and then use them for layout or part marking. Here is one example: https://www.youtube.com/watch?v=c3LhK2SAusk

As a side note, the MUJI gel pen from the 3rd image (Tesselations, August 2017) are amazing.