I think because of the sled, spring loaded is not needed. All of the iterations I have played with, the spring loaded designs have had too much x/y slop in the tip, making precise plotting or artwork not so perfect. I’ve now gone to a solid pencil and it’s much better…you just have to have the z height/home and your gcode target depth and steps set very carefully, and after a long run, you might have to pause and adjust the pencil downwards so fresh lead hits the surface. (Probably not an issue as much with a pen/marker)
If you can get a spring loaded to work with out x and y slop that’s amazing. Only 1-3mm of tip slop made my drawings/logos on an 8.5"*11" sheet of paper look like kindergarten work. But with stiff tip they come out near perfect.
Below you can see the slop from the computer version to the paper.
