I recently made a spring loaded pen plotter tool for my CNC Router I thought I would share. Before making this device I tried using a non-spring loaded plotter pen which was pretty expensive and it tended to skip or tear the paper.
The spring loaded device I made seems to work very well. The tool uses a Lamy M-22 ballpoint pen ink cartridge, a small spring, and a 5/16” set screw. I made the body of the tool out of 1/2” acrylic rod but it could also be made out of aluminum or just about any material. I chose the Lamy M-22 cartridge simply because it was the shortest. It’s a bit expensive, about $7 on Amazon and comes in different ball sizes and colors. I made the body on my CNC Mill but you could also make in on a good drill press if you are careful and accurate.
I use CamBam for most of my work and to plot something rather than cut it, I select all the lines, circles, arcs, etc. on the drawing and then define a machining process that does a profile cut using a tool with a specified 0" diameter I also specify the depth of cut at 0 and a clearance plane of .25". Before plotting, I position the spring loaded pen at the center of the paper and set the Z Axis to about .04" below the surface of the paper to load the spring.