This modification attaches to the left extruder fan bracket on the Prusa MK4s. I printed all pieces with a 0.4mm nozzle with PETG Filament. Supports are required for the main bracket piece, and are reccomended for the pen bracket.

This model utalizes 6 M3 bolts of varing sizes, I used leftover bolt from the MK4s build. The pen I used is a ballpoint sharpie pen, which seemed to work well. 

Special thank you to Abikloro and Gajowy for the pen plotter and fan bracket attachment ideas, respectively. Their designs linked below.

https://www.printables.com/model/827264-pen-plotter-attachment-for-prusa-mk4

https://www.printables.com/model/1178959-prusa-mk4s-pusher

Assembly tips:

1. Screw the bolts through both pieces of the bracket before attempting to install to thread them.

2. The model is not perfectly formed to the bracket geometry. To ensure the bracket is stable, you need to tighten down the two bolts HARD. I would reccomend tightening the middle bolt halfway first so that it is tfully through both brackets, then the top bolt all the way, then tighten down the middle one fully.

3. Move the printer to 0mm Z-height, and place the pen holder into the slot. Move the printer up to 4mm, and then press the pen into the slot so that the tip of the pen is touching the table. Then tighten both pen brackets to hold the pen tightly. This ensure proper pen height.

The bracket (at least for me), did not sit perfectly 90 degrees relative to the table. As far as I could tell, this did not impact the performance at all, as long as it is somewhat close. Just be sure to remove the pen before running a 3D print, as the pen would drag and cause a print failure. The bracket can stay attached with no problems, the printer retains a full range of motion with it attached.

I made online tools to generate toolpaths for images and svg files, this can be found at the link below:

***WARNING: THIS IS AN EXPERIMENTAL TOOL MADE BY SOMEONE WITH LITTLE CODING EXPERIENCE. WHILE IT WORKED WELL FOR ME, NEVER EXPLICITLY TRUST GCODE GENERATED BY THIS TOOL. ALWAYS MONITOR THE PRINT JOB CLOSELY, AND BE READY TO STOP THE PRINT JOB. I AM NOT RESPONSIBLE FOR ANY DAMAGE CAUSED BY THIS TOOL.***

GCode Generator: https://shunky59.github.io/PenPlotter.html

(This generator has the pen go over each line twice for some reason , I am working on it, but it still works well)

The gcode should home the machine first, (X,Y,Z), then foce the user to press the knob to begin. It should also allow the user to refine the z-height during the print. Be sure to measure your own pen offsets and overwrite the defaults in the generator.