Print settings:
Print without supports at 0.2 or lower, the screw in a M3 screw for securing the pen.

HOW TO USE IT:
1. You have to adjust your z offset, there are many ways, you can delete G28 (or G1 Z0) from your starting G-code and then put your z-axis at the right height, or you can print with a big first layer height and adjust the pen so it touch the bed.
2. In the slicer put the stl you want to draw under the bed so it will be only one layer high.
3. Set the hot end temperature at 0, in this way the extruder won't push material (it's a safety measure of marlin, if you aren't sure to have it just remove the filament)
4. set a big z-hop, so you wouldn't get unwanted lines
5. PRINT

If you have the stock ender 3 fan duct look at my old system:

https://www.printables.com/model/438157-ender-3-universal-pen-mount-plotter

If you made it please post a make and share all your beautiful drawing.
If you loved it you can buy me a coffee: https://paypal.me/GiorgioMiglia

If you want the Fusion 360 file contact me.