This model is designed to be mounted on the ender 3 hotend carriage with the screws that hold the hotend cover. Then you can use your printer as a plotter with a pen (I used a 4 colours bic pen) or a marker.
I also used a small clip to reduce vibration

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

(note that there is a x-offset, if you want to correct it you have to measure how much it is)

Print settings:
Print without supports at 0.2 or lower (may work with bigger layer height but I haven't tried it)
You may need to scale down the screw, 98% worked great for me

If you have the hydra fan duct look at my other model:
https://www.printables.com/model/438168-ender-3-hydra-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 files contact me.