SharpieTapePlotter

2 Nema17 motors
8 mm threaded rods, axles and ball bearings 
3 mm screwings of the motors etc.

Arduino Nano and CNC Shielt V4
A4988 stepper motor driver

Arduino Micro to control the SG90 Micro Servo

Software Grbl 1.1 
Lightburn Software to generate the code
(https://lightburnsoftware.com/)

I have included the firmware setting as a .jpg above.

How the servo works:

At the analog input of the micro is the spindle signal (Z+) of the CNC shaft.
I use this to raise or lower the pin accordingly.

With a button and a trimpoti I can set the corresponding response level.

I have attached the corresponding Arduino code here.