I’ve been working on this on and off for a while and I managed to make my first drawings with it recently.
It’s alive 
I wanted to have a self-contained box design with a moving pen. I’ve seen other plotters where the platen moves on one of the dimensions under the pen, or where a stepper motor is mounted above the drawing surface, but I wanted everything to be tucked away inside as much as possible. Maybe not the best engineering decision, but IMO it looks good.
For each axis there is a lead screw on one side only - I should probably have a lead screw on both sides and join them with a belt. I think that would improve accuracy.
So there are two stepper motors inside, and a servo motor for moving the pen up and down, all controlled by Arduino running CNC software. The wooden supports for the rods run along the x and y axis on cheap linear rails. (I started with some adapted drawer runners at first…)
I have a temporary pen holder tube for now until I get hold of a 3D printer to make a proper one. I also need to print a rack and pinion for the pen lifting mechanism as the current one doesn’t fit my servo properly so it works a bit inconsistently at times. Actually I will redesign the whole wooden pen mount to be smaller as at the moment some of the end-stop switches can’t be reached, as the pen mount is too big and will crash before the rod supports can reach the end of their travel.
TODO:
Move the electronics inside the box
Add hardware controls
Redesign pen mount and pen holder
Print or find better rack and pinion for pen up/down
Then once it is reliable and making good 1:1 drawings I will be using it for some more interesting experimental outputs.
The ply parts were laser cut at the space
Pen mount with servo, designed in Fusion360
Inside, one of the stepper motors and lead screw
Tiltable pen position with wing nut
Servo
Inside the box again
Controller gubbins
You can just about see two of the end switches here
First test
Second test
I should make the obligatory time-lapse movie too, to show it in action.
