Some time ago I got a bit nostalgic about a pen plotter from 80's called Alfigraf. It was produced in Czechoslovakia and based mainly on parts of a construction kit called Merkur (fun fact - first contact lenses were created using machine built from Merkur). Long story short, first I built the plotter using Merkur parts and then I decided to make a design for 3D printing so I could put the Merkur parts back to the box.

Short video with the plotter in action is here on youtube.

It turned out to be quite simple and compact design using only parts that are printable or they can be easily bought on ebay/aliexpress together with your local DIY shop for all the metal parts.

The steppers are NEMA17 (17HS2408) drived by TI DRV8825 and controlled by grbl running on ARM Cortex M3. The pen-up mechanism is using a 5V solenoid with a solenoid driver that is reducing its consumption by applying full voltage only for the pen hit and then dropping to 0.5V just to keep the pen up. I tried using a servo but somehow I had a better experience with a solenoid. Both solutions have their pros and cons...

As a Gcode controller I used STM32F3 based board that can be cheaply bought online and its dimensions fit nicely with the plotter design. Useful information about the board is here.

The Gcode controller firmware is a port of grbl made for this particular MCU. It's repository is here on github.

I used SolveSpace for designing as I don't know any other 3D modelling tool. I know that to some it may appear a bit cumbersome but I like its simplicity. I used version built from latest git repository and cannot guarantee that it's fully compatible with the prebuilt version available in their download section. So if anyone wants to play with my design or reuse it, the latest version of SolveSpace may be required.

The git repository with the model sources are here on github.