This Arduino based G-code plotter is inspired by the BrachioGraph. The goal is to create a simple, cheap and easy do build plotter. A classic rainy weekend project.

I build the BrachioGraph hardware first and tried to use the BrachioGraph software. But it didn't show the best results with the Raspberry Pi Zero I had. Part of which might be the missing native PWM support of the Raspberry Pi. So I decided to replace the processing unit with an Arduino Nano Every.

Everything the BrachioGraph requires, minus a Raspberry Pi, plus an Arduino Nano Every (probably other Arduinos work as well) and a fineliner (I used a Stabilo point 88 fine 0.4).

Warning: Don't use cheap servos! I tried to use cheap servos at first (seemingly a fake of SG90 without the Tower Pro label) and the results were terrible (I still use one for the pen lifting servo, since no precision is required there). Now I am using Modelcraft MC-1811 and they work ok.

For the hardware follow the instructions on the BrachioGraph project. It helped to add a counter weight to the "upper arm" to allow the pen to glide more freely.

The software is a classic Arduino project:

Sketch uses 9319 bytes (18%) of program storage space. Maximum is 49152 bytes.
Global variables use 258 bytes (4%) of dynamic memory, leaving 5886 bytes for local variables. Maximum is 6144 bytes.

The plotter plots G-code (only some commands are supported, see source code). I used the tool jscut to generate G-code from svg images and all the G-code it generated is supported.

The lifting of the pen works as follows:

• G0/G1 movement with Z >= 0: pen switches to the up position
• G0/G1 movement with Z < 0: pen switches to the down position

The coordinate system is classic for G-code:

• X increases to the right
• Y increases upwards

To "talk" to the Arduino I use the Arduino's serial connection. The bash script plot.sh path/to/file.gcode sends all the G-code commands in a file to the Arduino (adjust the serial port before using it).

There are two example G-codes in the examples folder (both 70 mm x 70 mm, USB stick as size reference):

• Hello Globe (svg from this side)

• Derp (png from this side converted to svg using this side)

(The paper started to warp a little because of the wet ink, which caused the line between the eyes.)

An example on how you can create your own G-code, can be found here.

My settings for jscut can be found in the file settings.jscut. Make sure to click on "Zero lower left" before exporting the G-code.

The Plotter only supports absolute coordinates in mm.