Drawing Robots

There is something deeply satisfying about watching a robot pick up a pen and draw. It combines precise motion control, a splash of creative code, and a result you can hold in your hands.

What is a Drawing Robot?

A drawing robot — sometimes called a plotter — is a machine that moves a pen (or other tool) across a surface to create images, patterns, or text. The robot follows coordinates, curves, and paths generated by code or imported from vector files.

They come in many forms:

• Arm plotters like the BrachioGraph use servo-driven linkages to sweep a pen across paper. The maths behind them involves a bit of trigonometry, but the builds are wonderfully low-cost.
• Wall plotters (Polargraph / Scrawly Wally style) hang on a vertical surface, using two stepper motors and a gondola suspended on strings to drag a marker across a whiteboard or large sheet.
• CoreXY and Cartesian plotters move a pen on two linear axes — the same mechanism used in desktop 3D printers, just with a Sharpie instead of a hotend.
• Differential drive scribblers like BurgerBot use a two-wheeled chassis with a pen mount: perfect for Turtle-style drawing with simple movement commands.

Most accept G-code, SVG paths, or custom coordinate lists as input.

How a wall plotter finds a point

The wall-plotter (polargraph) is the most surprising of the bunch. Two motors at the top corners pay out or reel in string; the pen gondola hangs where the two string lengths meet. To move the pen to a target point, the code works out the two string lengths that put it there:

   M1 ●─────────────────● M2     ← two stepper motors
       \               /            (top corners)
        \ L1        L2/
         \           /
          \         /
           \       /
            ● pen gondola
          (hangs at the meeting
           point of L1 and L2)

   Want the pen at (x, y)?
   → compute string lengths L1 and L2
   → reel each motor to that length
   → gondola settles at the target

It’s the same idea as GPS trilateration, just with two strings instead of satellites — and watching a marker glide across a whiteboard tracing a path you coded is genuinely mesmerising.

Why robot builders care

Drawing robots punch well above their weight as learning tools. To make one work you need to understand servo or stepper control, coordinate systems, path planning, and — if you want anything more than a wiggly line — a bit of inverse kinematics. That is a huge slice of the robotics skill tree, all motivated by the very concrete goal of making something beautiful.

They are also supremely forgiving. A slightly wobbly line is charming rather than a failure. That makes them ideal first projects for builders who are still finding their feet with motion control.

On the software side, Python’s turtle module gives you a drawing robot in pure software — a great way to plan paths before committing them to hardware. SVG files can be parsed and converted into motor commands with just a few lines of code.

Get started

The quickest on-ramp is to build a BrachioGraph — a two-servo arm that costs almost nothing and teaches you a tonne. Kevin’s BrachioGraph Tutorial walks you through the full build, from assembling the arm to writing your first drawing program in Python.

If you want to go bigger (literally), the Wall Drawing Robot Tutorial shows you how to build a Raspberry Pi Zero-powered wall plotter using stepper motors and a hanging gondola marker.

For a Pico-based plotter you can build over a weekend, check out the Pico Plotter project — it uses MicroPython to drive the axes and is a great introduction to G-code-style motion.

Once you have a working plotter, try feeding it an SVG export from Inkscape. The jump from “robot that draws circles” to “robot that draws your logo” is surprisingly small — and very satisfying.