This CNC Plotter Draws Precise Images While Using Just Two Stepper Motors and Some Pulleys

Traditional CNC plotters

Computer numerical controlled (CNC) machines seem to be everywhere these days. Whether it is extruding layers of plastic to build a part or moving a milling bit over a block of wood, they are integral to how we build and prototype things. Some makers have taken this idea and run even further with it by creating CNC machines that are able to produce artwork with great accuracy. Nearly all of them use the Cartesian coordinate system which consists of moving the toolhead along a pair of perpendicular planes.

However, this approach can lead to complex and oftentimes expensive assemblies, which is why the YouTuber known as DAZ projects wanted to build a simpler version he calls the Interactive Programmable Arts Display or IPAD for short.

Meet the polargraph design

A polargraph CNC plotting machine differs from the traditional design in a couple of ways. First, it works on a single plane and has a basic servo motor to raise and lower the drawing utensil. Second, a pair of stepper motors are used to drag a string and adjust its length, and therefore where the pen is positioned on the canvas. This style of CNC plotting device was invented by Sandy Noble, and his firmware is what the IPAD's creator chose to use.

Components

As mentioned before, this polargraph machine uses a pair of 28BYJ48 bipolar stepper motors along with a series of pulleys to move a pen across the drawing surface. Driving those motors are two A4988 driver modules that have been placed into a generic GRBL Arduino Uno shield. There is a single micro servo within the toolhead that can raise and lower the marker to produce lighter/darker areas on the page.

Assembling the device

DAZ began by 3D printing several custom parts, including a pair of stepper motor mounts, five pulleys, a large central bearing mount for the toolhead, and the pen holding/lifting mechanism. He then mounted these pieces onto a sheet of particleboard that had an additional area for placing the Arduino Uno and GRBL CNC shield. After running two sets of string, the machine was ready to start drawing.

Drawing a picture

The Interactive Programmable Arts Display runs the Polargraph firmware which is responsible for reading incoming commands from the host device and converting them into motor movements. There is an accompanying piece of software called the Polargraph Controller that can read in images and translate them into toolpaths encoded in Sandy's custom C-code format. As seen on the Thingiverse page for this project, the resulting drawings look great, especially because they were drawn by such a simple machine.

You can watch the DAZ's YouTube video to see how he built the device or see his GitHub repository here.