Computer Numerical Control: Building the Hardware and Software of a Printer

Abstract

This work built the hardware and the software of a Computer Numerical Control (CNC) machine that draws on paper with a ballpoint pen. The hardware was assembled from parts of other printers and electronic scrap. The software consists of two programs. The first is a desktop application written in C with a GTK+ interface that offers the operator several ways of interacting with the machine: driving both axes with a joystick, drawing in a graphical editor, and selecting images from the computer for printing. In the latter case, the application previews how the image will look once printed in two colours. The second program runs on the microcontroller and carries out the high level commands received from the desktop application over a network protocol designed as part of the work. Because of the memory limit, images are sent in parts while they are being printed. The microcontroller drives the stepper motors of the X and Y axes and the direct current motor of the Z axis as it interprets the commands or the image it receives.