Instructables member “Lingib” has created a awesome Arduino powered Omni Wheel CNC pen plotter, powered by an Arduino Uno and Bluetooth module allowing the system to receive commands via a linked smartphone or tablet. If you’re not familiar with omni-wheels the unique wheels only provide traction in the direction of rotation. Any oblique force causes the wheel to move sideways. Check out the video below to learn more about its construction using four 28BYJ-48 stepping motors an SG90 servo connected to the Arduino development board.
The robot was built for less than $100 with the most expensive item consisting of the omni-wheels and couplings. Its creator explains a little more about its functionality and construction. “The CNC plotter has an on-board interpreter that recognises the g-code output from “Inkscape”. All that is required is an XON XOFF terminal that can send text-files one line at a time. Extremely large drawings are possible due to the Bluetooth design. The plotter accuracy is excellent providing the wheels don’t slip! The plotter has a resolution of 22 steps per mm”
“The video demonstrates a proof-of-concept plotter made from four 58mm plastic omni-wheels. The slight inaccuracies are due to wheel slippage and a tiny amount of back-lash in the 64:1 gearing in the 28BYj-48 stepper motors.”
Source : Arduino omni-wheel robot and pen plotter