Before you exclaim "Really! Does the world need yet another Spherebot design?" Consider the question "How about a Spherebot with a parts cost under $35?" Regardless of the answer, here it is. Is it accurate? Mostly-ish, Sometimes, Not very. Did I mention it was cheap and easy to build.

The bot is arduino powered using a slightly modified version of the Eggduino Firmware by Joachim Cerny making it compatible with the EggBot extensions for Inkscape. (3 cheers for Joachim) A few modifications allow the bot to use the very inexpensive 28byj-48 5v stepper motors and ULN2003 drivers. A TowerPro 9G servo is used to lift and lower a Ultra Fine Sharpie pen. Two 608RS bearings hold the idler arm and a small spring keeps the arm pressed against the sphere. Nerf dart suction cups are used to hold the sphere. It is assembled with M3 machine screws, nuts, washers, the hardware that came with the 9g servo and a small spring from a local hardware store.

The bot is optimized to print on standard 40mm table tennis balls. It is adjustable and could probably print on small eggs.

The video shows a few printing errors since I didn't have the ping pong ball centered well enough and/or have the servo lifting the pen far enough above the ball during some of the moves. This is a work in progress and I might tweak a few things before writing better documentation.

Update 04/07/16: Uploaded SCAD source files

Uses the following items from thingverse & github:9G Servo in OpenSCAD by TheCasePublished on September 4, 2012www.thingiverse.com/thing:2973428BYJ-48 Stepper Motor ModelMark Benson 23/07/2013Creative Commons Non Commericalhttp://www.thingiverse.com/thing:122070roundcube_simple module by Daniel "groovenectar" Upshawhttps://gist.github.com/groovenectar/292db1688b79efd6ce11