Mini Spherebot

thingiverse

Before exclaiming "Really! Does the world need yet another Spherebot design?" consider this 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 TheCase, published on September 4, 2012, www.thingiverse.com/thing:29734 28BYJ-48 Stepper Motor Model by Mark Benson, July 23, 2013, Creative Commons Non Commerical, http://www.thingiverse.com/thing:122070 roundcube_simple module by Daniel "groovenectar" Upshaw, https://gist.github.com/groovenectar/292db1688b79efd6ce11 Print Settings: Printer: Duplicator I3 Rafts: No Supports: Yes Resolution: 0.2mm Infill: 25% Notes: I printed the parts in the orientation they appear in the STL's. The armvert part was printed on its side to keep the tabs that hold the servo from breaking off (again) when removing it from the printer. Post-Printing: Firmware: UPDATE 01/08/17 Arduino 1.8.0 compatible firmware source code available from https://github.com/russhughes/EggDuino. Previous Firmware Modifications: In the EggDuino.ino file around line 40, change the servoPin define to 10: #define servoPin 10 In the Helper_Functions.ino file around line 96, add: rotStepsEBB = map(rotStepsEBB, 0, 3200, 0, 4076); Connect the Sphere rotation stepper driver board pins IN1,IN2,IN3 and IN4 to the Arduino pins 2,3,4,5 and the Pen stepper driver board pins IN1,IN2,IN3 and IN4 to the Arduino pins 6,7,8,9. Connect the Pen Servo's signal pin the the Arduino Pin 10. Modifications for the Inkscape EggBot Plugin Version 2.7.1: The 2.7.1 release of the EggBot extension only looks for the official eggbot board but we can change that pretty easily. Once you have Inkscape and the 2.7.1 EggBot extensions installed, edit the "ebb_serial.py" file look around line 49 and find the line that reads: if port[1].startswith("EiBotBoard"): and change it to: if port[1].startswith("EiBotBoard") or port[1].startswith("Arduino"): Now it should be able to find Arduino's running the EggDuino Firmware. Next look around line 67 and find the line that reads: serialPort = serial.Serial( comPort, timeout=1.0 ) # 1 second timeout! and increase the timeout to 2 or 3 seconds like this: serialPort = serial.Serial( comPort, timeout=2.0 ) # 2 second timeout or change to 3 if you still can't connect That should be all that's needed to make it work. It can be a little slow with the increased timeout if you have many COM ports.