David Schilling’s EggArt

Tuesday, April 10th, 2007

David built this 4-colour NXT Easter egg painting robot.

To use it, you open the egg-holder up, insert your blank (hard boiled) egg, make sure that it’s reasonably centered, and then fold it up to the pen unit and lock it in place. Select your program, and run it. Two motors control the egg position, one for rotating it about its long axis, the other for spinning the egg on its side. The 4 pens are held in a rotating cartridge. The third NXT motor controls moving the pens back and forth, as well as changing them. This is accomplished by pushing an axle with worm-gears on it (that only act as a rack here) back and forth with the motor. When the axle is all the way to the rear, it engages another wormgear, which then causes the axle to spin. This spin is
transfered to the pen-cartridge. A touch sensor can tell when the pen is getting close to being in place. Just as it releases, the pen is in position. A couple of rubber bands put light force on some beams which lock the pen into position. Of course you can only rotate through the colours in one order. Turning the motor the other way will push the currently selected pen forward again. (more…)

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