This is a device that allows your Makerbot (or other cnc machine) to draw/print/cut on cylindrical or spherical objects, in the manner of the EMS EggBot (http://egg-bot.com/). It works by connecting one of the machine's axises to a stepper motor, which then turns the workpiece.
The workpiece is held between two centers (several designs included) which are supported by two brackets: one holds the stepper motor, and the other holds a 608 bearing. The brackets are mounted on a dovetail way, which allows them to be positioned on the base, to accommodate different workpieces. After positioning, the brackets are clamped in place.
- Print the quantities of the parts listed in the parts list, along with your choice of centers. A heated build platform is not required, although it will help. You will need at least two centers; one for the motor ("5mm.stl" or "3mm.st", depending on your motor shaft diameter) and one for the bearing ("end__.stl").
- Insert the bearing into the End Bracket.
- Install the stepper motor into the motor bracket.
- For each bracket: Insert a bolt into a clamp (clamp.stl), and push the bolt through the hole in the bracket. Add a washer, then a wheel (wheel.stl), then a nut. Tighten the nut so it stays on the shaft, then insert the bracket into the base, making sure that the clamp is lined up.
- Connect the stepper motor to your machine. If you are using a Makerbot stepper driver, TURN OFF THE POWER BEFORE CONNECTING OR DISCONNECTING A MOTOR, or you will DESTROY THE DRIVER! If you are using a Makerbot, I recommend you connect the device to the Y axis.
Replicatorg does not handle angle coordinates, so you must establish a relationship between the linear distances in the gcode and the rotation of the motor. To do this, open the machines.xml file in your Replicatorg settings directory (on *nix systems, this is ~/.replicatorg). Duplicate the default definition for your machine, and give it a new name.
Now you must choose the distance in the gcode you want to correspond with a full turn. I recommend 10cm (100mm). Take the number of steps per revolution of your stepper motor, divide it by your chosen distance in mm, and insert the resulting value into the scale property for the axis you connected the device to (axis scale="...."). If your stepper motor has 200 steps per revolution, and you choose 10cm as your distance, then you would put 2 into the scale property.
Loosen the clamps by turning the wheels and move the brackets far enough to insert your workpiece. Push the brackets into place and tighten the clamps. The cup centers may have trouble gripping the workpiece, because they are make of plastic (unlike the EggBot's rubber centers). Add a dab of hot glue if this is the case.