NOTE: The instructable is still under construction. I wanted to publish it now though so people could see what the Eggbot can do and in case anyone wants to use any of my designs for their own Easter Eggs. I'll finish it up soon.
A couple of weeks ago I got an Egg-bot. My kids and I have loved it, so I thought I'd share some example of what it can do, a few designs we've come up with and some general tips.
If you're not familiar with an Egg-bot, it's essentially a little CNC lathe. You put somewhat spherical objects two plungers that are controlled by a stepper. There's also a pen arm that is controlled by a stepper that moves side to side. Between the two steppers (and a servo to lift and lower the pin) the Egg-bot is able to take instructions from a computer and use them to draw on an egg. The de-facto platform for creating drawings and plotting them on eggs is Inkscape (and open source Illustrator-like program).
I've found it surprisingly easy to use and a ton of fun.
Step 1: Quickstart
Put the Egg-bot together following these directions . Download the software for your platform following these directions from the Egg-bot site . After that you can follow these directions for your first plot , or if you want to get something going more quickly this is probably all you really need to do (then you can read the longer directions while your first egg is drawing):
1. Connect your Egg-bot to power and to your computer via USB
2. Put an egg (or whatever you're going to draw on in the Egg-bot).
3. Open your drawing in Inkscape (I'd start with something from the EB_Example_Set )
4. Open the Egg-bot control in Inkscape (Extensions -> Eggbot -> Eggbot Control)
5. Lift the Pen arm - in the Egg-bt control click the Setup tab, make sure "Toggle pen up/down" is selected and click apply, wait for motors to move, then click apply again (the first apply will set the pen at the "down" position, the second apply will move it up).
6. Put a pen in then pen arm. Then pen should over the center of the egg. It should be somewhere between 1/8" and 1/16" over the egg.
7. Move the pen arm from side to side to make sure it's not touching the egg when the pen arm is up. If it is touching you can adjust the "Pen up position" in the Setup tab of the Eggbot control. After you change the number click apply once, wait until the pen lowers, then click apply again. Now verify it's still not touching when you move the pen arm from side to side.
8. Move the pen far the the right, in the Setup tab of the Eggbot control click apply to drop the pen. Make sure the pen is touching the egg. If it's not you may need to push the pen lower in the arm, lower the arm using the screw, or adjust the "pen down position" in the dialog. Manually lift up the pen and move the pen arm over to the left and make sure it's also touches the egg there.
9. In the setup tab click apply to raise the pen arm. Now center the pen arm on the egg.
10. Click on the Plot tab in the Eggbot control and click apply, the eggbot will start drawing.
Step 2: Gotchas
Here are some gotchas I've run into and what I did about them:
1. When I first set up my Eggbot it would draw weird lines because the motor was moving as it was picking up the pen. There are a couple of ways to fix this:
a. Make sure you're lifting the pen up high enough (in the Eggbot control dialog, the Setup tab, the "Pen up position"
b. Make the "Pen down position" higher. This will make it so the servo doesn't need to move it up as far which makes it faster. Ideally the pen down position should be just enough for the pen to hit and write on the egg in every position.
c. Change the "Delay after pen raising" (Eggbot control, the Timing tab) to a higher value. This will slow down drawing but it will give the servo more time to lift up the pen before it moves to the next position.
2. Eratic drawings: When I first got my Eggbot it seemed very precise, then it got worse. After a little while I figured out some of the screws were a little loose. It's a good idea to check the screws every 20 or 30 eggs.
3. Markers not drawing on eggs: Make sure the egg is dry and draw on some paper to get the marker started before loading it into the pen arm.
4. Text: Don't use the built in text stuff in Inkscape, it doesn't render on the egg very well. Use Hersey text , after you install it, it will be in the render menu in Extensions. (it's always fun to give someone an egg that says "Suck it!"
Step 3: Samples
Step 4: Drawing on Other Stuff
Anything roundish should work. Here's a cup and an orange (this was around NCAA tournament time). The cup is one of the cheap little kid's cups from Ikea. The orange is just a normal orange ;).