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This wiki page is part of the documentation for the Egg-Bot kit.
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A few unusual, mostly unsupported tips and tricks for expanding the capability of your Egg-Bot beyond what it was designed for. ("Have fun playing, but please recognize that you do so at your own risk.")

Flipping the pen-arm chassis side wall

In normal practice, the pen motor is adjusted to its highest position-- where the shaft lies in the plane containing the "egg" axis -- when plotting on spherical objects. When plotting on elongated objects, such as eggs, the pen motor position is lowered and the distance between the motor axis and the pen is increased. This lets the pen travel in the path of a larger diameter circle, which is usually adequate for drawing on eggs and other elongated objects. But, what if you want to plot on an object that is wider (not narrower) at its equator than a sphere of the same height? In this case, you may want to raise the pen-motor position above the "egg" axis.

To do so, remove the six thumbscrews that hold the pen-motor side wall to the rest of the chassis. Remove the M3 screws that hold the pen motor in place. Re-install the motor, on the opposite side of the chassis side wall, the side with the scale markings. Then, re-install the side wall using the six thumbscrews, with the "bulge" near the motor now pointing up instead of down. Once you've made this change, you can now adjust the pen motor position as needed for round (lowest) or squat (raised) objects.

If you are using the white-chassis version of the Eggbot, which has integrated heat sinks, you should also be aware that the pen motor will run hotter after you invert the pen-motor side wall. There is no danger to the Eggbot from the higher operating temperature, but that motor can get surprisingly hot to the touch if you are not expecting it.


There has some success engraving surfaces with the Eggbot. First, it's possible to adapt a lightweight dental drill (for example, one of several air-powered types) to sit on the pen arm. Light weight is important as the stepper needs to be able to move it, and the servo motor needs to be able to lift it.

There is also an official Diamond Engraving Tool for Eggbot, as of June 2011.

Frickin Lasers

From the Egg-bot FAQ:

Can you put a laser on it?
Sure, maybe a laser pointer for pen centering? But we don't recommend using lasers capable of cutting/etching without really good safety controls, which are not a standard option for the Egg-Bot.

But, as long as we're the "Hacks" section, let's acknowledge that this is possible-- and if you do it, it's totally at your own risk. (Got it?) You'll need a moderate power laser (probably at least 1 W) to be useful for much. A neat application might be engraving wooden balls, or perhaps blasting away wax-- for traditional pysanky.

CO2 lasers are too large to fit on the pen arm, and the guiding optics for use with our geometry aren't attractive.
Diode lasers could be used, but you'll need to collimate and focus the beam. A good way to do that might be to put build a pen arm without a hinge (laser can be shut on and off, unlike a pen), mount a laser module and lens on the pen arm, pointing parallel to the pen-motor shaft. Add a 45-degree mirror above where the pen hole is, to point the beam straight down at the object.
Fiber coupled lasers of almost any type could be used. You could just mount the fiber right in the standard pen holder, with an appropriate collimating and focusing lens.

Whichever version you use, if you put a laser in it, recognize that this is potentially an extremely dangerous machine, capable of starting fires, poking out eyes without warning, or worse.

A related question, not on the FAQ: Can you put it in a laser?

Yes, you can. It is possible to use the Egg-bot as a rotational 3rd or 4th axis stage for laser cutting, laser engraving, or very light duty physical machining. However, these are not officially supported applications, and should be approached with caution.

Enlarging the chassis

You can replace any of the chassis parts with your own wood, plastic, or metal substitutes as needed to fit larger objects. There is also now an official Ostrich Eggbot Kit (store link), designed to fit larger objects including Ostrich eggs. The Ostrich Eggbot is available both as a stand-alone kit and as an upgrade chassis for the Eggbot.

External "Pause" Button

It is possible to pause a plot underway by pressing the "PRG" button on the EBB. You may want a larger, more accessible "Pause" button. It's possible to add one. As per the EBB command set, you can add an external input at location RB0 (RB2 for older v. 1.1 EBBs). This input should be connected through a normally open switch to ground, preferably through 1k resistor. (Be careful: B0 is NOT 5V tolerant. You could damage the input if you connect it to 5 V instead.) Evil Mad Scientist may offer a kit to make such a pause button at some point.

Directly talking to the EBB

Don't want to use Inkscape? You don't have to. The EBB has a fully documented command set, and you can talk to it directly from any environment or platform that supports USB-serial communication.

Limit switches

Idea for a hack, not yet explored: Add limit switches, interfaced to the EBB, to the pen arm to detect when the end of travel is reached. Use these to auto-preset the pen position before starting a plot.

Hinge options

The standard hinges provided with the kit are flexure hinges made of thin acetal-- a resilient plastic. You may prefer to use a traditional "door" hinge, or a flexure hinge made of metal (e.g., brass shim), fiberglass, carbon fiber, or thicker plastic that provides spring pressure to hold the pen (or engraver) tip down against what it's drawing on. You can use almost anything, so long as you can cut it to the same shape as the original hinges.

Other size pens

While the default pen holder fits many useful pens and similar objects, you may occasionally want to use a different pen holder-- for example a larger-diameter holder to fit broad-point Sharpie pens for drawing on balloons. The default pen holder can be machined out, can have smaller objects glued into it, or it can be replaced by one of your own design. Extra distal pen arms, wide distal pen arms, and blank versions are available through Evil Mad Scientist. For more information on various pen sizes, see the Pen choices page.

Upgrading the egg cups

The stepper motors in the Egg-Bot kit have a 5 mm shaft. Besides the standard 1/2" OD shaft collar and polyurethane cups, it's possible to use almost anything that can connect to the shaft as an "egg cup." For mounting large-mouth objects, it may be helpful to use a larger diameter shaft collar with a larger rubber bumper or even rigid coupling. One trick that has worked for objects as large as wine glasses is to use a timing belt pulley with a 5 mm bore as a giant "shaft collar", and then to glue or tape the object to the pulley. The precision egg coupler available from Evil Mad Scientist is made in a similar manner.

For glass ornaments, a trick that has worked is to use a suction cup attached to the shaft collar with adhesive. For example, craft and hardware stores sell small, clear suction cups with "S" hangers intended for hanging light objects from windows, refrigerator doors, etc. Remove the metal "S" hanger, trim flush the section of the cup to which the hanger was attached, and then use adhesive to afix the trimmed end to the shaft collar.