Eggbot Quality Troubleshooting

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Revision as of 12:40, 14 July 2014 by Steven Herzberg (talk | contribs) (Alignment of the egg in the egg cups)
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If you are having quality issues with your prints that might be due to a misalignment of some sort, we hope that this guide will help you to find the source of the problem. This guide contains some helpful pictures that show how configuring the EggBot in different ways can produce different outcomes.

"Hardware" issues

Our test file


This is the test file that we'll be using for our examples. Note that the print quality is fine and consistent. The "O's" have closed shapes, the vertical parts are vertical, the horizontal parts are horizontal, the slants of the "W's" have consistent width, and so forth. (Some of the examples that we'll show later do not have these properties!)

You can download the example file here. (TODO: ADD LINK)

This was printed with the Deluxe EggBot on a chicken egg with an Ultra Fine Point Sharpie. The egg was oriented with its "fat" side pointing towards the egg motor (headstock).

The print settings were as follows:

  • Timing tab:
    • Speed when pen is down: 300 steps/s
    • Speed when pen is up: 400 steps/s
    • Pen raising speed: 50 %/s
    • Delay after raising pen: 200 ms
    • Pen lowering speed: 20 %/s
    • Delay after lowering pen: 400 ms
  • Options tab:
    • Reverse motion of Motor 1 (pen): checked
    • Reverse motion of Motor 2 (egg): checked
    • Egg (x) axis wraps around: checked
    • Start with pen centered: checked
    • Return home when done: checked
    • Enable engraver, if attached: unchecked
    • Curve smoothing (lower for more): 0.2

Dry pen


A common problem that can happen when using old pens, or pens that have been left uncapped is that the pen does not start drawing immediately when you expect it to. It is usually easy to fix this problem by taking a scratch piece of paper and, right before you start your EggBot, "bleeding" your pen a little on the paper to get the ink flowing again, as shown below. Sharpie pens last approximately forever if treated well; if it doesn't start drawing immediately, you might consider leaving it capped for a few days and trying again, rather than throwing it out.


Alignment of the egg in the egg cups


This skewed image is the result of misaligning the egg within the couplers, like so (exaggerated for clarity):


In order to avoid this you should place the egg between the couplers with the egg as flush as you can get it against each coupler. To align the egg in place, turn the egg (or the egg coupler) and watch the egg as you turn it. (You may want to use the "Raise pen, turn off motors" option in EggBot Control to make this easy.) Adjust its position until there is as little wobbling as possible; that is, until it doesn't seem to "change shape" as you rotate it.


This egg is properly aligned.

Loose Eggs & Screws


If your plots look like this, with circles that don't close and differing widths of your letter parts, it likely means that something is loose. It can be either the egg itself-- slipping in the coupler -- or a loose screw somewhere on the EggBot. Make sure that the egg has a secure connection to the motor through its coupler, and can't wiggle independently of the motor. And, make sure that the screws on the EggBot are tight and secure.


If the hex screw below the pen arm's hinge is loose, the pen arm will move left and right as the pen is dragged across the egg. Try to gently wiggle the pen arm left to right, it should not move at all.


In this case, the screw that mounts the distal pen arm assembly to the proximal pen arm (shown below) was loose, with the kind of poor results that you might expect.



The plot above-- where the pen is wandering "all over the place" was caused by trying to draw when the screw that holds the pen was loose (about to drop the pen).


To check if the pen is securely fastened, gently try to pull it out.

Vertical position of the pen motor


The pen motor can be moved vertically to adjust the pen arm for drawing on oblong surfaces or circular surfaces. Here is an example of the pen motor being in the right position for a chicken egg. For a sphere, position the motor at the very top of its slots. For a more elongated egg (maybe a turkey egg?) you may need to go lower yet in the slots.


This change in aspect ratio is the result of the pen motor being positioned too high.



This one is because the pen motor was to low


Headstock / Tailstock position


When the headstock is correction positioned, the shaft of the pen motor points directly toward the thickest part of the egg (or sphere), as shown here


When the headstock and tailstock are placed too far to the left, you may get distortion.



This one when the headstock and tailstock were placed too far to the right.


Pen arm backer position


When the distal pen arm is in the correct vertical position-- essentially flat when it the pen is contacting the egg -- the tip of the pen should point directly towards the thickest part of the egg. If it does not, that may indicate that the pen arm backer is in the wrong position and that you need to move the whole pen arm closer to, or further from, the pen motor.

This pen arm backer is in the correct position, since pen points at the thickest part of the egg.


This is the result of the backer being inward too much, making the drawing curved to the right.



this is when the backer os too far outward, causing the drawing to be curved to the left.


Horizontal pen arm


This is the correct orientation for the pen arm and pen. Where the pen arm is horizontal and the tip of pen is flat against the egg when in the down position.


This occurs when the pen arm is not horizontal when in the down position, causing the pen to be skewed. The drawings can then come out slightly distorted. This is similar to when the backer is misaligned.


Bumping the pen arm


This drawing is a test of what the outcome should be when everything goes correctly.


This one is when the starting position of the pen arm was off and the pen arm bumped into the side of the EggBot. With the pen arm not being allowed to go any further, the EggBot continued the drawing at the position it was stuck at.




This is an example of the distortion created when trying to draw a circle in a square on an egg and a spherical ornament.


"Software" issues

Motor reversal issues


This occurred when the "Reverse motion of Motor 1 (pen)" was left unchecked when the egg was positioned so that its "fat" end was on the headstock. This can also happen when the "Reverse motion of Motor 1 (pen)" is checked, but the eggs "fat" end is in the tailstock.


This mirrored image of "Hello World" is the result of "Reverse motion of Motor 2 (egg)" being left unchecked while the "fat" end of the egg is in the headstock, and vice versa.

Timing issues


This is the result of the "Speed when pen is down" setting being set to 700 steps/s, which is too fast to create a neat drawing. The speed of the motor caused the lines to be jagged.


With the "Speed when the pen is down" setting set to 500 steps/s, while it is an improvement, is still too fast. There are still jagged lines.


This happens when the "Delay after lowering pen" setting is set too low. The EggBot will start to commence the drawing before the pen has actually made contact with the egg, leaving gaps in your drawings.


This is when the "Delay after raising pen" setting is set too low. The EggBot will start to move to the next destination before the pen is lifted off of the egg, leaving stray marks.