Difference between revisions of "Eggbot Troubleshooting"

Stair steps

Loud stepper motors

Does your plot appear to have "stair steps" or jagged lines? Are the stepper motors loud or whining? You likely need to adjust the "Current Adjust" control on the EBB board with a small screwdriver. This is a physical control -- a potentiometer -- on the EBB circuit board mounted to your Eggbot chassis. The control is labelled "CUR ADJ" on the board. If the current is too strong or too weak you may see (or hear) these symptoms. The current increases as you rotate the control counter-clockwise (CCW). Starting with the control turned all the way clockwise (CW), both motors should be very weak. As you increase the current -- turning the control with a small screw driver CCW -- you should be able to feel the motors increasingly resist moving by your hand. The ideal setting is one that provides smooth, relatively low-noise moves from the stepper motors, but has enough torque that the pen arm is not "floppy". Often, this is about half way CCW, maybe a little less. More current, while increasing the motors torque, leads to jerky moves, with position errors (e.g., stair steps).

NOTE: the stepper motors are the two large, metal encased motors which mount to the Eggbot's chassis. One rotates the egg while the other rotates the proximal pen arm. The smaller, plastic encased motor which raises and lowers the distal pen arm is a "servo motor". It's behavior is not controlled by the current adjustment.

Mirrored text

If your text appears "mirrored" (e.g., inverted from left to right) then first check the assembly directions to ensure that you have wired the egg motor correctly. Check that the ordering of the colored wires matches the picture. if they do not, then correct their ordering and try replotting. If you are sure that they are wired correctly then everything is still okay: some stepper motors are just backwards. From the Eggbot Control extension, check (or uncheck) the "Reverse motion of Motor 2 (egg)" checkbox on the "Options" tab. Then click the "Apply" button. Then plot your test again. If things are still reversed, then make sure that your change to the setting took effect. If there is still an issue, then perhaps you need to instead or also change the "Reverse motion of Motor 1 (pen)" setting. Note that after doing an upgrade of the Eggbot extensions, it is possible for this setting to get lost. In that case, simply set it again and save it with the Apply button.

Upside down text

Is your text plotting upside down? First, let us be clear: the (vertical) top of your Inkscape drawing should correspond to the pole of your egg closest to the egg motor. That is the end of your egg closest to the Eggbot's headstock. With this orientation in mind, if your text is plotting upside down then change the "Reverse direction of Motor 1 (egg)" setting. This setting is under the "Options" tab of the Eggbot Control extension. After changing the setting, click the Apply button to save your setting. Note that after doing an upgrade of the Eggbot extensions, it is possible for this setting to get lost. In that case, simply set it again and save it with the Apply button.

Circles look elliptical

Are your circles or other figures looking squashed? This can be expected once you realize that the Eggbot doesn't attempt to do any special transformations on your drawings when it plots them. As such there's two immediate sources of distortion when plotting your drawings. First, the horizontal component of line segments become physically shorter as they approach either pole of your drawing object. This is a consequence of the diminishing circumference of circles of latitude with increasing latitude (i.e., decreasing distance from either pole). A second effect comes into play when plotting on non-spherical objects such as eggs. Eggs are longer in one dimension than the other. Typically longer from pole to pole than they are wide. This means that a single step of the pen arm produces a longer stroke than a single step of the egg motor. As such, a vertical line in your Inkscape drawing can produce a longer stroke than a horizontal line of the same length, even at the egg's equator.

To counter this effect, you can try horizontally stretching your drawing by upwards of 150%. To do this

• Use the "Select All in All Layers" item of Inskcape's Edit menu.
• Then, under the Object menu, choose the "Transform" item.
• In the sub-window which appears on the right edge of the Inkscape window, select the "Scale" tab.
• Set the horizontal scale factor to 150% and the vertical to 100%; ensure that the "Scale proportionally" box is not checked.
• Click the "Apply" button.

Ends don't meet in plots

When the ends of figures do not line up, this strongly suggests an alignment or slippage problem with how your egg has been secured into the Eggbot chassis. To check the alignment, rotate your egg with the motors disengaged and see if there is any perceptible wobble. Sometimes it helps to life the Eggbot up and sigh down the long axis of the egg as you turn it. As regards slippage, the egg needs to be held in tightly by the tailstock spring. That spring should be compressed around two-thirds or more (but not fully compressed). See improving precision for many more tips on improving your plots.

"Paste in place" results in a bitmap copy (OS X)

"Paste in place" doesn't place the object in its original location (OS X)

On Macs, if your "Paste" or "Paste in Place" operations are resulting in bitmaps being imported into your Inkscape drawing, then you need to change your X11 preferences. X11 is the windowing system which Inkscape runs to manage its windows. If you click on any running Inkscape window, you will see in the Apple menu bar along the top of your screen the menu item "X11" just to the right of the Apple-icon menu item. Click on the X11 menu and select the "Preferences..." item. In the resulting popup "X11 Preferences" window, select the "Pasteboard" tab. In the resulting option set, unset the item "Update Pasteboard when CLIPBOARD changes".

Another symptom of this problem is that the "Paste in Place" operation does not paste the copied object back to its original location; instead it appears elsewhere on your drawing page. Furthermore, you can check to see if a bitmap was pasted by looking at the "Edit" menu. If the "Undo" item indicates that an "import" was done, then a bitmap was imported.