Improving precision

If you're getting sloppy drawings, you may need to do one or more of the following:

• Slow down your pen speed. The faster the pen is moving, the more vibration (and thus slop) you'll have when the pen stops moving. By slowing the speed at which the motors turn, or the servo lifts/drops the pen, you'll improve your drawings. The correct speed will depend upon your medium (egg shells, glass, etc) and your pens -- you'll need to experiment.
• Use a smaller/shorter pen. The pen arm grips your pen very close to the bottom of the pen. While this generally gives better precision, gripping the pen below the center of mass means that there will be more sway, particularly when the pen has been lifted or is being lowered.
• Clean your medium before plotting. If you remove surface dust and oils before drawing, you'll get a sharper plot.
• Maintain your pen(s). Clean them frequently, and don't let them dry out.