Incomplete polygons – a dramatization
One commenter posted that it took him a little while to really get the “incomplete polygon” or “open hole” method1 thought up by Zach to avoid oozing and threads around interior holes in objects. Above you can see my dramatization of how this works. 2 With a normal closed polygon hole, Skeinforge lays down a regular path all around the edge of the interior hole. However, the plastic extrusion is much thicker than the ideal mathematical path plotted out by Skeinforge. As a result, it can cause little blobbies to appear inside the hole.
With the method depicted at the bottom of the diagram shows how creating an incomplete polygon/open hole method means that the only real bit of blobbies that occurs with an extrusion is where the two sides of the incomplete polygon meet. And, if that gap is small enough, say 0.1mm or less, then although the Skeinforge path is drawn with them very close together – they end up fusing together. The end result is a complete polygon or whole hole3 with little to no blobbies inside.
Zach Clarification: The main reason this technique works well is because of the outline continuity. Current DIY extruders are not very good at precisely starting and stopping exactly when we want them to. When you have an outline + 4 holes, the extruder must start and stop 5 different times. The effect is that your holes do not come out very nicely. When you use this technique, you have one continuous outline and your holes have much better definition. Furthermore, since the gap is so small, the tiny gap ends up getting bonded anyway and you end up with nicely defined, gapless holes.
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