RepRap: Blog

"Thou shalt raise up the foundations of many generations, and thou shalt be called, the repairer of the breach, the restorer of paths to dwell in." Isaiah 58:12

Well. It seemed appropriate...

Inspired by Nophead's outstanding experimental results, I've added code to the Java host software (in the repository here) optionally to put foundation layers under a build. This works particularly well with ABS (above - not yet up to Nop's quality, but servicable). I suspect it should also work with PLA, though I haven't tried that yet.

The host starts by putting down several widely-spaced hatch patterns on top of each other, then a narrower pattern, but still with horizontal gaps, then finally a hatch at the normal infill horizontal hatch gap. This last layer, though, is not the standard height-gap above the previous one, but less. This means that it is forced into the gaps in the previous layer, giving a very strong bond. The first layer of the part is then plotted where it should have been had the gap not been reduced, giving a bigger gap than normal between the part being made and the foundations. Consequently it doesn't stick that firmly to the foundations and can be separated easily with a penknife blade.

Nophead has found that this process is sensitive to ambient temperature (hot days give more stick), so we may have to allow for that. He suggests simply lowering the extruder temperature by the same amount that the ambient temperature exceeds some norm (say 20^oC)

Foundations allow us to do two things:

1. Build on an absorbent or rough base to give good keying. This will prevent parts separating from the base as they cool and tend to curl up. The part above (the direct-drive extruder motor mount - see that link for what it does) came out flat as a pancake, even though ABS is prone to curl.
2. Experiment with layer separation strategies (like the changes in layer height that I mentioned). Once that is fully understood (or even before...) we can use the polymers as their own support for overhangs.