A week or so ago I sat down in OpenSCAD and spent some time modelling something I've wanted to make since I got my Makerbot almost a year ago. For a while, I hadn't made it because OpenSCAD's compiled binaries didn't support extrusion, which I needed to create a twist-y backbone. For a while after that, I was exceedingly busy with marriage and mousetraps. I still am busy with mousetraps but we all need a holiday now and then!
So, when I successfully printed my first DNA molecule, I was happy with the results, but I knew (being a geneticist and perfectionist) that it was only a sculpture, and that the real thing wouldn't print correctly on my Makerbot. The angles were too steep in real DNA, so I settled for a sculpture of the real thing for then. And what success! Three people have since printed their own DNA molecules, as can be seen from the Thingiverse page, and their copies are even prettier than mine.
But, I wanted more, so I recompiled the model using parameters matching real DNA, and created the updated “B-DNA” model, which had the correct diameter-to-turn-length ratio, the correct number of bases per turn, and the correct angle of the bases (about -1 degree from horizontal!). This model I put on my Shapeways store, and ordered immediately in their standard plastic material to see if it would work.
Today, I got it! The picture is of the model I just received. It's smooth and sturdy, slightly flexible too (unlikely to break!). At last, a perfect little model of my favourite molecule, something I've always wanted! Better yet, someday I can order it in gold-plated steel when I've made my fortune on DNA. :)
For those who have a Makerbot or a RepRap, the DNA model is here for printing, editing and sharing. It's under a Creative Commons Attribution, Sharealike license, so you're free to copy, edit, share and even re-publish the model as long as you give proper credit for the original model to me, and share your own derivatives under the same license.