Thursday, May 10, 2007
RepStrap 'Acorn' Shapes Up
The box came out looking quite elegant. No boards sticking out strangely. I think we drilled the holes too far down for the Y axis, but that is easy enough to fix. I also didnt have a chance to get the required threaded rod, so I'll have to stop at the store to get that before Saturday. It took us about 1.5 hours to build it, and half of that was discussing what exactly we needed to do. It went very smoothly.
After that was done, I decided to make more nozzles. Two very important orders came in. First was the cross slide vice I ordered from Harbor Freight ($60) and 100 aluminum acorn nuts ($90). The cross slide vice was a LIFE saver. It took me 45 minutes to drill 45 nuts. I only broke two drill bits (0.25mm and 0.40mm) That is a pretty darn good break ratio for drilling 45 nuts (0.25, 0.30, 0.35, 0.40, 0.70) I'll be doing some 0.55mm and some 0.75 nuts on saturday I think. These will definitely be up for sale in the future since it is a bit tricky to get the right setup to drill them.
Anyway, I investigated a structure similiar to your Acorn a month or so ago, using an old strudy cardboard box no less. The only weakspot I found was the open face where it meets the open top. The open top is needed of course, but the second open panel on the face creates an opertunity for sway in the structure that Darwin doesn't have.
Darwin only has the open top, and all for sides are cross braced. I'm sure you noticed this, but if you do find swaying causing a problem, then bracing the open face would solve that. I came up with a large 'U' like frame that surrounds the open panel and connects to the top crosspiece. Sort of like a picture frame the surrounds the opening. Makes things much stiffer!
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