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Hypocycloid Robot Arm Joint

by bkorsedal Jul 26, 2010
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This looks fairly interesting, but some documentation regarding assembly, ideally listing the needed parts, would be helpful. I also really appreciate it when folks upload STLs so that you can look at them in Thingiview, even if those STLs are not at all intended to be used and merely for illustration. You mentioned this was part of a larger project; did you get any farther on it?


There are several openscad scripts here on thingiverse which output dxf to be used as cutting templates lasers etc.

All the ones I've seen output a bunch of line segments. I have no idea how well a laser will parse it.

I can save a design to .dxf but I don't really like the output.

In OpenSCAD, all you need to do is pick $fa and $fs for sufficiently small detail and the laser's kerf takes care of the rest. The laser cutters operate in a cartesian coordinate system anyway, so you don't gain anything beyond a reduction in file size by capturing DXF using more complex constructs.

Export DXF from OpenSCAD and open the resulting DXF directly in InkScape. Set the colour(s) and line width as per their submission template requirements and you're set.

O.K. I guess I will try it with just a single reducer and see if it works.

Is there any way to extrude an object in OpenSCAD similar to how extrude works in inkscape? By extrude I mean if I extrude a circle with a diameter of 1 inch by 0.1 inches then I have a circle with a diameter of 1.2 inches. If I extrude a 1 x 1 inch square by 0.1 inches then I have a 1.2 x 1.2 inch square with rounded corners.

The reason I need this is because I need a really precise cut. The lasers I've used before have a beam width of about 0.22 mm. This might seem small but it makes a big deal in the fit of all the parts. I need to account for this beamwidth.

The usual way I do this is in inkscape. I take an o
bject and extrude it by 0.11 mm. This works perfectly (I have measured the parts with calipers to get the last 1/100th of an inch correct).

Without a really good fit, this design will not work well. Inkscape cannot extrude the .dxf's properly because they aren't solid shapes. They are just a b
unch of line segments.

Any suggestions?