[chuckknigh]

Well, it's a commercially available design, so overall rigidity can't be too bad. And, since errors are averaged in hexabot design, rather than additive like in X-Y-Z designs, the system should be able to hold to higher tolerances, without a vastly increased tolerance for each individual part. A homebuilder's dream. The downside is that there are no fewer than 6 steppers included in this design, and it's overkill for most folks.

My primary concern is not in building it, but in controlling it. Since posting my message, I've run through several dozen variations of this machine, in my mind. (Doesn't everybody do this?) Making it won't be a major problem...it'll be complicated, but not impossible, even with just a home woodworking shop.

My concern is that, as the struts move apart, they move in an arc...that means non-linear equations. They're not that hard to program, but does any easily available software support them? (And, does anyone have the math skills to figure them out? I've got a background that includes differential and integral calculus, but I'm rusty.)

It also means that resolution will be variable...increasingly coarse resolution as the base length shrinks. I think that's right...but that aspect is common to all hexapod designs, I think.

The genius of this unit is that it takes an already very flexible 5 DOF machine, and integrates a 6th DOF into its fundamental design. By rotating all the struts around the path, simultaneously, you get a rotational axis with minimal increase in complexity, and one which still averages the errors.

So, is anyone interested in helping me figure out the dynamics of this gizmo? ;-)

-- Chuck Knight