Universal gantry idea - here is something I came up with

After having the discussion about robotic workcells (or rather a
universal gantry) I spent the past few days with ideas rolling around
in my head about how to make a good design and yet a cheap design.

While rummaging around in my shop, I noticed the pool table slate
that I posted something about a few months ago. To refresh, it was
free (they tried to give me a lot of them, heh heh) and is a 1 inch
thick ~31 inch by ~50 inch piece of slate that has been ground or
milled flat. You can get them free because they come as a 3 piece
matched set for pool tables and sometimes one breaks in shipment. I
think they had a stack of 30 or so at my local dealer.

Anyway, I had mentioned the idea of using this as a base for a gantry
design, but then I forgot about it. Also, I didn't like the idea of
having to drill a bunch of holes in the slate. I guess it weighs
about 120 lbs or so.

Well, now I think I have a neat idea. Fabricate supports for 3/4"
ground shafting ($40 for a 48" section from Enco) that clamp to the
edge of the slate. I should draw something up in Rhino to make this
clear, but the picture in my head is a U-shaped channel with a gib
that is pressed against the slate by several screws. The top of the
U shaped channel would have a raised ridge that the ground shafting
would bolt to, and then open recirculating ball bearings ($25 from
enco) could be used. If you went for a moving table/fixed gantry
type design, you could bolt the y axis gantry structure to these U-
shaped channels, thus having a pretty rigid overall structure with
24" x 24" of travel. Just ballparking figures I bet the x-y of this
could be constructed with off the shelf parts for under $600 if you
used the 5/8" rolled ballscrews that are so popular on low cost
designs. I still don't quite see a way to a sub $1000 design, but
this seems a way to hit sub $1500 at least.

Opinions?


Thanks,

Rick (PS, I think my email spam filter was bouncing stuff, but it
should be working now)