Re: robotic workcell design

The main reason I suggested linear rails and carriages is because you
can bolt them directly to the extrusion for a very easy motion
solution. My shizuoka uses box ways...I don't see how box ways could
be cheaper than linear rails/carriages. Also, with box ways, if you
lose lubrication things get nasty pretty fast. When I visualized
this gantry, I pictured something that could be transported by two
individuals and did not require a lubrication pump :-)

The dead cheapest solution would be 3/4" ground shafting (about $15 a
foot from MSC) and Thomson Frelon 3/4" bearings (about $11 each).
Those bearings don't require lubrication and can actually operate
with *heavier* loads than the ball bearing type. They are maybe not
as accurate as the ball bearing type. Things get much harder if you
want to support the shaft. I was amazed at how much an unsupported
18" section of solid 3/4 inch shafting deflects when force is applied
in the center. Still, for a light duty machine, maybe?

I would not mind coming up with a 3 axis servo controller that
plugged into a PCI slot. There are very nice PCI bridge chips out
there now, and there is even a $199 card with a bridge and FPGA that
includes a core for a servo controller. The problem is that it would
be a lot of work and worthy of a series of articles by itself. :-)

I hate steppers, but maybe for a first run...


Circuit Cellar is another decent magazine that might be interested in
this type of article.


Rick