On Thu, Dec 10, 2009 at 06:34:01PM +0000, Andy Pugh wrote: > Neater still would be an air bearing arrangement. > Tighten the table down hard with belville washers.
That sounds inspired! OK, "hard" implies the washers wouldn't be series stacked, but parallel, I guess [1]. (I'm imagining one or more of them under a locknut on the tables's axle.) > When you want to rotate it, apply compressed air to the holes drilled > in the mating face that I forgot to mention earlier so it rotates on a > minimal thickness air-bearing. To clamp, turn off the air. Lacking fancy grinding facilities, I'd be tempted to try lapping the surfaces, to allow it to move with a "minimal thickness air-bearing", and lock with minimal jiggle. The simulation running in my mind locks tighter with a coned air bearing around the table perimeter, but if the cone is too acute, excessive air pressure is needed to free it. I wonder if 45° is anywhere near optimum? Now we just need one of those recirculating ball wormwheel contraptions to drive it with minimal backlash. > In case you doubt that this will work, it was how we clamped the tool > height adjusters on the testing machines I used to design. They were > for knocking balls off of ICs, and pulling out the tiny gold wires > from carrier to die. You were working under moderate magnification and > still could barely see the tool move as the air went on and off, the > clamping force was enough to scrape entire dies off of substrates, but > the sliding force when released was enough to not even mark the > substrate. (the process was release, land, clamp, back off a few > microns) Err, I'm not sure that I understand "land, clamp". I'd inferred that the great attraction of this approach is that landing is clamping? Erik [1] http://en.wikipedia.org/wiki/Belleville_washer -- "If you understand what you're doing, you're not learning anything." - A. L. ------------------------------------------------------------------------------ Return on Information: Google Enterprise Search pays you back Get the facts. http://p.sf.net/sfu/google-dev2dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
