[CNCCajun]

This is a snippet from MultiCAM's page . . .

They use this hemisphere device to hold sheet metal on a plasma table because the speed required to cut this thin of metal combined with warping caused by heat makes a Torch Height Control System impractical.

These thing fly on top of a plasma table . . . 100s of inches a minute . . .

Steve

[jimcolt]

HVAC cnc plasma machines have been in use since the mid 80's. They use a roller ball plate rider because 1. It is lower cost than a good quality arc voltage height control, 2. When these machines were developed in the 80's....height controls could not handle the cut speeds required (400+ ipm on 26 gauge). 3. You can pierce and cut materials thinner than 3/16" at the cut height.

If you buy a machine specifically built for HVAC cutting today (Vicon is the largest supplier, there are a few others) you can get it with a roller ball plate rider, or for more versatility (the ability to pierce and cut thicker materials, no scratching of the surface) with an arc voltage based height control. The height controls as used on industrial machines today have no problem with maintaining accurate height at high cutting speeds.

Jim Colt Hypertherm

[ger21]

I believe that you'll find a similar setup on a router somwhere in this thread.
http://www.cnczone.com/forums/excite...30_router.html