I have used this principal http://www.itemamerica.com/outside_catalog.asp for linear slide along an extrusion, I used the chrome steel rod top and bottom on the extrusion and also they supply matching roller sets to make up a travelling axis carrier.
One neat feature of some of the Item extrusions is they have galleries through the extrusion to pipe oxygen & gas to tap off for cutting torches etc.
( The item site go to Dynamic elements, Linear Slides, Shafts)
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.