[musicmkr]

I am interested in any comments on a concept that I've been developing for a bridge type 3 axis mill/drill machine.

My company machines tons of aluminum extrusions for use in an architectural application. I've been developing a 3 axis NC machine to do all of the drilling and notching required for one side of an extrusion in one setup. These extrusions are often over 25' long, and in order to use a linear motion system rigid enough for some light milling I was looking at several thousand dollars of rails and bearings, along with several more thousand dollars machining acceptable surfaces to mount the linear system. Plus all of that money would just be a waste since we only need to have an accuracy of +/- 1/32" (0.0312").

I would like to build this machine using a stationary Bridge (Y-Axis) and Ram (Z-Axis) configuration. However instead of having a traveling bed for the X-Axis I intend to drive the aluminum extrusion directly with drive rollers linked to a 1KW motor. A friction roller system obviously has the possibility to slip so to make sure the part has moved the distance requested my design would read the motion of the part with a rotary encoder. (See Sketch) By attaching two friction rollers to the same encoder I limit the possibility of slippage, and allow the end of the part to travel past the tool. This encoder will close the loop for the servo driver.

In order to home the machine in the X direction I plan to use a photoelectric through beam sensor to detect the end of the extrusion.

I would appreciate any comments or suggestions that you may have, and I would be extremely interested in anyone's experience with a similar application.