I just ran a test on Rockford rolled ball screws and their double nuts, using my DRO over 28 inches on the Z axis of my lathe that is being converted to CNC. Just for fun we loaded a 19 inch chuck and a 8 inch kurt vise in the cross slide to possibly duplicate weight and some cutting pressure.Using a simple Z program, back and forth at 51 ipm 22 times, then to home and back to 28 inches, a recorded error ( maxium) of .00087 was noted. It always returned to home at .ooo,(?), the biggest error at the 28 inch stop.The ways and ball screw were well lubricated.Unless you are making a commercial machine that must repeat at .0001- 24 hrs a day, I would say that a well set up system,using rolled ball screws and double nuts, would be fine for your application.Most errors occure due to poor bearing mounts, to include every thing that NC cams has pointed out many times concerning the correct way to engineer the mounts and pre-load.You could spend thousands on ground ball screws, but have horrible errors with out the correct bearing set up.
Adobe Machine ( old as dirt)  |