I WANT to backdrive a ballscrew

[macona]

I am doing a partial CNC mod on my Monarch 10EE lathe. I want to keep it usable as a manual lathe as well. What I want to do is use a higher pitch ball screw for the carriage and be able to back drive the screw when I am using it in manual.

What pitch would I need to use to keep resistance down?

I am driving with pretty high resolution AC Brushless Servos so I can belt them down quite a bit to bring up the torque. Max speed of ~3000 RPM at 400W output. I figure I could use an electromagnetic clutch to separate the screw from the motor gearing if need be.

[samco]

10EE are great! We have toyed around with cnc'ing ours also. (some would think that would be sacrilege). I (in my opinion) would not be worried about manual use. If you really think you will be manually running the lathe - get 2 jog wheels and have some 'virtual' knobs.

Similar to
http://www.centroidcnc.com/cncvideo/videolathempg.html

sam

[macona]

Yeah, the EE is a great machine. Got it last summer and have gone through it. In the process of replacing the motor-generator drive with a AC Brushless Servo.

I am planning on doing the conversion so it is as unnoticeable as possible so I dont want to go that route. I want to be able to use it totally without a computer. For the X axis I plan on mounting a ball screw assembly in the place of the taper attachment mounting in the same location.

I just remembered I have a ballscrew that might work for Z. If it will not backdrive easily I will come up with a locking slide where I can just unlock the carriage from the ball screw.