CNC stepper size/reduction

Hey folks, I'm making a homespun CNC conversion on a large mill/drill. RF45, not a full blown production machine by any means but still a fun jobbie.

I've got some 116 oz/in steppers for the CNC conversion and was wondering if I could get away with putting these right on the axes or would I want to "gear down" the motor through different sized timing belt pulleys.


Long term, servos on a larger machine. This is a low dollar learning experience for now.

Thanks,
-d

I can calculate the "break away" torque for the machine if you can give me the following details:
Dovetail slides? Aproximate width and travel.Screw pitch (turns / inch). Is the screw acme or ball? Provide me with this and I will plug it into my servo motor sizing program for milling machines and give you an answer.
Tracy

Machine in question is dovetail slide,
8"Y x 24"X leadscrew=10pitch, acme.

Thinking of moving up to 740o-i or 1050o-i

As a point of reference, MicroKinetics uses 470oz steppers for the X and Y Axis, and 160ox for the Quill (Z).

http://www.microkinetics.com/cncdmill.htm

George

the microkentics reference is mute because they are utilizing ballscrews which usually run at around 90% efficiency..where as leadscrews are lucky to achieve 20% if Im not mistaken.


Youre going to need to determine the maximum pullout torque you need in the worst case scenario, dependant on what you plan to mill with it, in order to determine the correct stepper sizing. If you dont know how to determine this, then GOOGLE to find someone who has used steppers on a RF45 or RF clone and worked, and go by that.

If you get too large of a stepper, the steppers will more than likely overheat and let the magic smoke that makes them run, come out, resulting in nice sized paperwieghts.
If you get some that are underpowered then you will lose massive steps(resulting in severe positional innaccuracy ....or when sent pulses the steppers/mill will just sit there doing nothing but humming a pretty tune to you.

If I were you.Id be thinking more along the lines of servos instead of steppers.. A little more complicated to setup but well worth the trouble I hear.