[MikeA]

I am in the process of building a 24" x 30" router basically for fun, since I have a commercial unit already. I have utilized linear rails and ballscrews from a previous commercial machine I had, so this thing will be stout and light on friction. That being said I want this thing to scream as far as rapids and cut speeds. The ball screws are an aggresive .5" lead so here in lies my questions. Much has been said about steppers but I am going to use servos.
How do you gauge the maximum amount of rpm you practically use on a servo motor even at rapids? I have read that you never will reach the maximum and don't want to, so is there a percentage that is the comfort zone or calculating zone for gearing?
I intend on using geckos, so my next question is power supply. I know for steppers you take the rated voltage and increase exponentially, how about with servos?
There are a wide spectrum of motors available and keeping in mind rapid moves, what criteria is felt is best? Smaller motors with higher rpm geared appropriately? Larger slower motors less ratio on gearing or even direct drive?
I currently have in my possession 36v 2.3 amp 3000 rpm motors, and 7500rpm 9.0 amp 24 volt motors which is better?
My next question is in regard to encoders. I haven't really done any research but I will ask here anyway. Do you base the count on a relationship to motor speed or do you want it to tie in to actual travel (did that make sense)?. If I use a higher speed motor with a higher gear ratio the motor will of course turn more revolutions to move the router a set distance than would a slower motor with a lower ratio.
Any other thoughts on setting up a servo system would be appreciated, Mike.