motor speed/gear ration

I am building my first CNC system and I can't seem to find what speed servo's
should be run at. I realize they can cover a wide RPM range but there must be
an ideal range. I am trying to determine my physical design so I need to
select a configuration/gear ratio that will work best for the motor.

I will be moving a 35-50lb carriage on THK linear bearings, travel will be
~40" @ 250 inches per minute. I have considered using a .2 or .25 lead ball
screw setup with a bayside reduction of ?? or possibly a rack/pinion setup due to
the high IPM rate if I can find a zero backlash option.

The pulling force should be rather low but I have no way of determining an
exact number.

I don't know if I should make the setup so it's running the servo at 200RPM
or 2000RPM???

Does anyone have an idea how much distance it will take to get the carriage
0-250 ipm and then back to 0 on the other end without beating the system to
death.

Thanks, Brad


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