Servos and gearboxes and cnc tables

[PlasmaGuy]

Hello,

I come from stepper background so servos are new to me. I am trying to learn about coupling a servo to a gearbox to drive a cnc plasma table.

1. Are planetary gearboxes the rule for servos?
2. What is the smallest NEMA motor that you would suggest for a 6 ft. wide gantry, 250.00lbs max weight?
3. AC or DC brushless

I told you I was a novice on these things

Thanks

Tom

[keebler303]

You want to gear down the motor so that at the machines desired max speed, the motor is going at its max (rated) speed. That will give you more torque (from the reduction) and so you will get the most power out of the motor by having it geared to use the whole speed range.

In high end commercial machines, planetary gear boxes would be the choice, depending on your drive method (leadscrew, rack & pinion, etc.), a timing belt reduction may be adequate and will cost MUCH less than a planetary gearbox.

How big of motor you needs depends on how fast you want to move your table. If you want to go at .01 inches per minute, maybe the motor out of cell phone will do. If you want to move at 2000 IPM, you will need a couple kW of motor. With some idea of the performance you want, someone could recommend a size of motor more accurately.

AC and BLDC are fairly similar, AC is a little smoother due to sinusoidal commutation (vs. trapezoidal for BLDC). I don't really know enough to say either way which is "better".

Matt