Mike,
The choice between stepper or servo is almost entirely power; if your app requires 100W mechanical or less, use steppers. If it is 200W or more, use servos; if in between, either will do.
Both are equally reliable as to positioning; the stepper is both a motor and a position transducer, a servo seperates into a motor and a position transducer (encoder).
The G320 is a PID position servo drive. The "I" term (integral) does not permit the motor to be statically off-position by more than +/- 1 encoder count. If it is, the integral term multiplies the motor's corrective torque to its full stall value.
If the motor cannot generate enough torque to keep up with the moving command position, it will fall behind. If it falls 128 counts behind where it should be, the G320 "throws in the towel", shuts the motor off and indicates a "Fault" output.
This happens anytime you ask for more than 100% of what a motor has to give. A stepper will stall; a servo has to be shut down because unlike a stepper, it is willing, able and eager to destroy itself when overloaded. Unlike servos, steppers cannot be harmed by overload; they simply stall to shed the load.
When either is operated within their abilities, neither will ever miss steps or position. Both are equally reliable to go where they are told.
Mariss Freimanis
Geckodrive Inc.  |