servo motor

[eloid]

can someone correct me but do servo motors have constant torque for wide range of rpm. If so why dont we see more people using them?

[ger21]

Fairly constant, yes. The reason that steppers are used more is because they are much cheaper. A 3 axis servo system will usually be about $800 and up, while you can get a HobbyCNC board and steppers for about $300.

[eloid]

whats involded in tunning servo for x, y? need someone to
explain whats different than stepper set up..

[unterhaus]

you will rarely see a stepper system that can overshoot. A servo system can be underdamped, and oscillations are possible. You generally want to be critically damped if at all possible. Need more info to give a better response than that.

[MaX-MoD]

the controller compares the wished position end the actual (real) position, and function of this applies more or lesse current (ie. torque) in the servo.
You'll usually have 3 parameters to tweak: P, I and D
google PID and you'll find more bout it.

usually servo are better because you don't suffer of the steps missing, have a more silent motor, no vibration (if well tuned), more speed etc. etc.

steppers are cheaper thought.
and don't be fooled by the microstep, they don't really makes your steppers more precise, just less vibrating.