Re: Stepper vs. Servo

Doug,

Good evening! The main reason for picking a servo over a stepper is
power. If what you are doing can't be satisfied with a triple stack
34 step motor then it is time to look at a servo.

Servos have a lot of drawbacks compared to steppers much in the same
way a Ferarri has drawbacks compared to a Chevy.

Servos develop their power at high RPMs with modest torque compared
to steppers which have high torque at very low speeds.

Steppers are "plug and play" while servos require tuning to make them
happy and behave.

What you get for your trouble of reduction gearing, encoder matching
and set-up tuning is 3 to 7 times the power delivered to your machine
when compared to steppers.

If you require 7 times more speed, or 7 times more thrust or "push"
than what you are getting with steppers and you are willing to put up
with engineering a system rather than going with what "feels right",
you may be a candidate.

Continuing the Ferarri vs. Chevy analogy, performance comes at a
price. Either will get you from here to there, except one will do it
far more quickly than the other. The price you pay for that
performance is care in design and careful matching the motor to the
load.

Mariss

--- In CAD_CAM_EDM_DRO@y..., dougwalker13@y... wrote:
> Anyone build a gantry flame cutter?
>
> How do you deal with arcs and corners?
>
> Do you use constant feeds or varying feeds?
>
> I'm building a large gantry flame cutter. The work envelope is
approx.
> 65"x65".I've tried 5A camtronics drives and achieved 1000ipm rapids
> with 150oz/in nema 34 motors. Feeded moves below 100ipm become very
> cogy, and create excessive vibration. Tried gecko g201, and got
> 1000ipm rapids and very smooth feeded moves down to 10ipm.
>
> I've got dozens of various nema 23,34 motors from 50oz/in to
450oz/in.
> Assuming I settle on an approprite sized motor, and can assume that
> lost steps will not be a problem.
>
> What would be the advantage of using servos and gecko 320/340s?
>
> Doug