RE: [CAD_CAM_EDM_DRO] Steppers vs Sevrvos?

Another thing:

Servos don't drop steps; steppers can. - Since the servo has some kind of
position feedback, it eventually gets to the point to which it was commanded
to move. Or, if the torque requirement is too great, it shuts down and lets
the operator know. Stepper motors, OTOH, simply drop a few steps along the
way and never let the user know. Now, if your motor design is good, there
will be sufficient torque so that you don't lose steps in normal operation.
But, everyone eventually tries to "speed up" the operation and can have
problems when they do so.

-- Jerry

| -----Original Message-----
| From: info.host@... [mailto:info.host@...]
| Sent: Monday, August 06, 2001 8:47 PM
| To: CAD_CAM_EDM_DRO@yahoogroups.com
| Subject: Re: [CAD_CAM_EDM_DRO] Steppers vs Sevrvos?
|
|
| Warp speed Mr Solo! Servos move much quicker. Steppers clunk from step to
| step and they have a holding current. That means that all the
| time they use
| the same current to make sure they don't get knocked off the step they're
| trying to hold. Servos don't use steps so they don't have a
| holding current,
| unless the motor is under force to move out of it's desired position. Even
| if a stepper has no force on it to move off it's step it will
| still be using
| power to hold the step. Advantage number one.
|
| Advantage number two, servos are 'smoother' since they don't use steps,
| quieter running. Some time you'll really wish you had gotten some quieter
| motors when the neighbours batter your door down for milling a scale model
| car's axle at 2am.
|
| Now come the disadvantages, of which there aren't many, but they are big.
| Servo controls, if you buy one new, are expensive! Much, much more than
| steppers. I was asking this same question a few days ago and it was
| suggested I try ebay. I have found it impossible to ever find
| four identical
| servos of the right torque and style on there. Many of the servos on there
| are for remote control planes etc and won't do. Dan from Camtronics is
| selling servos at the moment for $99 that he has used on his Sherline. He
| controls each with a G320 (Gecko). The motors he says will take
| up to 25lbs
| which is... is it 100oz? I could buy some steppers for $35 and power /
| control them with a simple $150 circuit and supply. It depends what you
| want, if you have a little extra and you're only using them on something
| small servo's wouldn't be too bad I think. Servos seem a little
| more complex
| to me than steppers. I'm still trying to figure it out myself.
|
| John
|
| > What are the +'s of Servos over Stepper motors and vice versa?
| >
| > Regards,
| >
| > Steve G.
| >
| >
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