Re: [CAD_CAM_EDM_DRO] PWM input Servo Amp / Universal Stepper Controller

Hi Jon,

What are the "PWM servo amplifiers " purpose?


Regards
Jess

----- Original Message -----
From: "Jon Elson" <elson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Saturday, May 01, 2004 1:53 AM
Subject: Re: [CAD_CAM_EDM_DRO] PWM input Servo Amp / Universal Stepper
Controller


>
>
> jess@... wrote:
>
> >Ok I have a question.
> >
> >Someone posted a link to US Digital on another topic so I surfed over and
> >found heaps of stuff about Encoders ie that can be fitted to various
shafts
> >for motion data.
> >
> >Here is my question.
> >
> >Considering the cost of servo motors with encoders is quite astronomical,
> >what about a stepper motor say in the hi torque 34 42 NEMA size with
encoder
> >from US Digital to over come the problem when a stepper loses steps.
> >
> >
> Having an encoder will prevent an undetected loss of position. But, it
> won't help a stepper to not LOSE the steps in the first place. When the
> stepper
> skips a step, it often stalls violently. When a servo gets behind, it
just
> keeps trying.
>
> Astronomical? I got 2 servo motors with 1000 cycle/rev encoders on eBay
> for $27.50, and another one that needed to have a better encoder put on it
> for $9.99! My new PWM servo amplifiers will be selling for $100 per
> axis. (I may have to come out with a cheaper, lower power servo amp for
> the lighter machines.) Note that the torque on stepper motors drops
> severely at higher speeds, while the torque on a servo is maintained to
the
> maximum speed. People use 600 - 1100 Oz-In stepper motors to get
> 250 Oz-In at rapid traverse speed. A 250 oz-In servo motor will
outperform
> the 1100 Oz-In stepper in many cases!
>
> >But which controllers and drivers are compatible to accept encoder
> >feedbackloop while driving a stepper?
> >
> >
> EMC, using the Dan Mauch encoder card, or my Universal Stepper Controller
> are the only way I know of driving steppers with encoder feedback.
>
> Jon
>
>
>
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