Re: [CAD_CAM_EDM_DRO] Re: Better servo performance: Ameteks at 60V, 80V ?

The next version of TurboCNC is supposed to have stepping rates well in
excess of 25 K steps/sec.

On Thu, 2003-09-11 at 00:04, Doug Fortune wrote:

>
> Here's my nickles worth (2 cents after taxes...):
>
> DeanC ( http://www.axxustech.com/ ) once told me, the supplied voltage
> to the Ametek motors could be increased (while limiting the maximum
> step rate in the software). I think he was monitoring the voltage
> at the motors, at the variously faster step rates.
>
> Of course, you have to use restraint, because then increasing the step
> rate of the software, increases the voltage seen at the motors (perhaps
> beyond their tolerance). Please contact Dean directly if you have questions
> on his method.
>
> I have no experience with the 40V Ameteks myself, but to answer your second
> question (in my 90VDC 2500rpm motor context):
>
> - Using a 75VDC powersupply driving the 80VDC max Gecko G320/G340 there
> is no over-voltage concern. However, the maximum rpm is then limited
> to 2500rpm * 75VDC/90VDC = 2083 rpm = 34.72 rps
>
> - Suppose your step engine (either software or hardware) can emit 25,000
> steps/sec max. Then an optimal rotary encoder (I'm assuming the encoder is
> mounted on the motor shaft) would be 25,000/34.72 = 720 steps-in-quadrature / revolution
> (or 720/4= 180 CPR cycles per revolution).
>
> - Suppose you actually had a 200 CPR encoder. Your step emitter source
> will be limiting your fastest speed to less than the theoretical maximum motor speed.
>
> - If you wanted to get the maximum speed from your motor (with your 25K step source),
> you would need to DECREASE your resolution down to 180 CPR. However, 180 CPR
> is uncommon, so you might consider a 150 CPR = 600 steps-in-quadrature encoder.
> Then your performance (but not your resolution) would be optimal under the
> circumstances (the circumstance being: voltage, motor rpm at that voltage,
> the max frequency of your step source, and the encoder resolution).
>
> Hope that helps.
>
> Doug Fortune
> http://www.cncKITS.com
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