Re: [CAD_CAM_EDM_DRO] I'm curious

I have used Compumotor and Pac-Sci drives for several years, True the
compumotor drives do offer some silly microstepping (somewhere around
16,000 steps per rev IIRC, been a while) but it's not likely to be seen
in the final drive. Frankly, anything over 10 microsteps is flat out non
repeatable by 99% of the modern motors. It's quite simply a hollow
number, now tell me more about your telescope drive, the last few I
built didn't need fast slewing, and (so far) have faired quite well,
using Gecko drives, too!. The gecko servo drives ARE closed loop (as you
dont' specify where to close the loop, I pick at the drive) tell the
drive to move x units, it either will or will issue a fault. those are
the only two options with any servo drive, not just the Geckos.

Funny thing, I retrofitted a router a few months back, was basically
built for a stepper drive system, about .5" per rev of the pinion gear.
Then in a fit of 'specmanship' was fitted with AC servomotors with some
ridiculously high encoder count, ~2048 spr (read in quad) or ~20,000
pulses per inch. Question, do you think that this router can resolve
40,000 discrete steps per inch? When retrofitted with a Gecko, 300w DC
servomotors and some (badly needed) gear reduction, it will now resolve
~10,000 spi, however the actual resolution is swamped by several
cyclical errors, due to the non cocentricity of several of the pulleys.
I was able to minimize it by a magnatude or two by careful tightening of
the hubs (clamping hub L series belts), but it is still the dominant
error mode in that machine. Now, do you honestly thing an error of half
a thou is that critical on a machine routing MDF 16 hours a day?
Customer said yes, paid accordingly; reality says I can induce 2-10 thou
of error by increasing the humidity of the material post cutting. Hell,
I can get the machine to grow nearly 1/8" over the 12' length by
measuring in the early morning and then again in the scorching
afternoon......


erie

>And I couldn't just "Drop one in" because it wouldn't drive at the
>resolution I require.
>Some said; "there's a reason it's on eBay". I guess they were referring to
>obsolete drivers, well the S and Zeta's certainly are not. Even the obsolete
>A and M Series drives far outclass the Gecko type drivers that seem
>prevalent here (A series only microsteps 25000).
>
>I guess my curiosity really had to do with understanding the thought
>processes here.
>
>.... I was about to formulate another question, but I don't think it get
>satisfactory response here.
>
>
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