On 1/4/24 10:08, andy pugh wrote:
On Thu, 4 Jan 2024 at 13:39, gene heskett <ghesk...@shentel.net> wrote:
Humm, that may call for a higher resolution spindle encoder than I have
on my Sheldon,
I have a resolver on the spindle of my lathe, which the Mesa 7i49
converts into a 14-bit number, so should have enough resolution.
(linearity of the resolver is not something that I have ever tested)
The linearity may not be the most important characteristic, although in
a lathe where the chuck is relatively massive it shouldn't matter that
much for steadily turning use, but in for instance a 3d printer, all
those conversions take time, which has bad effects on the nyquist
stability of the feedback loop regulating that speed. in the lathe case
it might mean a following error because by the time that position is
known, the spindle has turned further. This is not a problem with a
quadrature encoder as the position and direction is known fresh with
every edge that goes by. No time lag.
About 3 years ago one of the Chinese motor makers came out with the
ideal sized nema 17 motor, using a hall effect as the feedback
generator, while the hall effect can work at several times the optical
accuracy its always working with stale data, so it jerks to catchup.
Everyone who put the 42C motors on their printers, took them off the
next day as their prints looked like they were shingled. That motor is
a good motor, for something that needs a programmed position and
stopped. Great for a smaller tool changer. The same motor with an
optical encoder moves so smooth I had to grab the printhead to verify
klippers "stepper_buzz" motor tester was indeed moving the motor 1mm
back and forth. Originally intro-ed at about $35 to $40 USD, now they
can't give them away at $9.95
But I don't quite understand why you are worrying about whether you
can make Capto shanks on your Sheldon?
Take care, stay warm and well.
Cheers, Gene Heskett.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
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