On Saturday 11 August 2018 17:02:49 andy pugh wrote:

> On 11 August 2018 at 21:37, Gene Heskett <ghesk...@shentel.net> wrote:
> > Quite simplified, covers the basics but makes little or no mention
> > of the resolvers speed limits. So in both cases, the encoder is
> > king, and much cheaper to implement.
> Resolvers are absolute and much tougher.

It appears that Omron's use of precision bearings seems to addressing the 
toughness aspect. Mine, on the rear of the spindle motor with as high as 
a nominally 14/1 speed, seems to be bulletproof of anything but a 
setscrew in the drive untightened from the last re-assembly. I haven't 
tried it, but with the index still coming from the spindle, I'd imagine 
I can orient the spindle for a tool change to well with a degree. 
Meaning its absolute once an index has been seen after I change gears. 
And with the same type of logic chain as the tach and pid correction is 
done, either gear should be more than accurate enough to allow the next 
r8 to slide in and engage its drive pin. mpja has a small motor with an 
8" or so length of travel that should have the moxie to lower an r8, 
another smaller one to swing it halfway, then raise it to the top and 
swing it on over to the carousel and lower it into and empty socket 
there, a third motor moves the carousel to the next tool needed, engages 
it in the transfer arm, lifts it out of the carousel, swings back 
halfway, runs to the bottom of its travel, swings under the spindle, 
then lifts the new tool into the spindle, turning on the rattle wrench 
to loosen the drawbar, and tighten it again at the correct times.

First thing I'll need is a big sheet of 1/2" alu plate, bolted to the 
back of the post, to mount the bearings for both the carousel, and the 
transfer arm, shaft and serving as a reaction anchor for the motors that 
move stuff.

Oh, and another, shorter motorized screw anchored to the top of the post 
to lift the rattle wrench out of drawbar engagement. Or a fixed mount 
that engages when the Z is raised to the top of the post. That would 
only cost me the top half inch of Z, and I could lose that unless the 
drill is too long. So that shortcut is likely ruled out.

Thinking out loud...  Time to see if I can find some decently hard 1/2" 
thick sheet alu. And ask mpja just how much travel that particular 
motor/screw has since the little flyer doesn't say. And see how many 
outputs I have left on a 5i25's P2. Might have to spend another $200 for 
another 7i90HD & 3 ea 7i42TA's in order to get enough i in the i/o. In 
fact I'm sure of that.

> As for speed limits, that really only comes down to excitation
> frequency.

And the a/d conversions. High resolution takes time. And dual slope for 
accuracy is likely waaayyyyy too slow.

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)
Genes Web page <http://geneslinuxbox.net:6309/gene>

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