On Tuesday 08 September 2015 11:34:47 andy pugh wrote:

> On 8 September 2015 at 16:22, Chris Radek <[email protected]> wrote:
> > Tapping/threading will cause additional index resets later on - this
> > won't hurt orient, right?
>
> I would think that things were badly broken if it did. The spindle
> index really ought to be in the same place every revolution.
> I guess that with a long index it would be in a different place
> forwards and backwards, but you would have to make sure that you were
> consistent.
>
> > and it would be nice if there were a way to do the same here
> > (motion.spindle-is-homing?  motion.spindle-jog?)  Not sure how
> > important this is.
>
> I would expect a spindle.is-homing pin to be created to match the
> axis.N.is-homing.
> (Which in your case would need to be used to mask the spindle speed
> command)
>
> >  Is there a reference implementation somewhere I
> > missed, or are people creating this on their own?
>
> http://git.linuxcnc.org/gitweb?p=linuxcnc.git;a=blob;f=configs/sim/axi
>s/vismach/VMC_toolchange/spindle.hal;h=867a593045fc6a20a227b08173f632ec
>583db328;hb=HEAD

I'd expect thats been solved about as many ways as needs to solve it.  
The index pulse of the encoders I have made is generally the same width 
as the A/B pulses. And its almost in time and consistent enough that 
long sessions of G76 or G33.1 have never given me a hint that it was 
getting out of time.

But for a tool changer situation, I'd have trouble moving the spindle 
that slow without just pulsing the power for a millisecond at a time, 
perhaps 10x a second until the index was found, strong enough to 
overcome friction.  50 rpm commands are ignored on my 2 machines that do 
have an encoder, minimums for steady rotation seem to be around 80, 
although I did play some tricks with the PID's bias input in the hal 
file that got that down to about 30 rpm, but its so low powered it 
usless for anything but centering a 4 jaw because you can grab and stop 
it at the idicators high or low point and adjust the tension of the 
jaws.

It seems to me from following this list that most have solved the tool 
changer orient problem by activating a stop striker at the correct 
location and running it slow till it hits the stop. If that striker is 
part of the tool changer, just moving to the changer would engage it.

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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