On Sunday 04 February 2018 21:20:11 Gene Heskett wrote:

> On Sunday 04 February 2018 18:50:50 tom-...@bgp.nu wrote:
> > That is a good question, and one we have recently asked ourselves. 
> > In fact we changed our threading routine to fix the RPM because at
> > least then the spindle is not constantly accelerating and
> > decelerating. But, to be honest, CSS should work fine, all it does
> > it change the spindle speed for a given diameter.  It does add a
> > variable to the synchronization though (since it needs to
> > accel/decel).
>
> True, and in either case, g76 or g33.1, I never start closer than
> around 5 turns off the end of the workpiece. And once you see its not
> carving up the fixtures you must resist the temptation to up the
> spindle speed and get it done, for that, find some scrap in the
> corner, if it works, then crank it up and do it right.
>
> (but on coarse threads, stay below 50% of the axis speed capability.
> It must have that reserve to get properly synchronized)
>
> I just replaced a bob in my mills setup. Between the first bobs piss
> poor opto speeds, and the inductance of a 1600 oz/in motor, my z speed
> was maxed out and in danger of a stall at 27 ipm. Replacing the motor
> with an 8 wire 940 wired in parallel, driven by an ac powered driver,
> got me to around 65 ipm. Just recently I replaced that bob with a $22
> fleabay Sainsmart, no opto's in its outputs, and that same motor is
> now lifting the G0704's head at 110 ipm. The diff is the lag of the
> opto's that aren't there anymore. I still had to bypass the opto's in
> the encoder inputs, but then a 1000 line encoder on the back of the
> motor, which gives something over a 7000 for a scale, quit working
> with the opto's at around 275 real rpms. Without the opto's it tracks
> perfectly to 3000 rpms.
>
>
> Temporarily at least, I am a happy camper. Till I decide to find out
> how much faster I can move the xy's, (I might get them above 100 ipm
> too!) but ATM I am trying to see if theres a chance of a snowball in
> replacing the pi running the big lathe, with a rock64.

Having brought the subject up, I went out and played with the mills .ini 
file. When I sat down to do that, it was maxed at around 70" for xy. And 
around 90 for z. When I turned it and the lights off and got up, it had 
been moving at 140 ipm for the first 3 axis's for several minutes. Thats 
taking advantage of the much faster pulses coming out of the sainsmart 
bob.  It does make a difference! And I'll goto bed with a satisfied grin 
on my face. :)
>
> > However, even with fixed RPM we still cut better threads if we start
> > well off of the start of the thread giving the machine more time to
> > synchronize.  That is, when we start threading from 0.25 to -1 we
> > get better threads then we start threading from 0 to -1. -Tom
>
> Thats to be expected, and in round figures for the thread sizes I've
> cut, a good starting point. Bigger, coarser threads will need more
> room of course.
>
> > > On Feb 4, 2018, at 2:08 PM, Gene Heskett <ghesk...@shentel.net>
> > > wrote:
> > >
> > > On Sunday 04 February 2018 13:52:33 andy pugh wrote:
> > >> On 30 January 2018 at 22:42, <tom-...@bgp.nu> wrote:
> > >>> We read that G33 will wait for spindle-at-speed before looking
> > >>> for the index pulse.  But our spindle-at-speed signal seems to
> > >>> be high during the full cycle once the spindle speeds up the
> > >>> first time.
> > >>
> > >> How is your spindle-at-speed signal calculated?
>
> This is still a good question, Tom.  If using a wcomp, how is it being
> setup in your hal?



-- 
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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