On Friday 20 March 2020 00:41:23 John Dammeyer wrote: > > -----Original Message----- > > From: Phill C [mailto:[email protected]] > > Sent: March-19-20 9:36 PM > > To: linuxcnc-users > > Subject: Re: [Emc-users] A hal question? > > > > > On 20 Mar 2020, at 3:24 pm, John Dammeyer <[email protected]> > > > > wrote: > > >>> But it's here where I become a bit confused. A 60 tooth gear at > > >>> 1200 RPM produces 7200 edges per second or 1 about every 139 > > > > microseconds. > > > > >>> Say we're rigid tapping 8 threads which means a total of 57600 > > >>> pulses. If the hardware counter is 16 bit signed that's larger > > >>> than the 32767 before the counter rolls over. If it's a 32 bit > > >>> counter it's not an issue. > > >> > > >> I doubt if that would be a problem at 1200 because it would > > >> following error out from Z not being able to move that fast. > > >> Probably before the tap ever touched metal going in. Another > > >> problem would also rear its ugly heard is that the overshoot at > > >> the bottom of the hole would likely exceed the length of the tap > > >> at 1200. I got concerned about blind holes, and despite the belts > > >> yelping like michelin tires on hot blacktop, the overshoot at the > > >> bottom of the hole was over 3 turns at 300 rpms when swinging an > > >> 8" 40 lb chuck with a workpiece in it. Trade my 1hp motor for a > > >> 10 and a bigger vfd might speed up the turnaround but my place > > >> isn't wired for that kind of power. > > >> > > >> So I have modified most of my rigid tap routines to tell me how > > >> many turns and how far the overshoot is at that taps pitch and > > >> show me in the gui. So I can cut clear to the bottom of the blind > > >> hole w/o breaking the tap. > > > > > > Hi Gene > > > I can understand that one has to factor accel and decel into the > > > picture. > > > > The spindle won't stop suddenly and won't start instantly either. > > So the Z axis tracks the decelerating spindle and that needs to be > > factored into the depth of the hole of course. > > > > > The same is true for threading up to a shoulder. > > > > > > I have a spring loaded tap holder so even if there's a little bit > > > of error my > > > > system will ultimately not break the tap. Plus in the near future > > my spindle will be step/dir run with an AC servo so theoretically > > the tracking of Z verses rotation will be as good as the system can > > provide. > > > > > But it doesn't answer my question on how it works with a spindle > > > using 0- > > > > 10V plus DIR for the spindle while using STEP/DIR for the Z axis. > > How is the Z coupled to the spindle when the control over > > deceleration, as you explained about yours, is somewhat loose. > > > > I would assume that Z is �coupled" to the output of the spindle > > encoder and that the count is reset at each index > > <http://linuxcnc.org/docs/html/man/man9/encoder.9.html > > <http://linuxcnc.org/docs/html/man/man9/encoder.9.html>> > > This link is broken and Jon just mentioned that the index is only used > once at the start of tracked motion. John > Works just fine here, John. > > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users
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) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
