On Friday 20 March 2020 00:36:27 Phill C wrote: > > 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
Yes. I assume by scaling the G33 or G76 to the taps feed per full turn of the tap divided by the encoders pulses per turn. But there is a accell time that will muck up your threads if you change the spindle speed during the tap. So don't ever crank up the spindle revs in mid-tap. > and that the count is reset at each index Thats what the man page implies, and whats been driveing my line of questioning, but according to Peter and Jon I guess they are just synchronized at the start of a G76 or G33 related operation. > <http://linuxcnc.org/docs/html/man/man9/encoder.9.html > <http://linuxcnc.org/docs/html/man/man9/encoder.9.html>> The man pages could be clarified a bit. IMO. > > _______________________________________________ > 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
