> 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>> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
