> > > > 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. John > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
