On 08/10/2015 06:38 PM, David Bagby wrote: > Hi, > I'm planning a mill conversion to LCNC and I'd like it to be able to do > rigid tapping. > > I figure that this will require an encoder or equivalent) on the > spindle. I won't be able to to easily attach a common encoder disc to > the spindle, so I will probably have to create an encoder (which appears > easier than doing a remote encoder driven via a belt etc). > > I've looked but not found a spec for the required encoder resolution. > Does anyone have advice as to min spindle encoder resolution (ppr) required? > Has anyone gotten by with 8 or 12 pulses (32 or 48 quadrature) ? > > I've been doing it using the 81 tooth bull gear on my Bridgeport 1J head, and that works fine. That comes out to 324 quadrature counts/rev. I'd guess that your counts will likely work OK, too. You can figure out the steps/second the encoder value will show. For instance, at 100 RPM, the spindle will be turning 1.667 RPS, and 32 counts/rev will give 32 * 1.667 = 53.33 increments/second to the encoder value. Most machine controls don't have the bandwidth to keep up with that, and will just average over it.
The worst situation would be that this would feed a stairstep position to the PID (assuming a servo Z axis) and that the PID + drive combination would have some resonance at certain frequencies that could be excited by the stairstep. Jon ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
