Hi Gene, It's why I'm filtering. And yes. I agree, at this slow a speed I suspect what I will find is two different velocities reported from edge to edge. I'm guessing when the speed is fast (small gap) then a faster than required distance/vel is implemented. Then on the next wider pulse it's gone too far and now the drive stops because it has overshot.
I'm guessing. I'll let you know. John > -----Original Message----- > From: gene heskett [mailto:ghesk...@shentel.net] > Sent: August 14, 2023 1:31 PM > To: emc-users@lists.sourceforge.net > Subject: Re: [Emc-users] Rigid tapping > > On 8/14/23 15:53, John Dammeyer wrote: > > This thread has some good information about this > > > > https://sourceforge.net/p/emc/mailman/message/34363029/ > > > > > > > > For interest sake I set my mill up to turn 1 RPS with my 60 tooth > > non-symmetrical encoder (4mm slots, 2.5mm teeth) and then ran the > power > > tapping G-Code to see what the knee Z axis would do. > > > > > > > > What I found is that it moved in short spurts. Putting my finger on the > > knee and against the column it still appeared to move rather slowly with > > less of a jerk. All this makes sense of course. > > > Something might be off in the quadrature accuracy. Do you have a dual > trace triggered scope? That will likely be quite helpful. 60 teeth, > non-symetrical is going to generate a horrific amount of quantization > noise because neither waveform is going to be a 50/50 ratio in the time > domain. I got rid of all signs of that by putting my $20 Omron encoder > encoder on the rear of the spindle MOTOR, making and index pulse > generator on the spindle with a glued on screw and an ATS-667 hall > device, and tally switches on the heads gearshift knob to electronically > change gears. So the SCALE changes with the gearshift knob. And I can > run the pid's Pgain above 20. > > > > > My servo period is 1000000 nanoseconds or 1 ms. At 1 RPM that's one > tooth > > every second or 4 encoder edges per second meaning one edge every > 250mS. > > That's 250 servo periods. What I think I'm seeing is that every 250 servo > > periods the system detects the encoder edge and knows it's moved > 1/240th of > > the 20 TPI thread. (0.000208333") So it tells the Z axis to move that same > > distance and I suspect the velocity setting of 0.0002083333/250mS. > > > > > > > > Does that make sense? Is there a way to log each Z axis speed/distance > > command so I can see what it's doing? > > > > > > > > Or have I misunderstood how the power tapping synchronized motion is > done. > > > > Thanks > > > > John > > > > > > > > > > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > 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, 1940) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > Genes Web page <http://geneslinuxbox.net:6309/> > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
