On Saturday 26 December 2020 12:27:29 Jon Elson wrote: > On 12/26/2020 10:47 AM, Gene Heskett wrote: > > Two additional questions. That 70 ohm 300 watt braking > > resistor just walked up and rang my doorbell, so are you > > using one? and if so what settings mods have you made in > > the VFD? > > Mine has several settings. There is a minimum frequency, > below which it goes to DC injection braking.
Thanks, the booklet doesn't actually say that. What IU m seeing now hints at dc braking coming in below about 50 rpm. Coasting for several seconds before. > You don't want to use too much DC injection as it will cause > an abrupt stop of the motor. Quicker braking time will > cause more energy to go to the resistor, if you set it too > short, the DC link may go to overvoltage. You may have to > just experiment a bit to find out what decel times make > sense on your particular machine. What I have done, but not yet on this machine because these spindles aren't very amenable to being encoded, is a limit3 at the input to the pwmgen, no PID, and a combo of an xor to detect that the command and the actual dir disagree, so the present state of the dir is held in a sample-hold until a oneshot watching the encoder times out as the input to the limit3 is zeroed via a mux when the dirs disagree. Once the encoder times out indicating the spindle has stopped or nearly so, the new dir is allowed thru, the input to the limit3 is restored. and that re-accels the motor in the new direction. Wash, rinse and repeat at the M4->M3 turnaround at the top of the G33.1. Pause 4 secs to blow the tap clean and anoint it again, repeating that whole sequence with an increment in the depth until the hole is tapped to the needed depth. But without an encoder, I can't time any of that. I have considered a reflective IR lashup watching the ER-nut flats go by but how would I separate that for an index? So its not been attempted to be made into a working, albeit very coarse encoder. But that idea works very well on the Sheldon, and on the GO704, but TLM's magic has been limited to taper tricks with g73, that quick turnaround code has not been hauled to it. I should, but its propensity for breaking drive parts has made me a bit reticent to apply this quick turnaround code there. I do have a oneshot watching the encoder, but its there to issue an F2 off if I leave the head in neutral. Easy to do since the lever is on the back of the head and its position isn't tallied. > If you rigid tap, you > need a braking resistor to reduce the overrun after you get > to desired depth. Rigid tappiing also needs an encoder on the spindle, which it does not have. A floating tap holder maybe, but torque enough for more than a 4-40 tap is highly problematic. Is there an aftermarket encoder for these 24k rpm spindles? > Jon > > > _______________________________________________ > 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) 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
