On Sunday 30 June 2019 09:09:55 Roland Jollivet wrote: > I think I know how it can be done too. Will take a bit of work > though.. But such a circuit/software would be very useful for rigid > tapping on a regular milling machine with a normal 3-phase induction > motor. > > Roland
As long as you are driving that motor with a vfd, and an encoder of sufficient resolution is on the spindle it should just work. The only thing arguing for the vfd is its ability to quickly reverse the motor. Rigid tapping motor speed s/b irrelevant as as long as the in/out speeds follow the encoder. So theoretically the type of motor is a don't care as long as it can be quickly stopped and reversed at the bottom of the hole. My Sheldon can do it but one must subtract the overshoot distance from the depth command if you've a heavy chuck mounted. I can reverse that 3 phase 1 hp way faster than the belts can reverse an 8" 4 jaw while listening to the belts yelping from slipage. And yes, my chucks have back clamps to keep them from unscrewing themselves off the threaded spindle nose. The overshoot distance at 300 revs with the 8" chuck mounted is around 3 full turns of the chuck, so if the hole is blind, you'll bottom the tap and break it. :( You don't have to ask me how I know... So my Sheldons axis display now has displays that a pass cutting air tells me both how many turns of the chuck it overshoots and the extra distance to subtract as derived from the tpi or tpmm in the code. > > > On Sun, 30 Jun 2019 at 14:19, Nicklas Karlsson > <nicklas.karlsso...@gmail.com> > > wrote: > > On Sun, 30 Jun 2019 12:18:24 +0200 > > > > Roland Jollivet <roland.jolli...@gmail.com> wrote: > > > A while back there was some discussion on using an induction motor > > > as a servo motor. I can't find the thread.. > > > > I think I know how this should be done but had to fight it for a > > while. Now it seems performance is very good, maybe similar to a > > permanent magnet motor but I did not compare though good performance > > on higher rpm I am still a little bit uncertain about. I used a > > slightly different algorithm I did not find in books/articles that > > seems to work really well. > > > > Some drives have vector control of induction motor but do not know > > performance of these. > > > > > Yesterday, at the scrapyard I hauled two of these exact motors off > > > a > > > > roller > > > > > press; > > > > http://www.lithronix.com/komori/komorimatic-water-fountain-roller-ac > >tus-power-motor-rebuilt-ni20-200fg-x4kt > > > > > I was quite disappointed to find out there was no permanent > > > magnets in them, and there were no matching drives. > > > So they are induction, but perhaps made differently to your > > > general induction motor. > > > It's a beast of a motor for 200W... At least they come with a > > > 1000 P/R encoder > > > > 1000 P/R is most probably good enough. > > > > > > Nicklas Karlsson > > > > > > _______________________________________________ > > 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 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
