On Tuesday 01 August 2017 17:14:55 Ken Strauss wrote: > It doesn't answer your question but have you considered using thread > forming taps? Certainly no gullets to fill!
True Ken, but what is the difference in required torque? I am afraid that if I use a peck routine, it might get stuck and the spindle would not have the power to back it out. Not to mention the shanks aren't big enough for an ER-32 collet to get an adequate, slippage free grab at those torque levels. Thats only a 1 hp rated motor, and I'm running in backgear at 200 revs to even turn an 8mm tap. Thanks Ken. > > -----Original Message----- > > From: Gene Heskett [mailto:ghesk...@shentel.net] > > Sent: Tuesday, August 01, 2017 4:57 PM > > To: Enhanced Machine Controller (EMC) > > Subject: [Emc-users] Question on Z backlash vs rigid tapping > > > > Greetings everybody; > > > > One of the things I have noted recently was a correlation between > > the > > thread > > > fit, and a commercial bolt screwed into the hole, and I believe it > > has to > > do with > > > my use of a peck routine to do the tapping, more pecks=sloppier fit. > > > > My spindle doesn't have enough power to drive a 10mm tap in one > > pass, nor do I feel comfortable when the gullets of the tap get > > filled, so I peck at > > it so I > > > can clean and add a drop or 2 of buttercutt or rapidtap as I program > > a 3 > > to 4 > > > second pause at the top of the travel to give me time to do that. > > > > Doing some 8mm holes in 3" pipe walls, I drove it about as hard as > > the > > spindle > > > could manage to keep turning, so I drove it deep enough into the > > hole per > > pass > > > that it only took 6 passes to get the last of the taps taper out of > > the > > bottom of > > > the hole. > > > > The backlash fly in this soup is the filter I've put in the encoder > > path > > to average > > > the level of the last 4 edges out of the encoder, which works well > > for > > that and > > > allows lots more Pgain to be used. That represents a fixed number of > > spindle > > > degrees of lag, which of course causes the rigid tap to not follow > > the z > > motion > > > perfectly. > > > > I have considered adding additional backlash comp, but the required > > amount would change with the tpi, so while that would help, its not > > a perfect fix > > since > > > there is not a way to change it dynamically. > > > > I could take the filter out, but I'd have to reduce Pgain by at > > least 75% > > just to > > > keep it from hammering the gears in the head from the perceived > > errors in > > the > > > velocity signal caused by a 5% quadrature timing error wobble in a 4 > > step repeatable sequence. > > > > This is not an error the PID's can even see, let alone try to > > correct. > > > > Is it time to junk the optical encoder, and install a thin steel > > gear in > > its place, > > > and machine some sliding mounts for at least two of the 3 ats667's > > so that finer adjustments to reduce the quadrature noise can be > > done? I have bent and otherwise adjusted the opto-interrupters until > > there is no further improvements to be had. > > > > In which case, where might I be able to source a 30-60 tooth gear > > that is precisely enough made, is not more than 2.25" in diameter, > > and only 1/16" thick? > > > > The current optical setup gives me 268 edges per rev. 67 slots in > > the > > disk. > > > Mechanical errors in carving the disk would be reduced > > percentagewise by applying the error to fewer slots, but that seems > > counter-productive for > > rigid > > > tapping. > > > > What say you folks? > > > > Thanks all. > > > > 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) > > Genes Web page <http://geneslinuxbox.net:6309/gene> > > ---------------------------------------------------------------------- >------ -- > > > Check out the vibrant tech community on one of the world's most > > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > ---------------------------------------------------------------------- >-------- Check out the vibrant tech community on one of the world's > most engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > 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) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
