I totally agree that a silent failure mode (especially one that can break taps) is bad news. Perhaps thankfully, we've gotten away with it for a long time: based on the git history, the 10-rev overshoot limit and this silent failure mode has been around at least since the 2.6 days, maybe earlier.
I have a few ways in mind to fix this: 1. Throw an error and abort motion if it reaches some threshold of overshoot (say 90% of the maximum), or maybe if the position tracking error exceeds some threshold. 2. Check if the rigid tap motion + max overshoot exceeds the axis limits (currently we check before adding the overshoot allowance, which in theory could lead to motion past the soft limits) 3. (optional) Tell motion what the expected spindle acceleration is (via HAL pin), so that it can start reversing before it hits the bottom of the hole (reducing the overshoot). Leaving this pin at zero (default) would give you the current behavior. -Rob On Tue, Jul 21, 2020 at 2:17 PM Gene Heskett <ghesk...@shentel.net> wrote: > On Tuesday 21 July 2020 13:09:16 andy pugh wrote: > > > On Tue, 21 Jul 2020 at 18:03, Robert Ellenberg <rwe...@gmail.com> > wrote: > > > 1. The rigid tapping cycle allows a hard-coded 10 revolutions > > > > > > <https://github.com/LinuxCNC/linuxcnc/blob/master/src/emc/tp/tc.c#L8 > > >56> of overtravel beyond the nominal bottom of the hole when > > > reversing direction. > > > > That feels like there should be an error message. > > > > "Maximum rigid tapping limit exceeded. And furthermore I have just > > broken your tap" > > "Maximum rigid tapping limit exceeded. And furthermore I have just > broken your $85 carbide tap" > > There, I fixed it for you. :( > > 10 turns is way too far. I cut air at least once to measure the > turnaround (I have that stuff in my .hal file) and in what I have done, > that has led me to set a personal limit of 2 turns. Taking a broken tap > out of a valuable blind hole via EDM is a genuine PITA and I will do > whatever it takes to avoid that. But, I would not uncouple the spindle > from the tap either, killing the spindle drive ASAP instead, then one > might be able to back the tap out of the hole with the spindle, > salvaging the part so maybe the hole could be finished by hand. > > 10 turns, breaking the tap is the wrong thing to do. Shutting down, > leaving it coupled before the tap breaks is the best thing to do. > > 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 > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
