To touch the tool off I am physically cutting an OD, measuring that diameter and touching off the tool using that mic’d measurement, so the “actual tip” as you say. So, yes, we are cutting a tiny bit deeper.
However, what we were seeing (and have seen multiple times now but cannot yet re-create at will) is that even though our routine is commanding say, a diameter of .324, the DRO in Axis is showing the cutter down below that. Meaning there is a disconnect between the commanded position and where the machine is really is. The DRO is telling us the truth, if we measure the cut it makes it is indeed where the DRO said it was, but it should never have been cutting that deep. Something very broken is happening periodically (not infrequently) and it seems to be related (but we’re not yet 100% sure) to G76. We uncovered another (minor? perhaps not related?) bug in the G76 canned cycle. When G76 runs it sets the plane to G17 (we are in G18 on our lathe). In our script we save the modal state before entering, and restore modal state at the end of the routine. We also set G18 inside the routine, but G76 is setting G17 when it runs and the machine stays in G17 after leaving our subroutine. We even tried explicitly setting G18 before exiting our subroutine and it makes no different G76 puts the machine in G17 dammit. That seems like a bug. This is being executed out of Pyngcgui in Axis. -Tom > On Jun 2, 2017, at 2:24 PM, John Kasunich <jmkasun...@fastmail.fm> wrote: > > How are you touching off (or otherwise determining the X tool offset for the > insert)? > > For example, if you calculate the offset assuming a sharp-V geometry (the > simplest case), but touch off with the actual tip of the insert (not sharp), > the insert will be in deeper than LCNC thinks it is when you touch off. So > it will cut deeper later. > > > > On Fri, Jun 2, 2017, at 02:14 PM, tom-...@bgp.nu wrote: >> Ok, thanks for the responses. I found some thread gauge wires and with them >> have determined that we are cutting too deep. This would cause the pointy >> peaks and root, so the next question is why are we cutting too deep…? We >> believe we are entering the correct value for K (thread depth) but I was >> observing the DRO and Linuxcnc seems to be sending the cutter quite a bit >> below where it should stop. >> >> I am going to get some more definitive info what is exactly happening, but I >> am now wondering if there is a bug in the G76 cycle (causing it to cut >> deeper than it should) or if it is something on my machine… >> >> -Tom >> >> >>> On Jun 2, 2017, at 12:31 PM, Ed <ate...@mwt.net> wrote: >>> >>> On 06/02/2017 10:36 AM, tom-...@bgp.nu wrote: >>>> There is a custom adjusting screw that I buy commercially and when I get >>>> them the threads have a text-book geometry to them. That is, they have a >>>> small flat top on the major diameter and small flat bottom at the minor >>>> diameter or root. They are made to class 2 or perhaps even class 3. I >>>> know that these screws I am getting commercially are made using single >>>> point carbide insert tooling on a cnc lathe. >>>> By the way, this seems to happen for nearly every thread I have cut on the >>>> machine, but I haven’t cared as much in the past as the screws have been >>>> for my own purposes, but this one will be used in a product sent to >>>> customers. >>> SNIP >>> >>> >>>> >>>> I am wondering if I am doing something wrong with the insert I am using or >>>> what. Any thoughts? >>>> >>> Get an insert for that particular TPI, it will leave the proper flat on the >>> top and bottom of the thread. >>> >>> Ed. >>> >>> >>> ------------------------------------------------------------------------------ >>> 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 > > > -- > John Kasunich > jmkasun...@fastmail.fm > > ------------------------------------------------------------------------------ > 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
