Well, I cut a bunch of screws today, which was executing a repetitive series of gcode routines and I did not have this problem at all. I am now thinking it is caused by something we are doing outside of the G76. We were touching tools off and I am wondering if we did something that caused the discrepancy. It is either that or somehow my steppers lost steps and I didn’t notice it.
I do have a question on thread depth. When entering the theoretical thread depth I always seem cut too shallow (that is, now that I have the tool touched off accurately and am not having the problem with cutting deeper than commanded position). I have to increase the depth a couple thou and re-cut the thread to cut it deep enough. As John Kasunich pointed out it matters how the offset is determined for the tool. Currently I do that by cutting a diameter with the threading tool. I measure that with a micrometer and I enter the DRO value in the tool touch off for that tool (I have a routine that leaves the tool at the diameter after cutting so this works). But I am wondering, I don’t have a DIAMETER value in the tool table for the tool. Should I? Is a zero (or non-existant) radius value causing Linuxcnc to think the tool is longer than it really is when cutting? -Tom > On Jun 3, 2017, at 5:17 AM, andy pugh <bodge...@gmail.com> wrote: > > On 3 June 2017 at 01:11, <tom-...@bgp.nu> wrote: >> 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. > > Are you displaying commanded or actual position? ie, is the axis not > where LinuxCNC commands it to be, or is LinuxCNC not commanding the > numbers from your G76 command? > > The G76 code is here: > https://github.com/LinuxCNC/linuxcnc/blob/9e4641a816ab8fe4f6a09a48fac550cc8aef1dee/src/emc/rs274ngc/interp_convert.cc#L4590 > > That seems quite explicit: > double end_depth = fabs(k_number) + fabs(i_number); > > And the last moves are cut at start_x - end_depth > > -- > atp > "A motorcycle is a bicycle with a pandemonium attachment and is > designed for the especial use of mechanical geniuses, daredevils and > lunatics." > — George Fitch, Atlanta Constitution Newspaper, 1916 > > ------------------------------------------------------------------------------ > 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
