Yeah the probe input definitely works. I did get the G38.2 probe to work in some controlled circumstances.
Say that machine Zhome=0 is 7" above the bed, and ZMin= -7.0". In most cases this probe will be near the Z min (thin materials). Z min is not set absurdly low (or no limit) to at least guarantee people don't rub the NUT against the bed. The nut stops like 1/2" above the bed. The G38.2 is in work coords. The Z-target must be given, but that's in work coords, and it will fail to enter the .ngc call if the Z-target is outside machine limits. So, if you have no work offset, Zmachine and Zwork are the same, and G38.2 Z-6.5 works. But if the user already zeroed on one material, there might be a -5" work offset. Zwork=0 is Zmachine=-5. It won't matter where your z-axis currently is located, the G38.2 Z-6.5 becomes a command to move to machine coord Z= -11.5 which, as the error says, exceeds joint 2's negative limit. Someone's example I found online that I was copying started by declaring the current Z to be work Z=0. That's undesirable because if you abort or fail the probe cycle, your prior Z offset is still gone. In any case it won't actually do much to fix the z-limit problem. If you're at Zmachine = -5 and make that Zwork =0, your routine can only probe to z=-2 max in that case, but there's no way to know what that distance is when coding the .ngc. It could be -1" or -7". I guess that does mean that if you have one probe cycle fail to make contact with a -1" drop, you would just repeat until it does because the new cycle will reset Zwork=0 and G38.2 Z-1 down again. But that's a bit confusing. Danny ---- Gene Heskett <ghesk...@shentel.net> wrote: > On Friday 26 August 2016 00:27:00 dan...@austin.rr.com wrote: > > > I'm trying the G38.2 z-probe in an ngc call. I keep getting an error > > "Probe move on line 6 would exceed joint 2's negative limit". > > > > Problem seems to be that G38.2 uses the current coord system. I've > > got the Z-home working now, and machine coords knows the furthest it > > can go, whereas the active coord system Z-value is meaningless for a > > max probe target. > > > > I tried to prefix the G38.2 with G53 (machine coord operation), but I > > get an error that G53 only works on G0/G1. > > > > Am I looking at the problem right? How can I make this "probe to a > > fixed machine coord point"? > > > > Danny > > > Generally, give it a probe distance that would not exceed that limit. It > moves in the current co-ordinate system. So if your limit is set 1mm > above the table, the z-value you give it, shouldn't be lower than > 1.001mm at the end of the probe move from where its at at the start. If > the probe contact is not made by then, you get a different error. > > I assume you have verified with a halmeter, watching motion.probe-input, > that the probe circuit is working? > > ---------------------------------------------------------------------- > >-------- _______________________________________________ > > 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> > > ------------------------------------------------------------------------------ > _______________________________________________ > 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
