On Wednesday 31 January 2018 11:18:09 Kenneth Lerman wrote: > Jon, > > I have one question I have that I haven't seen a good answer to. > > Why is there a need to do a second touch? Can't you just back off at > low speed and see when the probe is no longer touching? > > I didn't see a significant difference when I did some tests. Everyone > seems to do it the way you're doing it, but I'd like to understand if > there is any evidence that way is better. > > Regards, > > Ken I think most of us are using a poor mans probe, routed into motion.probe-input by our hal files.
My probe consists of a 3" piece of 3/4" teflon, with a center hole about an inch deep, and cross drilled and tapped for a couple set screws to retain an reasonable straight piece of 14 gauge solid copper wire. Stick it in a TTS 3/4" holder, strip about 3/4" of whatever stranded wire gets in my way first, split the strands, push it onto the solid wire, bring the ends together and twist tightly on the solid 14 ga. Then, because its not always dead straight, I spin the spindle up to about a thousand, at which point the end of the wire is describing a perfect circle. I have a capacitor on the wire, and its chosen so that a logic zero from discharging the capacitor at 1st contact will be present long enough for LCNC to see its first contact, which you can do at 7.5 to 20 IPM. But because it can move quite a bit at the initial search speed, that first contact may nut be dead to the 4th place, so on contact, it backs away about 15 to 20 thou by a normal move, then comes back at .1 IPM and as shown by Jon's code, and that often gives an accuracy thats far better than most machines. I've done repeats and obtained the same answers to around .0003 many times. That, as an ex bro-in-law was fond of saying, is close enough for the girls I go with. If I break the wire off with bad code, I just replace it, then run the end of it against the work with the spindle on, forcing it to be bent straight. But don't overdo the push as that will quickly break off the new wire from excessive repeated bending at the mouth of the hole in the Teflon. This also disclosed what I will call a bug in LCNC, if the bounce away move is in the wrong direction, leaving a solid contact instead of opening it, LCNC should refuse to do the next G38.2 move, but it doesn't, and that broke my wire 2 times yesterday, until I saw the error in my code and if the bounce move is -0.015, do the second final pass with a 0.025 ending, which will throw up a move finshed error. All that is in mode G91, but it uses G90 to place the probe in the hole. Whats recorded is still in g54 travel. I added logging, and ran the final version twice, first with hole locations that were visual SWAGs, then used those results to update the holes center starting xy according to the first run, then ran it again, changed the logfile name, and ran it again. Everything was well within a thou of the first figures. Now I'll go pull the chuck off the table and fix the backing plate in its place, find the center of that, and rotate the co-ord until it matches the existing holes, then add the subroutine to drill them. Similar code, but bore the holes oversized so I can center it good. Maybe I'll have a usable Bison chuck when I am done. But I see by the clock that it will now be after I make dinner as its 17:33 local time, and I'd better go feed the missus. > On Tue, Jan 30, 2018 at 11:47 AM, Jon Elson <[email protected]> wrote: > > Gene, > > > > Here's a hole probe routine I have used with my touch probe. The > > constant 0.1526 is the effective radius of the probe tip. Due to > > the lag in sensing the probe, it makes a fairly rapid touch first at > > F10, backs off, and then does it again, from very close, at F1. It > > writes out the coordinate offset of the center as well as the > > diameter in that direction. > > > > > > g91 g1 F10 X-0.05 > > g91 G38.2 X0.5 > > G91 G1 F1 X-0.02 > > g91 G38.2 X0.1 > > #1001=#5061 > > g91 g1 f10 X-0.05 > > g91 G38.2 X-1.0 > > G91 G1 F1 X0.02 > > g91 G38.2 X-0.1 > > #1002=#5061 > > #1003=[[#1001+#1002]/2] > > #1001=[#1001-#1002+0.1526] > > (debug,X center #1003) > > (debug,X width #1001) > > G90 G1 F10 X#1003 > > g91 g1 F10 Y-0.05 > > g91 G38.2 Y0.5 > > G91 G1 F1 Y-0.02 > > g91 G38.2 Y0.1 > > #1004=#5062 > > g91 g1 f10 Y-0.05 > > g91 G38.2 Y-1.0 > > G91 G1 F1 Y0.02 > > g91 G38.2 Y-0.1 > > #1005=#5062 > > #1006=[[#1004+#1005]/2] > > #1004=[#1004-#1005+0.1526] > > (debug,Y center #1006) > > (debug,Y width #1004) > > G90 G1 F10 Y#1006 > > G10 L20 P1 X0 Y0 > > M02 > > > > > > > > ------------------------------------------------------------ > > ------------------ > > 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 > > [email protected] > > 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 > [email protected] > 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
