On Sun, May 06, 2007 at 09:03:19PM -0400, Gene Heskett wrote: > >* fix constraint violation right after a probing move > > I don't believe I hit that one, what might the symptoms be?
On steppers, a joint following error. The violation was minor so I doubt it would have been noticed on a servo machine. > >* abort if the probe does not trip before a probing move ends > > Now that's going to be a problem, Chris. I have it doing a probe right now, > that will probably still be running this time tomorrow. In order to get the > edges of an irregular shaped piece, like the floor plate of my deer rifle, it > is going to be a total miss for about 10% of the probes. If it aborts on a > full miss, then my 48 line program will have to be broken down into numerous > additional subroutines to prevent its ever going off the edge of the piece. > So this is one item that should somehow be selectable so it can be disabled. I'm sorry to hear this fix causes you trouble. It may have been a mistake for me to put it in 2.1.5. The danger of not having it is that if an error is not signalled when your probe doesn't touch anything, you get a reading anyway (the end of the probe move), even though that's some random point in the air. The RS274NGC authors definitely wanted it to be an error: "If the probe does not trip ... an error is signalled." http://www.linuxcnc.org/handbook/RS274NGC_3/RS274NGC_33a.html#1001097 Judging from this and their example uses of finding a hole center, finding a hole diameter, and testing parallelism in various planes, I suspect they did not intend/forsee that people would want to use G38.2 to probe a huge grid of points to digitize a complex shape. As you know, doing this works pretty badly since you have to go to the max height for each point. John and I have briefly discussed what it would take to allow a much smarter shape probing, which would march the probe over the shape with very little extra motion, instead of what we have to do now. I've added this to the list of discussion topics planned for the upcoming CNC workshop (June). We may get a chance to work on it if there's time and interest. One obstacle is that I don't think we have a probe among us. Chris ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
