On Friday 11 April 2014 22:36:19 Jon Elson did opine: > On 04/11/2014 12:07 PM, Gene Heskett wrote: > > In actual practice, at least here Jon, hitting the +Z > > limit is astronomically unlikely, assume +Z is to the > > right when viewing the lathe from the normal, spindle on > > the left, perspective. But my homing procedure, sets Z0.0 > > at the face of the chuck +.005". So while a tap is never > > homed against, its still possible for the forward, into > > the hole stroke of a g33.1, to exceed that MIN_LIMIT if > > the work is chucked too deeply. IMO to prevent work or > > tool damage, the reverse should be issued at the limit > > point, and coupling should be maintained during the > > turnaround until the tool is backed out at lest to the > > start point, then do the e- stop. > > While I haven't tested it, I think if you set up the home > switches > and axis limits in the normal manner, then the program would not > be able to be run if it would run out of -Z travel! You'd > hit run > and immediately get "Program exceeds minus Z limit at line 123". > Now, the one way you could get tripped up is that the -Z > travel actually > EXCEEDS the commanded depth as the spindle needs to stop and > reverse. > So, this leaves a small distance, depending on thread pitch > and how fast > the spindle can reverse where you could get into trouble. > > Jon
In that situation Jon I subtract the estimated coast from the desired depth. Generally, the hole will be drilled more than deep enough for over travel. That would be plenty to stop the broken tap. What I would do in that event, would be to loosen the chuck, back Z off, grab the tap and tap spindle reverse. Then contemplate how to salvage the part. That is why I suggested blocking the e-stop until the tap was back out of the hole. A somewhat similar scenario could be gotten into when using a single tooth boring bar to tap a hole using G76. My next project, ball screws in the mill, will need two such operations in the nut holder as I intend to compress the nut by dropping it into a hole, and screwing a cap against it, but with heavy felt wipers to clean the screw. Similar to the wipers on the 16mm screw in the lathe, they seem to be doing a good job of wiping the swarf, keeping it out of the nut proper. To that end I have obtained a set of single tooth, indexable carbide threading tools. Cheers, Gene -- "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> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS ------------------------------------------------------------------------------ Put Bad Developers to Shame Dominate Development with Jenkins Continuous Integration Continuously Automate Build, Test & Deployment Start a new project now. Try Jenkins in the cloud. http://p.sf.net/sfu/13600_Cloudbees _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
