I can always tell when a real CNC programmer answers a question.Stuarts way is usually the right way. I wish I had a dollar for everytime I have typed "G28G91Z0.0"
Terry On Fri Mar 6 22:48 , Stuart Stevenson <[email protected]> sent: >my use of g28 is as follows > >g91g28z0 - this homes the Z axis with no positioning motion >g90g30 - this move the machine to a predetermined tool change >position if that is what I want > >you would be able to do this also > >g91g28z0 - ditto >g91 Xnnn Ynnn - for a clearance move away from the part or machine component > >or > >g91g28z0 - ditto >g90g53 Xnnn Ynnn - move to a machine specific position independent of >any coordinate system offset > >thanks >Stuart > > >On Fri, Mar 6, 2009 at 7:48 AM, Jeff Epler [email protected]> wrote: >> On Fri, Mar 06, 2009 at 09:31:17AM +0100, Robert von Knobloch wrote: >>> Thanks for your solution, which worked perfectly. >>> Just for my benefit, I would like to know if I misunderstood the >>> command or does it not work as documented? >> >> I think the documentation is accurate but maybe not terribly clear. The >> key words are "the named axes" >> >> To return one or more axes to the predefined position by way of the >> programmed position, program G28 axes (or use G30). The path is made by >> a traverse move from the current position to the programmed position, >> followed by a traverse move of the named axes to the predefined >> position. >> >> This is also different than older versions of emc which did what you >> expected: first moved to the programmed point, then moved all axes to >> the predefined position. I know that this change was motivated by a >> user request, but I don't remember the exact reason. Here's what the >> docs say in the "differences from rs274ngc" section: >> When G28 or G30 is programmed with only some axis words present, >> EMC2 only moves the named axes. This is common on other machine >> controls. To move some axes to an intermediate point and then move >> all axes to the predefined point, write two lines of gcode: >> >> G0 X- Y- (axes to move to intermediate point) >> G28 (move all axes to predefined point) >> http://linuxcnc.org/docs/html/gcode_main.html#r8_1_5 >> >> One that comes to mind are machines with rotary axes (though I don't >> think this was the motivation for the change): until we do >> something about the way rotaries have to undo every revolution they >> performed to get back to 0, G28 would be really annoying on a rotary >> machine. >> >> Jeff >> >> ------------------------------------------------------------------------------ >> Open Source Business Conference (OSBC), March 24-25, 2009, San Francisco, CA >> -OSBC tackles the biggest issue in open source: Open Sourcing the Enterprise >> -Strategies to boost innovation and cut costs with open source participation >> -Receive a $600 discount off the registration fee with the source code: SFAD >> http://p.sf.net/sfu/XcvMzF8H >> _______________________________________________ >> Emc-users mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/emc-users >> >> > >------------------------------------------------------------------------------ >Open Source Business Conference (OSBC), March 24-25, 2009, San Francisco, CA >-OSBC tackles the biggest issue in open source: Open Sourcing the Enterprise >-Strategies to boost innovation and cut costs with open source participation >-Receive a $600 discount off the registration fee with the source code: SFAD >http://p.sf.net/sfu/XcvMzF8H >_______________________________________________ >Emc-users mailing list >[email protected] >https://lists.sourceforge.net/lists/listinfo/emc-users ---- Msg sent via CableONE.net MyMail - http://www.cableone.net ------------------------------------------------------------------------------ Open Source Business Conference (OSBC), March 24-25, 2009, San Francisco, CA -OSBC tackles the biggest issue in open source: Open Sourcing the Enterprise -Strategies to boost innovation and cut costs with open source participation -Receive a $600 discount off the registration fee with the source code: SFAD http://p.sf.net/sfu/XcvMzF8H _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
