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
