On 25 March 2010 11:19, John Guenther <[email protected]> wrote: > > At any rate, I out of habit use machine coordinates all > the time.
I think that is the problem. The machine coordinates are fixed to the axes and can only easily be relocated by a homing process. The machine will refuse to move outside these limits. I think you said that you have no home switches? In that case I can't remember what happens when you home the axis, I think that the current physical position becomes the point at which the machine absolute numerical position takes the value from the ini-file axis home position. > Perhaps a better example of what I would like to be able to > do is this. I use a manual tool height setter. I put it a new tool, > then jog Z down until the tool height setter shows 0 on its dial. Now I > need to be able to tell EMC that the Z axis is at 2 inches above the > work. How can I do this in EMC? I have tried the work offsets as > suggested and that is not working for me. In Mach3 I just click on the > Z axis DRO and enter 2.00 and I am ready to go. This is exactly what the working coordinate systems are for. If you change the view to "Relative" either from the menu or by pressing "#" then you will see the current working coordinate values. Note that you are _always_ on one of the working coordinate systems. You have to use special G-codes to move in the absolute machine coordinate space. The distinction might not be clear in cases where the working coordinate system has no offset from the machine coordinate system, and this will often be the case for a machine with no home switches. However, any G0, G1, G2, G3 etc move will always move in the current (probably G54) coordinates. So, for a machine with no home switches the start-up process would be: Select Absolute coordinate view Move to the extreme limits of travel of each axis. Home the axes from the GUI with the "home" button. I think you will see the machine coordinates take on the home position values from the INI file, but I could well be wrong. To save time and trouble you could set the home position to be mid-travel and set the axes limits symmetrical about this point. Change the view to Relative Coordinates Jog to where you want X=0 and Y=0 to be, set them to zero (or some other value) with the touch-off button. Bring your tool down to the height setter, select Z, press the touch-off button and type in your 2" tool height value. You should now be good to go. Clicking the DRO in Mach sounds to be doing exactly the same thing as EMC touch-off. There is also the option of touching-off into the Tool table, which can be useful for machines with multiple tool holders, less so for single collet machines. There is a lot more info on the Wiki, http://wiki.linuxcnc.org/emcinfo.pl?CoordinateSystems Bear in mind that my understanding of this issue is incomplete, and I don't have a machine here at work to experiment with. I still sometimes find myself in a bit of a tangle with offsets and "programmed move would exceed machine minimum...." when there is clearly lots of space left. -- atp ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
