Matthew Glenn Shaver wrote: > The interpreter manual says that, in a center format arc move (G2 or > G3), only one offset word (I, J, or K, whichever are appropriate to the > selected plane). Assuming for example that the XY plane is selected, and > only I is specified in a center format arc move block, what Y axis > offset value (J) will be used? > > The last declared J value? > > Zero? > > Basically, are I, J, and K modal? No, I J and K are incremental offsets to the arc center, and are not modal. That would be far more dangerous than having them default to zero if not specified. Some controls interpret them differently depending on whether you are in incremental or absolute coord mode, but the behavior in abs coord mode, which is what most people use most of the time is not modal.
it is quite common to have one of the axes in the plane stay the same to the arc center (like when doing a 180 degree arc that comes back to the same X coord, then I would be zero, and the start, center and finish would all lie at the same X cord, and J would be equal to half the difference between the start X and the end X. On EMC, the I,J,K words are signed to indicate the direction from the start point to the arc center. I think the above quoted text should read "Only one offset word is required". You definitely can have two. I think with the in-plane only arcs that EMC does, you can't have 3. Some controls allow arcs in arbitrary planes, and you can have an arc move with XYZ and IJK words! I can imagine all sorts of conditions where the plane of the arc is not uniquely defined. Jon ------------------------------------------------------------------------- SF.Net email is sponsored by: The Future of Linux Business White Paper from Novell. From the desktop to the data center, Linux is going mainstream. Let it simplify your IT future. http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
