On Thu, 1 Oct 2009 15:53:02 -0500, you wrote: > exactly 1 full turn requires using g91 > more than one full turn requires using g91
Argghhh... Noooo <G> One flavour of Fanuc only (15b)! Why follow a bad design? Fanuc, as is their habit, changed it. Sensibly later Fanuc controllers treat rotary axis just like any other. The telling statement is the last paragraph - NB - " One occurrence that is interesting - when the rotation in the same direction reaches 360.0 (a full circle), it continues to increase. It does not become zero degrees again." Also there is none of that G91 nonsense with more than one full turn. Here's what Peter Smid says in CNC programming handbook, and the following applies to ALL rotary axis, just that B is used in this example. (apologies if this doesn't format correctly it was OCR'd from a PDF) "Just like any other axis, the B axis can be programmed in the absolute mode or incremental mode, with the same behaviour as the linear axes B Axis direction and general descriptions The B axis is programmed logically the same way as the linear axes, including the mode of dimensioning. Either the absolute or the incremental mode can be used for indexing, using standard G90 and G91 commands respectively. The following example is in the absolute mode, showing two table columns. The first column is the programmed indexing motion in G90 mode, the second column shows the actual resulting indexing motion (Distance-To-Go) and its direction. All rotational directions are based on the perpendicular view to the XZ plane. ~ Absolute Mode - consecutive indexes: Programmed motion in G90 Actual indexing motion G90 G28 B0 Machine Bzero position G00 B90.0 CW 90 degrees B180.0 CW 90 degrees B90.0 CCW -90 degrees B270.0 CW 180 degrees B247.356 CCW -22.644 degrees B0 CCW -247.356 degrees B-37.0 CCW -37 degrees B42.0 CW 79 degrees B42.0 No motion (0 degrees) B-63.871 CCW -105.871 degrees The next table is similar. The first column is the programmed indexing motion in G91 mode, the second column shows the motion directions and the actual resulting absolute position. All rotational directions are based on the perpendicular view to the XZ plane. Programmed motion in G91 Actual absolute position G90 G28 B0 Machine Bzero position G91 G28 B0 Machine zero - no motion G00 B90.0 CW 90.000 B180.0 CW 270.000 B90.0 CW 360.000 B270.0 CW 630.000 B0 No motion B125.31 CW 755.310 B-180.0 CCW 575310 B-7531 CCW 500.000 B-75.31 CCW 424.690 B-424.69 CCW 0.000 Study both tables block by block, in the listing order. The results are always Important for understanding. Note the B-37.0 in the first table - exactly the same result could be achieved if the block read B323.0 as a positive value. In the second table, the first block is in the absolute mode to guarantee a start at B0. One occurrence that is interesting - when the rotation in the same direction reaches 360.0 (a full circle), it continues to increase. It does not become zero degrees again. That is something to watch. If indexing (in the incremental mode) takes place twice around, the absolute table position will be 720.000°, Indexing twice will also be necessary in the opposite way in order to reach absolute zero." Steve Blackmore -- ------------------------------------------------------------------------------ Come build with us! The BlackBerry® Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9-12, 2009. Register now! http://p.sf.net/sfu/devconf _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
