Siemens SINUMERIK 840C Installation Instructions Manual page 335

6 NC Machine Data (NC MD), NC Setting Data (NC SD)
6.6.4 Axis-specific MD bits 1 (axial bits 1)
Bit 4 Bit 4=1 To set a traversing path and direction with G90 programming which
corresponds to the program. The control behaves according to the G
function programmed:
G91: No modulo 360° calculation. The current ZO and TO are added to the
programmed position (more than 360° also possible) which results in a
new position and a new direction of movement.
G90: The current ZO and TO are added to the programmed position (±
359.999 degrees), a modulo 360° calculation is carried out and the
determined traversing path is traversed with the programmed direction
of travel (+ ... clockwise movement, – ... counter-clockwise direction)
(see example above).
G68: The current ZO and TO are added to the programmed position (0 to
359.999 degrees), a modulo 360° calculation is performed and the
midpoint is determined ( ± 180 degrees). The control can then
determine the shortest direction of movement.
Bit 3 The tool length compensations and the position of the tool nose are
mirrored for tool types 1 to 9 (lathe tools) depending on the axis-specific bit.
Bit 2 Bit 2=1 The rotary axis can be programmed to an absolute (G90) value of max. ±
359.999 degrees. The sign programmed determines the direction of
movement.
(See Programming Guide for programming rotary axes).
A rotary axis can also be programmed with G68 where positioning is along
the shortest path (max. ± 180 degrees).
If a rotary axis is programmed for the first time is a part program, the
control always selects G68, irrespective of the G function program (G68,
G90, G91). Automatic selection of G68 can only be deselected with G91 C0
(C ... rotary axis). Automatic selection of G68 is also performed after a
block search and can in this case only be deselected by traversing the axis
in REPOS. If a "Modulo" rotary axis is switched to follow-up mode, G68
automatically becomes active with NC start for the next traversing block of
this rotary axis.
If mixed programming of G90/G91 has been selected in the block (NC MD
5007 bit 5), it is always the last programmed G90/G91 function which
affects the programmed rotary axis position.
See Section Functional Descriptions for rotary axes.
Bit 2=0 The path programming and rotary axis traversing is the same as for linear
axes.
Bit 1 In the 840C, the X axis is a transverse axis with diameter programming as
standard. This bit activates the bits set in NC MD 5011.
Bit 0 No TO are calculated in this axis on PRESET.
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Siemens AG 1992 All Rights Reserved
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SINUMERIK 840C (IA)