Siemens SINUMERIK 840C Installation Instructions Manual page 874

12.93 12 Functional Descriptions
12.12.5 Influence of the modes on the path dimension function from the PLC
If a path dimension is passed down the command channel, the NC traverses the path
dimension as a fixed destination as in INC and REPOS modes. This applies whatever mode
has been selected at the machine control panel.
If the path dimension has been traversed and acknowledged to the PLC and the selected
mode is AUT or MDA, the axes moved by the PLC are actually in a different position from the
one specified in the NC program.
After NC start, the incorrect axis positions programmed in the block before the path dimension
are corrected, i.e. the end point of the block is approached again. The other axes are only
corrected when they are traversed again in the part program.
y
3.
Path dimension from the PLC
N30
4.
2.
N20
1. 5.
N10
A
x
As you can see in the above diagram, the axis positions are corrected to the end point of
block N20 (point A) after the path dimension has been traversed and NC start executed. Then
block N30 is executed (e.g. with a new tool).
Note:
If a path through several revolutions is programmed for rotary axes with G91, the programmed
end position is approached again (several revolutions) after NC stop followed by NC start.
(Same response as for part program interruption followed by NC start)
12–99
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SINUMERIK 840C (IA)