Siemens SINUMERIK 840C - Manual (Page 194)

09.95 6 NC Machine Data (NC MD), NC Setting Data (NC SD)
6.2 General machine data (general data)
Threshold for switchover intersection * 6
Default value Lower input limit Upper input limit Units
1 000 +0
16 000
2 000 (as from SW 4)
units (IS)
Active in
next block
One or two intermediate blocks are inserted for circle intersection (straight line/arc, arc/straight
line and arc/arc) with external contours with circle intersections and obtuse angles (90° <
< 180°) (see Programming Guide Section 10.4).
If the angle is nearly 180°, the paths to be traversed in the intermediate blocks become very
small and can cause a standstill in continuous path mode. The control can suppress the
intermediate blocks to prevent this. It either switches from ”TRC with intersection” to ”TRC
with transition circle” to avoid an intermediate block or it approaches the intersection of the
two blocks. In this case no intermediate block is generated.
R R R R R R
A C
B
A A C C
S
_
AC > MD6
_
AC < 2 · MD6
_
AC < MD6
Before switching over, the distance A to C is compared with machine data 6 (MD6). If the
distance from A to C is smaller than MD6, the intersection of the two blocks is traversed
(applies to all circle transitions with ”TRC with transition circle” G450 and ”TRC with
intersection” G451).
If the distance from A to C is smaller than 2 · MD6, the control switches from ”TRC with
intersection” G451 and transition arc/arc to ”TRC with transition circle” G450.
Caution:
When approaching the intersection of the two blocks the programmed arc(s) is (are)
increased. If the circle is enlarged to beyond 360°, only the section above 360° is traversed.
If there is no intersection or the intersection is located too far from the contour (> 1.5 . tool
radius), intermediate blocks are again inserted in the angular range 90° <
<170° as
otherwise a major contour error may occur. In the angular range 170° < < 180° the normal
circular block is approached and movement is then continued. Only a slight contour error
occurs.
No intermediate block. The correct compensation is not
reached until the end (E) of the block has been reached.
R
A
E
R
Contour error
_______
* As from SW 2
© Siemens AG 1992 All Rights Reserved 6FC5197- AA50 6–9
SINUMERIK 840C (IA)