HEIDENHAIN ITNC 530 User Manual page 241

Closed contours
You can identify the beginning and end of a closed contour with the
CLSD soft key. This reduces the number of possible solutions for the
last contour element.
Enter CLSD as an addition to another contour data entry in the first and
last blocks of an FK section.
Beginning of contour:
End of contour:
Example NC blocks
12 L X+5 Y+35 RL F500 M3
13 FC DR- R15 CLSD+ CCX+20 CCY+35
...
17 FCT DR- R+15 CLSD-
HEIDENHAIN iTNC 530
CLSD+
CLSD–
Y
CLSD+
CLSD–
X
241