HEIDENHAIN iTNC 530 (34049x-08) Cycle programming - Manual (Page 216)

216 Fixed cycles: contour pocket, contour trains
7.
12 THREE-D CONT
OUR TRAIN (Cy
cle 27
6, DIN/ISO:
G27
6) Please note while programming:
The first block in the contour subprogram must contain
values in all of the three axes X, Y and Z.
The algebraic sign for the cycle parameter DEPTH
determines the working direction. If you program
DEPTH=0, the TNC will execute the cycle using the tool
axis coordinates defined in the contour subprogram.
When using Cycle 25 CONTOUR TRAIN, you can define only
one contour program in Cycle 14 CONTOUR GEOMETRY.
The memory capacity for programming an SL cycle is
limited. You can program up to 4090 contour elements in
one SL cycle.
The TNC does not need Cycle 20 CONTOUR DATA in
conjunction with Cycle 276.
Make sure that the tool is in the tool axis above the
workpiece when the cycle is called; otherwise the TNC
will issue an error message.
Danger of collision!
To avoid collisions,
 Before the cycle call, position the tool in the tool axis
such that the TNC can approach the starting point of the
contour without collision. If the actual position of the
tool is below the clearance height when the cycle is
called, the TNC will issue an error message.
 Do not program positions in incremental dimensions
immediately after Cycle 276 since they are referenced
to the position of the tool at the end of the cycle.
 Move the tool to defined (absolute) positions in all
principal axes, since the position of the tool at the end of
the cycle is not identical to the position of the tool at the
start of the cycle.