HEIDENHAIN TNC 640 (34059x-04) Cycle programming - Manual (Page 210)

Fixed Cycles: Cylindrical Surface
8.2 CYLINDER SURFACE (Cycle 27, DIN/ISO: G127, software option 1)
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TNC 640 | User's Manual Cycle Programming | 3/2014
Please note while programming:
The machine and TNC must be prepared for cylinder
surface interpolation by the machine tool builder.
Refer to your machine manual.
In the first NC block of the contour program, always
program both cylinder surface coordinates.
The memory capacity for programming an SL cycle
is limited. You can program up to 16384 contour
elements in one SL cycle.
The algebraic sign for the cycle parameter DEPTH
determines the working direction. If you program
DEPTH=0, the cycle will not be executed.
This cycle requires a center-cut end mill (ISO 1641).
The cylinder must be set up centered on the rotary
table. Set the reference point to the center of the
rotary table.
The spindle axis must be perpendicular to the rotary
table axis when the cycle is called; If this is not
the case, the TNC will generate an error message.
Switching of the kinematics may be required.
This cycle can also be used in a tilted working plane.
The set-up clearance must be greater than the tool
radius.
The machining time can increase if the contour
consists of many non-tangential contour elements.
When you use local
QL Q parameters in a contour
subprogram you must also assign or calculate these
in the contour subprogram.