HEIDENHAIN TNC 320 User Manual page 153

Please note while programming:
Pre-position the tool in the machining plane to the starting
position (stud center) with radius compensation R0.
The TNC automatically pre-positions the tool in the tool
axis. Note parameter Q204 (2nd set-up clearance).
The algebraic sign for the cycle parameter DEPTH
determines the working direction. If you program
DEPTH=0, the cycle will not be executed.
At the end of the cycle, the TNC returns the tool to the
starting position.
At the end, the TNC positions the tool back to the set-up
clearance, or to the 2nd set-up clearance if one was
programmed.
Danger of collision!
Use the machine parameter displayDepthErr to define
whether, if a positive depth is entered, the TNC should
output an error message (on) or not (off).
Keep in mind that the TNC reverses the calculation for pre-
positioning when a positive depth is entered. This
means that the tool moves at rapid traverse in the tool axis
to set-up clearance below the workpiece surface!
Leave enough room next to the stud for the approach
motion. Minimum: tool diameter + 2 mm
HEIDENHAIN TNC 320 153