Please note while programming – HEIDENHAIN TNC 640 (34059x-01) Cycle programming User Manual
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HEIDENHAIN TNC 640
153
5.7 CIR
C
ULAR S
T
UD (Cy
c
le 257
, DIN/ISO: G257)
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
