HEIDENHAIN TNC 640 (34059x-02) - Manual (Page 199)

Approaching and departing a contour 6.3
6
TNC 640 | User's Manual
HEIDENHAIN Conversational Programming | 5/2013
199
Important positions for approach and departure
Starting point P
S
You program this position directly before the APPR block. P
S
lies outside the contour and is approached without radius
compensation (R0).
Auxiliary point P
H
Some of the paths for approach and departure go through an
auxiliary point P
H
that the TNC calculates from your input in the
APPR or DEP block. The TNC moves from the current position
to the auxiliary point P
H
at the feed rate last programmed. If you
have programmed
FMAX (positioning at rapid traverse) in the
last positioning block before the approach function, the TNC also
approaches the auxiliary point P
H
at rapid traverse.
First contour point P
A
and last contour point P
E
You program the first contour point P
A
in the APPR block.
The last contour point P
E
can be programmed with any path
function. If the APPR block also contains a Z axis coordinate, the
TNC will first move the tool to P
H
in the working plane, and then
move it to the entered depth in the tool axis.
End point PN
The position P
N
lies outside of the contour and results from your
input in the DEP block. If the DEP block also contains a Z axis
coordinate, the TNC will first move the tool to P
N
in the working
plane, and then move it to the entered depth in the tool axis.
Abbreviation Meaning
APPR Approach
DEP Departure
L Line
C Circle
T Tangential (smooth connection)
N Normal (perpendicular)
The TNC does not check whether the programmed
contour will be damaged when moving from the
actual position to the auxiliary point P
H
. Use the test
graphics to check.
With the APPR LT, APPR LN and APPR CT functions,
the TNC moves the tool from the actual position to
the auxiliary point P
H
at the feed rate/rapid traverse
that was last programmed. With the APPR LCT
function, the TNC moves to the auxiliary point P
H
at
the feed rate programmed with the APPR block. If no
feed rate is programmed before the approach block,
the TNC generates an error message.