HEIDENHAIN TNC 407 (280 580) ISO Programming - Manual (Page 139)

TNC 426/TNC 425/TNC 415 B/TNC 407 5 - 6
5 Programming Tool Movements
Fig. 5.10: Soft contour departure
Fig. 5.9: Soft contour approach
5.2 Contour Approach and Departure
Tangential approach and departure
The tool approaches the contour on a tangential arc with G26, and departs
it with G27. This prevents dwell marks.
Starting point and end point
Starting point S and end point E of the machining sequence are off the
workpiece near the first or last contour element.
The tool path to the starting point or end point is programmed without
radius compensation.
Input
• For the approach path, G26 is programmed after the block containing
the first contour point (the first block with radius compensation G41/
G42).
• For the departure path, G27 is programmed after the block containing
the last contour point (the last block with radius compensation G41/
G42).
Program structure
G00 G40 G90 X ... Y ... ............................................... Starting point S
G01 G41 X ... Y ... F350 .............................................. First contour point A
G26 R ... ..................................................................... Soft approach
Contour elements
X ... Y ... ...................................................................... Last contour point B
G27 R ... ..................................................................... Soft departure
G00 G40 X ... Y ... ....................................................... End point
E
The radius in G26/G27 must be selected such that it is possible to perform the circular arc between the contour
point and the starting point or end point.
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B
E
G40
R
G41
A
S
G40
R
G41