HEIDENHAIN TNC 640 (34059x-02) ISO programming - Manual (Page 332)

Programming: Miscellaneous functions
10.4 Miscellaneous functions for path behavior
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TNC 640 | User's Manual for DIN/ISO Programming | 5/2013
Rounding corners: M197
Standard behavior
The TNC inserts a transition arc at outside corners with active
radius compensation. This my lead to grinding of the edge.
Behavior with M197
With Function M197 the contour at the corner is tangentially
extended and a smaller transition arc is then inserted. When you
program Function M197 and then press the ENT key, the TNC
opens the
DL input field. In DL you define the length with which the
TNC extends the contour elements. With M197 the corner radius is
reduced, the corner grinds less and the traverse movement is still
tangential.
Effect
The Function M197 is effective blockwise and is only effective on
outside corners.
Example NC blocks
L X... Y... RL M197 DL0.876