HEIDENHAIN iTNC 530 (60642x-03) - Manual (Page 384)

384 Programming: Miscellaneous functions
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.4 Miscellaneous functions f
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Feed rate for circular arcs: M109/M110/M111
Standard behavior
The TNC applies the programmed feed rate to the path of the tool
center.
Behavior at circular arcs with M109
The TNC adjusts the feed rate for circular arcs at inside and outside
contours so that the feed rate at the tool cutting edge remains
constant.
Behavior at circular arcs with M110
The TNC keeps the feed rate constant for circular arcs at inside
contours only. At outside contours, the feed rate is not adjusted.
Effect
M109 and M110 become effective at the start of block. To cancel
M109 or M110, enter M111.
Caution: Danger to the workpiece and tool!
On very small outside corners the TNC may increase the
feed rate so much that the tool or workpiece can be
damaged. Avoid M109 with small outside corners.
M110 is also effective for the inside machining of circular
arcs using contour cycles (special case).
If you define M109 or M110 before calling a machining cycle
with a number greater than 200, the adjusted feed rate is
also effective for circular arcs within these machining
cycles. The initial state is restored after finishing or
aborting a machining cycle.