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TNC 426/TNC 425/TNC 415 B/TNC 407
5
Programming Tool Movements
M Functions for Contouring Behavior
Feed rate at circular arcs: M109/M110/M111
Standard behavior – M111
The programmed feed rate refers to the center of the tool path.
Constant contouring speed at circular arcs (feed rate increase and decrease) – M109
The TNC reduces the feed rate for circular arcs at inside contours such
that the feed rate at the tool cutting edge remains constant. At outside
contours the feed rate for circular arcs is correspondingly increased.
Constant contouring speed at circular arcs (feed rate decrease only) – M110
The TNC reduces the feed rate for circular arcs only at inside contours. At
outside contours the feed rate remains the same.
Insert rounding arc between straight lines: M112 E...
Standard behavior – without M112 E...
A contour consisting of many short straight lines is normally machined
such that the corners are cut as exactly as possible. When executing
programs without tool radius compensation, the feed rate is therefore
decreased to zero at corners.
Insert rounding arc between straight lines – with M112 E...
The TNC inserts a rounding arc between
two uncompensated straight
lines
. The size of the arc depends on:
• the permissible deviation from the programmed contour entered for E
(if no deviation is entered, the TNC assumes the permissible deviation
to be infinite)
• the lengths of the two straight line segments between which the
rounding arc is to be inserted
• the programmed feed rate (override setting 150%) and the circular
acceleration (defined by the machine tool builder through machine
parameters).
From these three criteria, the TNC calculates three rounding arcs and
inserts the arc with the largest radius. If necessary, the contouring feed
rate will automatically be reduced to comply with the programmed
tolerance.
The permissible deviation E should be less than the programmed
distance between points.
Parameter programming
You can also define E through Q parameters.
Duration of effect
M112 E... is effective during operation with feed precontrol as well as with
servo lag. To cancel M112 E..., enter M113.
Fig. 5.50:
Permissible deviation E from the
programmed contour
R
E
A
