FANUC Series 16/18/160/180-Model C Machining Center Operators Manual

When machining of the step is commanded by circular machining in the
case of a program containing a step smaller than the tool radius, the path
of the center of tool with the ordinary offset becomes reverse to the
programmed direction. In this case, the first vector is ignored, and the tool
moves linearly to the second vector position. The single block operation
is stopped at this point. If the machining is not in the single block mode,
the cycle operation is continued. If the step is of linear, no alarm will be
generated and cut correctly. However uncut part will remain.
The first vector is ignored
Tool center path
Programmed path
Center of the circu-
lar machining
An overcutting will result if the first vector is not ignored.
However, tool moves linearly.
Linear movement Stop position after execution of a single
It is usually used such a method that the tool is moved along the Z axis
after the cutter compensation is effected at some distance from the
workpiece at the start of the machining.
In the case above, if it is desired to divide the motion along the Z axis into
rapid traverse and cutting feed, follow the procedure below.
N1 G91 G00 G41 X500.0 Y500.0 D1 ;
N3 G01 Z–300.0 F100 ;
N6 Y1000.0 F200 ;
(500, 500)
N3:Move command in Z axis
After compensation
In the program example above, when executing block N1, blocks N3 and
N6 are also entered into the buffer storage, and by the relationship among
them the correct compensation is performed as in the figure above.
Then, if the block N3 (move command in Z axis) is divided as follows:
As there are two move command blocks not included in the selected plane
and the block N6 cannot be entered into the buffer storage, the tool center
path is calculated by the information of N1 in the figure above. That is,
the offset vector is not calculated in start–up and the overcutting may
D Machining a step smaller
than the tool radius
D Starting compensation
and cutting along the

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