FANUC Series 16/18/160/180-Model C for Lathe Operator Manual

PROGRAMMING
B–62754EN/01
15. COMPENSATION FUNCTION
253
In general, the offset value is changed in cancel mode, or when changing
tools. If the offset value is changed in offset mode, the vector at the end
point of the block is calculated for the new offset value.
N8N6
N7
Calculated from offset
value in block N6
Programmed path
Calculated from offset
value in block N7
When some vectors are produced between blocks N6 and N7, the vector
at the end point of the present blocks is calculated using the offset value
of the block N6.
When a negative offset value is specified, the program is executed for the
figure which is created by exchanging G41 for G42 or G42 for G41 in the
process sheet.
A tool machining an inner profile will machine the occur profile, and tool
machining the outer profile will machine the inner profile.
An example is shown below. In general, CNC machining is programmed
assuming a positive offset value. When a program specifies a tool path
as shown in 1, the tool will move as shown in 2 if a negative offset is
specified. The tool in 2 will move as shown in 1 when the sign of the offset
value is reserved.
Programmed path
1
2
WARNING
When the sign of the offset value is reversed, the offset
vector of the tool nose is reversed but the imaginary tool
nose direction does not change.
Therefore, do not reverse the sign of the offset value when
starting the machining meeting the imaginary tool nose to
the start point.
15.3.9
General Precautions
for Offset Operations
D Changing the offset
value
D The polarity of the offset
amount and the tool
nose center path

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