
B-63944EN-1/02 PROGRAMMING 5.COMPENSATION FUNCTION
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5.8 AUTOMATIC TOOL OFFSET (G36, G37)
When a tool is moved to the measurement position by execution of a
command given to the CNC, the CNC automatically measures the
difference between the current coordinate value and the coordinate
value of the command measurement position and uses it as the offset
value for the tool. When the tool has been already offset, it is moved
to the measurement position with that offset value. If the CNC judges
that further offset is needed after calculating the difference between
the coordinate values of the measurement position and the
commanded coordinate values, the current offset value is further
offset.
Refer to the instruction manuals of the machine tool builder for
details.
Explanation
- Coordinate system
When moving the tool to a position for measurement, the coordinate
system must be set in advance. (The workpiece coordinate system for
programming is used in common.)
- Movement to measurement position
A movement to a measurement position is performed by specifying as
follows in the MDI, or MEM mode :
G36 Xxa ; or G37 Zza ;
In this case, the measurement position should be xa or za (absolute
programming).
Execution of this command moves the tool at the rapid traverse rate
toward the measurement position, lowers the feedrate halfway, then
continues to move it until the approach end signal from the measuring
instrument is issued.
When the tool tip reaches the measurement position, the measuring
instrument outputs the measurement position reach signal to the CNC
which stops the tool.
- Offset
The current tool offset value is further offset by the difference
between the coordinate value (α or β) when the tool has reached the
measurement position and the value of xa or za specified in G36Xxa
or G37Zza.
Offset value x = Current offset value x+(α-xa)
Offset value z = Current offset value z+(β-za)
xa : Programmed X-axis measurement point
za : Programmed Z-axis measurement point
These offset values can also be altered from the MDI keyboard.