
B–61404E/08
6. REFERENCE POSITIONPROGRAMMING
79
Positioning to the intermediate or reference positions are performed at the
rapid traverse rate of each axis.
Therefore, for safety, the cutter compensation, and tool length
compensation should be cancelled before executing this command.
The coordinates for the intermediate position are stored in the CNC only
for the axes for which a value is specified in a G28 block. For the other
axes, the previously specified coordinates are used.
Example N1 G28 X40.0 ; Intermediate position (X40.0)
N2 G28 Y60.0 ; Intermediate position (X40.0, Y60.0)
In a system without an absolute–position detector, the first, third, and
fourth reference position return functions can be used only after the
reference position return (G28) or manual reference position return (see
III–3.1) is made. The G30 command is generally used when the automatic
tool changer (ATC) position differs from the reference position.
In general, it is commanded immediately following the G28 command or
G30. For incremental programming, the command value specifies the
incremental value from the intermediate point.
Positioning to the intermediate or reference points are performed at the
rapid traverse rate of each axis.
When the workpiece coordinate system is changed after the tool reaches
the reference position through the intermediate point by the G28
command, the intermediate point also shifts to a new coordinate system.
If G29 is then commanded, the tool moves to to the commanded position
through the intermediate point which has been shifted to the new
coordinate system.
The same operations are performed also for G30 commands.
G27 command positions the tool at rapid traverse rate. If the tool reaches
the reference position, the reference position return lamp lights up.
However, if the position reached by the tool is not the reference position,
an alarm (No. 092) is displayed.
The lamp for indicating the completion of return does not go on when the
machine lock is turned on, even when the tool has automatically returned
to the reference position. In this case, it is not checked whether the tool
has returned to the reference position even when a G27 command is
specified.
When the G28 command is specified when manual return to the reference
position has not been performed after the power has been turned on, the
movement from the intermediate point is the same as in manual return to
the reference position.
In this case, the tool moves in the direction for reference position return
specified in parameter ( No. 003 #0 to #3). Therefore the specified
intermediate position must be a position to which reference position
return is possible.
Explanations
D Reference position
return (G28)
D 2nd, 3rd, and 4th
reference position return
(G30)
D Return from the
reference position (G29)
D Reference position
return check (G27)
Restrictions
D Status the machine lock
being turned on
D First return to the
reference position after
the power has been
turned on (without an
absolute position
detector)