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reference point specified by the manufacturer, the forward limit points of X-axis, Y-axis and Z-axis as reference
points. Machine origin, also known as machine zero, is determined by the machine reference point indirectly.
When the machine starts, first of all, make sure the position of X axis, Y-axis and Z-axis returning to the zero, that
is returning to the reference point. So the NC device can confirm the location of the machine origin by reference
point, so as to establish a machine coordinate system by machine zero in the CNC system. Whether return to the
reference point before auto-run program, can be set by parameter 0876. Set reference point in the machine
coordinate system by parameters 080-1082.
7.2 Reference Position (G28)
Tools are automatically moved to the reference position via an intermediate position along a specified axis.
Therefore, should clear the tool radius compensation and tool length compensation before executing the
instruction for safety. The coordinate value of intermediate points stored in the CNC, only store the coordinate
values of instruction axis in G28 block each time. Using the previous coordinate values for the other axis.
Format:
G28 X_Y_Z_ ;
G28 X0 Y0 Z0;It represents the tool goes through the work coordinate system origin and then return to the
reference point,so it is easy to interfere with the tool and the workpiece fixture.
G91 G28 X0 Y0 Z0 ;It indicates the tool return reference point from the current point.
Common formats:
G91 G28 Z0
；
G28 X0 Y0
；
X _ Y_ Z_ represents the mid-point, its coordinates can be used with absolute value or incremental value. If
the increment value, the incremental value means an intermediate point relative to the current point tool. Set the
intermediate point, in order to prevent occurring interference with the workpiece or fixtures when the tool returns
a reference point. Using this instruction, should pay attention to the following issues:
1.
Usually G28 instruction is used to changing tools, should cancel the tool length
compensation and
radius compensation before executing the instruction;
2.
In the G28 block, not only memory the movement command value, and the mid-point coordinates.
也
That is for not specified axis in using G28 program segment, previous coordinate values in G28, as the coordinate
values of intermediate point on the axis .
For example
：
N01 G90 G00 X100 Y100 Z100
；
N02 G28 X200 Y300
；
（
Intermediate point is 200,300
）
N03 G28 Z150
；
（
Intermediate point is 200,300,150
）
7.3 Setting Returning Reference Point Speed
After power, before the establishment of the machine coordinate system at the first reference point,
the
speed of returning to the reference point
in manual and automatic modes and the speed
of automatic fast
moving are the same
，
set by parameter 0960-0962.Even after returning to the reference point, or the establishment
of the machine coordinate system, the speed of returning to the reference point in manual is the same as the setting
value by the parameter.
NOTE:
1.
Reference point speed can use the rapid traverse override (F0,25,50,100%), the setting value is the
speed value of 100% ratio.
2.
After returning to the reference point, or the establishment of the machine coordinate system, The feed
rate of automatic returning to the reference point will be consistent with the usual rapid moving speed.
