
B-63783EN-1/01 4.REFERENCE POSITION ESTABLISHMENT
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Servo position error and one-rotation signal
To perform manual reference position return when the reference
position has not yet been established, the tool must be fed, in manual
reference position return mode, in the reference position return
direction at a speed so that the servo position error exceeds the value
set in parameter No. 1836. At this time, the tool must cross the grid line
corresponding to a one-rotation signal from the position detector.
The servo position error is calculated from the following formula:
UG
F 11
60
1000
=amounterror position Servo ××
×
F: Feedrate
G: Servo loop gain [s-1]
U: Detection unit [mm]
(Example)
When the tool is fed at a feedrate F of 6000 mm/min with a servo
loop gain G of 30 s-1 and a detection unit U of 1 mm, the servo
position error is calculated as follows:
1
1
30
1
60
100060
errorposition Servo ××
×
=
= 3,333
By reversing the formula above, the following formula gives the
feedrate F needed to set the servo position error to 128 when the servo
loop gain G is 30 s-1 and the detection unit U is 1 mm:
30
1000
60128
F ×
×
=
= 230 [mm/min]
Therefore, when the servo loop gain is 30 s-1, the detection unit is 1
mm, and parameter No. 1841 is set to 128, the tool must be fed in the
reference position return direction at a speed of at least 230 mm/min
before manual reference position return.
Grid shift
The grid can be shifted by the distance set in parameter 1850, thus
shifting the reference position. The grid shift to be set in the parameter
must not exceed the reference counter capacity (parameter Nos.
1816#0 to 3 or 1896) (grid interval).