
B-63782EN/01 NC FUNCTIONS 20.AXIS CONTROL FUNCTIONS
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20.16 MULTIPLE ROTARY CONTROL AXIS FUNCTION
When absolute programming is selected, either of the following two
operations can be specified by the RSR bit (bit 2 of parameter 1007).
(1) The NC unit rounds down the value specified in the absolute
command (G90) to a value indicating a full turn or less. The
difference between the rounded value and the current position is
the angular displacement. When the bit 5(INC) in parameter No.
1007 is specified, short-cut control can be executed. When the
difference between the rounded value and the current position
indicates more than a half turn, the short-cut control function
allows reverse rotation up to the specified position.
(2) The sign of the specified value indicates the direction of rotation.
(The plus sign (+) indicates counterclockwise rotation and the
minus sign (-) clockwise rotation). The absolute value of the
specified value indicates the destination.
An absolute value of a position relative to the rotary axis is represented
by an equivalent value within the amount of travel for a single
revolution as specified in parameter 1260.
20.17 ABSOLUTE POSITION DETECTION
For an axis with an absolute pulse coder, there is no need to perform a
reference position return when the power is applied, because the CNC
maintains the machine position even when the power is turned off.
The absolute pulse coder consists of an incremental pulse coder and an
absolute counter for detecting the absolute position of the machine
according to the value in the counter. Even if the CNC power is off, the
absolute pulse coder can maintain the machine position, because it uses
battery power to maintain the contents of its memory. For an axis with
an absolute pulse coder, the current machine position is read from the
absolute counter when the CNC power is switched on, and the machine
coordinate system and workpiece coordinate system are automatically
set up according to the value received from the absolute counter.
Therefore automatic operation can begin promptly.
The restrictive phrase "Reference position return is required after
power is turned on" or "Usable after a reference position return is made
when power is applied" in the relevant operation manual does not apply
to those axes with an absolute pulse coder.