6 Before Starting Positioning Operation
6.9 Cautions for Positioning Operation
48
FX3U-1PG User's Manual
6.9 Cautions for Positioning Operation
• Set the relative travel distance (travel distance from the current value to the target address) in the
positioning operation to a converted pulse value within ±32 bits (-2,147,483,648 to +2,147,483,647 PLS).
When the relative travel distance exceeds ±32 bit in the pulse conversion value, the set value overflow
error occurs.
• Only in the variable speed operation and the external command positioning operation, can a negative
value can be set to operation speed I and operation speed II.
• When operation speed I, operation speed II, JOG speed, zero return speed (high speed), and zero return
speed (creep) is at the bias speed or slower, operation is executed at the bias speed. However, if the bias
speed is 0, operation is executed at 1 Hz.
• When operation speed I, operation speed II, JOG speed, zero return speed (high speed), and zero return
speed (creep) is at the maximum speed or faster, operation is executed at the maximum speed.
• Setting of the positioning parameter selection (BFM#32) determines whether the positioning parameter is
used or the extension positioning parameter is used. Set the buffer memories that correspond to the
selected positioning parameter.
• For approximate S-shaped acceleration/deceleration, set the acceleration/deceleration time within the
range from 1 ms to 5000 ms.
• When several operation start commands turn on at the same time in the operation command (BFM#25 b6,
b8 to b15), the positioning operation is not executed. The operation command multiple selection error
occurs.
• When another operation command is turned on during operation, the operation command turned on later is
ignored, and no error will occur.
• The FX
3U-1PG continues the positioning operation even if the PLC mode changes from RUN to STOP
during the positioning operation.
6.9.1 Command error when machine system units are used and when combined system
units are used
When the pulse rate is A, the feed rate is B and the relative travel distance is C, the value "C × (A/B)"
indicates the pulse quantity which should be generated by the FX
3U-1PG.
Even if the value "(A/B)" is not an integer, error is not generated in the command if the value "C × (A/B)" is
integer.
However, when C x (A/B) is not an integer, an error within 1 pulse when rounding off occurs.
When the operation is executed using the absolute address specification, an error within one pulse by
rounding off occurs. When positioning operation is repeatedly made using relative address specification,
errors accumulate.
Point
• Error accumulation does not occur in the case of the motor system unit.
• When the travel distance (PLS) exceeds ±32 bit, the set value overflow error occurs.
• When the maximum speed, bias speed exceeds 200 kHz, the numeral value set failure error occurs.
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