Mitsubishi Electric MELSEC iQ-R-RD75P4 User Manual page 4

[Design Precautions]
WARNING
● When connecting an external device with a CPU module or intelligent function module to modify data
of a running programmable controller, configure an interlock circuit in the program to ensure that the
entire system will always operate safely. For other forms of control (such as program modification,
parameter change, forced output, or operating status change) of a running programmable controller,
read the relevant manuals carefully and ensure that the operation is safe before proceeding. Improper
operation may damage machines or cause accidents.
● Especially, when a remote programmable controller is controlled by an external device, immediate
action cannot be taken if a problem occurs in the programmable controller due to a communication
failure. To prevent this, configure an interlock circuit in the program, and determine corrective actions
to be taken between the external device and CPU module in case of a communication failure.
● Do not write any data to the "system area" and "write-protect area" of the buffer memory in the
module. Also, do not use any "use prohibited" signals as an output signal from the CPU module to
each module. Doing so may cause malfunction of the programmable controller system. For the
"system area", "write-protect area", and the "use prohibited" signals, refer to the user's manual for the
module used.
● If a communication cable is disconnected, the network may be unstable, resulting in a communication
failure of multiple stations. Configure an interlock circuit in the program to ensure that the entire
system will always operate safely even if communications fail. Failure to do so may result in an
accident due to an incorrect output or malfunction.
● To maintain the safety of the programmable controller system against unauthorized access from
external devices via the network, take appropriate measures. To maintain the safety against
unauthorized access via the Internet, take measures such as installing a firewall.
● Configure safety circuits external to the programmable controller to ensure that the entire system
operates safely even when a fault occurs in the external power supply or the programmable controller.
Failure to do so may result in an accident due to an incorrect output or malfunction.
(1) Machine OPR (Original Point Return) is controlled by two kinds of data: an OPR direction and an
OPR speed. Deceleration starts when the near-point dog signal turns on. If an incorrect OPR
direction is set, motion control may continue without deceleration. To prevent machine damage
caused by this, configure an interlock circuit external to the programmable controller.
(2) When the positioning module detects an error, the motion slows down and stops or the motion
suddenly stops, depending on the stop group setting in parameter. Set the parameters to meet the
specifications of the positioning control system used. In addition, set the OPR parameters and
positioning data within the specified setting range.
(3) Outputs may remain on or off, or become undefined due to a failure of a component such as an
insulation element and transistor in an output circuit, where the positioning module cannot detect
any error. In a system where the incorrect outputs could cause a serious accident, configure an
external circuit for monitoring output signals.
● An absolute position restoration by the positioning module may turn off the servo-on signal (servo off)
for approximately 60ms + scan time, and the motor may run unexpectedly. If this causes a problem,
provide an electromagnetic brake to lock the motor during absolute position restoration.
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