Risk Assessment; Residual Risks (Common); Residual Risk (For Each Function) - Mitsubishi Electric MELFA CR750 Series Instruction Manual

1 Function and configuration

1.5 Risk assessment

To ensure safety, the user needs to assess all the risks and determines residual risks for the mechanical system
as a whole. Companies or individuals who configure the system will accept full responsibility for installation and
authorization of the safety system. Assessment for all risks and safety level certification are required for the
equipment/system as a whole. The following shows residual risks related to the safety monitoring function of this
product.
1.5.1

Residual risks (common)

(1) If the origin settings or parameter settings or programs of a robot controller are incorrect, unexpected
operation may occur and safety cannot be ensured. Fully check whether operations are as intended.
(2) Until correct installation, wiring, and adjustment are achieved, safety cannot be ensured.
(3) Only a qualified person is given the authority to install, start, repair, adjust, etc. the equipment to which
devices are installed. Installing or operating the equipment should be done by a trained engineer.
(4) For the safety monitoring function, perform the wiring separately from other signal wirings.
(5) Protect cables by appropriate means (installing inside the control panel, using a cable guard, etc.).
(6) It is recommended to use switches, relays, sensors, etc. conforming to safety standards. For using switches,
relays, sensors, etc. not conforming to safety standards, sufficient verification of safety is necessary on the
customer side.
(7) The safety functions targets only the Robot controller and the robot arm.The safety functions not contain the
additional axis (robot additional axis and user mechanism). When the customer uses the additional axis, the
customer shall do ensure and the evaluation of the safety of the additional axis and the robot.
(8) In order to diagnose the failure of the controller, at least once every six months, please turn off the robot
controller's power. The controller executes the fault diagnosis of the hardware when the power is turned on.
1.5.2

Residual risk (for each function)

(1) STO function
This function interrupts transmission of power to the motor installed in the robot arm, and may bring variation to
a posture of robot arms due to mechanical factors, such as break of timing belts or brake wear, etc. of the robot
arm. Periodic maintenance of the robot arm is required.
(2) SS1 function
This function controls and decelerates the motor speed installed to a robot arm. The movement cannot be
stopped immediately after deceleration is started.
(3) SLS function
This function monitors the TCP speed of the robot, not each part of the robot arm. Depending on the robot
posture, some parts of the robot arm may move at the speed higher than the monitoring speed.
As this function is activated only when the robot servo is turned ON, this function does not monitor the TCP
speed while the robot servo is turned OFF.
(4) SLP function
In the following cases, the monitoring position may exceed the position monitoring plane. The following shows
some concrete examples.

At the moment the position monitoring plane is applied, the robot position is beyond the plane.

At the moment the position monitoring plane is applied, the robot is moving near the plane at high
speed.

The robot posture changes with the robot brake released.
(5) STR function
This function monitors the motor torque for each axis of the robot, not the power generated at each part of the
robot.
1-4 Risk assessment