How Do Robot Maintenance Engineers Protect Themselves While 'Treating' Robots?

As the trend of 'machines replacing humans' accelerates, the demand for robot maintenance and upkeep from enterprises is also increasing. In the past week alone, several company owners have spared no expense in seeking repair personnel, with issues ranging from robot software system problems to robot body failures.

It's not hard to see that robot maintenance will be a highly sought-after profession in the coming years. However, industrial robots, while serving humans, are also 'steel monsters'. Once mechanical or program failures occur, they can cause serious injury to operators. How can we, Zhong Heng Biao Machinery maintenance engineers, protect ourselves while 'treating' robots?

In response to the requests from many robot enthusiasts, this edition's editor will discuss with everyone: What safety precautions should be taken when performing maintenance on industrial robots?

I. Grasp Safety Concepts

The 'Trajectory Intersection Theory' posits that within a system, when the formation processes of unsafe human actions and unsafe physical conditions intersect in time and space, an accident occurs. Therefore, when we 'treat' robots, on one hand, we must be familiar with the robot's safety equipment, and on the other hand, we must comply with robot safety operation procedures, prohibiting 'three violations' behavior.

II. Familiarize Yourself with Safety Equipment

If operated improperly, robots can cause very serious safety accidents. For this reason, many safety devices have been created to further reduce the probability of accidents and mitigate their harm. Taking a certain domestic robot as an example, let's briefly introduce the robot's safety equipment.

(1) Emergency Stop Equipment

The robot has the following emergency stop devices:
1) Teach pendant emergency stop button;
2) Control cabinet emergency stop button (disconnects servo power).
When an emergency stop button is pressed, the robot stops running immediately; external emergency stop input signals come from peripheral equipment (such as safety light curtains, safety fences, safety doors); the signal terminal block is inside the robot control cabinet.

(2) Mode Selector Switch

The mode selector switch is installed on the robot's teach pendant. Maintenance personnel can use this switch to select an operating mode. When selecting an operating mode via the mode selector switch, the corresponding information is displayed on the teach pendant (TP) liquid crystal display (LCD).

1. Operating Mode
2. The operation interface is active;
3. The robot program can be started via the start button on the teach pendant;
4. Safety fence signals are active;
5. The robot can run at the set speed.
6. Teach Mode
7. Programs can only be activated via the teach pendant (TP);
8. Robot operating speed does not exceed 250mm/s;
9. Safety fence signals are active.

(3) Safety Equipment
1) Safety fence (fixed protective device);
2) Safety door (with interlock device), safety pin and socket;
3) Other protective equipment.
These safety devices must comply with relevant national safety standards.

1. Safety Fence
2. The fence must be able to withstand foreseeable operations and surrounding impacts;
3. The fence must not have sharp edges or protrusions, and it itself must not be a source of danger;
4. The fence prevents people from entering the robot's protected area (i.e., the non-safe zone) by means other than 'opening the interlock device';
5. The fence is permanently fixed in place and can only be moved with the aid of tools;
6. The fence should obstruct the production process as little as possible;
7. The fence should be placed sufficiently far from the robot's maximum range of motion;
8. The fence should be grounded to prevent accidental electric shock.

2. Safety Door and Safety Pin
1) Unless the safety door is closed, the robot cannot operate automatically;
2) Before the safety door is closed, the robot's online operation cannot be restarted; this is something operators must consider;
3) The safety door is secured using a safety pin and socket; appropriate sizes must be selected;
4) The safety door must remain closed until before a hazard occurs (protective device with a guard), or opening the safety door while the robot is running must send a stop or emergency stop command (interlocked protective device).
Note: Ensure that interlock devices used to prevent hazards (such as stopping the robot system's hazardous operation) do not become a source of new hazards (e.g., hazardous objects falling into the work area).

III. Related Precautions

When we maintenance personnel perform repairs on robots, we often encounter situations where 'it cannot be repaired' or 'it has no repair value', and only component replacement operations can be performed. So what precautions are needed when replacing components?

(1) Precautions Before Replacement
Before operating the robot, check if the servo power indicator light is off when the front door emergency stop button on the control cabinet is pressed. If the robot cannot be stopped in an emergency, it may cause personal injury or equipment damage.
When performing teach operations within the robot's range of motion, please note the following:
1) Maintain a view of the robot from the front;
2) Strictly adhere to operating procedures;
3) Ensure that in an emergency, the operator can move to a safe location;
4) Robot movement caused by misoperation may lead to injury or fatal accidents; if there is a problem, immediately press any emergency stop button on the control cabinet or teach pendant;
5) Before performing robot teach operations, check for any abnormalities in robot movement and check for damage to external cable covers. If abnormalities are found, repair them promptly or take other necessary measures;
6) The teach pendant must be returned to its designated place after use. If the teach pendant is inadvertently left on the robot, fixture, or floor, it may collide with the robot or fixture when the robot moves, causing personal injury or equipment damage.

(2) Precautions When Replacing Control Cabinet Components
1) Always disconnect the power before opening the control cabinet door, otherwise there is a risk of electric shock;
2) Wait at least 5 minutes after cutting the power before replacing servo units, switching power supply units, system I/O units, contactors, and other components. During this time, do not touch the terminal blocks, otherwise there is a risk of electric shock;
3) During maintenance, post warning signs such as 'No Power On' or 'Do Not Close Power' at the main power source (knife switch, circuit breaker, etc.), control cabinet, and related control boxes;
4) The regenerative resistor is a high-temperature component; do not touch it, otherwise there is a risk of burns;
5) After maintenance is complete, do not leave tools inside the control cabinet, and confirm that the control cabinet door is properly closed.

(3) Precautions When Replacing Servos
1) When replacing servo units, always wait at least 5 minutes after cutting the power;
2) During this time, do not touch the terminal blocks, otherwise there is a risk of electric shock.

(4) Precautions When Replacing the System Main Unit
When replacing the system main unit, always cut the power, otherwise there is a risk of electric shock.

(5) Precautions When Replacing Components Like Contactors
When replacing electrical components like contactors, always cut the external power supply and confirm that no power is supplied to the robot control cabinet.

(6) Precautions When Replacing Batteries
1) Old batteries should be disposed of properly to avoid pollution;
2) Batteries should be replaced every 2 years. After battery replacement, confirm that the zero point position is correct.

Friends in the robot industry, Zhong Heng Biao Machinery's editor has only introduced safety precautions for one type of robot maintenance. As long as we master the safety operation requirements for different brands and models of robots and ensure our own safety protection, then a 'sick' robot is not scary.

Data archive number: 10761. Content organized from the old site database.