5 Essential Principles for Safeguarding Industrial Machinery

Machine Safeguarding remains a very important aspect of automation and robotics in industry, as well as commercial uses of automation. Machines must follow the First Rule of Robotics as given by Isaac Asimov, almost 100 years ago (“Runaround”, 1942): “Do No Harm”. This phrase is credited to the Hippocrates, who created an oath in medicine in 245CE. Thoughtful machine design with the support of sensors and controls prevent machines and robots from harming humans, both operators and casual visitors who might not know the danger presented by a machine. We have organized methods for protecting humans into five key categories that are presented here.

1. Mechanical Guarding Systems

Robot Enclosure Safety Guarding

Overview

Mechanical Guarding systems are physical barriers that prevent access to dangerous parts of machinery. These barriers can be fixed, movable, or interlocked and are crucial for protecting workers from hazardous machine elements.

Types of Guarding Systems

• Fixed Guards: Permanently attached to the machine and cannot be removed without tools. They are designed to provide continuous protection. They can be made of solid metal or mesh or can be clear plastic panels otherwise called “fencing”
• Movable Guards: These can be opened or removed to allow access for maintenance or operation but must be securely closed during operation.
• Interlocked Guards: These guards automatically shut down the machinery when opened, ensuring that operators cannot access hazardous areas while the machine is running.

Common Applications

• Manufacturing: Fixed guards are commonly used on machines like saws and presses to prevent accidental contact with moving parts.
• Construction: Movable guards are often employed in power tools, allowing for safe operation while still providing access for adjustments.
• Food Processing: Interlocked guards are frequently used in conveyor systems to ensure that operators cannot reach into moving equipment while it is operational.

Examples of Mechanical Guarding in Process Industries

2. Emergency Stops (E-Stops)

Overview

Emergency stop systems provide a quick means to halt machinery operation in case of an emergency. These systems are critical for preventing injuries and mitigating risks during unforeseen events. They provide a readily accessed method to immediately stop the motion of a machine

Key Features

• Location: E-stops are strategically placed around machinery, easily accessible to operators. They can be in the form of a button or a wire rope alongside a machine or conveyor.
• Redundant Systems: Many machines feature multiple E-stops to ensure that at least one is always accessible in an emergency. The contacts inside the switch are also redundant with forced safety
• Fail-Safe Design: E-stops are designed to fail in a safe condition, meaning that if they malfunction, they will stop the machine rather than allow it to continue operating.

Common Applications

• Manufacturing Plants: E-stops are widely used in assembly lines and heavy machinery to quickly stop operations in emergencies.
• Material Handling: In conveyor systems, E-stops can prevent accidents caused by jams or operator errors.
• Robotics: E-stops are essential in environments where robots and humans work in close proximity to ensure immediate cessation of robot movement if needed.

3. Presence Sensing Devices (PSD)

Overview

Presence sensing devices are used to detect the presence of individuals near hazardous machinery and take appropriate action to enhance safety. These devices use various technologies, such as infrared, laser, and microwave sensors, to monitor the area around the machine.

Types of PSDs

• Light Curtains: These are safety devices that create an invisible barrier; when the beam is interrupted, the machine will stop.
• Laser Scanners: These devices can create a 2D or 3D map of the workspace, detecting human presence and ensuring that machinery operates only when it is safe.
• Proximity Sensors: These detect the presence of operators or objects near the machine and can trigger shutdowns or slowdowns as necessary.

Common Applications

• Automated Manufacturing: Light curtains are extensively used around robotic arms to prevent operators from entering hazardous areas.
• CNC Machines and Press Brakes: A principal application of safety light curtains are the area in front of and behind a press brake to prevent the press from closing while a human body part is close to the press point
• Textile Industry: Laser scanners help ensure that workers are not in the path of moving machinery.
• Packaging and Shipping: Safety Light Curtains (PSDs) are often used for robotic palletizing systems to protect workers from the robot motion. Safety laser scanners (LIDARs) are another option for palletizing protection. Proximity sensors in packing machines help prevent injury by detecting operator presence before allowing machinery or robots to operate.

4. Safety Interlocks

Overview

Safety interlocks are devices that prevent machinery from operating under unsafe conditions. They ensure that machines can only be operated when certain safety conditions are met, thus reducing the risk of accidents.

Types of Interlocks

• Mechanical Interlocks: Physically prevent operation if a safety guard is removed or not correctly positioned.
• Electrical Interlocks: Use electrical signals to prevent machinery from operating until safety criteria are satisfied.
• Software Interlocks: Rely on programmed safety protocols within machinery controls to ensure safe operation.

Common Applications

• Injection Molding: Interlocks prevent the machine from operating if the safety guards are not in place, protecting operators during mold changes.
• Robotics: Used to ensure that robots cannot operate unless all safety conditions are satisfied, such as proper placement within the work area.
• Press Operations: Safety interlocks ensure that presses cannot operate unless the operator is positioned correctly and safely away from the danger zone.

5. Machine Safeguarding Controllers