Light Curtains

Safety light curtains, formally classified as Active Optoelectronic Protective Devices (AOPDs), serve as critical components in industrial functional safety systems. Each system consists of a transmitter and a receiver that create a synchronised array of infrared light beams. When one or more beams are interrupted by an opaque object, the light curtain sends a safety signal to the machine’s safety circuit, triggering an immediate stop or safe-state transition.

Unlike fixed mechanical guards, light curtains provide non-contact protection while allowing frequent and unobstructed access to the point of operation. Their integration is essential for high-speed automated environments where mechanical barriers would impede throughput or ergonomics. By leveraging rapid response times — often in the low millisecond range — light curtains ensure that hazardous motion is arrested before a technician can reach the danger zone, conforming to rigorous international safety standards such as IEC 61496 and ISO 13849.

Types of Safety Curtain Sensors

The selection of a safety curtain sensor is dictated by the specific risk assessment of the application, focusing primarily on the required safety integrity and the physical dimensions of the object that must be detected. Standardisation classifies these devices into distinct types based on their optical performance and fault-tolerance levels, ensuring they meet the necessary Performance Level (PL) or Safety Integrity Level (SIL) for machine safety in the hazardous zone.

By Safety Rating

• Type 2: Type 2 light curtains are designed for applications with lower risk profiles, generally aligning with Performance Level c (PL c) or SIL 1. They utilise a larger effective aperture angle, making them more susceptible to optical interference, and they perform periodic self-tests rather than continuous internal monitoring.
• Type 4: Type 4 light curtains represent the highest level of safety, suitable for high-risk machinery requiring PL e or SIL 3 compliance. These devices feature a narrow effective aperture angle to minimise the risk of optical bypassing and incorporate redundant internal circuitry with continuous self-checking to ensure immediate detection of internal component failure.

By Resolution

• Finger Detection: Finger detection curtains feature the highest resolution, typically with a beam pitch of 14mm or less. This allows for the detection of very small objects, enabling the curtain to be installed in close proximity to the hazardous point of operation, as the minimum safety distance is mathematically reduced by the increased sensitivity.
• Hand Detection: With a resolution ranging between 20mm and 40mm, hand detection sensors are the industry standard for general machine guarding. They are designed to trigger a stop command when a hand or arm enters the sensing field, balancing cost-effectiveness with reliable personnel protection for most assembly and fabrication tasks.
• Body/Access Detection: These sensors, often referred to as safety grids or multi-beam barriers, have a much wider beam pitch (typically 300mm to 500mm). They are used primarily for perimeter guarding and floor-to-ceiling access control, where the objective is to detect the presence of a full human body entering a restricted zone rather than a limb.

Industrial Applications of Safety Curtains

Safety light curtains are indispensable across various manufacturing sectors, providing a seamless interface between human operators and automated processes. Their ability to integrate with programmable safety controllers allows for sophisticated functions like muting and blanking, which differentiate between personnel and processed materials.

Machine Guarding

In metalworking and fabrication, light curtains protect operators of hydraulic presses, shears, and brake presses. The sensors are configured to stop the downward stroke of the ram instantly if the operator's hands enter the die area, preventing catastrophic crush injuries while allowing for rapid workpiece loading.

Material Handling

Automated conveyor systems utilise light curtains to secure transit paths where human pathways intersect with moving goods. By using muting sensors, the system can distinguish the profile of a pallet from a human, allowing goods to pass through the light curtain without tripping the safety circuit while maintaining a protective state for personnel.

Packaging and Sorting

In high-speed packaging lines, light curtains provide non-contact guarding around palletisers and shrink-wrappers. They are particularly effective here as they do not suffer from the mechanical wear associated with safety gates or interlocks, ensuring high uptime in continuous 24/7 production environments.

Access Control

For large-scale industrial cells, such as those found in automotive assembly, multi-beam light curtains act as electronic fences. They monitor the primary entry points to a work zone, ensuring that if an unauthorised individual enters the perimeter, all hazardous power is disconnected from the internal machinery.

Robotic Safety

In robotic welding or assembly cells, light curtains are often integrated with the robot’s controller to define 'slow-down' or 'stop' zones. This allows the robot to operate at full speed when the curtain is clear and transition to a safe speed or complete halt if a technician enters the vicinity for inspection.

The Leading Supplier and Distributor of Light Curtains in Singapore

RS is your trusted source for high-specification safety light curtains, offering a comprehensive range from market-leading manufacturers such as SICK, Omron, and ABB. Our inventory encompasses a variety of protective heights and optical resolutions at competitive prices, designed to facilitate the rapid integration of safety-related control systems into your industrial processes.

We also stock a wide array of complementary safety hardware, including safety relays and non-contact safety switches, to further secure your operational environment. Purchase your Type 4 safety curtains, multi-beam barriers, and safety-rated interlocks online today. For further details on our procurement process, logistical services, and shipping rates, please consult our delivery information page.