Safety light curtainsSafety light curtains are opto-electronic presence detection devices, often referred to as safety light barriers, safety light guards, light guards or light curtains. They are supplied as a transmitter and a receiver: the transmitter projects an array of parallel infrared light beams to the receiver, which consists of a number of photoelectric cells. When an object breaks one or more of the beams, a stop signal is sent to the guarded equipment. That might be an operator crossing into the guarded area, or in the case of a machine fault it could even be an item being ejected from the guarded area.
As an alternative to mechanical barriers and other forms of machine guarding, safety light curtains are ideally suited to applications where personnel need frequent and easy access to the hazardous area. In this kind of situation light curtains can help to deliver increased efficiency and productivity of machinery and processes by providing a more intelligent approach to protection. They can also help to speed up maintenance of machines and equipment, whilst aiding operability.
Light curtains are available to meet the most stringent current safety legislation. Different resolutions and protection heights can be provided to meet the specific requirements of individual applications, most commonly machine guarding applications to detect the presence of a person's finger, hand, limb or whole body.
Demanding safety requirements
That said, not all safety light curtains are created equal. As a long time partner of Datalogic, OEM Automatic offers a full range of safety light curtains, including the recently introduced SG2 Muting and SG4 Extended products. These are designed to satisfy the most demanding safety requirements in applications such as automotive, packaging, metalworking, materials handling, automatic and semi-automatic assembly lines, automated warehouses, woodworking and electronics.
An important feature of these new products is that there is no dead zone. With traditional safety light curtains, there is a dead zone at the bottom that is home to the status LEDs and the connectors. This has implications where space is at a premium, but also where users want to cascade two or more products for a greater area of coverage. The dead zone often requires a workaround which increases application complexity or adds cost. By contrast, the SG2 Muting and SG4 Extended ranges are designed such that the whole of the front face is active, giving maximum coverage of the complete area, whether hand or finger protection is required. The status LEDs are moved to the side and the connector is at the back, so there is no dead zone at all. Curtain heights from 300-1800mm are available, and up to three systems can be cascaded for greater areas of protection - again with no dead zone to worry about.
Operating distance is up to 20m, and the light curtains meet Safety Type 2 (PLd) or Safety Type 4 (PLe) requirements, with 30mm and 14mm resolutions respectively. Integrated muting and integrated blanking functions are provided as standard. Basic programming of the light curtains can be achieved through the BCM (basic configuration mode) buttons on the units themselves, or with a PC when programming of more advanced functions is required (advanced configuration mode - ACM). Further simplifying installation and operation, an 8-LED user interface on the left side of the control panel (on both units of the light curtain) provides a simple means for the user to control and check the operational status, for alignment mode, normal operation and for troubleshooting.
On the SG4, an Ethernet adapter is available, making the system flexible and addressable, and allowing features such as cloning, remote monitoring and remote programming.
Additional functions include reduced response time, which allows installation of the light curtains closer to the area of danger without compromising safety, so providing better usage of available floor space or allowing the reduction of machine dimensions. Where blanking is required, disabling a section of the sensing field to allow objects such as tooling, feed stock and work pieces to pass through the safety light curtain without triggering a stop signal, the SG4 Extended offers the flexibility of either fixed or floating beams, with the additional option of compulsory object detection.
Various muting options are also selectable, allowing the light curtain to be disabled during any non-hazardous periods of machine or process cycles. For example, in a given processing or conveyor application, it might be required that a pallet should be allowed to pass through the light curtain without bringing the production line to a halt, whereas a person breaking the beam could pose a significant threat to safety and would change the output status of the light curtain. The SG2 Muting and SG4 Extended offer the possibility of both entry and exit muting, with either fixed or external muting sensors, and the provision of an override function.
Rotating brackets enable installation in reduced spaces and ensure easy optical alignment in what might otherwise be challenging conditions. A further option is an EDM function, which enables the outputs to be connected to forced guided relays. Finally, an anti-interference option enables separate safety light curtains to be installed side by side without optical interference, eliminating the need for mechanical separating shields.
OEM Automatic UK has over 25 years experience in supplying leading products to industry, with a product range that is one of the widest and deepest on the market. The company operates in four key business areas: motors; panel products; machine/safety; and pressure/flow products. OEM Automatic can also help to select the best products for each application, and reduce the number of suppliers, so lowering the total cost of purchasing.
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