Basic understanding of safety circuits
Laser scanners function much like light curtains. However, instead of having a separate transmitter and receiver to maintain a barrier, laser scanners can monitor gateways as well as portal areas from a single piece of hardware. In other words, light curtains provide perimeter guarding whereas laser scanners provide protection for larger portals into areas such as conveyor and robotic cells. As with all safety components, use of laser scanners requires calculation of the minimum safety distance. This value depends on the overall system stopping performance and the access time. However, the overall system stopping performance is likely to be considerably longer for laser scanners than that for light curtains due to the additional processing involved. The electronic safety circuits and safety components of today afford plant and OEM design engineers flexible options for protecting personnel and equipment. Software and other supplier resources help simplify the specification of safety systems for traditional interlock arrangements, workspaces protected by trapped-key designs, and even flexible areas that require plant personnel or machine operators to work in close proximity to conveyors, robotics, and other moving equipment associated with industrial automation.
Figure 3: SX Series safety laser scanners from Banner Engineering can safeguard access points and areas in industrial applications. The
way. These types of interlock components tend to be used with physical guards and gates. They are covered well by the standards discussed above. Other types of safety components that may be used within safety circuits include light curtains, laser scanners, and safety mats. Safety mats use pressure sensors embedded in a rubber platform to provide a simple way of detecting when a person steps into a guarded area. These have, in recent years, been largely replaced by optical systems such as light curtains and laser scanners.
Light curtains can remove the need for physical guarding by creating a virtual guard to stop a machine axis if any of the curtain’s beams are broken. The light curtain consists of two parts — a transmitter and a receiver. The transmitter projects an array of parallel light beams. The receiver detects these beams and if any of them is broken, it triggers a machine stop. Benefits of light curtains include clear visibility of the working area as well as unrestricted access and rapid movement in and out of the protected area.
device continuously scans 275° to protect personnel and machinery with warnings and safety zones customizable with free configuration software. Muting functions are also configurable in this software that, along with muting sensors networked to the SX Series scanner, eliminate the need for an additional module or controller. (Image source: Banner Engineering)
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