Video: Fundamentals of light curtains

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Light curtains are critical equipment in many cases where there is the potential for a human worker to come into contact with dangerous machinery. These presence sensing devices will activate a kill switch whenever one of its beams of light are interrupted. Press brakes and various machining applications are common uses, although they are increasingly used in conjunction with automation and robots or cobots.

Light curtains are quite effective for two reasons: they remove physical barriers which might slow manufacturing and operator tasks, and they are automated, which mitigates the ability of a haphazard user from bypassing critical safety protocols.

Light is emitted from a transmitter and monitored by the receiver. Light sources are commonly infrared or laser. Light can be angled and cornered with the use of mirrors, although this will reduce transmittance range by approximately 25%. Distance between the light curtain and machine hazard should be considered in regard to OSHA’s safety distance formulas.

Light curtains are not suitable for machines with full revolution clutches. Additionally, curtain “mute” buttons can be offered without interrupting the machine’s upstroke, provided it still protects the user during downstroke movements. Light curtains should also fail open — all defects should prevent activation of the machinery until the malfunction is resolved.