How to Select Light Curtains
Image credit: Keyence; OSHA; Machine Guard Solutions
Light curtains are presence sensing devices that provide an infrared perimeter around perilous machinery or processes. When an infrared beam is interrupted between the transmitter and receiver, a killswitch arrests the hazard until the optical boundary has been reestablished.
Light Curtain Operation
RobotWorx provides a good...
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Q & A on Light Curtains
We asked our users for their input on Light Curtains. Here are the results of 112 users familiar with Light Curtains.Who Took Our Poll? | Design Trends | Applications and Use | Features | Buying Advice
Who Took Our Poll?Top
Being able to use muting, fixed and floating blanking in a standard priced light curtain so the customer who does not need those features will not need to pay for them, but in the future if the need arises, not have to change to a different type of light curtain. Also, having the ability to expand either in size or using multiple light curtains in series and not be concerned with the increase in response time that would cause a redesign to add distance to pinch point.
Led and photodiode technology. Specific ASIC that reduces part count, cost and reliability. Efficiencies in optic design and the use of redundant microprocessors.
Applications and UseTop
I have seen an application where the electrical controls were safe in operating sequence but not the physical machine. It is critical that the correct combination of ALL components is found to achieve a safe machine. ALL power must be removed from components that cause motion to reach a safe state. Closed center valves for pneumatic and/or hydraulic power, dump valves for pneumatic and/or hydraulic accumulators, mechanical brakes on motors, and other items must ALL be taken into account to insure that the machine will be stopped in a safe condition upon opening the safety circuit.
Good documentation. I have had sales people from several vendors tell me how great their product is, only to dig into the documentation and find it's very weak or non existent. That will make first time users (like me) or infrequent users call tech support for something that should be in the manuals.
The most common error is mounting too close to the danger zone of the machine because of errors in calculation of stop time of the machinery. Make sure the interface to the light curtain is fail safe and circuits connected to properly shut down machinery in case of a failure. Make sure the light curtain is sized correctly so an operator can not reach under or over. It may require mechanical guarding along with the light curtain. Pay attention to the machine environment, shock, vibration, oil water etc.
Don't pretend you know what you are doing if you don't! Read the selection guides and if you don't know ASK. It is very difficult to get any technical support on light curtains due to their safety status aka "potential lawsuit". But I have experienced many errors in application that are just due to ignorance or lack of reading the included documentation.
Protect from damage when loading unloading parts; vibration dampening on presses.