TO Cascade or NOT TO Cascade?
| By: Rod Karch, Safety Specialist at Leuze electronic USA
The typical definition of cascading in the world of safety devices would be a single unit working in series with other units (i.e. light curtain, safety scanner, multi-beam light device). So in the case of light curtains, all the units that are cascaded with one another make one long segmented light curtain but acting as one. Cost savings are realized since wiring is typically in series (one unit to another) with a single run back to a safety relay.
There are certain applications that take advantage of the cascading light curtain technology, while others... not so much. When implemented to the correct application they can save time and money (hardware and installation). When not used properly they can cause nuisance alarms and downtime.
Here are some examples of when TO and when NOT TO use cascading light curtains.
The use of a cascaded light curtain on a machine for "point of operation" guarding. The cascaded light curtains are in a "U" shape for 3-sided operator protection. A great example of when to use cascaded units.
Use of cascaded light curtains in an "L" shape to protect the machine front and bottom for operator protection. Another good use of the cascading light curtain.
Machines that operate independently and in close proximity to one another are not a good choice for cascading light curtains.
Work cells with duplicate stations that function independent of one another would not be a good cascading light curtain solution.
If you have an application that looks like there would be an advantage using cascading I would suggest looking the Leuze MLC520 cascading light curtain. The built-in connection cables make for easy installation.
Another option which is not dependent upon cascading technology would be the use of two standard light curtains wired into a standard safety relay for multiple devices (i.e. Leuze MSI-SR5B-01) or several standard light curtains tied into a programmable safety relay (i.e. Leuze MSI 400).
Whatever your application just remember that cascading light curtains are only meant for certain applications. If you have any doubts about your application please contact your safety product manufacturer for assistance. Good luck!