Safety, productivity can be compatible for machine control applications

Machine safety insights

• The risk of injury to personnel increases as automation’s role in manufacturing grows, particularly with the rise of mobile transportation systems and heavy machinery in facilities.
• Manufacturers with the best safety records are often also those with the highest productivity because their operations are streamlined and they have fewer incidents that shut down operations.

Highly productive and dynamic automation depends on optimizing the flow of materials between individual processes. Achieving close to a continuous flow is the ultimate aim, including at the end of a production line where goods need to be packed, palletized and transferred for onward distribution.

As the automation of materials handling increases, such as with use of mobile transportation systems, conveyors or articulated robots, so does the risk of injury to personnel. At the same time, production teams may well be under pressure to introduce greater manufacturing flexibility, minimize machine set-up time and to improve space utilization on shop floors.

In such circumstances, safety systems can easily and unjustifiably become characterized as necessary but counterproductive to achieving the most fast-moving and uninterrupted processes. The nuisance of physical guards, or manual stops and restarts, can be perceived as a barrier to productivity. They could even cause irritation that could tempt impatient operators to override systems and indulge in unsafe practices.

The good news is that developments in intelligent sensing systems have opened up more opportunities to optimize the onward flow of goods in high-speed production environments by using robust safety systems. They avoid unnecessary stoppages and downtime, while continuing to protect people.

Physical guards, tunnels

Especially for small objects such as bottles, workpieces or chocolate bars on a conveyor, a physical tunnel, designed with the correct safety distances to the hazardous area often could be used as a low-tech way of protecting personnel.

However, there are production set-ups where physical guards or tunnels may be unsuitable or take up too much space. Once built, tunnels cannot easily be adapted for variations in the shapes of products or cartons or to accept larger objects than the guard is built for. So, on many machines, for example conveying lines, electro-sensitive protective equipment (ESPE), like safety light curtains and safety laser scanners, is used.

Muting, a protective field

To ensure a continuous flow of materials, the ESPE must allow objects through the protective field without triggering a safety response that stops the machinery, but must still react if a person breaks the field by reaching into the area. The most common implementation is to temporarily “mute” the ESPE while the material is passing, by using additional sensors to detect either a recognized object or a person. But there are some disadvantages, muting systems still have a residual risk while the protective system is briefly bypassed. Muting sensors need extra space, take more time and effort to set up and maintain, and they are at risk of getting dislodged or damaged.

Light curtain systems can offer greater flexibility to install safe access protection with integrated entry/exit monitoring (muting). Pre-configured, plug-and-play solutions can now be specified as complete muting sets designed for rapid mounting, connection and commissioning.

Safety laser scanners

Like safety light curtains, safety laser scanners are ESPEs that can be used for human/material differentiation. Safety laser scanners are more commonly used to set up horizontal protective fields, for example on an AGV, but safety laser scanners can be used vertically. Their benefit is that, where safety light curtains can only mute a certain number of beams, a safety laser scanner can be set up to recognize shapes with more complex contours, and its fields can be changed dynamically. This removes the need for additional guarding or sensors to detect if a person is trying to gain access to a machine while the ESPE is muted.

The development in intelligent sensing systems has also enabled safety light curtain solutions to be marketed as pre-certified alternatives to classic muting. Any Type 4 ESPE can be configured to use the Safe Entry Exit, using just one safety controller to evaluate several material gates simultaneously.

More recently, plug and play safety light curtain solutions have become available that use intelligent pattern recognition to detect pre-determined objects without muting sensors.

People are often surprised when manufacturers with the best safety records are often also those with the highest productivity. Of course, machinery safety regulations and standards are there to protect employees, but a well-designed safety system will also be one that enables operating efficiency, rather than hinders it. Choosing the right safety solution is, therefore, paramount to achieving optimum material flows.

Intelligent sensing systems and software are now being developed for machinery safety that can enable operators to progress quickly to installed and fully-certified systems that can avoid unnecessary machinery downtime, while continuing to safeguard their workforce.

Dr. Martin Kidmanis safety solutions market product manager at Sick. Edited by Mark T. Hoske, content manager,控制工程、CFE Media and Technology,mhoske@cfemedia.com. This appeared on the控制工程Europewebsite on July 13, 2023.

KEYWORDS: Machine safety, safety sensors

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Safety and productivityare complementary, not contradictory.

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