Safety for man and machine

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Experience, tradition and passion - these values ensure the five-star quality at the five-brother company Bühler Bedachungen und Bauspenglerei from Romanshorn in Switzerland, a business specialising in roofing and architectural sheet metal. Quality is the top priority for the family business – particularly when it comes to selecting its partners and suppliers. Among these is the Swiss company Jorns AG, which supplied the new double bending machine, model TP-150G-RH-UV-SL-1250-CP200-6.4-mp, including safety concept for the architectural sheet metal area as well as the manufacturer for optical sensors, which ensures the corresponding safety at work for man and machine, Leuze electronic.

Safety for man and machineSafety for man and machine is required not only by safety-relevant, international standards. Protecting man and machine from dangerous processes is a matter of course for the 35-person company. Trained sheet metal worker Bruno Bühler says: “If a new machine is used, such as the new TwinMatic-Pro 150 bending machine from Jorns here in our architectural sheet metal operations, it must satisfy the latest requirements on safety technology.” When selecting the safety concept, he relied on the consulting expertise of the manufacturer of this machine, Jorns AG from Lotzwil. Thanks to positive experiences with other projects, Jorns used the RSL 430 safety laser scanner from Leuze electronic, which optoelectronically safeguards access to the long, front side of the machine. The RSL 430 is centrally positioned under the bending basin, ensuring that the maximum radial range of the sensor can be used. The area in front of the machine can thereby be safeguarded with just one sensor.

TwinMatic-Pro 150 is the name of the new bending machine from Jorns AG used in the architectural sheet metal area of the company, which replaced a nearly 20-year-old machine with similar functionalities here. The new machine enables the bending of a very wide range of types and thicknesses of sheet metals in a fully automated process: aluminium, zinc, copper, steel. Only when loading and removing the metal sheets does the machine need to be handled manually. As soon as the machine operator crosses the red line on the floor located approximately 80cm from the bending machine, thereby entering the danger zone of the machine, his movement is detected by the RSL 430 safety laser scanner and the machine comes to an immediate standstill. Should this safety monitor fail, there is a “safety net” in the form of a step bar. If this bar is actuated by the operator´s foot, it presses against an EMERGENCY-OFF command switch that brings the machine to a standstill in a fraction of a second. Bruno Bühler, who usually operates the bending machine himself, says: “It´s good to have a double safety net – fortunately, we´ve never had to make use of it. The RSL 430 safety laser scanner works reliably and fault-free, making it the optimum solution for us.”

Multiple awards

Due to its innovative capacity, the RSL 400 safety laser scanner – which is available in various models – convinced not only end users such as Bühler since being launched on the market at the end of 2015. It also convinced juries of experts, claiming multiple awards in 2016, including the GIT Safety Award, the Industriepreis as well as the Handling Award.

The safety laser scanner functions as follows: it transmits periodic light pulses via a rotating deflection unit. These are scattered in all directions by obstacles, such as persons entering the danger zone. A part of the light pulses is received again by the safety laser scanner and evaluated. The scanner calculates the precise position of the machine operator from the propagation time of the radiated light and the current angle of the deflection unit at that time. If this is located within the previously defined protective field, the safety laser scanner executes a safe switching function.

Pascal Guyot, director of control engineering at Jorns AG says: “In our case, this happens as soon as the machine operator crosses the safety line marked on the floor with red signal colour at the long, front side of the machine.” Should this occur, the safety-related switching outputs are switched off. The required safety distance is calculated on the basis of safety-related standard DIN EN 999. Playing a role here are factors such as the approach speed relevant to safety and height of the protective field above the ground. Furthermore, the stopping time of the machine as well as additional distances, for example, for system-related measurement errors, must also be taken into account.

All-round protection from all machine sides is, however, not provided by a single safety laser scanner positioned centrally under the bending basin of the bending machine. Depending on how they are attached, at least two safety sensors would be needed to achieve this. With just one safety laser scanner, cutting in automatic mode would only be possible in inching mode. Obstructions could also occur if the sheet was to protrude far outside of the machine when bending sheet metal top-down. Bühler therefore decided to mount a second RSL 430 safety laser scanner to monitor the machine room from above, thereby reducing the depth of the danger field to 80cm. The second scanner is attached to the ceiling with an iron chain and has an operating range of 8.25m with a resolution of 70mm and a detection range of 270 degrees.

The position of the safety laser scanner is always based on the sensor that monitors the bending line. Note that the control panel is also detected as an object and must therefore be located outside of the danger zone while in automatic operation. Bojan Zmijanjac, Area Sales Manager at Leuze electronic Switzerland says: “If the area of the control panel were to be removed from monitoring, blind zones would arise within the danger zone due to shadowing. In addition, blind spots would occur between the stands and behind the machine, which must absolutely be safeguarded.”

With the positioning of two RSL 430 safety laser scanners, Jorns Bühler recommended an integrated, comprehensive safety concept for all-round machine protection that has been proven in practical use and that convinces. Tobias Wüst, managing director of the Swiss subsidiary of Leuze electronic in Fluringen, emphasises the competence of the manufacturer and innovation leader in the area of optical sensors: “Safety sensors have a great deal to offer. Reliable safety laser scanners require many years of experience. With the RSL 400 safety laser scanner series, Leuze electronic has succeeded with a development that combines maximum reliability and performance with simple operation.”

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