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Total safety management for bending presses

03 June 2010

Jokab Safety has helped the Italian machine builder, Powertech to achieve full safety compliance for a fully automated double-bench bending press. Luca Tripodi and Neil Harvey describe how the individual safety components were integrated into a PLC platform that was also able to execute non-safety related functions

The double-bench bending press from Powertech is capable of bending sheet metal, whether manually or automatically fed, and is easily integrated into robotic manufacturing systems. Safety systems were a key consideration during the development of the machine, and Powertech’s choice of supplier for this particular aspect of the project was Jokab Safety’s Italian subsidiary based near Milan.

All safety functions, including safety barriers, foot switches, emergency stop push-buttons, and access controls, as well as in the monitoring of pneumatic and hydraulic valves is achieved within Jokab’s Pluto S46-6 safety PLC. Moreover, thanks to the I/O capacity available on this PLC, it was also possible to include the machine’s basic automation logic within the single platform, an integral LCD screen enabling the monitoring of both logic and safety functions at one location.

The Pluto B/S46-6 safety PLC complies with safety category 4 according to EN 954-1, PLe according to EN ISO 13849-1, and SIL3 according to EN IEC 62061. This 90mm wide unit is capable of supervising up to ten switches at these safety levels via a single input. The PLC has a total of 46 I/Os, six of which are individual safe outputs. Moreover, 16 I/Os can be used either as inputs or outputs, and 24 inputs are provided for safety components and other sensors. Programming is via the intuitive Pluto Manager ladder diagram software, and using a gateway, safety and control data can be transferred from the Pluto network to other bus systems, such as Profibus DP, CANopen, DeviceNet or Ethernet.

The safety controls
Jokab’s ‘Fox’ safety control device is suitable for operating machines by foot when the machine operator needs to keep both hands free. It provides a novel three-position function with dual contacts, thus achieving a high safety level. If, in an emergency, the operator depresses the pedal to its lowest position, a stop signal is sent immediately to the machine. The switch is subsequently mechanically locked into this position and it has to be reset before a new start can be made. The foot switch is available in a single or a double pedal version for steering back and forth. The unit is robustly housed and is protected to IP65.

The ‘Smile’ E-stop is designed for easy mounting on extruded aluminium machine guard frames and connection via one or two M12 sockets. Outputs include a choice of two dual breaking contacts or a ‘Tina’ interface that allows several E-stops to be connected in a dynamic safety circuit up to category 4. The buttons include LED status indicators: green for ‘ok’ and red for ‘stopped’.

Jokab’s ‘Eden’ non-contacting sensor pair for determining the open/closed status of interlocked gates, doors, hatches, flaps and covers, comprises an active element – ‘Adam’ - and a passive element – ‘Eva’. A coded signal is transmitted from the Pluto safety PLC via Adam to Eva, which modifies the signal and returns it. The sensor is only activated, if the door is closed and the two sensors are face to face. There is a wide tolerance for distance and misalignment between Adam and Eva, which greatly simplifies mounting.

In addition to the hardware and software implementation, Jokab was also able to offer assistance with the initial risk analysis and the final CE certification of Powertech’s machine.

Luca Tripodi is sales manager Jokab Safety (Italy), and Neil Harvey is general manager, Jokab Safety (UK)

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