The corrugated board manufacturing process is highly automated; the main functions of the shop floor workers is to ensure that reels of paper are received and fed into the start of the process, oversee production, and finally transfer pallets of finished product to storage areas. In 2005, DS Smith Converters further extended automation at its sheet feeding plant in Louth, Lincolnshire, by installing an automatic paper reel handling process, which transports paper reels weighing up to two and a half tonnes along a conveyor track set into the factory floor. Once the reel arrives, it is automatically picked up and loaded to one of five reel stands and then manually checked and spliced for the paper to be fed into the main corrugator machine.
With the movement of large, heavy paper reels and automatic handling processes, the production area, when in full operation, is a hazardous environment. And as the paper reel handling process results in continuous movement, it is impractical to have fixed guards preventing employee access to restricted areas. DS Smith Converters was inspired by recently updated guidance notes with regards to safety from the Confederation of Paper Industries (CPI), which was now recommending the use of electro sensitive protection equipment (ESPE). The business was therefore keen to explore the options for safety with regard to the new process, and to build on its already exceptional safety record.
DS Smith Converters’ plant operations manager, Neil Osborne, commissioned integrator, S Tech UK, to lead the development of a safety system that would allow for the free flow of paper reels and the general movement of the automated process, but would shut down immediately if an employee mistakenly entered a restricted zone without first switching the process to manual operation.
Sean Scott, managing director of S Tech UK, proposed an initial pilot involving the installation of a safety system on one reel stand. Mr Scott sought a supplier partner with a strong reputation for successful industrial safety installation, and chose Omron with whom he had successfully worked in the past.
“Two senior members of Omron’s safety team visited Louth and after a wide-ranging consultation we agreed on the implementation of the company’s SNC (Safety Network Controller) in conjunction with a dedicated DeviceNet Safety network.” recalls Mr Scott.
The pilot scheme focused on a single reel stand, with the installation of an Omron SNC contained in a master control unit. The wiring was routed to a local I/O box, close to the reel stand, and Omron safety light curtains (F3S-TGR-KXC) were positioned either side of the paper reel transporting conveyor. Mirrors were placed around the perimeter of the machine, ensuring a completely protected area.
During the six month pilot, many benefits became evident. The safety light curtains had an in-built ‘muting’ facility, enabling a paper reel of pre-defined dimensions to pass through them, but initiating a system shutdown in the event of an employee passing through the curtain whilst the process was in operation. This muting facility worked with 100% reliability.
Once the safety curtains were triggered during automatic machine mode, the safety system needed to shut down the process. It thus had to be networked into the wider automation process, as well as allowing for the process to be stopped when a manual override of the safety system was requested. DS Smith has a total of twelve Omron PLCs performing all major automation tasks across the Louth plant – and all these communicate via DeviceNet, with the DeviceNet cabling linking to local I/O boxes positioned along the production line.
STech used an SNC linked to an Omron CJ1M PLC, which communicated with the wider DeviceNet network. Mr Scott teamed up with Frank Bauder from Omron’s Sensor and Safety business team to integrate the SNC, and this involved further study of the reel handling process. When an operator switches to automatic mode, the machine interlocking and safety curtain functionality are checked to ensure they are in an active state. If there is any discrepancy at all, the machine will go into emergency mode. At the end of the automatic process, the safety system is deactivated, allowing the reel handler to feed in the next reel.
Mr Scott adds: “The way we have programmed the SNC ensures a smooth, seamless process, clear visual indication showing employees when the safety system is switched on or off. When the off light is shown, employees are fully confident it is safe to enter the reel stand.”
The Omron system features in-built maintenance counters to identify components reaching end-of-life, and these are linked to an Omron NS5 HMI to provide a visual indication of maintenance requirements.
Following the success of this pilot, DS Smith gave the go ahead for the system to be integrated to the remaining four reel stands, a task that has now been successfully completed.
DS Smith Converters’ plant operations manager, Neil Osborne reveals that this is only Phase 1 of the company’s enhanced safety system. Thanks to the flexibility of Omron’s SNC system, it will be adding the plant’s existing safety systems into the Omron scheme over a phased period to give it total visibility of the entire Louth safety system.
“Omron allows you to build a strong, flexible safety system around existing systems and machinery,” says Mr Scott. “It can be installed with minimum disruption, thanks to its distributed network architecture, and requires only a modest level of investment.”