Machine safety is in the bag for snack manufacturer

Installing the Pilz PNOZmulti2 configurable small controllers is said to have helped guarantee the consistently good and safe production of tortilla chips.

With its range of products, Poco Loco from Roeselare is said to be one of the market leaders in the area of Tex-Mex food products. To be able to offer a wide range of these products, efficient manufacturing processes are clearly  necessary, and the manufacturing process for the tortilla chips starts with the measuring and mixing of the ingredients. The dough is then processed by an extrusion press and sheeter, and following the drying process, the snacks are fried in the hot oil of a deep fryer to then be seasoned. Following quality checks the tortillas are then packaged for dispatch to the customer. As would be expected, precise and safe machine control remains a paramount aspect of continued and uninterrupted production.

Better control as part of a whole

“The decentralised control of the plant led to difficulties in the past,” reports the Poco Loco PLC programmer Jeroom Verstraete “Because the interlinked production line was installed by different machine builders and the plant control was also a combination of various PLCs and safety relays.” The machines were designed as separate units which ended up with manufacturing being a cumbersome process, and not only on the control level. Every plant section, for example, had its own emergency stop circuit which led to the emergency stops which at times also shut down safety zones independently of one another. Francky Maveau, Head of the Electronics department at Poco Loco, describes another major disadvantage of the ‘old way’: “When all the emergency stops were activated in series for one safety controller, it was often difficult to pinpoint precisely where the problem was in the event of failures. This frequently led to longer downtimes.” It became clear to the snack maker that a more efficient – and also safer  production line should be a goal.

After the retrofit by Pilz, the entire system is designed so that problems can be detected early and do not have any major or unnecessary knock-on effect on the overall process. The Pilz PNOZmulti  2 provided Poco Loco with a technical solution for this problem: every safety component is assigned a unique DIAG (Dynamic Information and Action Gateway) address in the software. Information can thus be transferred via a fieldbus system to a higher-level controller. These are prepared for diagnostics and shown on the display of the small Pilz controller as status messages, and the unit can directly transfer up to 20 different messages irrespective of the higher- level plant control system.

Technicians can therefore perform diagnostics immediately without having to connect a laptop for more detailed information. With the Pilz PNOZmulti Configurator tool, both the technicians responsible for the programming of the PLC and also other Poco Loco technical employees can create a PNOZmulti programme and even modify one with corresponding authorisation. To do this, the entire technical department at Poco Loco received training in the set-up and operation of the system. At the same time, the PNOZmulti Configurator can be used for easier diagnostics of an error when troubleshooting.

Moves more crisply, produces better snacks

The motion management for the plant was also optimised with regard to safety and diagnostics. As a part of this change, the production line was converted to drives with frequency converters that are equipped with the STO function (safe torque off). If an emergency stop is triggered, the connection via Pilz PNOZmulti 2 ensures that the drive is stopped in a controlled manner by the STO function. A number of safety switches are installed on the interlinked production plant for tortilla chips, in addition to fifteen emergency stops. The production line itself is divided up into zones so that shutdown in one zone now has no effect on another zone. For example the fryer section can continue to work when there is an error at the start of the line. 

The modernisation at Poco Loco saw the optimisation of the entire production process for the long term, with safety as standard and a central control component that ensures that downtime decreases and production efficiency increases.

For further information MachineBuilding.net readers can visit Pilz and enter ‘150439’ in the Search for information on the PNOZmulti 2 and ‘150399’ for the PNOZmulti Configurator. Or call Pilz direct on +44 1536 460766.