Case erectors benefit from Pilz safety controllers and switches

End-of-line packaging is no different from the rest of the packaging sector in demanding flexibility and efficiency: rapid changes to new formats, including the ability to adjust sensors and actuators quickly and simply, are essential issues relevant to Industrie 4.0 and 'batch size one'. Over the years, packaging machine manufacturers have swapped relay-based hardware for more reliable, flexible software systems that are less prone to problems. This went hand-in-hand with the optimisation of safety systems that essentially was also software-based.

In the process of redesigning a case erector, Wchter Packautomatik GmbH & Co KG was faced with renewing the control and safety technology. The family business, based in Bad Wnnenberg-Haaren in Westphalia, is dedicated to the automation of packaging processes. For over 43 years Wchter has planned, designed and constructed mainly special-purpose machinery for the packaging technology sector. The company currently employs around 200 staff and has a high level of vertical integration. Its range of services also includes the upgrade of existing machinery and the retrofit of older machinery. As such, Wchter has made a name for itself in the food, drink and flooring industry, as well as in other sectors.

Automation concept

There was a clear need for action because the previous model of the Tablomat LE no longer met the increased demands for performance and efficiency. Jrgen Schulte, Production Manager at Wchter, explains: "The mechanical safety switches that we used to use on the safety gates were prone to problems and sometimes produced implausible diagnostic messages. Besides, there were now convincing alternatives to intricate and complex wiring. That is just two of several reasons that prompted us to think seriously about sustainable automation and safety concepts."

Many years of trusted contact with Pilz suggested they bring in the automation expert from Ostfildern. It started with Pilz presenting its latest automation and safety technologies. During the course of subsequent consultations, relevant objectives were defined jointly.

Objectives

In addition to the plant design and installation requirements, this supplier of intelligent packaging systems set high standards for plant availability, reliability, flexibility and diagnostics. The requirement was for the diagnostic data from the sensors to be available to the machine controller (POC) in real-time via an EtherCAT or Profinet gateway. The plant operator was to have a comprehensive overview of the machine status at all times. Jrgen Schulte says "We worked with Pilz to develop a solution that would best satisfy both our own needs and those of our customers. It was an advantage that we were able test the potential Pilz products rigorously in advance."

The new Tablomat LE from Wchter Packautomatik is an automated tray and case erector measuring around 6 x 3 x 2.5m for manufacturing secondary packaging for a wide range of products. The machine produces up to 30 ergonomic, elegant secondary packaging items per minute, depending on the requirement. Hot glue is used to seal the packaging. With cartridges that can be exchanged quickly, simple spindle adjustment and large hinged and swing gates, format changes are quick and flexible to implement.

Centralised, electronic parameter and recipe management with a memory capacity of up to 25 different product recipes guarantees short setup times. An intuitive touchscreen panel ensures a simple, clear process for handling and monitoring, as well as rectifying faults.

First a tray is drawn from the magazine into the slot via a vacuum suction system. A servo motor-driven slider moves the pre-punched carton towards the tray punch. In an intermediate station the raw product is pre-folded; as it passes through, the glue is applied for final assembly. Finally, the punch pushes the carton through the format shaft and erects the tray for the finished secondary packaging.

Safety requirements

The risk assessment resulted a required Performance Level (PLr) of PL d in accordance with EN ISO 13849-1. The Pilz PNOZmulti 2 compact configurable safety controller is tasked with safe monitoring of the four safety gates, the installed emergency stop pushbuttons and communication of customised diagnostic data to the PLC via a fieldbus module. The narrow, 45mm PNOZ m B0 base unit provides 20 safe inputs and four safe semiconductor outputs and is modular, flexible and expandable where necessary. It just takes a few clicks to select the hardware and create the safety circuit via drag and drop. The graphics-based user interface conforms to the Windows standard; all the elements in a safety circuit are available as icons or in selection menus. As a result, certified blocks for emergency stop or safety monitoring, for example, are flexible to select and can be linked to the outputs via logic operators. Comprehensive diagnostic options with customised diagnostic texts reduce downtime. If a fault occurs, features such as plain text messages with precise information on the location, clearly defined responsibilities and integrated first fault display all ensure that production is quickly restarted.

As an open control system the PNOZmulti 2 can also be used flexibly and industry-wide, independently of the higher-level operational or plant control system. It communicates with every common fieldbus and, depending on the application, meets safety requirements up to PL e and SIL CL 3. The fieldbus modules can be exchanged without having to change the program and enable the PNOZmulti 2 to be connected to the various communication networks. The safety controller is certified worldwide and can be used internationally for safety and automation functions, irrespective of the machine and plant type or industry.

Guard monitoring and locking

Instead of the previous mechanical safety switches that were were prone to problems, the four safety gates on the Tablomat LE are now fitted with the Pilz PSENslock non-contact safety gate units. These combine safety gate monitoring with a non-contact magnetic interlock in one unit. This combination of safe position monitoring and process guarding makes the PSENslock suitable for universal use and satisfies high safety requirements. Signals from the emergency stop pushbuttons and PSENslock safety gate systems are evaluated through the PNOZmulti 2, with the status reliably displayed on the operator panel as part of the diagnostic function.

Jrgen Schulte concludes: "Together with Pilz we have achieved all the stated objectives on the Tablomat LE: the case erector is impressive with its clear, streamlined wiring and it can be reconfigured for new tasks in the shortest possible time. The plant is enjoying virtually trouble-free operation, the operator has a comprehensive overview of the current machine status at all times."

Follow the links for more information about the PNOZmulti 2 compact configurable safety controller and PSENslock non-contact safety gate units from Pilz.