High-speed machine utilises Pilz interlocks and controller

The new rotary applicator from Geyssel Sondermaschinen GmbH attaches up to 30,000 items such as drinking straws, spoons or forks to cups, cans or bottles per hour. And it always positions these items so that neither the logo nor the product information are covered, while also ensuring that safety is not compromised despite very high process speeds.

When looking for an integrated safety system, Geyssel opted for the Pilz PSENmlock safety gate system, which features safe interlocking and safe guard locking in a single device. Used in combination with the Pilz PNOZmulti 2 configurable and reliable safety controller, this creates a safety system that is suitable for universal use and also available for other applicators, packaging and testing machines.

The Cologne-based company's applicators, which are designed for flexible integration and dynamic mobility, are generally used at the end of bottling lines. Or, to be more specific, in places where manufacturers of convenience products would like to attach drinking straws, forks, spoons, gadgets or toys to their cans, cups, bottles or cardboard packaging. Both producers and lawmakers specify where these items can and cannot be positioned. Covering optoelectronically readable codes, company logos, trademarks and product information is not permitted. The newly developed rotary application systems therefore have to ensure that the drinking straws are always applied in the predefined position, even at high process speeds. This requires expertise in the fields of mechanical engineering, automation technology and control technology.

Accurate positioning at high speeds

The staff at Geyssel have known the drill since 1966. Employing around 35 members of staff, the small company develops and builds machines and applicators for the packaging and beverages industries, as well as other machinery. Depending on the type, the systems can apply objects such as drinking straws, spoons and sachets vertically, diagonally or horizontally on the desired side or on the top or bottom of packs, cups, bottles and much more besides as part of a fully or partially automated process.

Geyssel machines and handling systems are used all over the world. To understand how the system, which measures approximately 3x2m and is 2m tall, attaches drinking straws, you would have to ask the operator to switch to slow motion mode. At maximum speed, up to seven cups or cans stream out of the glass cell per second - so there is hardly any chance for the human eye to follow the actual application process.

This is how the rotary machine works:

• Either single- or multi-lane conveyor belts supply the ready-filled containers, while sensors record the filled products without any contact.
• A key element of the system is a rotary machine with 16 stations, which are grouped around the vertical drive axis.
• In the infeed area, an infeed worm ensures that the packaged products are evenly spaced, while an infeed starwheel transports them into the positions around the main shaft.
• Optical sensors detect the print marks on to the containers.
• The system controller causes the servo motors, mounted at each of the 16 intake stations, to rotate cans, cups or bottles into the correct alignment position.
• A nozzle adds glue dots to the container wall, while an application gear mechanism applies the objects to be attached.
• Generally, the items to be applied are supplied linked by strips of film via a transport wheel; a blade separates the individual items.
• The consistency of the adhesive, which in most cases is a hot melt, is designed to cure in an extremely short space of time so that the object can no longer fall off.
• The convenience product, which is now ready for packing, continues travelling along the shaft, is rotated into the desired position upstream of the discharge station, and moves to the final packing station via a discharge belt.
• Up until that point, the process is fully automatic, and packaging can also be performed by an automated handling unit upon customer request.

Machine safety concept

While the applicator was being redesigned, the matter of a powerful and flexible safety concept ultimately cropped up. Steffen Bienert, an electrical designer at Geyssel, explains: "With the predecessor model, we were still using classic relay technology, which was to be replaced by a powerful small controller in the new machine." Specific hazards particularly result from the central drive shaft and the rapidly rotating 16 stations. Four gates and a feed-in flap had to be safeguarded so that operators and people in the surrounding area would not be put at risk. In our case, safe interlocking combined with safe guard locking was required to make deliberate or accidental opening of flaps or safety gates impossible during ongoing operation.

Ruben Maas CMSE, a sales engineer and certified machinery safety expert at Pilz, comments: "The reliable safety gate system PSENmlock is particularly suitable for machines with a hazardous overrun and rotating objects, where safe guard locking is a must. If the operator wants to intervene in machines such as these due to a malfunction or an incorrectly aligned can, for example, the system does not release a gate or flap for opening under any circumstances. They can only be opened if the system has previously been brought to a safe standstill using the emergency stop function. If a can weighing roughly 250 grams slips out of its position in the rotary machine and hurtles towards a gate or flap, the mechanical lock withstands the impact."

It was crucial for Geyssel that the robust and compact PSENmlock safety gate system is the only one of its kind with mechanical fault exclusion. Steffen Bienert states: "We considered various solutions, and one of the reasons we opted for PSENmlock was because it offers interlocking and safe guard locking in a single device. The convenient installation and diagnostic features which make the device versatile are an added bonus."

Geyssel is ultimately keen to integrate the PSENmlock device in other applicator, packaging, testing and special machines. On the PSENmlock, LEDs on three sides of the housing makes them easy to read for diagnostic purposes, regardless of the installation orientation. A flexibly mounted actuator also provides high tolerance compensation - in case a gate should sag by a few millimetres, for example. Safe guard locking is performed via a dual-channel control. Geyssel found the Pilz PNOZmulti 2 compact, configurable safety controller was suitable for its purposes: the PNOZ m B0 base unit (pictured right), which measures a mere 45mm wide, has 20 safe inputs and four safe semiconductor outputs and can be flexibly expanded as required.

The Pilz PNOZmulti Configurator software tool makes configuration of the controller very easy; all of the functions required for the application cell are already integrated in the PNOZmulti 2 safety controller. The PNOZmulti 2 reliably monitors safety functions with certified hardware and software, and can be adapted to the application at hand in a modular fashion.

Equal partners

Steffen Bienert concludes: "The fact that Pilz not only offers high-quality products, but also provides factual support in all issues relating to automation and safety, was a deal-breaker for us. We use the compact safety gate system PSENmlock as standard wherever safe mechanical gate locking is vital. As a small company, we rely on innovative partners; our co-operative relationship with Pilz is always on an equal footing. So when it comes to automation and safety, we will therefore happily make the most of the expertise from Ostfildern in the future too."

For further information go to www.pilz.co.uk.