In one-second intervals, the puller pulls in the prepunched cardboard blanks and the tray former from Sema Systemtechnik GmbH folds, glues and seals these to form finished outer packaging. The interesting part: the cardboard blanks function as a movable guard. If the material feed runs empty, however, the operating personnel can reach right inside. For this reason, a TÜV Süd certified safety solution guarantees safety in every work step.
The tray former 1200 s from Sema Systemtechnik, a manufacturer of plant and machinery for the semifinished goods and packaging industry, produces up to 60 trays per minute. Cassettes that can be exchanged quickly and easily enable format changes at ultra-fast speed and thus high flexibility. The machine starts when the stack of prepunched blanks in the feed magazine has reached a depth of at least 80 millimetres. The vacuum-driven puller pulls the cardboard blanks in and presses them onto the carrier of a toothed belt. In the subsequent production steps, the tray former folds, glues and seals the blanks in one-second intervals. Once formed, the trays are carried on a conveyor either directly to the filling station or for onward transport.
Beware of the gaps
In regular operation, the cardboard blanks function like a movable guard. Because as long as multiple cardboard blanks cover the feed opening, the operator is unable to reach into the danger zone while the machine is running. If the material feed runs empty, however, this protection is no longer afforded. If blanks are smaller than the opening of the tray former, the area not covered is sealed by a Plexiglas pane made to the precise contours. This is replaced without the use of tools and scanned by the manipulation-proof coded RFID sensor safety switch PSENcode from Pilz.
A certified overall package
It became clear from the risk analysis that an effective safety solution restricting neither the operator nor the process had to be found for the case that there is “no cardboard in front of the feed opening.” Sema chose an integrated, TÜV Süd certified safety solution for PL d and Cat. 3 of EN ISO 13849–1 or SIL CL 2 of EN IEC 62061 from Pilz. In the meantime, two diffuse sensors at the material feed permanently monitor the presence of cardboard blanks. The sensors have to be located 30 mm to 100 mm away from the cardboard stack, which allows flexibility in positioning. If the sensors don’t scan anything, the safe small controller PNOZmulti 2 brings the hazardous movement of the machine to a safe stop. Once the cardboard has been replenished, the machine can be restarted after confirmation.
“We have been relying on the robust and reliable products from Pilz for more than ten years already. What’s more, many of our customers don’t want to see safety and security solutions from anyone other than Pilz in their machines,” emphasises Thomas Wehrhahn, responsible for hardware construction at Sema. The safety function was therefore implemented using the configurable small controller PNOZmulti 2. The small controller monitors multiple cardboard feeds at the same time with just one base unit. Only the necessary hardware inputs and outputs have to be considered in the configuration. The function blocks for the evaluation are included in the software tool PNOZmulti Configurator. If the sensors are operated in combination with PNOZmulti 2 or the new kind of modular safety relay myPNOZ, the users can be confident that this TÜV Süd certified solution for compact packaging machinery meets all safety requirements.
Safe, but with room for manoeuvring
The solution removes the need for rigid protective devices such as tunnels, while the blanks can be flexibly reloaded from both sides. To prevent the machine moving needlessly to a “safe stop”, a light sensor installed at the feed magazine acts as a notification stage.
Sema recognised that the focus is increasingly being placed on efficient safety solutions for end customers. That, after all, is how process efficiency can be improved, downtimes reduced and, ultimately, a competitive edge achieved. “We’re happy to work with Pilz because we always get detailed answers to our questions, are kept regularly informed of changes and new features and, quite simply, get good advice,” summarises Thomas Wehrhahn.