Sema Systemtechnik, based in Hüllhorst near Bad Oeynhausen, has been manufacturing machines and systems for the semi-finished products and packaging industry for more than 35 years. The main focus is on machines for packaging, transporting, palletizing, erecting and converting, especially of primarily packaged dairy products.
In normal operation, the carton blanks waiting to be processed act as a movable separating guard. However, if the material feed runs empty, the operating personnel can reach into the carton erector unhindered, which represents a considerable hazard. Two optical sensors are therefore fitted to the feed opening. If there are no more blanks in the feed, the safety function immediately triggers the stop of the hazardous movement. The TÜV-Süd-certified solution consisting of a configurable PNOZmulti 2 safety controller and special diffuse reflection light scanners with background suppression ensure that the carton erectors from Sema Systemtechnik meet high safety standards. The safe solution eliminates the need for complex fixed guards in the infeed area.

Flexible product adaptation

A case erector such as Sema Systemtechnik's Model 1200 s with top-mounted servo drive and large-area disc cover produces up to 60 crates per minute. The machine is a format-flexible system with short changeover times. "At its core, it's a standard product that we adapt in detail to meet specific customer requirements and offer as a stand-alone or fully integrable machine," says Thomas Wehrhahn, who is responsible for hardware design at Sema. For demonstration purposes, Wehrhahn places pre-cut blanks in the feed magazine: the machine starts when the stack has a thickness of at least 80 millimeters. The vacuum-based haul-off draws in the carton blanks and presses them onto the drivers of a toothed belt. The blanks are then folded, glued and sealed in several production steps at one-second intervals. A conveyor belt transports the erected crates either directly to the filling station or for onward transport.
As long as several carton blanks cover the infeed opening, the operator cannot reach into the danger area while the machine is running. Since some blanks are smaller than the opening of the carton erector, a contour-precisely manufactured Plexiglas pane closes off the area not covered by the blank. This is replaced without tools and interrogated by the tamper-proof, coded safety switch RFID sensor PSENcode from Pilz.

Integrated, TÜV-Süd-certified safety solution

In the course of the risk analysis it was clear that an effective safety solution, which would not restrict either the operator or the process, had to be found for the case of "no carton in front of the feed opening." Sema opted for an integrated, TÜV-Süd-certified safety solution from Pilz. "We have trusted Pilz products for more than ten years. What's more, many of our customers don't want to see anything other than Pilz safety and security solutions in their machines," emphasises Thomas Wehrhahn.
The advantage of this solution is that the safety function can be implemented using devices from the PNOZmulti 2 family and can therefore also be implemented in existing applications. Similarly, several carton feeders can be monitored with just one base unit. All that needs to be taken into account in the design is the required hardware inputs/outputs. The function blocks for evaluation are included in the license-free PNOZmulti Configurator V11.0 and in previous versions.
At the material feed, two diffuse sensors permanently check whether cardboard blanks are present. The sensors must be mounted at a distance of 30 mm to 100 mm from the cardboard pile, thus allowing flexible positioning. They can be mounted on the side or, as in this case, conveniently at the top of the infeed opening and thus detect all formats run on the machine. This means they do not get in the way during loading. If the sensors sense nothing, the safe mini control system PNOZmulti 2 stops the dangerous movement of the machine. Once the supply of cardboard boxes has been replenished, the machine can restart after acknowledgement.

Accepted solution saves costs

The solution eliminates the need for rigid guards such as tunnels. In addition, the blanks can also be reloaded from both sides from an ergonomic point of view. In order to prevent the machine from entering the "safe stop" without any emergency and stopping in the middle of the cycle, a photoelectric proximity switch installed on the infeed magazine serves as a signaling stage: it continuously checks the level and indicates when carton blanks need to be reloaded.
For compact packaging machines such as the carton erector, Pilz offers a TÜV-Süd-certified solution for PL d or Cat. 3 in accordance with EN ISO 13849-1 or SIL CL 2 in accordance with EN IEC 62061. If the sensors are operated in combination with PNOZmulti 2 or the myPNOZ modular safety relay, users can be sure that all safety requirements are met with this solution.
In addition to monitoring the feed magazine guarding, PNOZmulti 2 evaluates the signals from the safety gate systems PSENslock, which are installed as magnetic process interlocks on doors and hoods, and those from the installed emergency stop buttons. The plain text messages from PNOZmulti 2 are primarily used to immediately identify potential problems and quickly rectify stoppages. "Pilz's configurable mini control system PNOZmulti 2 is used exclusively in our carton erectors. As a rule, it has to monitor at least ten or more inputs and outputs there. In conjunction with the feeder protection, PNOZmulti 2 offers sufficient flexibility for adjustments and real added value for our customers," explains Thomas Wehrhahn.

Author
Sven Jungmann, Sales Engineer