Open for efficiency

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.

Trusting cooperation

“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.