Access guarding without muting sensors

Inno­v­a­tive strength, a down-to-earth cul­ture and strong com­mit­ment are the val­ues that have made Witron – based in the Upper Palati­nate region of Ger­many – the com­pa­ny that it is today. Witron is con­stant­ly work­ing on devel­op­ing even bet­ter, even more cost-effi­cient logis­tics solu­tions for its cus­tomers, to make them even more suc­cess­ful. In the area of automa­tion and fur­ther opti­miza­tion of ware­house logis­tics, the selec­tion of suit­able, com­pe­tent and inno­v­a­tive part­ners also plays a deci­sive role for Witron. Witron relies on cre­ative solu­tions from Leuze elec­tron­ic not only in its own pro­duc­tion and ware­house logis­tics. The com­pa­ny also real­izes effi­cient safe­ty solu­tions for its cus­tomers togeth­er with opti­cal sen­sor man­u­fac­tur­er Leuze elec­tron­ic. This includes the use of “Smart Process Gat­ing” (SPG), a process devel­oped by Leuze elec­tron­ic that enables access guard­ing with mate­r­i­al trans­port to be designed more com­pact­ly, sim­pler and safer.

Safety first

When man and machine meet in a tech­ni­cal envi­ron­ment, it must be pos­si­ble to stop machine and sys­tem parts with­in a frac­tion of a sec­ond. “The safe­ty of all per­sons who work in one of the many logis­tics cen­ters of our cus­tomers around the world – whether in indus­try, retail or ser­vice – is the asset most wor­thy of pro­tec­tion,” explains Stephan Schmid, expe­ri­enced project engi­neer in the area of devel­op­ment and con­trol tech­nol­o­gy at Witron. This means: appro­pri­ate areas are equipped by Witron with safe­ty devices or fenc­ing that meets the applic­a­ble stan­dards and norms so as to elim­i­nate acci­dent risk before it can even occur. But because it is not pos­si­ble to com­plete­ly fence in all areas in which man and machine meet in a net­worked, mech­a­nised sys­tem, Witron is work­ing on, e.g., con­vey­or lines with safe­ty light cur­tains. These must reli­ably dis­tin­guish between peo­ple and merchandise.

The classic safety solution

Espe­cial­ly in intral­o­gis­tics and in the auto­mo­tive and pack­ag­ing indus­tries, affect­ed areas must be safe­guard­ed by opti­cal safe­ty sen­sors. To unam­bigu­ous­ly rec­og­nize trans­port­ed goods as they approach a pro­tec­tive field and to bridge this for pas­sage of the goods at the prop­er time, mut­ing process­es with sig­nal-emit­ting mut­ing sen­sors were used across the indus­try in the past. These sen­sors were installed in addi­tion to the safe­ty light cur­tains and enabled pal­lets and trans­port­ed goods to move in and out with­out inter­rup­tion. In front of and behind the safe­ty light cur­tain, how­ev­er, quar­ters are usu­al­ly a bit tight. The addi­tion­al use of bridg­ing sen­sors often required more space, lead­ing to an even less-com­pact sys­tem design. The instal­la­tion and ser­vice effort for the addi­tion­al set-up, align­ment and re-align­ment of these sen­sors also result­ed in addi­tion­al work. “This led Witron to search for a solu­tion that com­bines process reli­a­bil­i­ty, sys­tem avail­abil­i­ty and eas­i­er oper­a­tion with one anoth­er,” explains Schmid.

Muting reinvented

At that time, Leuze elec­tron­ic did not yet have a prac­ti­cal answer to this require­ment, but did already have a project idea: “Smart Process Gat­ing” – based on its MLC safe­ty light cur­tains. Leuze elec­tron­ic pre­sent­ed this to its key cus­tomer Witron in a very ear­ly devel­op­ment phase. Witron was quick­ly con­vinced of this idea and accom­pa­nied the cre­ative Leuze devel­op­ment in numer­ous prac­ti­cal tests. “Smart Process Gat­ing” was then put through its paces at and by Witron on its test tracks in its com­pa­ny head­quar­ters in Park­stein in the Upper Palati­nate region where it was opti­mized togeth­er in detail. “The result is impres­sive: a clever solu­tion was cre­at­ed that com­bines the require­ments for safe­ty at work with high process reli­a­bil­i­ty and sys­tem avail­abil­i­ty,” explains Josef Apfel­beck, key account man­ag­er and spe­cial­ist for intral­o­gis­tics at Leuze elec­tron­ic. With “Smart Process Gat­ing” a new process was cre­at­ed that enables mut­ing process­es to be exe­cut­ed more eas­i­ly, more com­pact­ly and more sta­bly. With the SPG prin­ci­ple devel­oped on the basis of its MLC safe­ty light cur­tains, it is pos­si­ble to com­plete­ly forego the pre­vi­ous­ly nec­es­sary sig­nal-emit­ting sen­sors. Con­vey­or sys­tems can thus be made more com­pact. Dur­ing the oper­at­ing phase, the risk of mis­align­ment or dam­age to the sen­sors is also elim­i­nat­ed as are the costs for their main­te­nance and ser­vic­ing. The avail­abil­i­ty of the entire safe­ty device is there­by increased and oth­er prac­ti­cal­ly ori­ent­ed risks reduced.

With SPG, the first mut­ing sig­nal comes from the process con­trol (PLC), while the sec­ond mut­ing sig­nal is gen­er­at­ed by the pro­tec­tive field itself. Smart Process Gat­ing requires a con­trolled mate­r­i­al flow so that the nec­es­sary PLC con­trol sig­nals are made avail­able in the expect­ed time win­dow. The MLC 530 safe­ty light cur­tain vari­ant with Smart Process Gat­ing is TÜV-cer­ti­fied for safe­ty. In com­bi­na­tion with a stan­dard con­trol, a per­for­mance lev­el PL d can be achieved, which is suf­fi­cient for many appli­ca­tions in intral­o­gis­tics. With a safe­ty con­trol, per­for­mance lev­el PL e is also achievable.

Nothing is possible without

Leuze elec­tron­ic and Witron are linked by a long-stand­ing cus­tomer-sup­pli­er rela­tion­ship that goes back to the ear­ly 90s and is based on a trust­wor­thy col­lab­o­ra­tion with mutu­al respect. “Many hours of hard devel­op­ment work, joint project plan­ning, dis­cus­sions, test­ing on the mate­r­i­al locks of test con­vey­or lines with Witron as a strong part­ner at our side have led to an impres­sive result,” says Apfel­beck proud­ly. Schmid explains: “Attrac­tive for Witron are, above all, the sta­bil­i­ty and high avail­abil­i­ty of the safe­ty device – all with less work. This is con­firmed by our on-site teams and by our cus­tomers alike.” Since the fall of 2016, Witron has used Smart Process Gat­ing and this new tech­nol­o­gy as a stan­dard solu­tion in all of its projects world­wide – in both the retail sec­tor as well as in indus­try and the ser­vice field. Sys­tems designed by Witron with SPG as safe­ty devices can now be found in France as well as in Nor­way or the USA. Like every­thing that leaves the fac­to­ry in the Upper Palati­nate des­tined for end cus­tomers, the safe­ty mod­ules were test­ed on the test track in Park­stein by Witron. Witron also uses “Smart Process Gat­ing” for its own inter­nal train­ing pur­pos­es as well as oth­er sen­sor solu­tions from Leuze elec­tron­ic: whether AMS mea­sur­ing sen­sors in Witron’s high-bay ware­house or the BCL 300 bar code read­er for iden­ti­fy­ing codes. A recent addi­tion in the area of high-bay stor­age devices at Witron is the Leuze DDLS 500 data trans­mis­sion pho­to­elec­tric sen­sor with Ether­CAT inter­face. “Noth­ing leaves our fac­to­ry before we have thor­ough­ly test­ed a new com­po­nent or new tech­nol­o­gy our­selves. We only rec­om­mend solu­tions to our cus­tomers that have proven them­selves in prac­ti­cal tests – that’s our phi­los­o­phy,” says Schmid: “The Smart Process Gat­ing prin­ci­ple also had to with­stand a num­ber of hard­ness tests. Today, it con­vinces us on all counts and is used as a stan­dard solu­tion in projects with mate­r­i­al flow.”