Efficient and process-controlled 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: worldwide one of the market leaders in the planning and realization of highly dynamic warehouse and order picking systems in the field of intralogistics. 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.

Figure 1: Process-controlled access guarding in intralogistics.

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."

2019 GIT Security Award for SPG
Not only WITRON and Leuze electronic as the inventor of Smart Process Gating swear by the new SPG technology. A jury of experts with representatives from BHE, TÜV, VDMA, ZVEI, integrators and users voted "Smart Process Gating" to the top 10 of the 2019 GIT Security Award. Readers of the GIT Sicherheit, GIT Security and messtech drives Automation trade magazines and their online communities even chose the SPG muting process, which completely forgoes the need for signal-emitting sensors, as the gold winner of the award, thereby also nominating it for the "Best of Industry Award 2019."

Box text:
Smart Process Gating - the advantages at a glance
- Extremely compact, space-saving system design, since there is no need to make space for muting sensors in front/behind the light curtain.
- Outstanding reliability and availability of the safety device and low installation and service costs at the same time (no set-up alignment, no realignment of muting sensors).
- Easy handling and operation for personnel.
- Even interrupted parts and pallets with distances between loading are reliably transported.


Pictures



Figure 2: Process-controlled access guarding in the packaging industry.



Figure 3: Josef Apfelbeck, Leuze electronic (l) and Stephan Schmid, WITRON (r) have collaborated for many years.







Figure 4: GIT Award winner "Smart Process Gating," based on the MLC 530 safety light curtains from Leuze electronic, is nominated for the "Best of Industry Award."

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