The new spiderMaxx cassette filter:
inspired by nature
Some time ago, the US magazine the “New Yorker” printed a cartoon showing two researchers. They were standing in front of a blackboard covered with formulas to the left and right of them. In the middle of the board were the words “Then a miracle occurs.” As an outsider, you sometimes get a similar feeling when innovations are created. Someone has a great idea, and bang, the finished product is suddenly there. The middle part, which is difficult and usually both time-consuming and nerve-wracking, remains invisible.
Patrick Weber and Sascha Schumacher are responsible for this seemingly inexplicable middle part at Freudenberg Filtration Technologies. They ensure that an idea becomes a marketable product, as was the case with the new spiderMaxx cassette filter.
The project could not have started under more unfortunate circumstances. In 2020, Coronavirus pandemic was just picking up steam throughout the world and the team had to work together while physically separated. The development of the eMaxx cassette filter, which is used in supply air filtration for gas turbines in power plants and industrial compressors, was on the agenda. “Our global sales community is in close contact with our turbomachinery customers, has analyzed in detail potentials for improvement, and has worked out the application-related requirements for the new development,” says Patrick Weber, Technical Product Manager at Freudenberg Filtration Technologies. “The turbomachine industry is technically very demanding. The new cassette filter should exceed the core requirements of the users: These include absolut operational dependability even under rough environmental conditions with high dust- and moisture load, paired with a low flow resistance and a longest possible service life.”
Such a situation is a challenge for the development process, because many aspects and functions can influence each other. Sometimes they can even work against each other. The first task, therefore, is to understand which requirements have which consequences. The sooner this happens, the lower the risk heading off in the wrong direction.
What happened next is typical of projects of this kind. A set of specifications was prepared. This was followed by some (entirely virtual) brainstorming sessions to find technically viable ways to move forward. The team was deliberately kept lean to allow intensive and agile exchange and focused discussion. This core team was not cut off from the rest of the world though. Instead, it regularly put out feelers, tapping into external resources whenever appropriate, and getting a fluid, efficient workflow rolling.
It is also typical of the development phase that several solution variants were pursued in parallel. This is because what might look good on the drawing board or even in the simulation can fail as a prototype or in the actual application. There are simply too many parameters and unpredictable interactions.
This means that any simulation, no matter how good, is only an approximation of reality. In the end, what counts is what is observed and measured on the physical prototype.
The spider web provided an efficient construction to distribute the forces acting upon it evenly. The team then used simulation methods to calculate the optimum structure. Thus, over time, what was a multitude of possible designs became increasingly concrete. So, this "miracle" that just happened consisted of an observation of nature that, with a lot of computing power, turned into a workable concept.
The idea for the new front plate, on the other hand, was already on the back burner for a while. It is manufactured in one piece, a novelty for this type of cassette filter, and can thus boast outstanding performance data in terms of robustness and torsional rigidity. “Fewer parts also mean a lower risk of leakage. The spiderMaxx is therefore even more reliable than its predecessors,” adds Schumacher.
It was a special moment for everyone when the first prototypes of the spider web design were built and were placed in the flow chamber. It was also very revealing, because the simulation values were confirmed by the real test.
Such developments face all sorts of obstacles. One of them is the knowledge of tooling technology. Even the best design is useless if it cannot ultimately be produced. The design and manufacture of the tools, a process that laypersons are rarely even aware of, has a massive impact on the schedule for such projects — and ultimately on the chances of success. As a trained tool mechanic, however, Schumacher knew the typical pitfalls.
In this way, the typical production-related problems of the tool design for the spiderMaxx could be proactively avoided and the time schedule was adhered to.
As with the spider web, other details were based on natural phenomena. The transfer of phenomena from nature to technology is called bionics. Nature provides a suitable solution for many challenges, especially in the case of the mechanical optimization of products.
“Of course, as a technician, you keep an eye on nature,”
says Patrick Weber.
“It’s the best builder, because it’s exposed to certain forces and perfectly designed for such loads: the spider web is also a response to a mechanical strength problem.”
This is most obvious in the hexagons of honeycomb media or the ribs of pocket filters, which in the case of the hydroMaxx pocket filter are designed like tree trunks, becoming slimmer towards the top. The fundamental question is not if there is a solution from nature for a particular technical challenge, but rather how the solution can be adequately transferred to and implemented in the product. Although it was a long journey from initial idea to finished product, it was worth it.
