Liquid Seals For Plastic Parts

Developers and designers often have to determine the function of a specific component at a very early stage in the project. For this reason, sealing solutions with high process accuracy, reproducible manufacturing quality and flexible freedom of design are becoming increasingly important in this context. Pöppelmann K-Tech can meet these requirements with its PUR seals using the FIPFG process.

Production processes are continuously implemented and materials are tested. This also applies to the combination of plastic parts with a sealing component in which Pöppelmann has specialized. "Traditionally, static solutions are installed or seals are applied using 2-component injection molding," explains Dirk Stubbe, Sales Project Manager at Pöppelmann. "Locally foamed PUR seals are a cheap alternative to these processes."

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Seamless tightness

Because the seals are foamed directly in the component in this case, one speaks of the FIPFG process (Formed In Place Foam Gasket). A CNC-controlled dosing head ensures that the seal is applied precisely to the groove provided on the plastic part. The two components polyol and isocyanate meet in the mixing chamber of the dosing head. The water contained in the polyol reacts with the isocyanate with elimination of CO ₂, which together with the physically introduced air forms the later foam. Due to the fully automatic control of the process, the foaming process can be reproduced at any time. Since the foam grows into one another at the coupling point, there is no seam in contrast to the inserted cord seals.

The degree of hardness as well as the height and width of the foam seal can be set using this method. “Locally foamed PUR seals are basically used in two areas of application. On the one hand, they can take on classic sealing tasks, that is, protect them from dirt, oils and greases, chemicals and water,”says Dirk Stubbe. "On the other hand, they also reduce vibrations, noise and vibrations." The latter plays a role above all in the automotive industry, because the vehicle acoustics should contribute significantly to the comfort of the driver. But also in electrical engineering and in machine and apparatus construction, designers have to consider the so-called noise vibration harshness.

Efficient and flexible

With this method, the reject rates are low and there are no punching or waste losses. On the other hand, the fully automatic process enables high productivity: there is less effort for the personnel, at the same time short cycles and high production speeds can be achieved. “A very important advantage over other processes is that there are no additional tool costs. After all, the seal is applied directly to the component,”emphasizes Dirk Stubbe. "The time-consuming machine set-up process for complex tools is also eliminated." The automatic component recognition also allows chaotic parts feeding.

Seals do not necessarily have to be foamed into a groove in the component. This is made possible by so-called free-form designs. By means of plasma pretreatment of the plastic part, the designers can also ensure without groove that PUR seals hold their position. The free-form seals not only allow even more flexibility, they also save installation space and thus expand the possible uses. "Already in the development phase it is decided how economically the component can be designed as an injection molded part in the mold and later foamed," says Stubbe.

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Foam and save

Pöppelmann K-Tech has implemented certified quality management so that customers can always rely on optimal quality. There is a separate protection class test chamber for this in accordance with DIN 40050. "We are therefore able to test and document our plastic parts and seals in accordance with the required IP tightness classes," explains Dirk Stubbe. Using prototypes, the tightness of the components can be assessed as early as the development phase. Due to the tool-free and chaotic manufacturing possibilities, the PUR seals can be produced under series conditions and evaluated in their own test chamber - quickly and easily. (br)