Functional testing of additively manufactured hydraulic rod seals

Hydraulic rod seals are crucial machine elements in a lot of applications. Malfunction of rod seals can cause huge economic loss by long shutdown times for repair. Especially if equipment is used in remote areas in the nature, malfunction can also cause severe environmental damage by spilled polluting hydraulic fluid. The delivery time of dynamic rod seals for hydraulic applications can last weeks or even months as these seals are often manufactured on demand. In addition, the last years have shown that also geopolitical incidences like a war or a pandemic can have a huge impact on international channels of trade. In order to avoid, or at least minimize, machine shutdown times, it seems to be desirable to have local production solutions for rod seals by using easy to handle machinery and a single, simple raw material. A possible solution to circumvent delivery challenges can be the use of an additive manufacturing (AM) method. The research question addressed in the presented study is whether it is possible to produce functional rod seals using simple AM methods. The results of the method screening and the preliminary investigations were presented at the 21st International Sealing Conference in Stuttgart in 2022. One of the results was the choice of Fused Filament Fabrication (FFF) as the additive manufacturing method for the study and thermoplastic polyurethane (TPU) as the material class to be used. Our latest results, the outcomes of two series of functional tests conducted with these different filaments, will be the core of the presentation that we plan to give at this year’s conference. Parts that are produced by using the Fused Filament Fabrication method are never fully dense due to the process. Nevertheless, the functional tests conducted on a rod seal test rig showed that the research question can be answered in an affirmative way for tested pressures up to 15 MPa. Even in a long-term test the function of the additively manufactured seals met the demands.