FST Creates PU Seals to Meet the Demanding Needs of Cobots

PUdaily | Updated: November 21, 2023

Freudenberg Sealing Technologies (FST) has developed specialized seals catering to the distinct needs of a collaborative robot (cobot) manufacturer. These seals, crafted from polyurethane, play a crucial role in safeguarding the cobots' joints from dust, water, and other contaminants, ensuring uninterrupted functionality.

Initially, PTFE seals were employed, proving efficient without compromising the speed of the robot arms. However, they fell short of providing the necessary IP54 protection. The challenge involved creating seals that could endure long-term exposure to temperatures as high as 60°C, while also maintaining low material elongation for effective performance across diverse operating conditions, given that cobots are deployed for various tasks within a factory setting.

In response to the cobot manufacturer's request for a redesign, FST began with a polyurethane U-ring. Yet, the initial design faced challenges, as the relatively large surface led to frictional forces exceeding the specified maximum of 1N/m. To address this, the geometry was modified to a z-profile, accompanied by the integration of a second groove. These adjustments reduced contact pressure, meeting the friction requirement. However, practical tests revealed excessive wear, primarily due to the rough surfaces of the lightweight aluminum cobots. The solution involved the development of a three-component solid film lubricant coating to minimize wear.

Further changes in cobot design prompted additional alterations to the seal geometry. The final version retained the z-geometry but featured optimizations to the dynamic seal lip, along with the construction of a static area with an external groove.

The seals are constructed from FST's 92 AU 21101 grade of polyurethane, known for its softness and flexibility, coupled with a robust tensile strength of 59MPa—well surpassing the required 50 MPa. With minimal elongation, the material remains compatible with temperatures ranging from –50°C to 110°C.

FST highlighted the efficiency of its Freudenberg Xpress service, capable of swiftly producing one-offs and small production runs at the same high standards as full-scale manufacturing. This, combined with in-house development, facilitated the rapid implementation of the seals. Product developer Alexander May emphasized the company's agility in delivering products promptly, particularly in the niche of one-off products and short production runs, underscoring the blend of expertise and quality standards comparable to large-scale series production.

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