Marco Gohs

Abstract

The Back-Structured Shaft Seal (B3S) 1 was developed to achieve an optimal balance between static and dynamic tightness, thermal and chemical resistance, as well as high reliability and durability for PTFE shaft seals. Structures on the back of the sleeve create an active pumping mechanism in the sealing contact. This paper sums up the results of a stamped version in comparison to the laser engraved version. The stamping process causes significant alterations to the material properties of the seal. All prototypes underwent both static and dynamic tests which demonstrate that the B3S principle can be successfully implemented in a stamped version. However, the design of the structures must take additional influencing factors into account.

Abstract

Rotary shaft seals are an established standard for sealing rotating shafts 1. The geometry has been optimized over decades and adapted to the material properties to ensure an optimum sealing capability 2. With the widespread availability of 3D printing technologies, there is a growing interest in printable seals for replacement parts or prototypes. This means that failed parts can be replaced as quickly as possible and the development process can be significantly accelerated. However, geometries established for conventional production cannot be implemented as 3D printed variants without accepting severe functional restrictions. A seal that can be successfully 3D printed must therefore be specially adapted. The following findings provide an overview of the latest research and development in the field of 3Dprinted rotary shaft seals.

Abstract

Although rotary shaft seals have been used successfully in many industrial applications for decades, their tribological behavior is still not completely understood. In-depth knowledge of the structural mechanics is essential for the design and optimization of such sealing systems. High complexity results from the multiscale interactions in the tribological system rotary shaft seal. Large macroscopic deformations occur due to the hyperelastic material behavior of elastomers coupled with microscopic tangential distortions of the sealing edge surface in the contact area. This paper includes both numerical and experimental studies on the tribological behavior of rotary shaft seals. A multiscale finite element model provides the simulation of the macroscopic deformations and the microscopic displacements. A test rig equipped with a hollow glass shaft enables in situ visual contact analyses, qualitative determinations of pressure distributions and quantitative measurements of elastomer surface distortions. The optical phenomenon of frustrated total internal reflection enables qualitative evaluations of the pressure distribution. Particle image velocimetry (PIV) is employed to quantify the tangential distortions. The test rig enables the measurement of the friction torque with the same configuration. The results of the numerical and experimental investigations for the radial load, friction torque and tangential distortions are compared and discussed. This serves to validate the simulation methods and the correlation of the measured parameters. This finally results in a solid and validated basis for further tribological investigations of rotary shaft seals.