Case Study: MicroLip™ – Robust Rotary Sealing in Cutting-Edge Robotics

Technological advancements in the area of robotics have led to more and more life-like creations existing only in works of science fiction a few decades ago. Development in autonomous logic processing and sensing allow bipedal robots to walk over uneven ground, up and down stairs, open doors and carry loads. Fast response to dynamic and unpredictable real-world environments is critical for the future use of robots in true-life service and practical employment in the years to come.

While software and sensor development remain the primary focus of most research, the physical mechanics of next-gen robotics is also continually progressing. Physical components and control systems such as hydraulic pumps and cylinders, servo motors, and structural members are under pressure to continually be lighter, stronger, more efficient and less expensive. 

Increased demands on the physical components facilitates the need for innovative solutions in design and material usage.

Advancements in construction and technology have spilled into all areas of robotic mechanisms and the many seals located throughout the system need to meet the challenges of tomorrow. Eclipse has been at the forefront of this research and has developed innovative solutions pushing the boundaries of conventional sealing devices. 

MicroLip™ by Eclipse is a prime example of most demanding applications forging new technologies in the sealing world.

The Client's Issue

Eclipse was approached by a leading robotics company looking for sealing solution operating under a challenging set of conditions. While many components of tomorrow’s robotics are now controlled and actuated by servo/stepper motors and various electronic devices, the heaviest and most powerful movements are still driven by traditional hydraulics.

The constant demand for more powerful hydraulic actuation in ever deceasing size and weight requirements has put tremendous strain on component design. But if robots are to progress to the point where they are usefully employed in the world, high power in a compact design is necessary. A robot, for example, used to survey and assist in a disaster zone too unstable for normal rescuers, must fit through doorways and over obstacles yet still be physically strong enough to render assistance.

Large hydraulic systems are capable of moving extremely heavy loads but size and weight constraints of a humanoid size robot limit potential. The robot’s internal power supply to drive all components is also a limiting factor.

Our client was developing a new hydraulic pump to drive all major motion aspects of their robotic systems. Their main objective was to minimize the pump’s physical size as much as possible while increasing output and improving power consumption efficiency. This means higher pressures and speeds on increasingly smaller and lighter components.

Application Parameters:

Shaft Diameter: Ø9.5mm

Seal Housing Envelope: 5mm radial cross-section by 6mm axial width

Rotational Speed: 3,500 RPM nominally; 6,000 RPM max

Operating Pressure: 125 PSI min, 225 PSI nominal, 350 PSI max

Surface Finish: 0.04µm

Media: Hydraulic Oil

While the above combination of pressure and speed might present difficulties for any conventional seal alone, the client’s extremely small physical envelope to house the seal further complicated the matter. 

If that wasn’t enough, the application presented the additional sealing challenge of up to 0.003” [0.08mm] of shaft runout. As part of the downsizing of all components in the pump, shaft support bearings were minimized leading to the possibility of runout. The wobbling effect of the shaft creates problems as the sealing lip has follow a moving, uneven mating surface, therefore potential leak-paths are created. Wear life can also be compromised due to higher concentrations of uneven loads.

The combination of high pressure, high speed, high runout and minimal gland size present a worst-case scenario for a typical seal. Unsurprisingly, the client faced leakage of hydraulic fluid after only short periods of service with any conventional seal they had tested.

Eclipse knew the had the perfect solution for this application. One developed to handle such extreme rotary sealing conditions: MicroLip™