How to Increase Load Handling Capacity in Humanoid Robotic Joints

At a Glance:

Joints in humanoid robots endure load combinations that require precision components. Oftentimes this means custom bearing solutions.
Modern bearing selection takes into account the complete system design and overall performance.
Custom integration case study: How a crossed roller bearing was designed for a humanoid robot shoulder.

The Next-Gen Challenge

Humanoid robots are rapidly evolving, arguably faster than most other emerging technologies. As interest in these machines grows, so does the pressure to design more capable, human-like robots that can operate reliably in real-world environments.

One of the areas that is seeing rapid advancement is humanoid joints. They must be compact, lightweight and highly durable, all while supporting multi-axial loads and performing with precision.

As hardware engineers move closer to finalizing joint designs, many are turning to customized, integrated solutions. These provide several advantages such as higher load handling capacity, increased stiffness, fewer components to source, faster assembly and reduced overall cost. Those enhancements are critical in such a competitive, fast-moving field.

CCTY high-performance custom bearing — CCTY develops high-performance custom bearings for robotics designs, which allows for movement adjustments depending on the robot’s environment.

Understanding Load in Robotic Joints

The joints in humanoid robots—particularly the hips, knees and shoulders—must endure a unique combination of forces. These include:

Radial loads. Forces perpendicular to the axis of rotation.
Axial loads. Forces acting along the axis, in both directions.
Moment loads. Torque or twisting forces.

These loads are not static; they fluctuate with every movement, requiring the bearing systems inside to be both strong and precise. In such applications, crossed roller bearings are commonly used on the output side due to their ability to handle complex load combinations while maintaining high accuracy and rigidity.

However, standard off-the-shelf bearings are often insufficient for the performance demands and compact form factors required. The solution lies in customization and integration.

Customization: Designing for the Robot, Not Around the Bearing

Look for a manufacturer whose approach to customization focuses on designing the bearing to fit the robot, rather than forcing the robot to adapt to standard components. Each bearing type is tailored with application-specific modifications to maximize performance, integration and reliability in humanoid robotics.

The following illustrates the approach CCTY takes to customizing bearing types:

Crossed roller bearings. Custom holes or threads in the inner or outer ring simplify mounting and improve assembly alignment.
Thin section ball bearings. Mating components can be integrated directly into the bearing rings, eliminating the need for separate adapters and reducing assembly time.
Spherical plain bearings. Extended inner rings allow for larger swivel angles, offering greater joint flexibility and range of motion.
Rod ends and linkages. Rod ends can be fully customized to meet the specific mounting geometry and motion requirements of the application. Additional customizations may include optimized clearance, tailored friction torque and application-specific swivel angles.
Bushings. Offered in cylindrical, flanged or washer configurations using self-lubricating materials such as steel-backed bronze composite with a PTFE layer for long-term, maintenance-free operation.

By utilizing a custom bearing system, engineers can:

Enhance the bearing stiffness by increasing the bearing wall thickness.
Increase the bearing’s radial, axial or moment load capacity.
Streamline the assembly process by having fewer overall components.
Reduce tolerance stack-up, which is critical for maintaining motion precision.
Minimize potential failure points by eliminating the need for multiple assembled parts.

When a manufacturer has an in-house forging plant, unlimited customization is possible. These tailored solutions not only ensure mechanical compatibility but also enhance the precision, durability and overall performance of robotic joints.

Spherical plain bearings are suitable for bearing arrangements where oscillating movements are required and can accommodate misalignment. Their extended inner rings allow for larger swivel angles, offering greater joint flexibility and range of motion.

Case Study: Custom Integrated Systems

A humanoid robot shoulder needed the joint to handle high moment loads while maintaining a low-profile design. A standard bearing solution would have required multiple parts, adding weight, increasing assembly time and introducing alignment challenges.

Instead, the design team opted for a custom crossed roller bearing with:

A built-in mounting flange for a mating part.
Integrated housing interface.
Optimized internal geometry for higher moment load capacity.
Custom threads added to the inner ring to enhance both stiffness and torque consistency.

These changes delivered substantial results. By optimizing the internal structure and maximizing material efficiency, the design not only boosted load capacity but also allowed for slimmer joints and a more natural robot profile. The simplified assembly process also enhanced efficiency and shortened production time. This kind of application-focused engineering is exactly what’s needed to meet the high-performance demands of robots.

Beyond Bearings: Rethinking Joint Architecture

Meeting modern performance requirements means moving away from the traditional mindset of component selection. Rather than asking, “What bearing should we use here?” engineers are shifting to, “What should this joint look like, and how can the bearing be built into it?”

This integrated design philosophy enables improvements across the board. Working with bearing manufacturers early in the design phase allows roboticists to co-engineer systems that are precisely tailored to the robot’s real-world needs, rather than relying on pre-existing components with compromises.

Designing for the Future

As humanoid robots continue to push the boundaries of motion, agility and real-world application, the demands on joint design will only grow. To meet these challenges, engineers must move toward customized, integrated bearing systems that are designed not just to fit but to perform.

By combining component integration with tailored material selection, precision engineering and collaboration with bearing specialists, roboticists can unlock higher load capacities, slimmer bearings and longer component life.

In short, the future of humanoid robotics depends not just on better joints, but smarter, more cohesive joint systems.

FAQ: Custom-Bearings

How long does it take to design and manufacture a custom bearing?

It depends on the manufacturer and the design. For example, a heavily customized crossed roller bearing was completed with a 30-day turnaround at CCTY. However, lead times can vary based on the complexity of the design, material availability, forging schedules and other factors.

What information will the bearing manufacturer need?

The most important details are the mating dimensions (where the bearing interfaces with other components), the intended function of the bearing and the expected loading conditions. The more information provided upfront, the better the manufacturer can assess feasibility, recommend the right solution and avoid potential issues or failures later in the process.

Are CAD drawings required?

A 2D engineering drawing is highly recommended, as it speeds up the design process. If tolerances are included, the manufacturer can review the design for manufacturability and reach out if there are any concerns. It’s not always mandatory, but it definitely streamlines the process.

What should I know about the manufacturer before starting the project?

Look for a manufacturer with responsive engineering support in your time zone, or close to it. In robotics, ongoing collaboration is critical. Without frequent communication, projects can easily lose momentum. It’s also a major advantage if the manufacturer has in-house forging capabilities, as this can significantly cut lead times. Of course, whether forging is required depends on the specific product and application.