The harmonic drive is a brilliant mechanical innovation—a precision device capable of converting high-speed, low-torque input into low-speed, high-torque output. A harmonic drive is composed of three major components:

But how does it function inside humanoid robot joints? What technological barriers define its performance?

How the Harmonic Drive Works

When the wave generator is inserted into the flexspline, it deforms the flexspline into an elliptical shape. This causes the flexspline’s external teeth to engage with the circular spline’s internal teeth at both ends of the ellipse’s major axis, while disengaging along the minor axis.

As the wave generator rotates, it forces the flexspline to undergo periodic radial deformation.
Since the flexspline has two fewer teeth than the circular spline:

This fundamental tooth difference produces a high reduction ratio and torque amplification.
Because the harmonic drive is extremely compact, it has become widely used in humanoid robot joints.

Core Technical Barriers

1. Flexspline Material & Fatigue Resistance

The flexspline undergoes frequent elastic deformation at microscopic scales. This requires materials with:

Special steels must be used, with precisely controlled heat-treatment time and temperature, to achieve the required toughness and strength.

2. Circular Spline Rigidity & Wear Resistance

During engagement, the circular spline must remain essentially undeformed so that all deformation introduced by the wave generator is transferred to the flexspline. This requires materials with:

3. Advantages of PEEK5600CF30

PEEK5600CF30 offers:

Circular splines made from PEEK5600CF30, when paired with steel flexsplines, can maintain transmission precision while offering:

In humanoid robot applications, harmonic drive assemblies made from PEEK can achieve:

Weight reduction increases the robot’s payload capacity and extends battery life.

4. Gear Tooth Profile: Precision Determines Performance

Tooth profile design governs:

A well-designed profile ensures continuous, smooth, zero-backlash engagement, minimizing transmission error.

5. High-Precision Manufacturing Requirements

Manufacturing the flexspline and wave generator requires micron-level accuracy, relying on:

Equipment is expensive, and operators require high technical expertise.

For scalable mass production, manufacturers must ensure:

Only then can high-precision harmonic drives be produced at low cost and high volume.

Future Outlook

The humanoid robotics industry is experiencing explosive growth as leading companies worldwide accelerate R&D and industrialization. As a core component of robotic joints, harmonic drives are seeing sharply rising demand.

Current Usage in Mainstream Humanoid Robots

Forecast for Global Market Demand

According to Dongwu Securities:

Junhua’s Role in the Future of Humanoid Robotics

As a specialized supplier in the PEEK materials industry, Junhua Group possesses a fully integrated production chain and is committed to providing PEEK-based application solutions for humanoid robots.

We support customers through the entire development process—enabling lightweight, high-performance components and cost-efficient mass production for the next generation of humanoid robots.