⚡ Key Takeaways
- Four product families: high-strength anti-loosening screws; shoulder screws plus rod-end bearings; threaded inserts; anti-loosening washers.
- High-strength bolts: alloy steel in classes 12.9 and 14.9 with special thread forms and finishes; titanium in 10.9/12.9 and aluminium in 6.8 for lightweighting.
- Shoulder screws do three jobs at once — fastening, locating and pivot support — and are a key joint component.
- Rod-end bearings are the core articulation part in linear actuators and linkages, allowing controlled multi-axis movement.
- Where they go: finger joints, tendon drive pulleys, hip, knee and shoulder joints, torso frame and enclosure panels.
- Weight: a humanoid robot uses 1,000–5,000 screws; titanium cuts fastener weight by about 40%.
1. Why humanoid robots need purpose-built fasteners
2. High-strength anti-loosening screws
3. Shoulder screws and rod-end bearings
4. Threaded inserts and anti-loosening washers
5. Selection logic and FAQ
1. Why humanoid robots need purpose-built fasteners
A humanoid robot has 40–60 degrees of freedom and uses 1,000–5,000 fasteners:
- Constant vibration: joints reciprocate, so nothing may come loose;
- Light weighting: battery life is tight, every gram counts;
- Precision: joint clearances must stay small and location must repeat;
- Light-alloy frames: aluminium, magnesium and carbon fibre need reinforced threads.
2. High-strength anti-loosening screws
| Material | Class | Typical use |
|---|---|---|
| Alloy steel | 12.9 / 14.9 | Load-bearing joints, enclosure panels |
| Titanium alloy | 10.9 / 12.9 | Weight-critical locations |
| High-strength aluminium | 6.8 | Magnesium frames (galvanically matched) |
Where they go: the whole body, finger joints, fingertip actuators, tendon drive pulleys, sensor modules and enclosure panels.
3. Shoulder screws and rod-end bearings
Shoulder screws
A key base component of humanoid joints and motion structures, combining fastening, locating and pivot support in one part — one of the core mechanical elements that make high-precision, multi-axis motion possible.
Rod-end bearings
The core articulation part between linear actuators (screw-driven push rods) and linkages. They provide a compliant joint that allows controlled multi-directional swing, which is central to biomimetic robot motion.
Applications: knee joints, ankle joints, dexterous hands and actuator mounting.
4. Threaded inserts and anti-loosening washers
Threaded inserts
In humanoid robots these mainly reinforce threads in lightweight structures, solving three problems:
- Preventing thread stripping;
- Raising joint strength;
- Extending service life.
Applications: torso frame, arm frame and the main load-bearing structure of the legs.
Anti-loosening washers
Carbon and stainless steel dominate, with high-strength alloy steel and lightweight composites gaining ground in premium applications to meet high-frequency vibration, precision and long-life requirements. Applications: hip, knee and shoulder joints, the torso load-bearing frame, sensors and precision modules.
5. Selection logic and FAQ
Three questions
- Is it a load-bearing joint? Then a shoulder screw plus a class 12.9 bolt.
- Is weight critical? Then titanium class 10.9.
- Is the frame a light alloy? Then reinforce the thread with an insert.
FAQ
Q: How many screws does a humanoid robot use? Typically 1,000–5,000, of which shoulder screws are 5–10%.
Q: How much lighter is a titanium bolt than steel? Titanium has a density of 4.5 versus 7.8 for steel, so roughly 40% lighter.
Q: Why micro screws in finger joints? Space in a finger is minimal, so M1.2–M2 micro screws are used with pre-applied threadlocking adhesive.
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