What type of adhesive is used for the joints and motors of humanoid robots?

It is difficult for the joint motors in humanoid robots to rely on a single type of adhesive to cover all operating conditions; the stator windings, rotor magnets, control circuit boards, and wire harness terminals each require different adhesive materials—such as potting compounds, structural adhesives, three-proof protective coatings, and housing seals. For high-integration joints, the key to selecting the appropriate adhesive lies not in finding a universal adhesive that works for every scenario, but in first clarifying the thermal load, mechanical load, electrical insulation requirements, and environmental challenges that each specific point must withstand, and then matching the material solution accordingly.

Frameless torque motors are inherently designed to achieve high torque density and extreme compactness; within their small joint cavities, multiple stresses are superimposed: concentrated temperature rise, continuous vibration, and alternating mechanical stress, while available spatial margin is extremely limited. The stator windings therefore emphasize thermal conduction, heat dissipation, and hermetic encapsulation, whereas the rotor magnetic steel focuses on long-term, reliable structural fixation.

The application scenarios for humanoid robots are defined by their mobility capabilities. The dynamic performance, load capacity, environmental adaptability, and safe and compliant characteristics of the motion system are prerequisites for successful scenario implementation. The differing requirements for gait, interaction, and disturbance rejection across various scenarios further influence the selection of underlying materials and components, including joint motors, transmission systems, and bonding and encapsulation technologies.

Magnetic steel bonding

A ring of neodymium-iron-boron magnets is attached to the rotor; during high-speed rotation, the resulting centrifugal force is substantial. Even more problematic is that the joints of humanoid robots undergo repeated start-stop cycles and repeated direction changes; consequently, the magnets are subjected not to a continuous, steady centrifugal force, but to successive waves of impact loads.

This requires the magnetic steel bonding adhesive to simultaneously meet three requirements:

First, high-temperature resistance. When the joint motor operates continuously, the rotor temperature can rise above 150°C; at this temperature, the strength of ordinary epoxy resin declines. Therefore, an H-grade temperature-resistant system must be selected, which has a sufficiently high thermal deformation temperature and can maintain its bonding strength at high temperatures.

Second, vibration resistance. Under repeated directional changes and repeated impact, the adhesive layer must not gradually fatigue and fail. Both shear strength and peel strength must be sufficient, and the material must also possess adequate toughness; it must not be overly brittle.

Third, high bonding strength. Since the surface energies of the magnetic steel and the rotor core differ, the adhesive must simultaneously firmly bond the two materials together, preventing interfacial delamination.

Potting of stator coil windings

The stator windings are the primary source of heat generation in a motor. Humanoid robot joint modules are sealed and miniaturized; if heat cannot be dissipated, the situation becomes problematic.

Therefore, the primary function of the stator potting compound is to rapidly conduct heat from the windings to the housing. This requires that:

First, high thermal conductivity. The thermal conductivity coefficient should be at least 1.2 W/m·K or higher; for better performance, it can reach 2.0 or even higher. Otherwise, the process will be no different from not performing it at all—the heat will remain trapped within the windings.

Second, it must have good fluidity. The die is densely packed with copper traces, and a PCB sits on top, creating extremely narrow gaps; the solder must be able to flow into these gaps and reach the bottom without trapping air bubbles or leaving voids. Otherwise, the areas that are not filled will become dead zones for heat dissipation.

Third, avoid cracking. The joints of humanoid robots undergo several cycles of thermal expansion and contraction each day; if the encapsulant has high brittleness, it will crack after just dozens of such thermal cycles, immediately compromising its thermal conductivity and insulation properties. Therefore, a system with good toughness and a low coefficient of thermal expansion should be selected.

Bearing retention

The bearings in the joints of humanoid robots are all miniature precision bearings with extremely tight tolerances. The fit clearance between the shaft and the inner ring of the bearing, as well as between the outer ring of the bearing and the bearing housing, is minimal.

What adhesive is used in this type of application? Anaerobic retention adhesive.

Why choose anaerobic adhesive? There are two reasons:

First, rapid initial curing. With tight production cycles, there is no time to wait half a day for the adhesive to set. Under anaerobic conditions within metal gaps and in an oxygen-free environment, the adhesive can achieve initial curing within ten to several dozen minutes, after which it will fully cure.

Second, high permeability. The fit clearance between the bearing and the shaft may be only a few micrometers to over ten micrometers; the adhesive cannot be forced out during assembly and must fill the entire mating surface. Only when the clearance is fully filled can the adhesive provide a holding effect and prevent micro-movement wear.

Outlet fixation

The output port of the joint module is the point where the wiring harness passes from inside the motor to the exterior. This location is the weakest point of the entire module: it serves as both the wiring harness outlet and a site of mechanical stress concentration, as well as a gap in the sealing and wiring protection.

The outlet fixed sealant must address three issues:

First, ensure fixation. When the wiring harness undergoes repeated swinging at joints, it must not swing back and forth; prolonged swinging can cause the harness cover to wear through and the solder joints to loosen. Adhesive must securely fasten the wiring harness to the housing.

Second, sealing. Water vapor, dust, and oil contamination must not penetrate through the outlet; if they do, this will result in short circuits, corrosion, and failure.

Third, it must be flexible and resistant to bending. When the joint moves, the wiring harness near the wire outlet will bend accordingly; therefore, the adhesive should not be too rigid, which would cause the wires to become permanently bent. It should have sufficient flexibility so that it moves with the harness rather than locking it in place.

Verified JOME Engineering Grades & Specification Cross-Reference

To qualify an industrial-grade adhesive, potting compound, or thermal interface material for this application, compare verified Shanghai Jome Industrial Co., Ltd. (JOME) formulations below or explore our primary category hubs: Anaerobic Threadlockers & Retaining Adhesives and Industrial Structural Adhesives.

JOME Grade / SKU	Polymer Chemistry & Cure	Key Verified Specification	Primary Industrial Application
JOM 3107	Anaerobic Magnet Structural Bonding Adhesive	High impact & centrifugal shear (>20 MPa) \| +150°C rated	Servo motor, traction motor & humanoid robot rotor magnet bonding
JOME 1767 / JOME 2029A/B	1K Heat-Cure & 2K High-Temp Motor Epoxy	Continuous service up to +180–200°C \| High Tg & chemical resistance	High-speed turbine rotors, rare-earth & ferrite magnet bonding
JOM 638	High-Strength Cylindrical Bearing Retaining Compound	Fills 0.05–0.25 mm radial clearances \| Prevents fretting wear	Motor shafts, harmonic drive bearings, gears, bushings & sleeves
JOM 263/277 & JOM 204/93	Liquid Anaerobic & Microcapsule Pre-Coated Threadlockers	Breakaway torque 20–42 N·m \| Oil-tolerant & dry-to-touch film	Chassis bolts, robot joint fasteners, mass pre-coated screws

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Matched JOME Industrial Formulations: For production bonding, potting, and sealing qualification in this application, evaluate General-purpose epoxy potting compound (black, white, red, clear), 10:1 Condensation type high bonding strength silicone potting compound, 2-Part Clear epoxy adhesive thin layer Potting Compound, and Clear long-term yellowing-resistant polyurethane encapsulation coating compound (ISO 9001:2015 and CTI RoHS 2.0 verified; free engineering samples shipped via UPS freight collect).

Frequently Asked Engineering Questions

Q: Which JOME adhesive or potting grades are recommended for what type of adhesive is used for the joints and motors of humano?
Depending on substrate pair, continuous operating temperature, and curing line constraints, Shanghai Jome Industrial Co., Ltd. (JOME) recommends evaluating JOM 3107, JOME 1767 / JOME 2029A/B, and JOM 638. Review our full specification table on this page or request a customized formulation sample.

Q: Can JOME customize viscosity, cure speed, or thermal conductivity for our automated production line?
Yes. JOME's Shanghai RandD laboratory customizes A/B mix viscosity, thixotropic index, pot life, Shore hardness, and thermal filler loading (0.75 to 25.0 W/m·K) to match your dispensing equipment and environmental test standards.