How to bond magnets ?

27/07/2026

As electric motor technology advances, the demand for higher performance, efficiency, and reliability continues to rise. One key process that significantly impacts these aspects is magnet bonding : the method used to secure permanent magnets to the rotor or stator of a motor. Unlike mechanical retention systems such as shrink-fits or sleeves, magnet bonding relies on adhesive technology to secure magnets to the rotor core. This method offers significant design flexibility, improved efficiency, and reduced noise and vibration, making it the preferred choice for high-performance electric machines.

Permanent magnets play a central role in the operation of synchronous machines, brushless DC motors, and traction motors used in electric vehicles. These magnets are typically mounted on the rotor either on the surface (surface-mounted permanent magnet rotors) or embedded within slots (interior permanent magnet rotors). Traditional mechanical retention methods often introduce additional mass and inertia, reduce available space for magnets, and can generate stress concentrations. Magnet bonding, by contrast, provides a lightweight, precise, and reliable fixation that ensures uniform stress distribution and improved dynamic balance at high rotational speeds.

However, these magnets are subject to significant mechanical, thermal, and chemical stresses in their daily use :

Centrifugal forces at high rotational speeds
Thermal cycles due to load variations
Vibration and shock in demanding environments
Corrosive exposure in harsh operating conditions

If magnets shift or detach, the motor’s performance and safety can be compromised. This is why magnet bonding adhesives have become a preferred solution for ensuring reliable assembly.

01. Properties

The adhesives used in magnet bonding are typically epoxy-based structural adhesives due to their high shear strength, excellent adhesion to metals and magnets, and resistance to thermal and chemical stresses. For high-temperature environments, such as traction motors in EVs, formulations capable of withstanding temperatures up to 180–200°C are required. Some key characteristics of adhesives for magnet bonding include :

High shear and peel strength to prevent magnet detachment during high-speed operation.
Thermal conductivity to aid in heat dissipation from the rotor to the shaft.
Resistance to oils and solvents typically present in the motor environment.
Low shrinkage during curing to maintain precise magnet positioning and air gap consistency.