Backlack: Motor Lamination Stacking And Bonding

Backlack technology represents a significant advancement in the manufacturing processes of electric motors, particularly in the precision stacking and bonding of motor laminations. It employs a specialized bonding varnish, commonly known as Backlack, which is applied to the electrical steel before they are assembled into stacks. This technology is crucial for achieving optimal motor performance, durability, and efficiency.

Self Bonding Lamination Stacks

Lamination Bonding Process: The Joining Technology For Perfect Lamination Stacks

Cleaning Electrical Steel Lamination

Each silicon steel sheet or electrical steel lamination must be thoroughly cleaned to remove any surface impurities, oils, or contaminants. This cleanliness is crucial as it ensures that the Backlack varnish adheres properly to the laminations without any interference from foreign particles.

Typically, specialized industrial cleaning agents are used, followed by a drying process to ensure that no moisture remains on the surfaces.

Coating Bonding Varnish

Application of Backlack Varnish Once the laminations are clean and dry, the Backlack varnish is applied. This coating process can be done using automated systems, depending on the volume and precision required. 

We provide EB540, EB546, EB548, and EB549 bonding varnish. Backlack is applied by roller coating on one or both sides of the core plate.  For single-side coating, we recommend a coating thickness of 5..7µm (200..280µin), and for double-sided coating 3..5µm (120..200µin), depending on the roughness of the sheet metal.

electrical steel coating

Curing Self Adhesive Varnish

We can be controlled using curing oven adjustments. In the case of moderate curing temperature, a dry, flexible, and still reactive coating can be achieved.

Cutting And Stamping Stator And Rotor Cores

The stator and rotor cores of electrical machinery are manufactured using thin sheets stacked together in order to minimize eddy current losses.

We employ laser cutting, wire cutting, and stamping processes to manufacture motor stator and rotor stacks. Our self-bonding motor lamination shapes and dimensions can customized to customers.

Alignment and Stacking Lamination Stacks

We can design lamination fixtures to be custom-built for your application. The fixture holds the lamination in the correct position and ensures that pressure is applied evenly. The laminations are then stacked in a straight or skewed manner based on the customer’s drawing call-out.

Second Curing Motor Lamination

After stacking, the laminations undergo a curing process where the varnish is hardened into a solid resin, bonding the laminations together permanently. This process typically involves the application of heat and pressure for a specified duration, which activates the thermosetting properties of the Backlack varnish.  In our lab heat press, the final bonding strength can be achieved in the 20s at 240°C.

Quality Control

Coating liquid detection: viscosity, density, and solid content of the coating liquid.

Uncoated electrical steel detection: electrical steel magnetic properties detection, surface roughness detection.

Self-bonding electrical steel detection: adhesion, paint film hardness, coating thickness, insulation detection between silicon steel sheets, and electrical steel high voltage resistance detection.

Self-bonding motor core detection: bonding strength (T peeling, rolling peeling, shear strength).

Self-adhesive motor lamination failure analysis and aging resistance test: high and low temperature oil resistance failure analysis, motor core iron loss detection, etc.

quality control for bonding lamination

Advantages of Full-Surface Bonding Techniques With Backlack

Versatility and Design Freedom

Backlack bonding technology allows complete design freedom, leading to optimal motor engineering. Manufacturing constraints like interlocking positions or weld seams are not a concern, enabling the creation of more efficient electric motors.

Enhanced Thermal Conductivity

Bonded lamination stacks produced with tight manufacturing tolerances improve heat dissipation by enhancing heat transfer between the laminations and the housing. This allows for smaller, lighter, and less expensive cooling units. These compact stacks also exhibit excellent stacking behavior and provide effective electrical short-circuit protection due to their favorable insulating properties.

Mechanical Stability and Dimensional Accuracy

Full-face adhesive bonding rotor and stator cores ensure adherence to the narrowest tolerances and excellent shape stability since the laminations cannot expand. Unlike welding, which introduces heat and causes core tensions, adhesive bonding avoids this issue, maintaining structural integrity.

Preservation of Magnetic Properties

Bonding is our least damaging joining technique, having no adverse effects on the magnetic properties of electrical steel. In contrast, interlocking and welding can significantly damage the microstructure, impairing the material’s magnetic performance.

Reduce Noice

The viscoelastic properties of Backlack dampen vibrations in laminations, reducing noise levels in selected electric machines.

laminations bonding prototype

Conclusion

Backlack stator and rotor lamination technology has demonstrated its capacity to revolutionize the motor manufacturing industry through its innovative lamination stacking and bonding methods. By employing self-bonding varnishes, Backlack facilitates precise and durable lamination stacks, essential for enhancing motor performance and efficiency. This technology supports various industries, from automotive to renewable energy systems, highlighting its extensive application potential.

Try to contact us for high-quality motor cores in China.