The process that connects. The processing of materials and the stack bonding technique contribute substantially to the behavior of the electrical steel inside an electric motor. The most non-damaging and flexible process is full-face bonding of the laminations.
The bonding process
After the laminations have been punched, they are thermally bonded in a two-step bonding process.
Phase 1: Softening of the bonding varnish layer. Complete melting in phase 1 results after complete chemical reaction in high bonding strength and a high level of resistance to a variety of different media.
Phase 2: Further increase in temperature. The self bonding varnish hardens and becomes a stable, highly cross-linked duroplast with high viscosity and high bonding strength between the laminations.
Why Backlack is the technology of the future
Freedom of design
With bonding varnish technology, the thinnest webs and smallest tolerances can be achieved without having to take welding seams and clamps into consideration.
With bonding varnish, an extremely compact stack is created which does not allow the laminations to fan out and can be milled by the magnet manufacturer.
Retention of magnetic properties
Since there are no welding seams and packer knobs, the structure of the base material is not changed. Best magnetic properties are the result.
Improved thermal conductivity
Compared to other stacking methods that always result in air inclusions, full-surface bonding features much higher thermal conductivity.
The bonding varnish between the laminations has a strong damping effect, which makes motors run more smoothly.
Performance enhancement and environmental compatibility. All types of Backlack made by voestalpine are water-based systems.
A layer thickness in the range of 3–5 μm per side meets the highest requirements with regard to adhesive strength, mechanical stability or acoustic behavior. Even with reduced layer thicknesses in the range of 1–2 μm per side, a large part of the advantages of bonding varnish are retained when compared to conventional bonding processes.
These include, for example, improved acoustics due to an intermediate layer with a damping effect, improved thermal conductivity due to the reduction of hollow spaces, improved 3 magnetic properties due to damage-free bonding and freedom of design because bonding points do not have to be taken into account.
Another advantage becomes clear with respect to stack strength compared to interlocked stacks —despite a thin bonding layer with reduced bonding strength—especially in thin electrical steel.
The stator and rotor cores of electrical machinery are manufactured using thin laminations stacked together by our customers in order to minimize eddy current losses. There are several ways to join these laminations, and the most efficient way is to use Backlack.
Electric motors need an iron core, and highly efficient electric motors need an iron core made of individually stacked laminations made of electrical steel. But how are these individual laminations optimally bonded with a perfect fit? In a mouth- watering video, Professor Metin Tolan lifts the secret of how this works with Backlack on isovac® electrical steel. We invite you to learn more.