Nanocrystalline and amorphous cores are usually tape wounded. XIANYU rarely provide bare cores to customers, as bare cores are brittle and would be damaged easily during shipment. To protect these cores and make the electromagnetism property stable, several kinds of encapsulations should be adopted. Below are some of the popular methods, all can be manufactured by us.

Epoxy resin coating

Epoxy resin coating, or epoxy resin painting, make the surface smooth and the appearance is similar to that of ferrite cores. No special tooling is required and labor cost or material cost are both very cheap. Epoxy resin coated nanocrystalline cores are especially suitable for applications of compact size. But the production process is usually not environment-friendly, and therefore, is strictly limited by the authority in China.

Crepe paper wrapped

The process of crepe paper wrapping usually cannot be implemented by machines. We usually finish the crepe paper wrapped nanocrystalline cores by hand, no matter toroidal, oval or rectangular shape. So, the labor cost is high and small cores cannot be applied. But for a small lot of big cores, that is very suitable as there’s no tooling cost.

Insulation tape wrapped

Insulation tape wrapped cores have a relatively smooth surface. Other conditions are similar to crepe paper wrapped cores.

Plastic box

For small cores, the labor cost is very low if we choose a plastic box. But sometimes there is no plastic box of suitable size in existing, and a plastic mold should be developed in advance. In that case, it only suitable for mass production. Besides that, plastic box nanocrystalline cores usually have better magnetic properties than the same size of epoxy resin coated cores.

Aluminum box

The aluminum box is strong enough for very large cores. It can provide good mechanical protection for direct windings of large-scale wires. And it has one advantage that of the plastic case: no plastic mold is required. But the material cost for each piece is very high and the application is limited. So, aluminum box nanocrystalline cores are not so widely used.

We choose aluminum boxes/cases to make protect the bare nanocrystalline cores inside. For a small lot, there’s one advantage, i.e, we can manufacture the boxes without metal stamping dies.

Stainless steel box

The stainless steel box is similar to the aluminum box. But it’s made of steel sheet welding together, and there’s no top lid. So, the epoxy resin should be pouring to make the final core strong. Therefore, stainless steel box nanocrystalline cores require more labor cost than plastic box cores.


Below is the table, comparing the 6 typical methods of encapsulation.

EncapsulationsLabor costMaterial costTooling cost
Epoxy resin coatingLowLowNone
Crepe paper wrappedHighLowNone
Insulation tape wrappedHighLowNone
Plastic boxLow Low High
Aluminum box LowHighLow
Stainless steel box LowHighLow
Finish Types of Wound Cores