Common Process Of Bonded NdFeB Magnets

NdFeB strong magnet is one of all permanent magnet types. It belongs to rare earth permanent magnet materials, and its production process is also very different. Therefore, this article will tell you about several manufacturing processes of bonded NdFeB magnets. 

 

The bonding process of bonding neodymium magnets is an important part of magnet preparation, and there are 4 production methods:

 

1. Calendering

The magnetic powder and the adhesive are mixed uniformly in a volume ratio of about 7:3, rolled to the required thickness and then solidified to make a finished product. Generally, vinyl and nitrile rubber are used as adhesives to bond Connect with ferrite or part and a small amount of NdFeB. Generally, no surface treatment is required, and film protection or decoration is required, and nickel plating is required for NdFeB.

 

2. Injection molding

The magnetic powder is mixed with the binder, heated and kneaded, pre-granulated, dried, and then sent to the heating chamber by the spiral guide rod for heating, injected into the mold cavity for molding, and the finished product is obtained after cooling. Generally, nylon 6, polyamide, polyester and pvc are used in an amount of 20%~30% (volume fraction), and rigidly bonded permanent magnets with complex shapes are used. After ferrite, samarium cobalt magnets and neodymium iron boron magnets, no surface treatment is required.

 

3. Extrusion

It is basically the same as the injection molding method, the only difference is that after heating, the pellets are extruded into the mold through a cavity for continuous molding. Nylon 6, polyamide, polyester and polyethylene are also used to produce thin-walled cylinders or ring-shaped longer magnets that are difficult to achieve by other processes, such as ferrite, samarium-cobalt magnets and neodymium-iron-boron magnets.

 

4. Molding

Mix the magnetic powder and the binder according to the ratio, granulate and add a certain amount of coupling agent, press into the mold, solidify at 120°~150°, and finally get the finished product. Use solid epoxy resin or phenolic resin, the addition amount is 1%~5%. Permanent magnets can be bonded according to larger size and simple shape. Generally, cathodic electrophoresis, spraying, evaporation and other methods are used for coating protection.

 

The molding process of bonded NdFeB magnets is basically divided into these four types, the most commonly used of which are injection molding and compression molding.

 

Detailed process flow:

1. Magnetic powder, coupling agent → adhesive → batching → non-magnetic field pressing molding → curing treatment → magnetization → inspection and packaging

2. Magnetic powder, coupling agent → adhesive → batching → magnetic field compression molding → degaussing → curing treatment → magnetization → testing and packaging