How to make magnetic ring

What is a magnetic ring?

Magnetic ring is a kind of anti-interference electronic components made of rare earth permanent magnetic materials. Its function is to suppress high-frequency interference signals. Therefore, it is like a low-pass filter, allowing signals below the cut-off frequency to pass through, and suppressing absorption for high-frequency signals. In fact, its suppression principle is reflected by the impedance characteristics. As shown in the figure below, different magnetic rings have different impedance characteristics at different frequencies. As the frequency increases, the impedance increases.

Brief introduction of rare earth permanent multipole magnetic ring

Classification of multipolar magnetic rings

According to the material classification, multipole magnetic ring is divided into ferrite permanent magnetic multipole magnetic ring and rare earth NdFeB permanent magnetic multipole magnetic ring; according to the manufacturing method classification, it is divided into isotropic and anisotropic as well as sintered magnet and bonded magnet; anisotropy can also be divided into radiation orientation and polar orientation. At present, among all the multi pole magnetic rings, the polar anisotropic sintered NdFeB multi pole magnetic ring has the highest performance and is widely used in magnetic materials and micro motor industry.

Polar anisotropic magnetic ring

The performance of sintered Nd-Fe-B multi polar anisotropic magnetic ring is higher than that of any other multi polar magnetic ring. The surface magnetic flux density of sintered Nd-Fe-B multi polar anisotropic magnetic ring is about 5 times higher than that of isotropic ferrite and more than 2 times higher than that of bonded Nd-Fe-B magnetic ring. Compared with the magnetic ring bonded by several sintered NdFeB tiles, it is not only easy to assemble, save time, labor and materials, but also has higher reliability, and the magnetic flux density is increased by about 20%.

Radiation oriented anisotropic magnetic ring

Radiation oriented sintered Nd-Fe-B magnetic ring is also a research hotspot in China. Its characteristic is that radiation oriented magnetic ring can be used in specific occasions. In theory, any number of even poles can be charged.

Performance comparison of polar and radiation oriented anisotropic magnetic rings

In the comparison of the above two kinds of magnetic rings used in motor, the performance of multi pole anisotropic magnetic ring is better than that of radiation anisotropic magnetic ring. The reasons are as follows:
(1) The surface flux density generated by the former is a sine wave state, while the latter is a square wave state.
(2) The surface flux density of the former is about 1.5 times that of the latter, and the energy produced by the former is much higher than that of the latter. Multi pole anisotropic sintered Nd-Fe-B magnetic ring is widely used in Brushless DC motor and AC brushless synchronous motor. It has become an indispensable key component in its extended products, such as:

• (1) Spindle motor (hard disk, floppy disk drive, etc.);
• (2) Servo motor (precision control system of robot, numerical control equipment, etc.);
• (3) Automobile motor (electric power steering, etc.);
• (4) Various actuators.

How to make magnetic ring?

Preparation process of NdFeB magnetic ring blank by polar orientation sintering

The following is the preparation process of multipolar anisotropic pole oriented sintered NdFeB magnetic ring. It mainly includes the following steps:

Formulation design of NdFeB→Selection and ingredients of raw materials→Vacuum melting→Coarse crushing→Milling→Magnetic field oriented molding→Sintering and tempering→Surface plating treatment→Performance test→Inspection package

(1) According to the size of the surface flux required by the magnetic ring, the formula axbycmdn is selected, among which a is nd, B is Fe, C is B, D is one or several of Ho, Zr, Gd, PR, Dy, A1, Nb, TB and Co. the weight ratio of each element is 15% ~ 20%, M is 0.5% ~ 3%, 10% ~ 20%, y is the rest;
(2) After the ingredients are mixed, smelting is carried out in vacuum;
(3) The ingot was crushed;
(4) The average particle size is 3-5μm after fine grinding:

(5) The powder is injected into the molding die by the orientation magnetic field. The mold contains 4N (n is a positive integer) magnetic filling pole, and the outer diameter of the pressing ring is D. , ID is Di, and its inner diameter is Di and outer diameter D. , and the relationship between P and the number of poles is as follows:

The orientation magnetic field is generated by pulse current. The design of the orientation magnetic field is based on the relationship between the current I, the number of wire turns n, the distance d between the center line of the magnetic ring and the center line of the multi turn enameled wire or copper bar, and the magnetic field intensity: . Among them:;

Forming mould

Molding products

(6) Chamfering arrangement;
(7) The process design of sintering and tempering in vacuum sintering furnace is as follows: first, sintering at 900℃-1600℃ for 1.0-3.0h, then tempering at 400℃-600 ℃ for 0.5-3.0h, and then cooling rate is 0.5℃-10℃/min;

(8) Deburring of magnetic ring blank
(9) Surface plating treatment;
(10) Detection;
(11) Packaging treatment.

Note: The quality of a magnetic ring is also closely related to the mold. The mold is a part of the life of the magnetic ring. Without the mold, it will wait and have no magnetic ring. Because the mold is a tool for manufacturing magnetic rings, and the first step of producing magnetic rings is to press and form by mould, as well as mold and molding machine, ferrite materials, etc. These are all very important. To want high-quality magnetic rings, we must grasp these steps well, because these steps are the beginning of the production of magnetic rings, and they are not done well at the beginning, let alone those processes behind. Firstly, ferrite materials can not be loaded on the molding machine after granulating and grinding to powder. Otherwise, the surface of the magnetic ring produced will be rough, easy to crack and fragile. It is important to adjust the mold during forming. The mold is not adjusted. During stamping, it is easy to damage the mold, and the magnetic ring produced will also deform. At the same time, different mold shall be made according to the design drawing for magnetic rings of different shapes or specifications. During forming, the stamping force must be adjusted well, too much force will also lead to mold damage, too small production of the density of magnetic ring is not enough, not strong enough, and grinding will also lead to cracks or easy to break the magnetic ring. Therefore, in the beginning of manufacturing magnetic rings, we must close every step. At the beginning, every process in the back should follow up and pay attention to. No matter what process is concerned, it is necessary to do it carefully so as to make the magnetic ring the best product.

Magnetization process of Nd Fe-B magnetic ring in polar orientation sintering

Introduction to the principle of multipole magnetization process

Multipole magnetization refers to the magnetization process of magnetic steel filled with two or more pairs of poles on the same magnet. The multipole magnetization technology involves the following performance indexes:

• (1) The working characteristics of the charger;
• (2) Design scheme of magnetic head (or magnetizing coil);
• (3) The properties of permanent magnet magnetic steel.

At present, the main technology of magnetizing permanent magnet magnetic steel with pulse magnetic field is a typical R → L → C circuit. The pulse strong magnetic field generator composed of capacitor bank, silicon controlled circuit, charge discharge control circuit and magnetic head (or magnetizing coil) produces large current for instantaneous discharge, and the permanent magnet magnetic steel is magnetized by the generated pulse strong magnetic field.

The magnetic ring is pressed out by the die. Why is there positive and negative tolerance?

Magnetic rings have tolerances. For some people who have little contact with them or who have just contacted them, they are puzzled. Many people ask why there are positive and negative tolerances on the dimensions of magnetic rings because they are all pressed out with dies? In order to better understand the positive and negative tolerances of the magnetic ring and the reasons for the positive and negative tolerances of the magnetic ring for the people who need the magnetic ring, we make it public on the website, hoping to further understand the knowledge of the magnetic ring for the users and lovers of the magnetic ring.
The reasons for the positive and negative tolerances of magnetic rings are as follows:
In fact, the size of the formed magnetic ring is very standard, which is the same as the size of the mold, and there is no error at all. We all know that the magnetic ring is not only formed, but also produced through a number of processes, such as firing furnace, grinder, ultrasonic cleaning machine, etc.
Presumably we all know that the grinding machine mainly grinds the magnetic ring flat, smooth and bright, so at the same time, there will be positive and negative tolerances on the magnetic ring. If the grinding time is too long, the greater the deviation will be, so we must control the time well. Many customers say that there will be no positive and negative tolerances without grinding the magnetic ring. In fact, we want to give up this step of process, but we can’t, there is no problem There is burr in the ground magnetic ring, which is what we often call the “Pifeng”. There is a certain intention to grind it.

What is the difference between the positive and negative tolerances of the magnetic ring?

Many customers will ask before buying magnetic rings. Usually, the positive and negative tolerances of magnetic rings include outer diameter, inner diameter and height, with positive and negative tolerances. The positive and negative tolerances of outer diameter and inner diameter of a magnetic molded magnetic ring are about 0.3 and the height is about 0.15.
Source: China Magnetic Ring Manufacturer www.rizinia.com