Multipole ring magnets produced through multipole orientation technology are known as polar anisotropic ring magnets. The orientation magnetic field is generated by pulse coil similar to multipole magnetizing fixture. This magnetic field travels from the north pole to the adjacent south pole, resulting in a curved distribution of the powder within the mold cavity. As a consequence, multipole orientation is also recognized as multipole non-uniform orientation or Halbach orientation. The orientation fixture should be tailored to the dimensions and pole number of each polar anisotropic ring magnet. Following their manufacture, the magnets should then be magnetized with the same pole number and direction.
- The dimensional adaptability of polar anisotropic ring magnets is limited.
- Polar anisotropic ring magnets lack flexibility in magnetization patterns. Notably, achieving skewed magnetization is not possible with this type of magnet.
- Multipole ring magnets based on radially oriented ring magnets are typically exhibit square wave in magnetic flux density waveform. Achieving a sinusoidal (sine) wave necessitates intricate adjustments and matching of the polar head and parameters of the magnetizing fixture. However, magnetic flux density waveform of polar anisotropic ring magnets naturally distributes in sinusoidal pattern.
- A polar anisotropic ring magnet can attain a markedly higher surface magnetic flux density compared to its radially oriented counterpart.
- The peak deviation and angle deviation in the magnetic flux density waveform are higher for polar anisotropic ring magnets than for radially oriented ring magnets.
- Due to the substantial difference in the coefficient of thermal expansion between the c-axis and a-axis of Nd2Fe14B grains, the sintering shrinkage of polar anisotropic rings is non-uniform. To achieve a ring shape, the polygon blanks must undergo processing. Consequently, radially oriented ring magnets exhibit a significantly higher material utilization rate.
- Magnetic performance characterization of polar anisotropic magnets typically relies on magnetic flux density waveform or installation testing rather than demagnetization curves.
In addition to cost considerations, we recommend choosing the appropriate option between these two magnets based on the output characteristics of motors, including factors such as torque, speed, cogging torque, and control accuracy.
Miniaturization is the current development tendency in varies industries, notably in consumer electronics and medical equipment. Micro devices inevitably utilize high accuracy micro motors, leading to a heightened demand for micro multipole ring magnets. For micro magnets, radially oriented ring magnets and hot pressed ring magnets are constrained by orientation systems and process principle, respectively. However, mutlipole orientation technology provide a specific feasible solution: machining a hole in a polar anisotropic cylinder magnet.
The proliferation of high-speed hair dryers in China has enabled the commercialization of this solution. The limit dimensions of outside diameter (O.D.) and inside diameter (I.D.) are now available at 2.5mm and 0.8mm, separately. Nevertheless, magnetic performance of micro polar anisotropic ring magnets often falls short of their nominal grade. For this reason, opting for full-density isotropic magnets produced through the hot pressing process proves to be a much more ideal choice.
