The production process is almost same between Neodymium tube magnet and ring magnet. The type of the production process, especially for the axial magnetized sintered Neodymium tube magnet varies in magnet sizes including inner diameter, wall thickness, outer diameter, etc.
Most Neodymium tube magnets or ring magnets are magnetized through length, height or thickness. The main magnetic properties and magnet orientation is decided in the production process of semi-finished magnet blocks. And then the machining process will make the Neodymium magnet blocks to required shape and size of the final magnet product. If the outer diameter is big, for example D33 mm, we may produce a rough cylinder directly in the pressing and orientation process. After sintering and heat treatment, the rough cylinder needs testing magnetic properties, like Br, Hcb, Hcj, BHmax and HK, etc. If magnetic properties are OK, it will go to several machining steps such as drilling, inner circle grinding and outer circle grinding to get a long tube, but much magnet materials are wasted during machining process and then material cost is shared to the final Neodymium tube magnet price. The length might need slicing to several shorter tubes.
Why not press a rough tube directly so as to reduce material waste and the magnet price? It is subject to the consideration about efficiency, NG rate and cost. For some tube magnets with bigger out diameter and inner diameter, if the quantity is large, pressing a rough tube can be considered, because the magnet materials saved from the inner hole will be much higher than the machining cost from a magnet cylinder to a tube. But it’s more difficult to ensure quality for tube magnets than cylinder magnets during magnet block pressing, machining, magnetization and inspection processes. Therefore it will take long time or steps to have more trial productions to evaluate the quality and efficiency. The stepper motor is the typical application field for the Neodymium tube magnets or ring magnets.
Often the size for ring or tube magnets is large and then magnetic force is difficult to shield so as to ship via air. We have been packing the large magnes in wooden cartons with heavy steel sheets to shield the magnetic force successfully.
