Choosing the material, shape and size of a magnet are usually the first steps in finding the correct magnet for your application. There are different ways that a magnet can be magnetized, but the direction of the north and south pole must be defined prior to manufacturing so the magnetic field is correct. In an earlier blog we discussed the manufacturing process, and in this blog we will overview the magnet orientation to ensure the north and south pole end up in the right direction.
There are several terms that define the Direction of Orientation, or as some define it, the Direction of Magnetization. Below are the most common Direction of Orientations that we use when assisting customers with their designs.
Axially Oriented: This refers to a magnet that is typically magnetized through the thickness and has the north pole on one face of the magnet, and the south on the other. For example, a disc magnet that is axially oriented and is 5 mm diameter by 1 mm thick, will have the north pole and south pole going through the thickness. The picture below is an axially oriented rectangle magnet.
Diametrically Oriented: This orientation direction means that the magnet is magnetized across the diameter of a disc, ring, cylinder or tube magnet, and has a north and south pole from one side of the diameter to the other side of the diameter. The below picture shows a diametrically orientation. While an axially oriented magnet is typically through the thickness, in a rectangle magnet it can also be magnetized through the width or length.
Radially Oriented: A radially oriented magnet is a ring or cylinder magnet with the magnetic field on the outside diameter (OD) of the magnet instead of the face. This requires a ring magnet to be manufactured specifically as a radially oriented magnet, which is a different manufacturing process then a regular magnet. But, a radially oriented magnet is also able to be made in multiple segments. A “one piece” radially oriented magnet will also require a specific magnetizing fixture unique to the magnet to achieve the radial magnetization.
A radially oriented magnet may have all of a similar pole on the OD, with the opposite pole on the ID. This Direction of Orientation can be accomplished by making the ring magnet out of multiple pieces, or in some cases, can be made from one piece. The pictures below represent a “one piece” radial ring (the picture with the blue and red field), and a “multiple piece” radial ring.
A Radial magnet can also be made so there are multiple, alternating poles on the OD / ID of a ring magnet. Below is an example of a radially oriented multiple pole ring magnet.
There are only certain grades of material available as a single piece radially oriented magnet. However, if a radial ring magnet is required that cannot be made out of one piece, we can suggest making this magnet out of multiple pieces to achieve a radial pattern that is close to a single magnet design.
Multi-Pole Magnet: This magnetizing is similar to an axially magnetized magnet, however there would be at least 2 different poles on one face of the magnet. Depending upon the size and shape of the magnet, this can either be done with a single magnet, or made from several smaller magnets in an alternating pole assembly to appear as one magnet. This can be done on square magnets, ring magnets, rectangle magnets and disc magnets. A couple of examples of multi-Pole magnets are below.
Skewed / Angular Orientation: While this is not a common request, it is worth mentioning as a possibility since this orientation is used in Halbach assemblies, motor designs and designs requiring a certain shape that has a field pointed in the correct direction.
When a block of magnetic material is cut to the shape required, we are able to “tilt” the material to achieve a magnetic field that is angular. This is not common because achieving an angle exactly as requested is very expensive and difficult. If an angular orientation is required, we usually inform the customer that the tolerance of the magnetic angle can be +/- 8-10 degrees. An example of a magnet with an angular orientation is below.
When determining the orientation of a magnet, first look at your design. What is the magnetic field requirement, and what shape, size, material and orientation best achieves the goal? And take into consideration that the orientation of a magnet has a tolerance. We let our customers know that a magnet can have a tolerance in the magnetic angle of the orientation for axial, diametrical, radial, and multi-pole of +/- 5 degrees. We have been able to hold a smaller tolerance of the angle of the magnetic field, but almost all designs can accommodate the tolerance of +/- 5 degrees on the magnetic field.
Finally, we understand that each design and application are unique, which means that the Direction of Orientation is extremely important.
About SM Magnetics: SM Magnetics is privately owned company, providing assistance with permanent magnets, magnetic design & optimization, engineering support, and production. SuperMagnetMan is the online retail division of SM Magnetics offering neodymium magnets and other materials.