China Neodymium And Ferrite Magnets Manufacturer & Supplier 
Magnets in the production process, it is inevitable that some of the missing corners or edge of some of the cases, especially the rare earth permanent magnet material itself is relatively brittle characteristics, no matter how meticulous processing, there will be some missing corners. So these magnets missing corners on the magnetic performance impact?
The effect of missing corners on the magnetic properties of a magnet depends mainly on the size of the missing corners. We know that the magnetic flux value of magnets of the same grade is proportional to the volume. If a certain specification of magnet is measured with intact magnet and missing corner, they may have the same magnetic flux value, why is there such a result? This may be because the missing volume is so small that the missing volume may be less than one-thousandth of the magnet's volume, which has a negligible effect on the flux value. So in general, as long as the size of the total missing volume is less than three-thousandths of the magnet's volume, there is no problem with the normal use of the magnet.
Neodymium round magnets with missing corners
NdFeB and SmCo permanent magnets are both brittle materials, it is normal to see some chipping and chamfering during processing, including the chipping of magnets caused by the mutual bumping of magnets and the stress of processing. Of course, the unsightly places will be polished off by mechanical chamfering and vibration chamfering during the processing. Therefore, the final product will not have a particularly large proportion of missing edges and corners.
So, generally will set what kind of missing corner standards?
More precise products can be stipulated, the size of the missing corner is not more than 1/10 of the length, width and height of the magnet, do not need to be particularly precise, the size of the missing corner is not more than 1/5 of the length, width and height of the magnet, or the total volume of the missing does not exceed 1%.
As an example, a D15.5 x 6mm disc magnet, chamfered to R0.6, the customer wants to deliver all perfect magnets, but the manufacturer said that the price may need to go up by 20%, because the pass rate can not reach that high. And the magnetic properties and size of those small missing edges do not affect the customer's use. Finally the two sides finalized a standard: 1 piece of magnet steel drop corner number not more than 2, each drop corner is not greater than D1.5 x 1, the same batch of drop corner ratio is not greater than 10%. In the end, everyone reached an agreement with this compromise.
In the actual production process, the factory can increase the chamfering to ensure the appearance of the yield. But the chamfering increases the magnetic flux loss. So a compromise is needed.
Instead of focusing too much on the appearance of the magnet, it is better to focus more on the consistency of the magnet's magnetic properties.
In the actual application of magnets, whether it is the magnets used in motors or the magnets used in instrument sensors, we need to pay attention to the consistency of the magnetic flux in the same batch as well as the consistency between batches. Because a lot of magnets that do not look good appearance, the total volume of missing corners are less than five thousandths of a percent, while the actual performance of the same batch of blank material deviation can reach 1-3%, so the main thing is still to be the consistency of the material blank is stable, in order to better ensure that the consistency of the finished product is stable, and the final product can be stable.