Can finished magnets undergo secondary dimensional processing? For example, if there is a deviation between the required magnet size and the existing finished product, can the finished magnet be modified through secondary processing? Will this operation affect the magnetic performance of the magnet?
Can Finished Magnets Undergo Another Dimensional Processing?
The answer to this question is that, in principle, processed magnets should not undergo secondary processing; instead, they should be scrapped.
Therefore, during the design phase of the magnet, actual application requirements should be fully considered to accurately determine the size specifications. During the production phase, strict process controls should ensure that the dimensions of the magnets are correct. In the acceptance phase, the dimensions of the finished magnets should be carefully measured to avoid the risks associated with later secondary dimensional processing.
Risks of Secondary Dimensional Processing of Finished Magnets
Some people mistakenly believe that magnets can be processed using conventional metal machining methods, such as lathes, milling machines, or grinding machines, to correct the dimensions of finished magnets, especially under tight project schedules. This misunderstanding comes with many potential risks.
| Magnetic Field Interference: Magnets made from rare earth materials like neodymium-iron-boron or samarium-cobalt possess very strong magnetic properties. During the cutting process, their strong magnetic fields can absorb a large amount of iron filings and magnetic debris. These impurities are not only difficult to clean but can also severely interfere with the normal operation of the processing equipment, significantly reducing processing efficiency and possibly causing processing interruptions, leading to failures.
| Heat Demagnetization Issues: Mechanical friction generates heat during processing, which can raise the temperature of the magnets. For neodymium-iron-boron magnets, an increase in temperature can easily lead to demagnetization. If effective cooling measures are not carried out on time during the processing, the magnetic performance of the magnets may suffer irreversible damage.
| Destruction of Coating: Sintered neodymium-iron-boron magnets have reactive chemical properties, making them susceptible to rusting in the air, which can lead to a rapid decline in their magnetic performance. To extend their lifespan, they are typically treated with protective coatings such as nickel plating, zinc plating, or epoxy coatings. Secondary processing inevitably damages these magnet coatings, thereby reducing the magnets’ corrosion resistance and shortening their actual service life.
| Material Brittleness: Magnets are generally made using a sintering process, which imparts high hardness to the material while also making it exhibit significant brittleness. This is fundamentally different from metals like steel, copper, and aluminum, which possess good ductility. The processing of magnet blanks requires specialized techniques such as blade cutting, wire cutting, and grinding. If conventional lathe, milling, or planing methods are applied to finished magnets, it is easy to cause cracks or chipping, resulting in high scrap rates.
Handling Secondary Dimensional Processing of Finished Magnets
When it is indeed necessary to perform secondary processing on finished magnets due to schedule requirements, the following operational guidelines should be strictly followed to reduce processing risks:
| Tool Selection: Priority should be given to using non-magnetic tools or tools with special coatings. These tools can effectively reduce the interference of the magnetic field during processing, ensuring smooth operation.
| Processing Parameter Control: A slow feed rate and shallow cutting methods should be adopted to reduce the mechanical stress generated during processing, thereby minimizing the chances of the magnets fracturing due to stress concentrations.
| Temperature Control: A strict temperature monitoring and control system should be established to continuously cool the magnets during processing, ensuring that their temperature remains within a safe range to prevent demagnetization due to overheating.
NOTE: From the perspective of product quality control, finished magnets should not undergo secondary processing; instead, they should be redone according to actual standards. If secondary processing is necessary due to special circumstances, it is crucial to fully understand the risk factors involved in reprocessing finished magnets.
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