We listed the most commonly asked questions, but if you have a question and it is not listed on our FAQ section, please contact us with your question.
Q: Would more power applied during magnetizing mean a stronger magnet? Is there a limit to how strong a magnet can become due to the density and the size of the materials being used to make a magnet?
A: During the magnet production process, raw materials are combined to make up the chemical composition of the specific material. So, for example, if we were producing a neodymium 48 material (N48), we would follow the recipe to make N48 just like a baker would follow the recipe for making a specific type of bread. Once all of the ingredients for making N48 (Nd, Fe, B, Dy) are put together and ground into a fine particles (approximately 3-5 micron), they are then pressed into the shape of a block or cylinder. It is during this pressing stage that an electrical field is applied, which forces the block to have a defined orientation. At this point the magnet is not magnetized, only the internal particles are aligned to determine where the north and south poles will be once magnetized.
So after pressing, the magnet goes though another pressing process, called an iso-static press. This process increases the density of the magnet, thus making the domains and particles come closer together, which will make the magnet strength better. Just like the first pressing process, once the block of magnet material is finished with this process it is still not magnetized, just a better oriented magnet.
The next step is that the block of material will get cut into the shape the customer needs. This is the fabrication process that utilizes wire EDM, wire cutting, or some other fabrication method to make the magnet the correct shape per the customer print.
After the magnet is cut to the appropriate shape, it is then coated with something to prevent corrosion and help with protection. The most common coating is nickel coating, which is great for corrosion resistance, protecting the magnet, and provides a nice finish.
Finally, the magnet gets magnetized. This is where your main questions come in, and I’ve defined the other steps so it could help with my magnetizing overview. The finished/coated magnet is placed into a magnetizing coil or on a magnetizing fixture where about 1,000 volts, or 3-4 Tesla is shot through the magnet. This causes the aligned domains to “stand up” in the same direction, producing the north and south pole that you find on a magnet. During the first pressing process this orientation is defined, so trying to magnetize a magnet in a different direction will not work and cannot be done. The magnet can only be magnetized in the direction determined by the first pressing process.
About the question using high voltage or more energy to make a magnet stronger, this is not how the magnet works. During the process of determining the recipe of the magnet, we are really determining the strength of the magnet. So, once manufactured, the strength is set and it cannot become stronger with a higher magnetizing field. So, for example, it is like a glass of water. Once you fill the glass to the top, it cannot handle any more water. This is the same with a magnet…once you saturate it with energy and get all of the domains inside the magnet aligned in the same direction, it will only be as strong as the recipe dictates. So pushing through 2000 volts, or even 10000 volts during magnetizing just means that everything over 1,000 volts is wasted and not causing any more strength. And like the glass of water example, once you fill the glass with water that is all the water that you can hold. If you keep pouring more it is just wasting the water.
So, the key factors in determining strength of the magnet are really done at the recipe stage. Density of the material and particle size are the key. Currently we have the ability to produce a N55 material, but there is constant research trying to get the strength higher.
Q: What magnet do I need for my application?
A: Choosing the correct magnet for you application is critical. The short answer is “it depends”. It depends on many factors and variables. As you start to consider which magnet is correct for your application, here are some factors to consider:
- What is the application (motor, medical, holding, etc.)
- What is the maximum temperature that the magnet will be exposed?
- What is the environment that the magnet will be operating in (salt water, chemicals, etc)?
- Will this magnet be in an assembly and possibly affected by other materials that are ferrous?
Q: What magnet materials are available?
A: There are many different magnet materials available, which we are able to provide. These include neodymium, samarium cobalt, alnico, ferrite, bonded neodymium, bonded samarium cobalt, bonded ferrite, injection molded neodymium, injection molded samarium cobalt, rubber stripping, and FeCrCu. If there is another material you wish to procure, please contact us.
Q: What will cause a magnet to demagnetize?
A: In general, if you have selected the correct magnet for your application, you should not see any demagnetization of a magnet. However, some of the factors that can cause demagnetization are exposure to very high and low temperatures, another magnetic force, or shock. If you are unsure of the correct material for your application to avoid demagnetization, contact us for information.
Q: Will a coating on a magnet have an effect on the strength?
A: The coating around a magnet will not have an effect on the strength of the magnet, but the thickness of the coating needs to be considered. The thicker the coating means the more air gap between the magnet and its intended use. Coatings are measured in microns, with coatings varying in size from 5 – 35 microns. For a complete list of coating options, visit our coatings section.
Q: Do all magnets need to be coated?
A: Neodymium magnets should have a coating applied to avoid corrosion. Since Neodymium magnets are made from metallic materials, corrosion will occur if not coated. Samarium Cobalt magnets do not need to be coated unless there is an environment that is working under vacuum or is acidic. Some applications will require a coating for cosmetic purposes.
Q: Can I machine a magnet to a different size?
A: No. And Yes… Actually, it depends on the machining equipment being used. Magnets are very hard and brittle and cannot be machined or fabricated using common machining equipment. This will cause chipping and breaking. And, for magnets that are coated, machining them will compromise the coating and expose the magnet to oxidation. In order to grind, cut or drill magnetic materials, special tools are required, and a knowledge of machining magnetic materials is critical so no injury will occur.
Q: What is the strongest magnet that I can get?
A: Neodymium magnets are the strongest materials available, and range in strength from 35 mgo to 55 mgo. But the more important question should be “what is the correct magnet strength that I need for my application?” Call one of our technical sales people to understand what material strength may be best for your application.
Q: What is the best size and shape for my application?
A: With advancement in machining and assembly processes, magnets can now be produced in almost any shape or size imaginable. For a list of size and shapes that we carry, visit our products page, but this list is definitely not all inclusive. We have worked with customers that have asked us for shapes that are unique an individualized, which we have been able to engineer and machine to meet specs.
Q: Why didn’t my magnet measure the same gauss that was published in the magnet table?
A: The Residual Induction (Br) is the measurement of flux density in a closed circuit. The gauss reading will be much less on the surface of the magnet, and will vary depending upon the position of the gauss probe.
Q: How do I test the magnetic strength of my magnet?
A: Magnet strength can be determined by using a gauss meter or hysteresis graph. But, most important is to test the magnet in the application where possible. If your magnet is being used in a motor, then you will want to test the flux density of the entire magnetic assembly using a coil, or measuring torque. If your magnet is being used in a holding application, then testing pull or shear force will be required. Selecting the correct magnet at the beginning is very important, but making sure the magnet is performing according to your specification each time will determine the appropriate test needed.