Custom Magnet & Magnetic Assembly Design
Bunting-DuBois (formerly Magnet Applications, Inc.) provides complete engineering, design and consulting services. Our expert engineering team complements your design and manufacturing team to develop a permanent magnet or a complete magnetic assembly specific to your need and application. From single assemblies to complete designs, from sensor applications to permanent magnet motors, we have the equipment and skilled personnel to meet any project demands. We collaborate with your team, innovate through world-class design and accommodate with consistent, well-designed, flawlessly manufactured custom products.
- Complete engineering, design, magnetic evaluation and consulting services
- Magnetic field mapping
- Holding force calculations
- Insert and over-molding designs
- World-class design and instrumentation equipment
- All new assembly development or reverse-engineer to match existing component
- Rapid prototype guarantee
Bunting’s experience accumulated through decades of magnetic designs has provided us valuable insight into the changing needs and rigorous demands of our customers. As a result, our engineers have developed a profound understanding of the design and performance of all types of magnetic materials to know which best fits your need and application.
We design and manufacture magnets from advanced materials, including, Neodymium, Alnico, Ferrite and Samarium Cobalt. Our custom magnets are utilized for a multitude of applications across many industries. Our North American facility is ISO 9001:2015 certified, and ITAR registered. We can manufacture as few as 200 or as many as 2,000,000 pieces or more per month. Learn More
Our location in Pennsylvania means our North American customers receive their goods quicker and at lower freight costs. We can work seamlessly with your lean replenishment programs, employing JIT, Kanban, Dock-to-Stock, etc., to ensure your magnets are available when you need them. Learn More
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Magnetization & Saturation
Magnetization & Magnetizing Equipment
The initial objective of magnetization is to magnetize to saturation, even if it will be later demagnetized for stabilization. Magnetization is accomplished by exposing the magnet to an externally applied field, which can be created by other permanent magnets or by currents in coils.
The use of permanent magnets is only practical for low coercivity or thin sections of material. Removal of the magnetized specimen from the permanent magnet magnetizer can be problematic since the field cannot be turned off and fringing fields may adversely affect the magnetization of the part.
The two most common types of magnetizing equipment are the DC and Capacitor Discharge magnetizers.
Saturation Fields Required
Some rare-earth magnets require very high magnetizing fields in the range of 20 to 50 kOe. These fields are difficult to produce and require large power supplies with carefully designed magnetizing fixtures. Isotropic bonded NdFeB materials require magnetic fields in the range of 60 kOe to be fully saturated. However, 98% of saturation may be achieved by fields near 30 kOe. Ceramics require fields near 10 kOe, while Alnicos require fields near 3 kOe for saturation. Because of the ease by which Alnico 5 can become inadvertently demagnetized, it is preferable for this material to be magnetized just prior to or even after final assembly of the magnets into the device.
Multiple Pole Magnetization
In certain cases, it may be desirable to magnetize a part with more than one pole on a single pole surface. This may be accomplished by constructing special magnetizing fixtures. Multiple pole magnetizing fixtures are relatively simple to build for Alnico and Ceramic, but require great care in design and construction for rare-earth materials. Magnetizing with multiple poles will sometimes eliminate the need for several discrete magnets, reducing assembly costs, although a cost will be incurred for building an appropriate magnetizing fixture. Multiple pole fixtures for rare-earth magnets may cost several thousand dollars to build, depending on the size of the magnet, the number of poles required, and the fields necessary to achieve saturation.
Modern Magnet Materials
Magnets are an important part of our daily lives, serving as essential components in everything from electronic motors, loudspeakers, computers, disc players, microwave ovens and the family car to instrumentation, production equipment and research projects.
Their importance is typically overlooked because they make up the devices that we use, out of sight. Magnets function as transducers, transforming energy from one form to another, without any permanent loss of their own energy.
General Categories of Permanent Magnets:
- Mechanical to Mechanical: Such as attraction and repulsion
- Mechanical to Electrical: Such as power generation and microphones
- Electrical to Mechanical: Such as motors, loudspeakers and charged particle deflection
- Mechanical to Heat: Such as eddy current and hysteresis torque devices
- Special Effects: Such as magnetoresistance, hall effect devices and magnetic resonance
Classes of Magnets:
There are four classes of modern commercialized magnets, each based on its material composition. Within each of these classes there is a family of grades with specific magnetic properties. The general classes are as follow:
- Neodymium Iron Boron (NdFeB)
A rare-earth magnet, NdFeB is the most recent commercial addition to the family of modern magnet materials. NdFeB magnets exhibit the highest properties of all magnet materials.
- Samarium Cobalt
Another rare-earth magnet, samarium cobalt is manufactured in two compositions: Sm1Co5 and Sm2Co17 (or SmCo1:5 and SmCo2:17) types. The 2:17 type, with high HCI values, offer greater inherent stability than the 1:5 types.
- Ceramic Magnets
These are also known as Ferrite Magnets and have been in commercial use since the 1950’s. They continue to be a popular option due to its low cost. A special form of ceramic magnet is “flexible,” and is made so by bonding ceramic powder in a flexible binder.
- Alnico Magnets (AlNiCo)
Alnico magnets were commercialized in the 1930’s and are still used extensively today.
These materials span a range of properties that accommodate a wide variety of application requirements. The following pages are intended to give a broad but practical overview of the factors that must be considered in selecting the proper material, grade, shape, and size of magnet for a specific application. The chart below shows typical values of the key characteristics for selected grades of materials.
Basic problems of permanent magnet design involve estimating the distribution of magnetic flux in a magnetic circuit, which may include permanent magnets, air gaps, high permeability conduction elements, and electrical currents. Exact solutions of magnetic fields require complex analysis of many factors, although approximate solutions are possible based on certain simplifying assumptions. Obtaining an optimum magnet design often involves experience and tradeoffs.
Finite Element Analysis
Finite Element Analysis (FEA) modeling programs are used to analyze magnetic problems in order to arrive at solutions, which can then be tested and fine tuned against a prototype of the magnet structure. Using FEA models flux densities, torques, and forces may be calculated. Results can be output in various forms, including plots of vector magnetic potentials, flux density maps, and flux pattern plots. The Design Engineering team at Bunting has extensive experience in many types of magnetic designs and is able to assist in the design and execution of FEA models.
Permanent Magnet Stability
The ability of a permanent magnet to support an external magnetic field results from small magnetic domains “locked” in position by crystal anisotropy within the magnet material. Once established, these positions are held until acted upon by forces exceeding those which locked the domains. The energy required to disturb the field produced by a magnet varies for each type of material. Permanent magnets can be produced with extremely high coercive forces (Hc) which will maintain domain alignment in the presence of high external magnetic fields. Stability can be described as the repeated magnetic performance of a material under specific conditions over its life.
Factors affecting magnet stability include time, temperature, reluctance changes, adverse fields, radiation, shock, stress, and vibration.
Bunting: Total Magnetic Solutions
Bunting-DuBois manufactures prototypes for high volume custom magnets and magnet assemblies. We specialize in providing Total Magnetic Solutions through injection and compression molding of Neodymium Iron Boron magnetic materials, as well as other rare-earth magnets. In addition, we stock a large inventory of Neodymium Iron Boron, Samarium Cobalt, Ferrite, Alnico and Flexible magnetic materials.
Our engineers and technicians work with clients in the automotive, defense, aerospace, semiconductor, medical, oil field equipment, and communications industries to design and manufacture critical magnetic components.