Best Practices in Designing a Magnet for Your Application

Designing an industrial magnet is a sophisticated process requiring careful consideration of material properties, desired magnetic field strength, shape, environmental factors, and specific functional requirements. With advancements in magnetic materials and manufacturing techniques, magnets are now integral to diverse applications, including electronics, automotive, robotics, renewable energy, and heavy machinery. Here’s a guide to the best practices for designing an industrial magnet tailored to your application.

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1. Define Application Requirements

The foundation of any successful magnet design starts with understanding the application’s requirements. Knowing the magnet’s purpose and operating environment helps guide all design choices. Key aspects to define include:

• Magnetic Field Strength: Determine the field intensity required to meet performance standards. Stronger fields are often necessary for applications like heavy lifting or high-speed electric motors, while weaker fields may suffice for sensors or electronics.
• Temperature Tolerance: Some magnets lose strength at high temperatures, so defining operating temperature ranges is crucial, especially in automotive or aerospace applications.
• Mechanical Durability: Consider forces like shear, tensile, and compressive loads that the magnet will encounter. This helps in selecting the right materials and ensuring longevity.
• Size and Weight Constraints: Account for any physical limitations, especially in space-restricted applications like medical devices or compact electronics.
• Environmental Exposure: If the magnet will be exposed to corrosive environments, humidity, or extreme temperatures, it may need coating or special housing.

2. Select the Right Magnetic Material

Choosing the correct material is essential, as different materials exhibit distinct properties:

• Neodymium Iron Boron (NdFeB): Known for its strong magnetic field, NdFeB is commonly used in high-performance applications like motors and electric vehicles. However, it is sensitive to high temperatures and can corrode easily, so coatings or encapsulation may be necessary.
• Samarium Cobalt (SmCo): This is an excellent choice for high-temperature environments and offers good corrosion resistance, making it suitable for aerospace and high-end industrial applications. Although SmCo is costlier than NdFeB, it is often ideal when durability under extreme conditions is paramount.
• Alnico: With strong temperature stability and good mechanical strength, Alnico is often used in high-temperature industrial applications. However, it has lower field strength than NdFeB and SmCo, so it is less suited for miniaturized applications.
• Ferrite (Ceramic): Inexpensive and corrosion-resistant, ferrite magnets are widely used in motors, speakers, and basic industrial applications. They have lower field strengths and are brittle, so they are best used in low-cost or non-demanding applications.

3. Determine the Optimal Shape and Dimensions

Magnet shape significantly impacts field distribution and strength. Custom shapes like discs, cylinders, and horseshoes allow specific alignment of magnetic fields with the application’s needs. Key considerations for shape include:

• Field Focus: Shapes like U-shaped or horseshoe magnets help focus the magnetic field at the poles, which is ideal for lifting and gripping applications.
• Space Constraints: Use compact shapes, like cylindrical or flat magnets, for tight spaces in electronic devices and sensors.
• Field Uniformity: For applications requiring uniform fields, such as MRI machines or scientific instruments, consider ring or disc shapes, which offer consistent field strength across the magnetic plane.
• Ease of Assembly: Choose shapes that can be easily incorporated into the assembly process, especially if the magnet needs mounting or integration into a device.

4. Simulate Magnetic Field and Flux Distribution

Magnetic field simulations are critical to predict how the magnet will perform within the device. Use tools like finite element analysis (FEA) to model field distribution, ensuring your design meets requirements without trial and error in physical prototypes. Simulations can optimize:

• Magnetic Flux Paths: Check for undesired flux leakage that could interfere with nearby components.
• Field Homogeneity: Achieve consistent field strength across the desired area.
• Field Intensity: Ensure that the magnet generates adequate field strength to meet performance metrics, and modify geometry or material if necessary.

5. Design for Manufacturing (DFM)

The magnet design should also consider manufacturability, as overly complex shapes or exotic materials can increase costs or complicate production.

• Simplify Geometry: Design simple, easy-to-manufacture shapes to keep costs low and simplify assembly.
• Tolerances: Define precise tolerances for dimensions, as variations can affect magnetic properties and fit within an assembly.
• Material Availability: Ensure that materials are readily available or that substitutes can meet the same magnetic specifications if cost is a major factor.
• Protective Coatings: Consider if a coating is needed to protect the magnet from environmental exposure or wear and tear. Common coatings include nickel, epoxy, or rubber.

6. Test the Design in Real-World Conditions

Testing is essential to verify that the magnet meets all performance, durability, and safety requirements under actual operating conditions. Key testing practices include:

• Thermal Stability: Subject the magnet to the full temperature range it will experience in operation, checking for demagnetization or performance loss.
• Vibration and Shock Testing: Especially important in applications subject to movement or impact, these tests ensure the magnet and its assembly will hold up over time.
• Field Measurement: Use gauss meters to measure magnetic field strength and confirm it matches the design specifications.
• Environmental Exposure: Perform corrosion or oxidation tests to ensure the magnet can withstand harsh environments, especially if used outdoors or in industrial settings.

7. Optimize for Sustainability and Cost Efficiency

As industries move towards more sustainable practices, optimizing for efficiency and cost savings is crucial. This might include:

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• Recycling and Reuse: Design the magnet to facilitate recycling or reuse, especially for applications with high turnover rates, such as consumer electronics.
• Raw Material Sourcing: Use environmentally-friendly materials when possible, and work with suppliers who emphasize sustainable practices.
• Reduce Rare Earth Content: If high-strength rare earth magnets like NdFeB are necessary, aim to minimize waste by optimizing material use. Alternatively, explore less costly alternatives, such as ferrite, for applications with lower performance requirements.

Conclusion

By following these best practices, designers can create magnets tailored to meet specific industrial needs while balancing performance, durability, and cost. Successful magnet design requires understanding the application’s unique requirements, selecting appropriate materials, and rigorously testing and optimizing each element. With thoughtful planning, your magnet design will be efficient, reliable, and perfectly suited to its intended industrial role.

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Magnetics® is a manufacturer of three types of soft magnetic cores: powder cores, ferrite cores, and tape wound cores. Each material type has unique attributes and varying applications, but a commonality among the materials is that their primary purpose is power conversion in electronic appliances.

Powder Core products are distributed air gap cores that are primarily used in power inductor applications, specifically in switched-mode power supply (SMPS) output filters, also known as DC inductors. Other power applications include differential inductors, boost inductors, buck inductors, and flyback transformers. Notable characteristics of Magnetics’ Powder Core materials are high resistivity, low hysteresis and eddy current losses, and excellent inductance stability under both DC and AC conditions. Magnetics Powder Core products are available in 12 materials; Kool Mµ®, Kool Mµ® MAX, Kool Mµ® Hƒ, Kool Mµ® Ultra, Edge®,High DC Bias Edge®, Molypermalloy (MPP), High Flux, XFlux®, XFlux® Ultra, High DC Bias XFlux®, and 75 Series. These materials range in permeability from 14µ thru 550µ and are available in a variety of shapes including toroids, E cores, U cores, blocks, round blocks, EQ shape, LP shape, EER shape, and cylinders. 

Magnetics soft ferrite cores are an oxide made from Iron (Fe), Manganese (Mn), and Zinc (Zn) and are commonly referred to as manganese zinc ferrites. They have a low coercivity and are also known as soft magnetic ferrites. Because of their comparatively low losses at high frequencies, they are extensively used in switched-mode power supply (SMPS) and radio frequency (RF) transformers and inductors. Ferrite cores for the high frequency power supply and high quality communication markets are produced in a variety of shapes and sizes for inductors, pulse transformers, high frequency transformers, and noise filters. Notable characteristics of Magnetics’ ferrite materials are high permeability, good temperature properties, and low disaccommodation. Magnetics offers eleven materials which range in permeability from 900µ to 15,000µ and are available in a variety of geometries including toroids, shapes, and pot cores.

Magnetics Tape Wound cores are often key components of complicated electronic circuitry found in high reliability applications including military, aerospace, telecommunications, downhole drilling, and nuclear reactors. Tape Wound and Bobbin cores are made from thin strips of high-permeability nickel-iron alloys such as Orthonol®, Square Permalloy 80, Round Permalloy, Supermalloy, and Alloy 48, or grain oriented silicon iron known as Magnesil®.  Specific applications for tape wound cores include magnetic amplifiers (MagAmps), converter and inverter transformers, current transformers, and static magnetic devices. Magnetics Nanocrystalline cores are a choice solution for compact and energy efficient designs due to their high permeability, low power loss, and high saturation. Common mode chokes (CMCs) made with nanocrystalline material are used in a wide range of applications including switched-mode power supplies (SMPS), uninterruptible power supplies (UPS), solar inverters, frequency converters, and EMC filters. High permeability amorphous cores are also available.

There is no universal answer to this question, as selection depends on the application and application frequency. Any material selected is subject to tradeoffs. For instance, some materials may keep heat rise to a minimum and are expensive, but if one is willing to put up with more heat, perhaps a larger component or less costly one will do the job.  With Magnetics design tools, you can find the appropriate Magnetics core in a multitude of ways.

• Based on your application, the Selection Guide will direct you to the appropriate soft magnetic material.
• Based on a competitor part number, the Competitor Cross Reference tool will help you to find the corresponding Magnetics part number.
• Based on design parameters, the Design Tools will recommend the optimum Magnetics part number.
• Based on the Magnetics part number you were given, the Datasheet Search will provide parameters for the given part.
• Based on core shape, dimension, or permeability requirements, the Advanced Search feature will guide you to the available Magnetics parts that meet your requirements.

If the design tools are not able to provide the assistance you need, the knowledgeable Magnetics Application Engineering staff will be available to assist you.

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