Designing with Permanent Magnets: 10 Tips

Every millimeter of air gap reduces flux density at the working surface. If you can halve the gap, you roughly double the useful field. Design your assembly to minimize and control air gap tolerances.

A mild steel plate behind your magnets provides a return path for flux, increasing the field at the working face by 20–60% depending on geometry. Back iron also reduces stray flux and improves safety.

Choose a temperature grade with a 30–50°C safety margin above your worst-case operating temperature. This is far more important than chasing the highest BH Max number.

Coatings add 10–50 μm per side. For tight-tolerance applications, specify the finished (coated) dimension and let us manage the pre-coating machining size.

Standard tolerance (±0.1mm) is sufficient for most applications. Tighter tolerances (±0.05mm, ±0.02mm) significantly increase cost due to additional grinding passes and inspection requirements.

Magnetization direction is set during pressing and cannot be changed later. Axial, diametral, and multi-pole patterns require different tooling. Confirm this with your supplier before prototyping.

NdFeB magnets are powerful and brittle. Design your assembly for safe installation — consider guided insertion, spacers, and magnetic shielding during storage and shipping. Large magnets (>50mm) require specific handling procedures.

Use FEA (Finite Element Analysis) tools like FEMM, ANSYS Maxwell, or COMSOL to simulate your magnetic circuit before ordering prototypes. This saves at least one iteration cycle.

How will the magnet be installed in production? Adhesive bonding, press-fit, insert molding, and mechanical retention each have different requirements for coating, tolerance, and surface finish.

Involve your magnet supplier at the design stage — not after the design is frozen. We can suggest geometry changes, grade optimizations, and manufacturing-friendly modifications that reduce cost without compromising performance.