Two different materials. Two distinct bonding processes. One manufacturing-first approach. Here's what every engineer needs to know before specifying a bonded magnetic assembly.

Why the Distinction Between 'Magnetic' and 'Magnet' Assemblies Matters

In the magnetics industry, two terms are often used interchangeably—but shouldn't be. Magnetic assemblies and magnet assemblies refer to fundamentally different products, made from different materials, using different bonding processes, for different applications.

Getting this distinction right matters before you specify, quote, or begin development on a bonded assembly. The material properties, adhesive requirements, fixturing challenges, and performance outcomes are different in every meaningful way.

Magnetic Assemblies (Ferrite Cores)

A magnetic assembly is built from ferrite cores—materials that guide and shape magnetic flux. Ferrite is not a permanent magnet. It's a ceramic material used in transformers, inductors, and EMI suppression components because of its ability to conduct magnetic flux efficiently at high frequencies.

When engineers bond ferrite cores together, they're creating larger raw-material structures—UCores, ECores, or other geometries—that can't be manufactured as single pressed pieces. The goal is a continuous, low-reluctance magnetic circuit with a custom cross-section or length.

Magnet Assemblies (Permanent Magnets)

A magnet assembly involves permanent magnets—neodymium iron boron (NdFeB), samarium cobalt (SmCo), ceramic ferrite, or alnico—bonded to steel backing structures to create functional components for motors, linear drives, and precision motion systems.

Here, bonding isn't about creating a larger magnetic material—it's about integrating a functional magnet precisely into its working structure. Position, retention, and field geometry are what matter.

Side-by-Side: Ferrite Core Gluing vs. Permanent Magnet-to-Steel Bonding

Purpose: Ferrite gluing creates larger raw-material cores for custom transformer and inductor manufacturing. Magnet-to-steel bonding integrates permanent magnets into functional motor, drive, and motion system hardware.

Why it's difficult (ferrite): Porous surfaces, brittleness, bond line thickness control (10–50 µm), alignment sensitivity, and repeatable production demands.

Why it's difficult (magnets): Magnetic forces during assembly, thermal expansion mismatch, gap control for rotor balance, fatigue resistance, and environmental durability.

Adhesive approach (ferrite): Low-shrinkage formulations compatible with porous ceramic surfaces; bond line control is critical to preserve circuit performance.

Adhesive approach (magnets): Structural epoxies, two-component epoxies, or acrylics selected for shear strength, fatigue resistance, and environmental performance.

Typical applications (ferrite): Custom transformer cores, large-format inductors, EMI suppression components, power electronics magnetics.

Typical applications (magnets): Rotors, linear motor magnet tracks, shaft-integrated magnet assemblies, precision motion hardware, defense actuation systems.

What Both Processes Have in Common: A Manufacturing-First Mindset

Despite their differences, both ferrite bonding and permanent magnet-to-steel bonding share a critical requirement: the bonding process must be designed for production from the beginning, not adapted after the fact.

This is where many bonding projects run into problems. An adhesive that works on a bench prototype may not deliver consistent results in volume production. A fixturing approach that works for ten units may not hold tolerances for a thousand. Cure conditions that perform in a controlled environment may not translate to a manufacturing floor.

At Allstar Magnetics, both processes start with a production-readiness review before adhesive selection, fixturing design, or prototype build. Material behavior, tolerance strategy, alignment requirements, and process scalability are evaluated as a system—so the prototype that passes validation is the same process that runs at volume.

How to Know Which Process You Need

If you're designing a transformer, inductor, or EMI component that requires a core geometry beyond standard catalog options—you need ferrite core gluing.

If you're building a motor, linear drive, or precision motion system that requires magnets bonded to steel—you need permanent magnet-to-steel bonding.

If you're not sure which applies to your design, Allstar engineers can review your application and recommend the right approach.

Questions to Ask Before Specifying a Bonded Magnetic Assembly

• Is your material ferrite (for flux guidance) or a permanent magnet (for field generation)?
• What are your tolerance and alignment requirements for the bonded interface?
• What mechanical and environmental loads will the assembly see in service?
• Does your supplier have documented, validated bonding processes—or are they developing them on your program?
• Is the process designed to scale from prototype to production without changes?

The Allstar Advantage: One Partner for Both Processes

Allstar Magnetics is one of the few magnetic component manufacturers with deep engineering expertise in both ferrite core bonding and permanent magnet-to-steel bonding. That breadth matters when a single program requires both—or when requirements evolve as a design matures.

With AS9100, AS9120, and ISO 9001:2015 certifications and ITAR registration, Allstar serves customers across industrial, defense, aerospace, and power electronics markets where bonded assemblies must perform reliably from first prototype through high-volume production.

Contact Allstar Magnetics to discuss your bonded assembly requirements: sales@allstarmagnetics.com

(360) 693-0213

SmCo Is Exceptional. It’s Also Unforgiving.

Samarium cobalt magnets are chosen for demanding applications precisely because they perform where other materials fail. That performance comes from a highly ordered crystalline structure that is, by nature, hard and brittle. Engineers who understand this from the start design better programs. Those who don’t encounter problems at the worst possible time: during prototyping, assembly, or qualification.

Constraint 1: Brittleness Is the Governing Design Variable

SmCo magnets chip and crack under mechanical stress, impact, or vibration. Unlike ductile metals, they have almost no tolerance for tensile loading or localized stress concentrations. This is not a defect—it is a material property that must be designed around.

What this means in practice:

• Assemblies that expose SmCo to shock or vibration require mechanical support, encapsulation, or protective housing
• Press fits are high-risk—adhesive bonding or compliant retention is preferred
• Handling procedures must be defined and enforced from prototype through production

Constraint 2: Conventional Machining Doesn’t Apply

SmCo cannot be drilled, turned, or milled with standard tooling. Material removal requires abrasive grinding or EDM, typically completed before magnetization. Complex features—sharp internal corners, thin walls, small holes—significantly increase fracture risk and drive scrap rates up.

Best practice:

• Favor near-net-shape designs that minimize post-sinter machining
• Limit machining to critical dimensions only
• Avoid features that concentrate stress or require multiple setups

Constraint 3: Tolerance Strategy Requires Early Decisions

Tight tolerances are achievable with SmCo — but they cost more and increase fracture risk. Engineers must decide early how dimensional variation will be managed in the assembly. The most reliable approach is to design assemblies that can accommodate realistic tolerances through adhesive bonding, compliant features, or mechanical retention rather than demanding precision that adds risk and cost.

Why These Constraints Are Manageable—With the Right Process

None of these constraints are reasons to avoid samarium cobalt. They are reasons to approach SmCo programs with a manufacturing-first mindset. When brittleness, geometry, and tolerance strategy are addressed at the design stage—not after the first prototype fails—SmCo programs run smoothly from development through production.

How Allstar Removes the Risk 
Allstar Magnetics reviews SmCo designs for manufacturability from the first conversation. We evaluate geometry, tolerance allocation, handling risk, and assembly method before design is locked—reducing the chance of surprises at prototype or qualification.

Read more: Samarium Cobalt Design and Manufacturing Considerations ⇒

Talk to an Engineer: Before you finalize your SmCo design, speak with one of our engineers ⇒

WORK WITH ALLSTAR

Not every magnet challenge has an obvious answer — but the right conversation usually finds one. If you're dealing with a sourcing problem, a legacy spec, or a design that needs a second look, talk to Jason directly

Jason Berry
Sales — Permanent Magnets (West)
jberry@allstarmagnetics.com
360-200-5675 DIRECT DIAL  

ADDITIONAL RESOURCES

Neodymium (NdFeB) magnets offer unmatched magnetic strength, but selecting the right grade is more complex than simply choosing the highest energy product available. Many designs fail not because the magnet is too weak—but because it was over‑specified in the wrong direction.

Start with operating conditions, not peak strength.

Standard NdFeB grades perform well up to ~80°C. If your application experiences higher continuous temperatures, thermal suffix grades (H, SH, UH, EH) become essential. Insufficient coercivity at temperature can lead to irreversible demagnetization—even if the magnet initially met performance targets.

Balance magnetic output with coercivity margin.

High energy product grades like N52 deliver impressive strength, but lower‑energy grades with higher coercivity often outperform them in motors, actuators, and high‑load environments. The goal is stable performance over the product’s full lifecycle—not maximum force on day one.

Consider supply‑chain resilience early.

Higher coercivity grades often rely on heavy rare earth elements (HREs) such as dysprosium or terbium. Where operating conditions allow, HRE‑free grades can reduce cost volatility and sourcing risk without sacrificing performance.

Think system‑level, not component‑level.

Air gaps, steel flux paths, magnet geometry, and tolerances all influence real‑world magnetic output more than datasheet values alone.

Key takeaway:

The “right” neodymium magnet is the one that maintains performance under real operating conditions—not the one with the highest nominal strength.