Electric vehicle traction motors
Speed envelope, magnet retention, temperature and rotor balancing.
Magnetic Rotor Assemblies — Ready to Install
Engineered magnetic assemblies for motors, pumps and specialized industrial systems — from individual magnets to validated, ready-to-install rotors. Magnets bonded or insert-molded onto shafts and lamination stacks, magnetized, dynamically balanced, and flux-verified.
For Procurement
MOQ, lead time, packaging and commercial terms — go straight to a quotation.
Request a Quote →For Engineering
Grades, drawings, process data and design support for your DFM review.
Magnet Design Guide →For Quality / SQE
Certificates, inspection planning, traceability and PPAP / FAI support per project.
Certificates & Documentation →Assembly Anatomy
What Goes Into a Rotor Assembly
Every component, from the magnet grade to the balancing plane, is engineered and verified as one system.
●
→Magnets
NdFeB / SmCo / bonded — grade matched to temperature and performance spec
◉
→Shaft
Stainless, carbon steel or Alloy 42 — machined and ground to ±0.005 mm
◎
→Lamination Stack
Silicon steel 0.2–0.5 mm — die-cast or interlocked
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→Bonding / Overmold
High-temp epoxy, anaerobic or insert-molding — shear-tested
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→Sleeve (optional)
Stainless or carbon-fiber containment for high surface speeds
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Validation
Magnetization, flux signature, runout and dynamic balance
Product Range
Rotor Assemblies — Product Gallery
Representative product forms for reference. Final geometry, material and finish are agreed for each project.
Why Buy Complete Rotor Assemblies?
Magnet handling, bonding, magnetizing, and balancing are specialized processes — outsource them to us and focus on your motor winding and final assembly.
- ✓No magnet handling on your line — we deliver magnetized, balanced rotors — safety and quality improve immediately
- ✓Project-defined flux verification — agree pole-flux limits, measurement method, inspection frequency and release records before production
- ✓Dynamic balancing included — G2.5 as standard, G1.0 on request — your motor runs smoother and lasts longer
- ✓One supplier for magnets + machining — shafts, laminations, magnets, and coatings from a group quality framework
Applications
| Application | Typical Spec | Why This Material |
|---|---|---|
| BLDC Motor Rotors | N42SH arc segments on lamination stack | Efficient, compact motor cores |
| Pump Rotor Assemblies | Overmolded magnets on stainless shaft | Hermetically sealable wet rotor designs |
| Compressor Rotors | SmCo segments for high-temp | Refrigeration and HVAC compressors |
| Fan Rotors | Injection-molded ring magnets | High-volume cooling fan production |
| Automotive EPS Rotors | N48UH with high-retention adhesive | Steering systems needing extreme reliability |
Rotor Assembly Specifications
Typical capabilities — send your drawing for a specific quote.
| Parameter | Capability | Notes |
|---|---|---|
| Magnet materials | NdFeB N35–N54, SmCo 1:5/2:17, bonded NdFeB | Grade matched to your temp and performance spec |
| Shaft materials | Stainless 304/316/416, carbon steel, Alloy 42 | Machined and ground to ±0.005mm |
| Lamination stacks | Silicon steel 0.2–0.5mm | Die-cast or interlocked stacks |
| Bonding | High-temp epoxy (180°C), anaerobic, or overmolding | Shear testing and sampling per the agreed plan |
| Magnetization | Radial, diametric, multi-pole, skewed | Pole-flux verification per the agreed inspection plan |
| Balancing | G2.5 standard, G1.0 available | Two-plane dynamic per ISO 21940 |
| Runout | ±0.01mm TIR on magnet OD | Grinding and inspection per the agreed drawing and sampling plan |
Assembly Types
Assemblies We Build
Rotor Assemblies
Magnets on shaft / lamination stack — balanced and ready to install.
Halbach Arrays
One-sided, uniform-field arrays engineered to your air-gap target.
Overmolded Magnets
Insert-molded magnets for sealed rotors and harsh environments.
Couplings & Custom
Magnetic couplings and custom assemblies built to your drawing.
Engineering Controls
The Five Controls That Define Assembly Quality
Magnetization
Radial, diametric, multi-pole or skewed — pole pattern and verification method agreed for the project.
Bonding
High-temp epoxy or overmolding; shear-test method and sampling agreed before production.
Balancing
Two-plane dynamic balancing to G2.5 (ISO 21940) standard, G1.0 on request.
Concentricity
Ground magnet OD and journals — runout limits, datums and inspection frequency agreed for the project.
Flux
Flux measurement method, acceptance limits and reporting agreed for the magnetization pattern and assembly geometry.
Documentation
Flux data, balance records and dimensional reports per the agreed inspection plan.
Assembly Process
From Components to Validated Assembly
1
→Component Prep
Magnets, shafts and stacks received or produced; dimensions verified
2
→Assembly
Bonding or overmolding under controlled process parameters
3
→Magnetization
Magnetized in fixture; pole pattern and flux verified
4
→Balancing
Two-plane dynamic balancing to specified grade
5
Testing
Final flux signature, runout and dimensional release
Validation & Inspection
Confirm the following checks and release records in the project inspection plan:
- ✓Dimensional — critical dimensions and runout by gauge / CMM per inspection plan
- ✓Magnetic — agree the flux measurement method, acceptance limits, sampling and records
- ✓Dynamic balance — residual imbalance reported against the specified grade
- ✓Project documentation — FAI / PPAP per project requirements
Design Considerations
Send us your drawings — we'll flag these before quoting:
- ✓Magnet retention — surface speed, temperature, and interference fit determine whether adhesive alone suffices or a stainless sleeve is needed
- ✓Skew angle — 1–2 pole skew reduces cogging; costs nothing if specified before production
- ✓Sleeve for high-speed — Inconel or stainless sleeves contain magnet fragments above 100 m/s surface speed — we manufacture these in-house
What We Need to Quote
Provide any of these — the more complete, the faster and more accurate the quote:
- ✓Rotor drawing — magnet dimensions and grade, shaft dimensions, lamination stack details, tolerance callouts
- ✓Performance spec — torque, speed, back-EMF constant, temperature range — we can design the magnet circuit if you prefer
- ✓Volume — prototype quantity and annual volume for tooling amortization
- ✓Testing requirements — flux spec per pole, balancing grade, insulation class, and any OEM-specific standards
Production & Supply Planning
Magnetic Rotor Assemblies: A Defined Route to Repeat Orders
Agree the process, acceptance criteria and shipment plan before production starts. The quotation identifies the producing site and the controls required for your part.
Confirm the manufacturing route
Review shaft and core interfaces, magnet integration, retention, magnetization and balancing operations.
Approve the inspection plan
Define runout, balance class, magnetic output and any project-specific overspeed or functional test.
Qualify before repeat supply
Define sample approval, drawing revision and lot identification. Agree how material, process or site changes will be reviewed before implementation.
Plan releases and delivery
Confirm order quantities, capacity allocation, packaging and shipping terms against your forecast. Delivery dates and any buffer-stock arrangement belong in the agreed supply plan.
Application Engineering
Where magnetic rotor assemblies Fit
Typical component uses and the requirements to discuss before quotation. Suitability depends on your design and validation criteria.
Industrial servo motors
Field consistency, positional accuracy and shaft interfaces.
Wind turbine generators
Thermal duty, corrosion environment and mechanical retention.
Appliance and HVAC motors
Efficiency target, vibration, working temperature and production quantity.
Case Study — EV Drive-Unit Rotor
N38UH segmented rotor with in-house sleeve assembly and dynamic balancing — 180 °C continuous operation.
Frequently Asked Questions
Do you supply the lamination stack too?
Yes — we source or manufacture lamination stacks per your drawing, or accept customer-supplied stacks for assembly. Die-cast aluminum and interlocked stacks are both available.
How do you verify magnetization?
We agree the magnetization pattern, flux measurement method, acceptance limits and inspection frequency during project review. The inspection plan defines the required test records and how nonconforming assemblies are handled before release.
Can you balance to tighter than G2.5?
We balance to G1.0 for high-speed applications like turbocharger and aerospace components. Below G1.0, material inhomogeneity in the magnets themselves becomes the limiting factor — we can discuss achievable limits for your specific design.
What's the typical lead time?
Prototypes: 2–4 weeks including magnet production. Volume production: 4–8 weeks depending on annual volume and tooling requirements. We hold safety stock for repeating programs.
Have an Assembly Drawing or BOM?
Send it to our team for engineering review and quotation — assembly drawings and BOMs welcome.