Custom Permanent Magnet Rotor Assemblies — One Supplier, One Responsibility

Speed capability is a design result, not a catalog number — it depends on rotor diameter, magnet mass, sleeve pre-stress and temperature. As reference points: bonded SPM rotors typically run to ~20,000 rpm, carbon-fiber sleeved SPM rotors are routinely designed for 40,000–100,000+ rpm. Tell us your rated and overspeed targets plus rotor OD, and we will confirm the retention route with a safety margin calculation before quoting.

Carbon fiber wins on electromagnetic performance: it is non-conductive, so it adds no eddy-current loss, and its high strength-to-weight allows thin walls. Metal sleeves (stainless, Inconel, titanium) tolerate higher continuous temperatures and are simpler to shrink-fit, but they carry eddy losses at high electrical frequency. Under ~180°C and high speed: carbon fiber. Hot environments or moderate speed: metal. We compute both options against your speed and temperature before recommending.

For general industrial drives up to a few thousand rpm, ISO 21940 G6.3 is often enough; most servo and pump rotors specify G2.5; high-speed spindles, traction and aviation applications usually call for G1. Balance must always be specified and measured on the finished assembly — after sleeve and magnetizing operations — so put the grade (or a residual unbalance in g·mm) on the rotor drawing, not on the shaft drawing. Tell us your speed and bearing arrangement and we will recommend a grade.

That choice is usually made in your electromagnetic design, but the manufacturing trade-offs are these: SPM gives the cleanest air-gap field and simplest stack-up but needs retention above moderate speeds; IPM protects magnets mechanically inside the lamination stack and enables field weakening, at the cost of more complex lamination tooling. If you have a motor design, send it — we flag manufacturability risks in either direction. If you are still choosing, tell us speed, torque and temperature targets and we will share what similar projects used.

Work backward from worst-case magnet temperature, not ambient: winding temperature plus rotor losses plus 20–30°C margin. NdFeB SH series covers ~150°C, UH ~180°C, EH ~200°C, AH ~230°C; beyond that, SmCo runs continuously to 250–350°C with far better flux stability. The wrong grade fails slowly and irreversibly — flux loss that looks like a winding problem. Send us your thermal profile and we will specify the grade with the margin shown.

Both routes exist and the choice matters. Pre-magnetized arcs simplify SPM assembly but make handling and bonding slower and risk chipping at edges. Post-assembly magnetizing keeps production clean and is often the only practical route for multi-pole rings and IPM stacks — but it needs a fixture that can reach every pole with enough field. We decide per project based on pole count, coercivity of the grade and your field-uniformity tolerance.

Yes — most rotor projects start with 2–10 prototype units before production tooling. What we need: rotor drawing (DXF/PDF/STEP), rated and overspeed, operating temperature, balance grade, and annual volume estimate. We work under NDA as standard for custom rotor programs — send the NDA first if your process requires it. Prototype lead time is typically 3–5 weeks depending on sleeve tooling; production follows after your spin test sign-off.