No spin reorientation
Sintered NdFeB undergoes a spin-reorientation transition below roughly −138 °C and loses coercivity there. SmCo has no such transition — magnetisation stays stable down to cryogenic temperatures.
Technology
Two decisions determine what a pole ring can do: how it is magnetised and what it is made of. We made both differently.
The process
Five steps — one of them is the decisive one.
Machine the carrier
A stainless-steel carrier ring is machined, the bore to tolerance class H7. This establishes the mechanical reference before anything is magnetised.
Apply the SmCo layer
A thin high-performance samarium-cobalt layer is applied to the carrier. No binder, no polymer, no adhesive — the bond is fully metallic.
Measure the runout
The part's actual geometry is measured against its intended axis of rotation. Every eccentricity is then known rather than estimated.
Magnetise with runout compensation
The pole pitch is written to the axis of rotation, not to the part. The measured error is compensated during magnetisation — this is the step that does not exist elsewhere.
Verify and document
Runout deviation, field strength and pole pitch are verified and documented. You get measured values, not assurances.
The decisive step
Runout compensation
Mechanical eccentricity can never be fully machined away. Every fixture, bearing and fit carries a residual error. Conventional processes write the pole pitch to the part — and thereby carry that error into the magnetic field.
What the sensor sees
A sensor does not measure geometry — it measures field transitions over time. An uneven pole pitch therefore produces exactly what disturbs a control loop most: amplitude variation and phase error once per revolution.
- Runout deviation ≤ 25 µm — guaranteed, not merely typical
- This makes runout a known quantity in your error budget, not an assumption
- At a ring radius of 25 mm that corresponds to 206 arcseconds of angular error
- Of 23 ring products reviewed, none states a guaranteed runout
- Higher system accuracy at lower manufacturing cost on your side
| Ring ⌀ | Penalty [″] | Penalty [m°] | Penalty [°] |
|---|---|---|---|
| 20 mm | 206 | 57.3 | 0.057 |
| 25 mm | 165 | 45.8 | 0.046 |
| 44 mm | 94 | 26.0 | 0.026 |
| 50 mm | 83 | 22.9 | 0.023 |
| 57 mm | 72 | 20.1 | 0.020 |
| 100 mm | 41 | 11.5 | 0.011 |
| 120 mm | 34 | 9.5 | 0.010 |
The penalty is constant in absolute terms: at ⌀ 50 mm, 10 µm more always costs 83″ — whether from 25 to 35 µm or from 100 to 110 µm. In relative terms, starting from our ≤ 25 µm it is +40 % at any diameter.
The material
Why samarium-cobalt — and why without a binder
The choice of material determines the limits your application runs into. SmCo moves them in both directions.
No binder that can fail
Elastomer- and polymer-bonded magnets live and die by their binder: it embrittles in the cold, degrades in the heat and is attacked by solvents. A fully metallic design has no such weak point.
Resistant to aggressive media
Resistant to all common oils and greases, organic solvents, saltwater, salt solutions and aqueous alkaline solutions. After years of exposure more than 94 % of field strength remains and runout is unchanged.
Inert to radiation and EMP
Radioactive radiation and electromagnetic pulses leave the material unaffected. Demagnetisation is practically impossible — relevant wherever a failure cannot be repaired.
Speed and temperature together
No restriction on speed, none on temperature — and, unlike most alternatives, none on both at once.
Efficient use of material
The high energy density of SmCo allows very thin layers. That saves magnet material, lowers mass and moment of inertia and makes extreme lightweight design possible.
Operating range
From −273 °C to +300 °C — verified
Every magnet class has two limits: one low, one high. For most of them those limits sit uncomfortably close together.
What this means
What you get from this in your system
- Clean sensor signal with no per-revolution amplitude or phase error
- Less effort for calibration and compensation in software
- Lower demands on the surrounding mechanics — the axis is relieved
- No corrosion protection, coating or encapsulation required
- Smaller moment of inertia and therefore higher achievable dynamics
- Less installation space for the same bore — or a larger bore in the same space
- One material for cold and heat instead of two variants in your portfolio
- A fraction of the magnet material per ring — less exposure to rare-earth raw material markets
Let's talk about your application.
Send us your requirements — diameter, pole count, temperature range, media exposure. You will get a substantive technical answer, not a brochure.