How to Define Magnetization and Coating in Your NdFeB RFQ

In practical RFQ review, phrases like "standard magnetization" or "normal coating" are frequent failure points. Each supplier interprets them differently, so quotes look similar while technical risk is not.

This guide focuses on the exact fields that should be locked before quote comparison and sample approval.

Lock these items before supplier comparison

1. Magnetization direction that actually matches your assembly.
2. Field verification method so supplier and buyer measure the same thing.
3. Coating stack matched to environment and handling.
4. Pre-PO risk checks that prevent repeated re-quoting.

1) Define magnetization by assembly geometry, not by habit

Use a direction statement that engineering and supplier can both verify.

For ring and arc parts, text-only direction is high risk. Always include a sketch with a clear view direction and polarity marks.

2) Define magnetic acceptance with a measurement map

Do not stop at "pass gauss". Use a fixed measurement map so both sides run the same check.

Minimum acceptance fields:

• Test fixture condition (with or without yoke, with or without steel backing).
• Measurement point IDs (for example P1, P2, P3) and exact location rules.
• Instrument type and probe direction.
• Pass window per point (for example min/target/max).
• Sampling plan (how many pieces per lot, and how outliers are handled).

Sample measurement map structure:

3) Select coating from environment and handling profile

Coating name alone is not enough. Declare environment and handling context first.

Note: exact performance depends on process control, substrate prep, and thickness window. Confirm target values with supplier data sheets.

4) Control dimensional impact from coating

Coating changes dimensions. If this is not defined, sample fit issues are common.

In RFQ and drawing package, include:

• Whether key tolerances are pre-coating or post-coating.
• Coating thickness window for functional faces.
• Faces that must not be overbuilt (insertion surfaces, countersinks, tight mating zones).
• Edge/chamfer treatment expectation to reduce chipping during assembly.

5) Failure modes to test in sample phase

Treat samples as a risk screen, not only a schedule step.

6) RFQ block you can copy directly

Use this in inquiry email or supplier portal:

Subject: RFQ - NdFeB Magnetization & Coating Definition - [Project Name]

1) Drawing revision and date:
2) Magnetization type (axial/diametrical/radial/custom):
3) Polarity orientation sketch reference:
4) Measurement point map and instrument method:
5) Acceptance window per point:
6) Sampling plan for sample and production lots:
7) Coating family and target thickness window:
8) Environment profile (humidity/corrosion/temperature):
9) Handling profile (manual/automated/insertion load):
10) Critical post-coating dimensions and tolerances:
11) Sample quantity and validation deadline:
12) Pilot and mass-production forecast:

7) Red flags before you release PO

Hold PO if any of the following is unresolved:

• Magnetization described only in text, without a polarity sketch.
• Field acceptance says "standard test" but no point map exists.
• Coating is quoted as "equivalent" without thickness or environment match.
• Post-coating critical dimensions are not declared.
• Sample pass criteria are not documented and signed.

8) Reference standards to align early

To reduce technical ambiguity, buyers usually reference standards explicitly in RFQ notes or acceptance sheets:

• ASTM B117 / ISO 9227 for corrosion test method alignment.
• ISO 2178 for non-destructive coating thickness measurement method (where applicable).
• ISO 2859-1 for lot sampling and acceptance logic.

Always confirm test conditions, exposure duration, and pass criteria in writing. A standard number alone is not enough.

9) Worked acceptance-sheet example (pilot lot)

Below is a practical example for one ring magnet program. Use it as a template, then replace limits with your own application values.

Execution notes:

• Define whether gauss values are measured with fixture/yoke, and freeze that condition.
• Keep the same probe orientation between sample and production lots.
• Store raw point-by-point logs, not only averaged values.

10) Coating thickness window by assembly risk

These ranges are planning baselines for buyer discussion, not universal standards.

11) Magnetization and measurement alignment map (visual)

Final note

When magnetization and coating fields are explicit, quote comparison is cleaner and sample loops are shorter.

For technical review or RFQ feedback, contact [email protected] or WhatsApp +8618857971991. Related buyer resources:

• NdFeB Shape Selection Guide for OEM RFQ
• Sample-to-Mass Production Quality Gates for NdFeB OEM Programs