Custom Magnet Drawing Checklist for RFQs

The drawing is one part of the engineering package

A magnet can meet its standalone drawing and still fail in the product if the air gap, temperature, surrounding steel, bonding, rotor geometry, sensor position, or assembly sequence is missing. Send enough context to explain what the controlled features protect.

Drawing review table

Area	Include	Avoid
Material	Approved grade or required performance and operating envelope	Choosing the highest grade without circuit context
Geometry	Nominals, tolerances, functional datums, edge conditions, and critical interfaces	Tight general tolerances on every feature
Coating	Finish, coated-state dimensions, masking, appearance, and validation need	A coating name with no exposure or assembly context
Magnetization	Direction, polarity, pole map, physical reference, and delivery state	“Standard” or “north side” without a datum
Inspection	Critical characteristic, method, location, sampling, and evidence	Field or dimension values without a reproducible setup
Commercial	Prototype quantity, annual demand, target timing, and revision	Mixing prototype and production assumptions

1. Material and magnetic performance

• Material family: sintered NdFeB, sintered SmCo, bonded magnet, or performance-led review.
• Grade and coercivity family when already approved.
• Field, force, torque, flux, or sensor target at a defined location.
• Continuous, peak, assembly, storage, and fault temperatures where relevant.
• External demagnetizing fields and allowable irreversible change.

2. Geometry, tolerances, and datums

• 2D controlled drawing and useful 3D model.
• Functional faces, bore, outside diameter, bond surface, air-gap surface, and assembly datum.
• Critical-to-function characteristics separated from non-critical dimensions.
• Holes, slots, thin walls, edges, chamfers, and fragile features.
• Geometric controls that reflect assembly, such as runout, flatness, parallelism, or pole position where required.

3. Coating and assembly

• Exposure, contamination, corrosion, appearance, and handling requirement.
• Whether dimensions apply before or after coating.
• Masking, bonding, adhesive, cure, press fit, sleeve, hub, overmolding, or housing details.
• Magnetized handling constraints and assembly sequence.

4. Magnetization

• Axial, diametrical, radial, through-thickness, or controlled multipole pattern.
• Polarity, pole count, pitch, sequence, viewing direction, and start reference where applicable.
• Mechanical reference for angular clocking or orientation marking.
• Magnetized or unmagnetized delivery state.

5. Inspection, evidence, and revision control

• Critical dimension and magnetic acceptance characteristics.
• Measurement location, air gap, orientation, fixture, and method.
• First-article, sample report, material evidence, coating evidence, or other required documentation.
• Drawing number, revision, units, scale, applicable standards, and conflict hierarchy.
• Owner and status of every open technical decision.

What to do when information is not yet known

Do not invent a grade, tolerance, coating, or test merely to make the drawing look complete. Mark the item “for engineering review,” then provide the product target, envelope, environment, assembly, quantity, and decision deadline. A visible open question is safer than a false requirement that becomes embedded in quotation and tooling.

Before sending the RFQ

1. Remove obsolete files and identify the controlled revision.
2. Check units, datums, coated state, and magnetization viewing direction.
3. Mark critical features and explain their product function.
4. List open decisions and the evidence needed to close them.
5. Include prototype and expected production quantities separately.
6. Use a secure agreed channel for confidential drawings.

Use the existing one-page RFQ checklist, compare magnet materials and product routes, review custom manufacturing capabilities and quality planning, or start with the RFQ form.

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Engineering note: This checklist improves communication but does not replace project-specific DFM, material, fixture, inspection, commercial, or confidentiality review.