Motor Factory Audit Checklist: What to Check on a Visit to a Chinese Factory

Before the visit

• Confirm the legal entity, factory address and ownership match the contract party.
• Ask for the process flow chart, control plan and the last three months of yield data for your motor family.
• Check certificates (ISO 9001, IATF 16949, ISO 14001) on the issuing body's website.

Incoming materials

• Magnets: grade, coating and a demagnetisation-curve or flux check per lot.
• Laminations: steel grade and thickness, burr height, stacking factor.
• Enamelled wire: insulation class and a spot check of diameter and breakdown voltage.
• Bearings: brand and grade traceable to a distributor invoice.

Production line

• Winding: automatic winders with turn-count and resistance check on every stator.
• Insulation: impregnation or powder coating process with recorded cure temperature and time.
• Magnetising and balancing: recorded flux or back-EMF, and residual unbalance to the drawing grade (e.g. G6.3).
• Press fits: force–displacement monitoring for bearings and shafts.

End-of-line testing

Every motor should pass a 100 % end-of-line test, typically hi-pot (insulation withstand), insulation resistance, winding resistance, no-load current and speed, direction, back-EMF or Hall timing, and noise or vibration. Ask to see the tester's limits and a day's records, and how failed parts are segregated.

Traceability and change control

A label or laser mark should link each motor or batch to its material lots and test data. Agree in writing that the factory will not change magnets, wire, bearings, lamination steel or sub-suppliers without your approval — unannounced material changes are the most common cause of field problems.