The four-stage factory QC process
1. Incoming material inspection
The approved bill of materials should identify the heating element, surface and inner materials, insulation, controller, power cord, plug, connectors, zipper, and temperature sensor by specification and revision. Inspect incoming lots against that list. Material certificates and supplier declarations can support the review, but the factory also needs physical checks for thickness, surface defects, dimensions, conductor continuity, and connector fit where relevant. Record lot numbers so a later field complaint can be traced to the affected batch.
2. Heating-line installation and in-process tests
Before the blanket is sealed, verify that heating elements are routed and fixed according to the approved drawing. Check spacing, bend radius, strain relief, terminations, sensor placement, and any protective layers. Test continuity and resistance against model-specific limits; investigate outliers before they are hidden inside the finished product. A simple power-on demonstration is not enough to reveal a pinched conductor or a sensor mounted away from the intended control point.
For multi-zone designs, identify and record each zone separately. Use the approved sample and fixed specifications as the reference for production. FITKANG describes incoming-material inspections, process checks, final testing, and approved reference samples in its OEM/ODM service process.
3. Controlled aging or burn-in
An aging run can expose early failures in controllers, connectors, heaters, or sensors that pass a brief functional test. The proposed four-hour burn-in should be written into the purchase specification only after the factory confirms that it applies to the selected model and every production unit. Define the supply voltage, temperature setting, ambient conditions, supervision, allowable temperature range, fault response, and record format. Ask whether the unit is cycled on and off or operated continuously, and whether it is retested after cooling.
“Four hours tested” is not useful if the test conditions and pass criteria are missing. Likewise, an aging period does not replace formal electrical safety evaluation or long-term reliability testing.
4. Finished-product and pre-shipment inspection
Check the complete unit: surface finish, seams, zipper or closure, controller display and buttons, timer, heating behavior, labels, serial or batch identification, plug, manual, and packaging. Test electrical safety and performance against the approved work instruction. FITKANG states that finished units receive appearance, function, electrical-safety, and performance checks before packing. For an importer, the evidence to request is the model-specific inspection plan and a sample of batch records, not a generic certificate alone.
A separate pre-shipment inspection can use an agreed sampling plan for cosmetic and packing defects. ISO 2859-1:2026 provides attribute-sampling schemes indexed by an acceptance quality limit (AQL). Sampling is a lot-acceptance method; it does not mean every unit is defect-free and should not replace required 100% safety checks. ISO’s standard overview explains the distinction.
Specify electrical and thermal tests precisely
Electrical safety should be documented by model and destination-market configuration. Ask which edition of the applicable appliance standard, test method, rated voltage, limits, and sample or production frequency the factory uses. IEC 60335-2-17:2022 covers flexible electrical heating appliances and their supplied control units, but applicability and national deviations should be assessed for the actual product. See the IEC standard scope.
Insulation strength and leakage current
A high-voltage dielectric withstand test applies a specified test voltage for a specified duration between defined parts to check insulation integrity. It is not the same as normal-operation leakage-current measurement. Both need a recorded pass limit and a calibrated instrument. Do not accept “zero leakage” as a technical specification: real measurements have finite resolution and applicable standards set limits rather than requiring a literal zero. An importer should ask for the test circuit, applied voltage, duration, maximum permitted leakage or trip threshold, and actions taken after a failure.
Low EMF measurements
“Low EMF” has little meaning without a value, operating mode, instrument, frequency range, and measurement distance. Ask the supplier for a report on the actual blanket and controller at representative settings, with measured electric and magnetic fields and the method used. IEC 62233 specifies measurement methods for electromagnetic fields around household appliances; it does not by itself create a universal “zero EMF” label. The IEC 62233 overview describes measurement positions and conditions.
NTC sensor and overheat response
If the design uses an NTC temperature sensor, test the full control loop: sensed temperature, controller response, timer, and independent protective device where fitted. Challenge the system under defined fault conditions such as a disconnected or shorted sensor, using a validated test procedure. Record whether heating stops safely and how the fault is indicated. An NTC is a sensing component, not proof of fail-safe protection by itself. The acceptance criteria should match the specific circuit, product standard, and approved design.
Learn more about our factory-tested build quality in the Infrared Sauna Blanket Series.
Set B2B warranty terms before production
An infrared sauna blanket warranty should be a written commercial agreement tied to the approved model and purchase order. Define the start date, duration, covered components, exclusions, claim process, and remedy. Avoid relying on a retail warranty page to settle a wholesale relationship.
Agree how defect rates are calculated
State the denominator and observation window. For example, a return rate based on units sold is different from a factory defect rate based on units received. Separate confirmed manufacturing defects from transit damage, misuse, normal wear, and no-fault returns. Define the evidence needed for a claim: serial or batch number, photos or video, fault description, and purchase date. Agree on the threshold that triggers a joint investigation or corrective action. No single percentage suits every product or market, so the threshold should be negotiated rather than copied from another supplier’s contract.
Define the remedy and spare-parts plan
Specify whether a verified defect receives a replacement unit, replacement controller or cord, repair support, credit, or a refund, and who pays freight and customs charges. For spa chains, controller and cord availability may matter more than a credit on the next container. Ask how long replacement parts will remain available after the final production order and whether revised parts remain compatible with earlier batches.
Keep technical support traceable
Set response times, escalation contacts, and the format for root-cause and corrective-action reports. A recurring field failure should feed back into the bill of materials, work instructions, and subsequent inspection plan. FITKANG publicly describes issue analysis, replacement-parts support, corrective actions, and follow-up; buyers should confirm the service levels and warranty remedies for their particular contract.
Purchasing manager’s QC checklist
Use this matrix as a starting inspection standard. Fill in the actual acceptance limits, test frequency, and document owner with the factory before signing off the production specification.
|
Inspection point |
Evidence to request |
Acceptance criterion to agree |
When to check |
|
Approved BOM and materials |
Approved sample, component specifications, incoming-lot records |
Correct revisions, materials, and traceable lot IDs |
Before production and at receipt |
|
Heating-line assembly |
Routing drawing, continuity and resistance records, in-process photos |
Model-specific limits; no pinched lines or unsupported joints |
Before sealing |
|
Aging or burn-in |
Work instruction and time-temperature logs |
Confirmed duration, settings, fault response, and pass band |
After assembly |
|
Electrical safety |
Dielectric, insulation and leakage-current test records |
Applicable standard, test conditions, calibrated equipment, defined limits |
Validation and agreed production frequency |
|
EMF and temperature control |
Measurement report, sensor and fault-test records |
Declared values at stated conditions; safe response to specified faults |
Design validation and after relevant changes |
|
Finished unit and packing |
Final inspection sheet, label and carton checklist |
Approved appearance, function, market configuration, and pack contents |
Before packing and shipment |
|
Warranty support |
Signed warranty terms, spare-parts list, claim workflow |
Defined coverage, remedies, investigation trigger, and support contacts |
Before purchase order |
Request proof for the exact model
Good B2B sauna blanket quality control is visible in records: a controlled bill of materials, an approved sample, test methods with limits, batch traceability, and a route for handling failures. It is also reflected in a warranty that tells an importer exactly what happens when a unit fails in the field.
If you are evaluating FITKANG for a wellness brand or spa chain, send the model, destination market, order volume, and target warranty terms. Ask the team for available factory audit material, relevant model-matched QC or test report copies, an inspection-plan summary, and a quotation with the support terms written into the purchase agreement. Document availability and scope should be confirmed for the selected model.
