How to Audit a Chinese Window Factory: What a European Brand Should Verify

You have shortlisted a supplier and you are now going to visit. That is a different job from choosing which supplier to visit — and it needs a different document.

The supplier verification checklist covers the decision: what to ask before you commit, and how to read the answers. This article covers the execution: what to request before you travel, what to look at while you are there, and how to test in twenty minutes whether the quality system is real.

The difference matters because an audit is not a tour. A tour produces impressions; an audit produces evidence you can file next to the technical documentation for your product.

Before you book the flight

Ask for these in advance — ideally two weeks ahead, so you can see how the factory behaves when it has time to prepare honestly rather than to rehearse:

• A factory production control record from a comparable order, not a blank template.
• The organisation chart of the quality function, with names and reporting lines.
• A list of the equipment used at each production step, with calibration status.
• An example of a change notification previously issued to a customer.
• The document you would receive at shipment: inspection report, packing list, and whatever else accompanies the goods.

How a factory responds to this list tells you as much as the documents themselves. Fast, specific answers indicate a system that runs every day. Vague answers, or a sudden enthusiasm for discussing anything except the documents, tell you the opposite.

What factory production control records must contain

"Factory production control" is a defined term, not a slogan:

> "'factory production control' means the documented, permanent and internal control of production in a factory, in accordance with the relevant harmonised technical specifications" > — Regulation (EU) No 305/2011, Article 2, point 26

Three words in that definition do the work: documented, permanent, and internal. A record created for your visit fails the second test; a record that lives only in the quality manager's head fails the first.

In practice, a credible set of records contains:

1. Incoming material checks — profiles, glass, hardware, seals, sealants — each with a batch or delivery reference and a pass/fail result.
2. In-process checks at each production station, recorded against the run, not against the day.
3. Final inspection results with the unit or batch identified, so a specific window can be linked to a specific record.
4. Equipment calibration records for the measuring and cutting equipment that the checks depend on.
5. Non-conformance and corrective action records, including what was done about it.
6. Operator training records for the people performing the checks.

If items 5 and 6 are missing, the system is probably documentation theatre. A factory that never records a non-conformance has either invented perfection or stopped writing things down.

The five places to look on audit day

Skip the showroom first. Walk the line, in the order the product moves.

1. The material store. Are profiles identified by batch? Can a storekeeper tell you which batch a particular profile came from, and when it arrived? This is where traceability succeeds or fails, long before the finished window exists.

2. The thermal break insertion station. Ask how the barrier material is controlled, and how the operator knows it is the specified material on this run. Ask what happens if a supplier delivers a different batch.

3. The corner assembly and glazing line. Watch a corner being assembled and glazed. Ask the operator to explain the checks performed at that station, and where they are recorded — then look at the record for the run currently on the line.

4. The inspection area, and the file where records live. Read one completed record set end to end. Is it filled in fully, in real time, and signed? A record with suspiciously uniform handwriting across a week is a warning sign.

5. Packing and dispatch. Look at how units are identified for shipment and whether the identification can be traced back to the production run. This is the last point at which traceability can quietly break.

The traceability drill (twenty minutes)

This is the single highest-value test you can run, and it is easy to do badly by asking politely.

Pick a product — ideally one already shipped to a customer — and ask the factory to walk it backwards: to the production run, to the profile, glass and hardware batches used, and to the inspection records for that run. Then ask a question the file should answer but nobody expects you to ask, such as which operative performed the final inspection.

• What a pass looks like: records produced in minutes, from a system, with names, dates and batch numbers that agree with each other.
• What a partial pass looks like: records exist but must be assembled by several people, with gaps explained verbally.
• What a fail looks like: a narrative. It may be an honest narrative, but it is not traceability.

Change control: the questions to ask

Change control is where a supplier most easily damages a customer without meaning to. These questions are worth asking in the room:

• Who decides that a change is significant, and against what written criteria?
• Which changes do you notify automatically, and which only if asked?
• How much notice do you give before a changed material or profile reaches production?
• What happens to an order already in production if a supplier changes a profile or hardware model?
• Has any change been made in the last twelve months that you did not notify to the affected customer?

That last question is uncomfortable, and the answer is the most informative part of the audit. The longer-form treatment of this topic, including the minimum traceability fields and the re-testing decision, is in managing change control and traceability.

Printable audit checklist

Twenty questions, grouped, in the order an audit day usually runs.

Print it, write in the answers, keep it with the file. In two years, when someone asks why you qualified this supplier, that page is the answer.

Frequently Asked Questions

What should a factory production control record contain?

At minimum: incoming material checks with batch references, in-process checks at each production station, final inspection results with the unit or batch identified, equipment calibration records, non-conformance and corrective action records, and training records for the operators performing the checks.

Can I audit a window factory remotely?

Document review can be done remotely, and a live video walk-through is better than nothing. The two steps that lose most of their value at a distance are the traceability drill and the line walk, because both depend on being able to follow a physical unit and ask unexpected questions.

What is a traceability drill?

You pick one finished window, or better one already shipped order, and ask the factory to walk it backwards: to the production run, to the profile, glass and hardware batches used, and to the inspection records for that run. A factory with real traceability can do this in minutes; one without it will produce a narrative instead of records.

What if the factory cannot show factory production control records?

Treat it as a qualification gap, not a detail. Either the factory builds the system with a defined timeline and you verify it before the first order, or you accept the risk knowingly and document that decision internally. Informal quality is not the same as controlled quality.

How do I know the samples tested are the same as production?

Three things make the link: factory production control records that show the same specification was held, batch traceability from the tested sample to the production run, and an advance notification obligation so that no material, hardware or process change reaches production without your knowledge.

How long does a factory audit take?

As a working rule, one full production day on site is enough for one product family, plus preparation beforehand and a document review after. Trying to audit several product families in a single day usually means inspecting none of them properly.

Next step

An audit is the moment a supplier either becomes a partner or stays a quotation. We work from a customer's drawings and specification in Yantai, and we expect to be audited — before the first order and afterwards. Our contract manufacturing page sets out how we handle production control records, change notification and traceability, and what we will show you when you visit.

> This article is practical guidance for buyers. It is not legal advice, and it does not state that any approval is held by us.