Quality inspection is not the moment a finished window gets a quick look before it is wrapped. It is a chain of checkpoints woven through cutting, joining, glazing, hardware fitting, finishing, and packing — each one built to catch a specific failure mode before the next layer of work buries it. If you are sourcing aluminum windows and doors, understanding that chain is what lets you tell a system manufacturer from a reseller with a catalogue.
This article walks through what a credible inspection process looks like on the factory side, what ALPES's published build facts mean when you read them as inspection evidence, and the checklist you should run the day your units arrive.
Three distinct activities get bundled under one phrase, and they answer different questions:
A supplier can be strong at the first two and still leave you exposed at the third if the documents do not travel with the goods. Keep all three in view.
The order follows the build sequence, because each checkpoint catches the errors that step introduces.
Every profile length is checked against the cut list. Mitre angles are verified so both faces of the cut meet the blade at the same angle. A piece outside tolerance is rejected rather than hoped into place during crimping — it will not close up later.
Both diagonals of the frame are measured; equal diagonals confirm the frame is square within a tight tolerance the factory sets. Corner rigidity is checked by racking opposite corners — a properly joined frame feels rigid with no flex.
After glass is set and gaskets seated, a water check is run on the external face while the frame is held at a slight angle, and the interior face and glazing rebate are watched for penetration. This exposes gasket gaps, blocked drainage, and misplaced packers that visual inspection alone misses.
Every moving part is operated through its full travel several times — sashes opened and closed, all locking points engaged, friction stays tested at several angles, sliding sashes run back and forth for smooth travel and secure interlock at close. Listen for scraping, feel for binding.
Before wrapping, every visible surface is checked for scratches, dents, sealant smears, and swarf contamination. Drainage weep holes are confirmed clear. Protective film is verified intact on surfaces exposed during transport and installation, and each unit is labelled with its opening reference and orientation so it is not installed upside down or in the wrong opening.
The exact thresholds above — how many cycles, how tight the diagonal tolerance — vary by shop. Ask the manufacturer for its own written QC standard rather than assuming one number fits every line.
Inspection starts before the first cut, with the incoming materials.
As a tilt and turn window manufacturers with two production centers, ALPES publishes build details that double as inspection evidence you can ask to see:
When the goods reach site, the inspection moves to your hands. Request these documents with the shipment:
Then run the physical checks:
If you are planning a casement window replacement or ordering a glass sun room alongside the doors, run the same checklist on those units — the failure modes are the same even when the product name changes.
A note on what a factory can and cannot sign for: ALPES can supply material certificates, test evidence, and section drawings, and can confirm its own production process. It cannot act as the approving body for your project's local code compliance, and a test certificate attaches to the producing factory, not to the brand name. Confirm which signatures are yours before you rely on a number in a brochure.
Knowing the usual failure points tells you what to look for:
| Defect | Typical root cause | What good inspection catches |
|---|---|---|
| Gap at the mitre joint | Dull blade, wrong angle, or poor clamping | Full glue-injection corners remove the clip weakness, but the cut still has to be square |
| Weak or loose corner | Low crimp pressure or swarf left in cavity | Blow out swarf before crimping; verify diagonal equality afterwards |
| Water ingress through bottom rail | Blocked weep hole from sealant overspill or packer over slot | Confirm drainage path open; on sliding lines check valve or eave-style drainage intact |
| Swarf or sealant on visible faces | Housekeeping failure | Caught at final visual inspection before wrapping |
| Question | Why it matters | What a good answer contains |
|---|---|---|
| What is your written QC standard at each checkpoint? | Tells you inspection is planned, not hoped | A documented list of checks with acceptance limits |
| Can I see intake records for alloy grade and wall thickness? | Confirms the profile is what was quoted | 6060-T66, measured 1.8 to 2.5 mm per series |
| Which hardware brand and batch ships on my order? | Separates genuine German hardware from look-alikes | ROTO / Winkhaus / CMECH / Wehag with batch docs |
| What test evidence do you provide, and for which configuration? | A number without its specimen is not a result | Report names the exact series, size, and glass build |
| How are corners joined, and are seals continuous at corners? | Corner is where leaks and flex start | Glue-injection or welded corners; continuous seal lines |
| What documents travel with the goods? | Without them, incoming inspection is blind | Drawings in your mm, batch and colour records, test reports |
No fixed term is printed in the product specifications; ask for the written warranty document and read the exclusions. This article deliberately does not quote a number.
They are system values for specific configurations: 1.3 (AW90), 1.6 (C120), 1.7 (C116). Sliding series do not publish a whole-window value; request the calculated figure for your glass.
Check the stamped marking and the batch documentation supplied with the order; specify the brand in the contract.
Frame and sash dimensions against your approved mm drawing, diagonals, colour at the unit, glass condition, weep holes, and hardware function.
No; code approval is the buyer's responsibility. The factory supplies evidence and drawings.
Transit damage is easiest to claim when the crate and unit are photographed at the moment of opening, before any handling.
