Supplier evaluation guide · Foshan, Guangdong · 7 extrusion lines, one site
How to vet an aluminium extrusion supplier before you commit a die
Buyers shortlist on price and on the sample. Both are easy to get right once. What actually decides whether a project runs is narrower and less comfortable: who owns the die, which tolerance class you are really buying, and who pays when the profile arrives wrong. This page is the checklist we would use if we were buying from someone else — with our own answers, and the four things we decline to do.
Part one
Seven questions, and where to verify the answer
Ask these before the first order, not after the first complaint. The right-hand column is the part most suppliers leave out — it tells you what document or sample settles the question, so you are not relying on a sales reply.
| Question | Why it decides the project | Our answer | Verify by |
|---|---|---|---|
| 01Who owns the die? | If the tooling belongs to the supplier, moving to a second source later means paying for a new die and re-running first article. You are single-sourced from day one, whatever the contract says. | Tooling is invoiced to you once, and ownership transfers on payment. We store it, maintain it, and release it on request — including to another extruder. | Die invoice in your company name; die number stamped on the drawing and on the die card. |
| 02Which tolerance class am I buying? | EN 755-9 (general) and EN 12020-2 (precision) differ by roughly a full grade on wall thickness and twist. A quote that says “±0.1 mm” without naming a class is not a specification. | We quote EN 755-9 as standard and EN 12020-2 when the drawing is marked precision. The class is printed on the drawing, the quote, and the inspection report. | Put your drawing tolerance table next to the class on the first-article report. |
| 03Can my section be made on their press? | A section outside the press envelope still gets quoted, still gets tooled — and then gets quietly relaxed until it “fits”. You find out at first article, three weeks in. | We check circumscribing circle, wall-thickness ratio and tongue ratio before quoting, and put a written no on the table if it will not run. | Ask for the circle and the limiting ratio in the quotation reply itself. |
| 04Will batch 12 match the sample? | Paint lots shift. Anodizing shifts more on 6061 than on 6063. Buyers usually discover this on site, at installation, with 400 m already fixed. | One approved sample per colour is retained and signed. Film thickness and ΔE are measured against it on every lot, and the reading ships with the batch. | Ask what happens when a later lot fails the ΔE check — then write that answer into the PO. |
| 05Machine before or after finishing? | Machining after anodizing leaves bare aluminium at every cut edge. Machining before it traps burrs under the coating. Both are visible, and both are blamed on the extruder. | We machine first, deburr, then finish — and mask or plug features that must stay conductive or thread-clean. | Ask for a sample that is machined and finished, not two separate samples. |
| 06What is in the crate? | Your customer’s engineer will ask for a material certificate and a dimensional report. If those arrive three weeks after the profiles, you carry the delay and the argument. | Material certificate to EN 573, first-article dimensional report, coating report and batch release — issued with the shipment, not after it. | Request a sample document pack before placing the first order. |
| 07Who pays when it is wrong? | “We will investigate” is not a remedy. The difference between suppliers shows up in the second order, after something has already gone wrong once. | Non-conforming lengths are replaced or reworked at our cost. Where the fault is ours, we cover the surface leg of the freight. | Put the remedy and the response window into the PO, not into an email thread. |
Part two
Projects break at three handoffs, not at six stages
Every extruder draws its process as six equal boxes. That diagram hides where the risk lives. In practice, almost every failure we are asked to rescue happened at one of three transfers — and each transfer has a signature failure mode.
- 1Diedesign and tooling
- 2Pressextrusion and quench
- 3Finishingcoating or anodizing
- 4Machiningcut, drill, assemble
- 5Inspectionmeasure and release
Die → press: the trial loop
When the die shop and the press line belong to different companies, nobody owns a die that will not balance. The extruder blames the die; the die shop blames the billet temperature and the press speed. You pay for each iteration and you cannot tell who is right.
Here the die is cut and trialled on the same site, so the loop is internal and short — typically one to two trials instead of three or four.
Press → finishing: defects you cannot coat over
Die lines, chatter marks and handling scratches do not disappear under powder. They telegraph through a 60 µm film and are more visible on gloss than on matte. Anodizing is worse: it is transparent, so every extrusion mark stays legible and the colour shifts between 6063 and 6061 on the same rack.
Finishing is quoted against an agreed surface acceptance sample, and lines that would show through are rejected before the parts reach the line.
Finishing → machining: the sequence decision
This is the handoff buyers most often get wrong without noticing. Drill after anodizing and every hole shows bright bare metal, which fails a salt-spray review. Drill before it and the burr sits under the coating, which fails a fit review. The sequence has to be chosen per feature, not per order.
We agree the sequence feature by feature at quotation, and state which faces will be masked, plugged or left mill-finish.
Part three
Four things we do not do
A capability page that lists only strengths is not usable for a sourcing decision. These are the limits we will tell you on the first call rather than at first article.
- No 7xxx alloys
- We run 6063-T5, 6061-T6 and 6005-T5. If your design depends on 7075 strength, we are the wrong supplier and we will say so before you spend money on tooling.
- No forging or die casting
- Our chain is extrusion-based. Parts that need to be forged or cast are outside it, even when the finished geometry looks similar on a drawing.
- No sections over 320 mm
- The circumscribing circle is capped by our largest press. Oversize sections are common in façade work, and we would rather decline than quote a relaxed tolerance you cannot build with.
- No in-house corrosion lab
- Salt spray and accelerated weathering are run at an accredited third-party laboratory, not in our building. We send the reports; we do not manufacture the numbers.
Send one section drawing and we will answer all seven questions against it
Not a brochure reply. You get the die type we would use, the press it runs on, the tolerance class we can hold, the finish options that work with that alloy, and the lead time to first article — in writing, within one working day.
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