The first order is an engineering test, not a price test
An aluminum extrusion quote is a compressed set of assumptions. A number such as $4.10 per kilogram can look exact while leaving critical questions open: Is the material 6063-T5 or 6063-T6? Is the finish mill, anodized, or powder coated? Are profiles shipped in six-meter lengths or cut to 1,200 mm? Is the price FOB, CIF, or delivered? Does the quote include inspection and protective packaging?
Those questions control whether a part fits, survives, and arrives usable. For a first order from China, the central procurement task is to turn the application into a specification that a factory can manufacture and an independent inspector can accept. A first-order sourcing guide is most useful when treated as a control document rather than a list of shopping questions.
The first order has two jobs:
- Deliver conforming parts.
- Qualify a repeatable process for subsequent releases.
A sample proves a profile can be made. A controlled production run proves it can be made repeatedly.
Why a low per-kilogram price can be a false comparison
Per-kilogram pricing is sensible because billet and conversion costs scale with weight, but it is not a complete product price. Consider 10,000 pieces weighing 0.85 kg each. The order contains 8,500 kg of aluminum. A $0.25-per-kilogram price difference changes the quote by $2,125.
Now assume, purely as an illustration, that the lower-priced lot has a 3% rejection rate because a critical slot or finish does not meet the agreed requirement. Three hundred pieces may need sorting or replacement. Their raw material value at $4.10 per kilogram is about $1,046, before replacement machining, inspection, expedited freight, or assembly downtime. One shift lost on a production line can erase the nominal savings even when the defective metal itself does not.
A lower quote can be legitimate; a supplier may have a more efficient die, better yield, or a larger production run. The comparison becomes meaningful only after the basis is identical:
- The same alloy and temper.
- The same cross-section, wall thickness, and tolerance.
- The same cut length and secondary operations.
- The same surface treatment and inspection level.
- The same packaging and Incoterm.
- The same rule for metal-price adjustment and actual versus theoretical weight.
The price is the output of the specification. It should not be used to discover what the specification might have been.
Start with failure modes, not an alloy catalog
Words such as strong, weatherproof, precise, and premium finish describe intent, not acceptance criteria. Before a supplier sees a drawing, the requirement should answer five practical questions:
- What load, span, deflection, impact, or fatigue condition must the profile withstand?
- What temperatures, humidity, salt exposure, chemicals, or UV conditions will it encounter?
- Which surfaces must mate with glass, gaskets, fasteners, bearings, panels, or another extrusion?
- Which faces are visible, and what appearance is acceptable after finishing?
- What annual quantity, release pattern, and cut length will the manufacturing process support?
The same nominal size can require very different specifications. A window frame needs gasket channels, thermal-break compatibility, glass retention, and weather-sealing features. A machine frame needs slot geometry, joint strength, flatness, and repeatable cut lengths. An LED heat sink needs a defined thermal path, base flatness, fin spacing, and airflow assumptions. Simply asking for a 40 mm aluminum profile does not control any of those outcomes.
Volume belongs in the technical discussion because it affects die amortization, setup loss, minimum finish batches, and packaging. A custom die may be economical at 50,000 kg per year but difficult to justify at 500 kg. Conversely, a standard profile can appear inexpensive while adding several machining operations that make the finished assembly more costly than a custom extrusion.
Build a specification that cannot be misread
The strongest extrusion specifications connect each requirement to a failure mode. Material, geometry, finish, secondary processing, and packaging must describe one finished product rather than five disconnected quote lines.
Material means alloy, temper, and evidence
Do not write 6063 aluminum alone. State all of the following:
- Exact alloy designation.
- Temper, such as T5 or T6.
- Governing product and tolerance standard, such as ASTM B221 or applicable EN 755 requirements.
- Minimum tensile strength, yield strength, and elongation when mechanical performance is critical.
- Heat or lot traceability and the required material test certificate.
6063 is generally selected when extrudability, surface appearance, corrosion resistance, and anodizing response matter. 6061 is often chosen when higher structural strength, machinability, or load-bearing performance matters more. Neither alloy is automatically correct; the section design, temper, loading, and finish all affect the decision.
T5 and T6 are not interchangeable suffixes. They define different heat-treatment conditions and therefore different mechanical properties and manufacturing routes. A T6 profile may require solution heat treatment after extrusion, while a T5 profile typically relies on controlled cooling and artificial aging. Those differences can affect strength, distortion, lead time, and price.
A certificate of conformity only states that the supplier claims compliance. A material test certificate tied to the production lot provides stronger evidence. For a structural or safety-related profile, require actual test results and identify the test method before production begins.
Geometry needs datums and criticality
A dimensioned 2D cross-section should be the master document because the die creates the cross-sectional geometry. A 3D CAD model can supplement it, but it should not replace toleranced dimensions and a clear datum scheme.
The drawing should identify:
- Nominal dimensions and wall thicknesses.
- Critical mating surfaces and reference datums.
- Slot, hole, and cavity dimensions.
- Straightness, twist, bow, and cut-length requirements.
- Saw squareness, burr limits, and any post-extrusion machining.
- Dimensions that are reference-only rather than critical to function.
Extrusion tolerances depend on section size, wall thickness, alloy, die design, and the applicable standard. Applying a blanket ±0.05 mm tolerance to every feature often forces expensive sorting or machining without improving the product. A loose tolerance on a mating slot, however, can stop assembly completely.
For a profile that slides into a channel, a functional go/no-go gauge may communicate the requirement better than dozens of isolated measurements. For a structural base, flatness relative to a defined datum may matter more than an overall width measurement. The supplier should review the design for extrudability before die fabrication and document any proposed radius, wall, or cavity change through a drawing revision.
Finish is part of the functional fit
Surface treatment is not just a color choice. It affects corrosion protection, appearance, wear, dimensions, and the visibility of extrusion defects.
Anodizing creates an oxide layer from the aluminum surface. It offers durable protection and does not peel like an applied paint film, but it can emphasize die lines, scratches, and differences between production lots. Alloy chemistry, extrusion direction, surface preparation, coating thickness, sealing, and color all influence the result. Specify the anodizing class or thickness, color range, sealing requirement, visible faces, and acceptable surface variation.
Powder coating provides broad color and texture options, but its film build can change tight slot and mating dimensions. The specification should identify the color reference, gloss or texture, coating thickness, pretreatment, adhesion requirement, and whether the finish meets the intended exterior exposure. PVDF may be appropriate for high-UV or prominent architectural applications, but the coating system and performance standard need to be named rather than described only as weather resistant.
Appearance approval should use a finished sample or limit panel made through the intended production route. Define viewing distance, lighting, visible surfaces, acceptable color variation, and limits for die lines, scratches, orange peel, pinholes, and touch-up marks. A cropped factory photograph cannot establish those conditions.
Secondary operations and packaging complete the specification
An extrusion can meet its cross-section and still fail at assembly because the cut length is wrong, a hole is misplaced, or a burr damages a gasket. State whether drilling, tapping, CNC machining, punching, welding, or assembly is included. Identify the order of operations when finishing and machining interact. A hole machined after anodizing may expose bare metal; a powder-coated slot may need masking or post-finish sizing.
Packaging belongs in the product requirement because long finished profiles are vulnerable to handling and transit damage. Specify interleaving or individual wrapping, protective film, end protection, bundle weight, pallet construction, moisture protection, and the location of straps. Metal bands should not contact a visible finished surface. The profile that passes final inspection at the factory is not a conforming delivery if it arrives scratched, bent, or contaminated.
Ask for a compliance quote, not a headline price
An RFQ should force the supplier to expose assumptions. It should connect the technical drawing to the commercial offer through a clear set of requirements:
- Product identity: Include the part number, drawing revision, 2D cross-section, supporting CAD file, cut lengths, intended use, and forecast quantity.
- Material and process: State alloy, temper, material standard, mechanical requirements, die status, heat treatment, and lot traceability.
- Geometry and finish: Identify critical dimensions, straightness and twist, anodizing or coating requirements, colors, visible faces, and secondary operations.
- Quality evidence: Specify first-article measurements, production inspection, material test certificates, coating checks, defect limits, and the definition of a production lot.
- Tooling: Separate die cost from piece price, identify die ownership, state the number of included correction rounds, and define what happens if the die does not meet the approved drawing.
- Commercial and logistics terms: Request MOQ, quantity tiers, actual weight per meter, packaging, lead time from a defined milestone, Incoterm, payment terms, quote validity, and any metal-price adjustment formula.
Ask every supplier to return a compliance matrix marking each line as compliant, deviation, or assumption. A supplier that cannot identify a deviation before production may still be capable, but the buyer has no reliable way to price or manage the risk.
Lead time also needs a defined starting point. The phrase eight weeks can mean eight weeks from deposit, drawing approval, die completion, sample approval, or production release. Those are materially different commitments, especially when a custom die and final surface treatment are involved.
Verify capability with evidence, not certificates alone
ISO 9001 can indicate a functioning quality-management system, but it does not prove that a supplier can hold a particular slot, finish, or straightness requirement over a six-meter run. In supplier audits, the most revealing evidence is usually a recent inspection record from a comparable production route, not a polished showroom sample.
Useful capability checks include:
- Press capacity and die envelope for the section, alloy, hollow ratio, and expected extrusion ratio.
- Recent production records for a similar profile size, alloy, temper, and finish.
- Calibrated measurement equipment for dimensions, straightness, coating thickness, color, and mechanical properties.
- Traceability from billet or heat number through extrusion, aging, finishing, inspection, and packing.
- A documented process for handling die corrections, nonconforming product, and customer changes.
For a 20.00 ± 0.10 mm slot, one passing measurement is weak evidence. Measurements from multiple pieces at the beginning, middle, and end of a run reveal drift and die wear. When the dimension is genuinely critical, a capability study or repeated measurements across several lots is more useful than a statement that the die was tested.
An independent pre-shipment inspection can verify execution, but it cannot repair an ambiguous drawing. Inspection becomes effective only after the buyer and supplier agree on datums, gauges, sampling, test methods, and rejection criteria.
Use the pilot order to qualify repeatability
A controlled first order should move through a sequence that separates design approval from volume production:
- Design review: The supplier confirms wall thickness, corner radii, hollow sections, die feasibility, press selection, correction allowances, and tooling ownership. Any design change receives a new drawing revision.
- Die trial and first article: The sample uses the intended alloy, temper, die, press, heat-treatment route, and final finish. Inspect critical dimensions, mass per meter, straightness, twist, cut length, mechanical results, and surface quality.
- Pilot production: A normal production batch tests consistency, not just possibility. Inspect multiple pieces and bundles, preserve lot traceability, and check packaging before shipment.
- Production release: The approved drawing, sample identification, inspection report, and packaging standard become the baseline for repeat orders.
A mill-finish sample should not approve a powder-coated product, and a short hand-polished sample should not represent a long anodized production run. Final approval must reflect the process that will actually produce the shipment.
The approved sample is a useful visual reference, but it is not a substitute for measurable requirements. If a supplier changes an alloy source, temper, die, coating line, subcontractor, or packaging method, the change should be disclosed and approved before release.
Price the conforming part at the dock
Landed cost = material and conversion + tooling + finishing + machining + packaging + inspection + freight + duties and taxes + expected rework.
The formula is more useful than a single per-kilogram number because it exposes where a low quote may be transferring cost. Ask whether the aluminum value is indexed, whether billing uses theoretical or shipped weight, and whether yield loss is included. Confirm whether the price covers cut-to-length work, protective film, testing, and export packaging.
Tooling is a fixed cost that should be evaluated against the expected lifetime volume. A standard profile may avoid a die charge but require extra machining, adapters, or compromises in assembly. A custom die may carry more upfront cost while reducing material use, labor, and failure points on every subsequent piece.
FOB, CIF, and delivered pricing are not interchangeable. The same factory price can produce very different landed costs after ocean freight, destination charges, duties, brokerage, and domestic transport. Comparing those terms only makes sense after the product specification is identical.
The useful benchmark is the cost of a conforming, protected profile delivered to the assembly operation, not the lowest number printed beside kilograms of aluminum.
Put the approved specification into the purchase order
The purchase order should reference the controlled drawing revision and approved sample rather than relying on a sales quotation alone. It should define:
- Alloy, temper, material standard, mechanical requirements, and lot documentation.
- Critical dimensions, inspection methods, sampling plan, and acceptance limits.
- Finish system, color reference, coating or anodizing requirements, and visual criteria.
- Cut length, machining, burr limits, protective wrapping, bundling, and pallet requirements.
- Tooling ownership, storage, maintenance, correction responsibility, and access if the supplier relationship changes.
- Incoterm, price basis, metal-price adjustment, delivery milestone, and quantity tolerance.
- The remedy for nonconforming product, including sorting, rework, replacement, credit, inspection costs, and freight.
- Written change control for material source, die, process, finish line, subcontractor, and packaging.
An approved sample should carry the part number and revision so that it cannot be confused with an earlier trial. Emails and messaging can clarify details, but the final requirement should be incorporated into the drawing, inspection plan, or purchase order.
The decisive question before the deposit
Can an independent inspector, using only the purchase order, controlled drawing, approved sample, and inspection plan, determine whether the shipment passes? If the answer is no, the quote is still a proposal for different interpretations.
Once the requirement is measurable, supplier comparisons become fair. Press capacity, finish quality, lead time, yield, packaging, and price can be evaluated against the same product. The first aluminum extrusion order then does more than buy metal: it produces evidence that the design, supplier, and process can support the next release.