Aluminum Extrusion Profile

Alloy Grade Selection: 6063 vs 6061 vs 6082

Aluminum extrusion alloy selection determines mechanical strength, surface finish quality, and machinability. Chinese factories produce all three architectural-grade alloys, but default to 6063 unless otherwise specified. Specifying the wrong alloy is a common sourcing mistake for structural applications.

6063-T5 (architectural standard). The dominant alloy for architectural and window/door profiles. Mg-Si alloy with excellent extrudability — allows thin walls (0.8–1.0mm) and complex hollow sections. 0.2% proof stress: 130 MPa (T5 temper). Excellent surface for anodizing: bright, consistent color. Suitable for curtain wall mullions, window frames, door frames, handrails, and decorative trim where moderate structural loads apply. The majority of aluminum window systems in Europe (Schüco, Wicona, Reynaers) are based on 6063-T6 or T5 profiles.

6061-T6 (structural). Mg-Si-Cu alloy. 0.2% proof stress: 275 MPa — more than double 6063-T5. Used where structural loading is the primary specification: marine boat frames, aerospace structural members, architectural canopy beams, industrial conveyor tracks. The copper addition makes anodizing slightly less bright and less consistent in color than 6063 — specify 6063 if anodized aesthetics are the priority. 6061-T6 is the standard alloy for North American structural profiles.

6082-T6 (high-strength EU standard). The European counterpart to 6061. 0.2% proof stress: 260 MPa. Preferred in European structural applications (EN 755-2 covers 6082 specifically). Good weldability and corrosion resistance. If your product targets EU structural or industrial applications, specify 6082-T6 rather than 6061 — 6082 is what European engineers design to.

Temper notation: T5 (artificially aged after extrusion, no solution heat treatment) vs T6 (solution heat treated + artificially aged). T6 temper requires an additional heat treatment step at the extrusion facility — confirm the factory has an in-line solution heat treatment furnace for T6 production. Not all Chinese extrusion plants operate T6 temper, particularly smaller facilities.

Custom Die Tooling: Cost, Lead Time, and Ownership

Die tooling is a one-time cost that amortizes across production runs. Understanding die ownership prevents disputes when switching suppliers.

Die material and cost. Extrusion dies for aluminum are machined from H13 tool steel. Die cost scales with profile cross-section complexity: a simple solid rectangular bar die costs $150–300; a complex hollow multi-void window frame die costs $800–1,500. Multi-cavity dies (two identical profiles extruded simultaneously on a wide press) have higher die cost but reduce extrusion cost per kilogram by 30–40%.

Die lead time. Standard die machining at a Chinese factory or die-making subcontractor: 10–20 days from approved 2D die drawing to first sample. Precision thin-wall dies (<1mm wall) require EDM machining and may take 20–30 days. Rush service (5–7 days) is available at 30–50% premium.

Die ownership. Die tooling paid for by the buyer is the buyer’s property. Include explicit die ownership language in the purchase order: “All tooling, dies, and molds paid for under this order are the exclusive property of [Buyer] and will be returned or destroyed at Buyer’s written request.” Without this clause, Chinese factories may retain and resell dies — especially common for standard architectural profiles where the die serves multiple customers.

Design for extrudability rules:

• Minimum wall thickness ≥1.0mm for standard press; ≥0.8mm for precision press
• Avoid wall thickness ratios >3:1 (thick sections cool slower than thin, causing distortion)
• Maximum circumscribed circle (the die circle that contains the profile): typically 150–200mm for medium presses, up to 350mm for large presses
• Provide 2D DXF drawing with full dimensional tolerances per EN 755-9 (straightness, twist, flatness)

Surface Finishing: Anodizing vs Powder Coat vs PVDF

Surface finishing is specified by the buyer and is a critical factor in architectural life expectancy and maintenance cost.

Anodizing (AA-10 / AA-15 / AA-20 / AA-25). Electrochemical conversion of the surface aluminum to aluminum oxide. Thickness grades per QUALANOD standard: AA-10 (10μm, interior), AA-15 (15μm, exterior mild), AA-20 (20μm, exterior aggressive), AA-25 (25μm, marine / industrial). Anodizing is integral to the aluminum — it will not peel or chip, unlike coatings. Color is limited to natural silver, electrolytic bronze/black, and electrocolored options (gold, champagne). For consistent color across a project, specify the anodizing batch together — different extruder batches can produce visible color variation even within the same alloy grade.

Powder coating (Qualicoat Class 1 / Class 2). TGIC polyester powder applied electrostatically, cured at 180–200°C. Dry film thickness: 60–80μm. Qualicoat Class 1: adequate for exterior applications in temperate climates. Qualicoat Class 2: superior UV resistance, required for facades in high-UV or marine environments (Mediterranean, tropics). Powder coat offers full RAL color range and custom colors. Adhesion per EN ISO 2409 (cross-cut test): 0/1 is acceptable. Gloss retention after 1,000h accelerated weathering (EN ISO 11507): Class 2 profiles retain >50% gloss.

PVDF coating (Qualicoat Class 3). 70% PVDF liquid paint, 25–35μm dry film. Highest UV and chemical resistance — equivalent to ACP PVDF coating performance. Specified for landmark facades, marine environments, and any project with a >20 year maintenance-free design intent. Requires liquid spray application (not powder) and specialized curing ovens — not available at all Chinese extrusion plants.

REACH / RoHS compliance. Powder coatings must be SVHC-free under REACH Regulation 1907/2006. Request the REACH declaration from the powder coating supplier, not just the extrusion factory. Lead chromate yellow pigments (banned SVHC) are occasionally still used in budget powder coat batches — a REACH-compliant declaration specifically covering SVHC above 0.1% is required for EU market entry.

Dimensional Tolerances and Inspection Verification

Aluminum extrusion tolerance standards are defined per EN 755-9 (general tolerances) and EN 12020-2 (precision tolerances for 6063). The key parameters to verify:

Wall thickness tolerance: EN 755-9 Table A.3 — for a 2.0mm nominal wall, general tolerance is +0.25/-0.20mm. Precision grade (EN 12020-2): ±0.15mm. For tight-assembly applications (window frame joints, curtain wall drainage channels), specify EN 12020-2 precision tolerances explicitly.

Straightness and twist: EN 755-9 limits straightness to 1mm per 300mm for standard profiles. Twist: 1° per meter. For long architectural profiles (>4m), request straightness measurement on a flat surface plate — profiles stored vertically or in high-humidity warehouses can develop permanent bow.

Inspection protocol for production batches:

• Measure 10 pieces per production run at five cross-section points each (four corners + center)
• Verify anodizing thickness with eddy-current gauge (25μm nominal → reject if <20μm on any spot)
• Salt spray test per EN ISO 9227: anodized profiles should show no corrosion after 1,000h; powder-coated after 1,500h (Qualicoat Class 2)

Our sourcing service includes die engineering review before tooling is cut, reducing rework risk on first-run samples.