Aluminium Extrusion Process: From Billet to Profile

[IMAGE: aluminium-extrusion-billet-heating-furnace.jpg | Alt=”Aluminium billet being heated in furnace before extrusion at NA-VIEW factory”]

What Is Aluminium Extrusion?

Aluminium extrusion is a manufacturing process that forces heated aluminium alloy billets through a shaped die opening under high pressure. To illustrate, think of it like squeezing toothpaste from a tube — the paste takes the shape of the opening. With aluminium, a 7-inch diameter billet heated to roughly 450 to 500 degrees Celsius gets pushed through a steel die at pressures up to 15,000 tons. As a result, the process produces a continuous length of aluminium profile with a consistent cross-section.

The process works because aluminium becomes soft and malleable when heated — similar to soft butter — without melting. Meanwhile, the alloy stays in a plastic state, which allows it to flow through complex die shapes while retaining its metallurgical properties. For this reason, most architectural and industrial profiles use 6063 or 6061 aluminium alloys. These alloys are chosen for their balance of extrudability, strength, and corrosion resistance.

Why Extrusion Matters for B2B Buyers

If you are importing aluminium profiles for doors, windows, curtain walls, or industrial frames, the extrusion process directly affects three things: dimensional accuracy, surface quality, and mechanical properties. However, a poorly controlled extrusion run produces profiles with inconsistent wall thickness, visible die lines, or weak spots. These defects may not be obvious when you inspect a few samples. Still, they show up during fabrication or on-site assembly — and by then you have already paid for the shipment.

That is why checking a supplier’s extrusion capabilities matters as much as checking their prices. Moreover, you need to know whether they run continuous casting or direct casting, what tonnage presses they operate, and how they handle die correction when profiles go out of tolerance.

The Aluminium Extrusion Process: 7 Steps from Billet to Profile

Every aluminium profile you have ever handled went through the same basic sequence. Still, the difference between suppliers lies in how well they control each step. Therefore, here is the full process, with the key quality checkpoints you should ask about.

Step 1: Die Design and Manufacturing

The die is a steel disc with a shaped opening that defines the profile cross-section. Consequently, die design determines approximately 70 percent of extrusion success. Nevertheless, a poorly designed die causes uneven metal flow, which leads to twisting, warping, or wall thickness variation in the finished profile.

Modern extrusion suppliers use 3D simulation software to model metal flow through the die before cutting any steel. This saves time and material. At NA-VIEW, our tooling engineers design dies using finite element analysis to predict and correct flow imbalances before production starts. In addition, standard die manufacturing takes 5 to 7 working days. Meanwhile, complex multi-cavity dies or hollow profile dies with mandrels take 7 to 12 days.

[IMAGE: aluminium-extrusion-die-design.jpg | Alt=”Aluminium extrusion die with complex cross-section design for custom profiles”]

Common Die Types for Aluminium Extrusion

Die Type	Used For	Typical Lead Time	Cost Factor
Solid Die (Flat)	Solid bars, angles, channels, T-sections	5-7 days	1x (baseline)
Hollow Die (Porthole)	Tubes, hollow chambers, thermal break cavities	7-10 days	2-3x
Semi-Hollow Die	Partially enclosed sections with narrow gaps	7-10 days	1.5-2x
Multi-Cavity Die	Small profiles produced in parallel for efficiency	8-12 days	1.5-2x

Step 2: Billet Casting and Preparation

Aluminium billets are cast from primary aluminium ingots, recycled scrap, or a blend of both. However, the casting method matters. For example, continuous casting produces billets with a finer, more uniform grain structure compared to traditional direct chill casting. Therefore, a uniform grain structure means more consistent flow during extrusion and better surface finish on the final profile.

Before extrusion, billets are cut to length — typically 600 to 1200 millimetres depending on press size — and preheated in a gas-fired or induction furnace. The target billet temperature range is 450 to 500 degrees Celsius for 6063 alloy. Too cold and the billet will not flow properly, causing die wear and surface tearing. Conversely, too hot and you risk surface oxidation, blisters, or grain boundary melting.

A reliable supplier logs billet temperature for every extrusion run. If a factory cannot show you these records, they are not controlling one of the most basic quality parameters. Furthermore, they should be able to tell you the billet alloy source and whether they use homogenised billets. In particular, homogenisation is a heat treatment that evens out the alloy element distribution and improves extrudability substantially.

Step 3: Extrusion Press Operation

This is the main event. First, the preheated billet is loaded into the extrusion press container. Then, a hydraulic ram pushes the billet against the die with force ranging from 600 to 15,000 tons depending on press size. Consequently, the aluminium flows through the die opening and emerges as a continuous profile on the other side.

Press tonnage determines the maximum profile size a factory can produce. For example, a 1,000-ton press handles smaller profiles like door tracks and window glazing beads. Meanwhile, a 2,500-ton press can extrude large curtain wall mullions and heavy structural sections. Therefore, if your project needs profiles wider than 200 millimetres, you need a supplier running at least a 1,800-ton press.

[IMAGE: aluminium-profile-emerging-from-extrusion-press.jpg | Alt=”Aluminium profile emerging from extrusion press with cooling system at NA-VIEW manufacturing plant”]

Several parameters must stay within tight ranges during extrusion. For instance, ram speed typically runs at 5 to 50 millimetres per second, adjusted based on profile complexity. Slower speeds suit thin-walled or intricate profiles, while faster speeds work for simple solid shapes. Meanwhile, exit temperature — measured at the point where the profile leaves the die — should stay between 500 and 580 degrees Celsius. If exit temperature exceeds the alloy’s solidus point, the profile tears. Conversely, if it drops too low, the metal hardens prematurely and may stick in the die.

Step 4: Quenching and Cooling

Immediately after exiting the die, the hot profile passes through a quenching system — either air fans, water spray, or a water bath. The quench rate must be fast enough to lock in the alloy’s mechanical properties but controlled enough to prevent distortion. However, too rapid quenching can warp thin-walled profiles. On the other hand, too slow quenching allows coarse precipitates to form, reducing strength.

For 6063 alloy, the critical temperature range during quenching is 450 to 200 degrees Celsius. The profile must pass through this range at a minimum cooling rate of 1 degree Celsius per second. Most architectural profiles use forced air quenching. In contrast, industrial and structural profiles needing higher strength often use water spray quenching.

Ask your supplier about their quench system. Factories that use a single cooling method for all profiles — regardless of wall thickness or alloy grade — are cutting corners. Therefore, different profiles need different cooling rates, and experienced extrusion operators adjust the quench accordingly.

Step 5: Stretching and Straightening

Profiles come out of the press slightly curved from thermal stress. Therefore, the stretcher grips both ends of each profile — now cooled to room temperature — and applies 0.5 to 2 percent elongation. This stretch straightens the profile, relieves internal stress, and slightly cold-works the material. In general, the standard stretch is 0.5 to 1 percent for most architectural profiles.

Under-stretching leaves residual stress that causes the profile to warp later — especially after cutting, machining, or welding. Over-stretching, however, can cause dimensional changes or surface defects. Skilled stretcher operators use feel and experience, but the best factories also measure final straightness with a straight edge and feeler gauge. The industry standard for profile straightness is 1 millimetre deviation per metre of length. For demanding applications like curtain wall transoms, tighter tolerances may be required.

Step 6: Ageing and Heat Treatment

After stretching, profiles go into an ageing oven for precipitation hardening. In fact, this is what gives 6063 and 6061 alloys their final mechanical strength. During ageing, the profiles are held at 170 to 200 degrees Celsius for 4 to 8 hours, depending on the alloy and target temper.

6063 alloy typically goes to T5 temper — air quenched and artificially aged. This gives tensile strength around 160 to 180 megapascals at a 5 to 8 percent elongation. In contrast, 6061 alloy goes to T6 temper — solution heat treated and artificially aged — achieving 260 to 310 megapascals tensile strength. Consequently, the ageing cycle must be precise. Under-ageing leaves the profile too soft. Conversely, over-ageing reduces elongation and makes the profile brittle.

Common Temper Designations for Extruded Aluminium Profiles

Temper	Alloy	Process	Tensile Strength (MPa)	Typical Application
T4	6063	Solution treated + naturally aged	130-150	Architectural shapes needing bending
T5	6063	Cooled from extrusion + artificially aged	160-180	Window, door, and curtain wall profiles
T6	6061	Solution treated + artificially aged	260-310	Structural, automotive, marine profiles
T66	6063	Cooled from extrusion + special ageing	200-220	High-strength architectural profiles

Step 7: Cutting, Inspection, and Packing

The final step cuts profiles to ordered lengths — typically 5.8 or 6 metres for container loading — and inspects for surface defects, dimensional accuracy, and mechanical properties. Specifically, a proper inspection includes:

• Visual inspection for die lines, pick-up marks, blisters, and scratches under adequate lighting
• Dimensional check using callipers, go/no-go gauges, or CMM for critical dimensions
• Hardness testing with a Webster or Vickers hardness tester to verify temper
• Tensile testing on sample coupons cut from each batch

Profiles that pass inspection are packed with protective film on visible surfaces — especially important for anodised or powder coated profiles. Meanwhile, wooden crates or export-grade pallets protect against handling damage during shipping. Finally, every bundle should carry a label with the heat number, alloy, temper, and order reference for traceability.

[IMAGE: aluminium-profiles-quality-inspection.jpg | Alt=”Quality inspector checking aluminium profile dimensions with precision calliper at NA-VIEW factory”]

Common Aluminium Extrusion Defects and How Good Suppliers Prevent Them

Every extrusion run produces some scrap. However, what separates a quality supplier from a budget factory is the scrap rate and what they do about it. Therefore, here are the most common extrusion defects — and the process controls that prevent them.

Extrusion Defect Types and Prevention

Defect	Appearance	Root Cause	Prevention
Die Lines	Longitudinal scratches or raised ridges on profile surface	Worn die bearing surface, debris in die	Regular die polishing; nitrogen or liquid nitrogen cooling
Pick-Up	Small particles of aluminium stuck to surface	Metal build-up on die bearing	Die nitriding; proper billet temperature control
Blistering	Raised bubbles on profile surface	Gas trapped in billet; billet overheated	Use degassed billets; control billet temp below 520 degrees C
Twisting	Profile rotates along its length	Uneven metal flow through die	Die design correction; adjust die bearing lengths
Wall Thickness Variation	One wall thinner than others on same profile	Die deflection under pressure; misaligned die	Reinforced die design; regular die inspection
Surface Cracking	Small cracks perpendicular to extrusion direction	Exit temperature too high; ram speed too fast	Reduce ram speed; lower billet temperature

How to Spot Process Control Problems

These defects are not mysterious. In fact, a factory that properly controls billet temperature, ram speed, die condition, and quench rate produces consistent profiles with very low scrap rates. Therefore, when you evaluate a new supplier, ask about their average extrusion scrap rate. A well-run operation keeps it under 3 to 5 percent. Conversely, anything above 8 percent suggests poor process control — and you will eventually pay for that scrap through higher prices or quality problems in your shipments.

How to Evaluate an Aluminium Extrusion Manufacturer

Not every aluminium extrusion factory produces the same quality. Therefore, when you are comparing suppliers — especially when sourcing from overseas — focus on the following questions rather than just comparing price per kilogram.

Press Tonnage and Capacity

Ask what tonnage presses they run and how many. For example, a factory with one 800-ton press cannot produce the same range of profiles as one with multiple presses from 600 to 2,500 tons. Therefore, press tonnage directly limits the maximum profile circumscribing circle — the smallest circle that contains the entire profile cross-section. The Aluminium Extruders Council provides reference tables matching press tonnage to profile size capability.

Billet Quality and Alloy Sourcing

Ask whether they use primary aluminium billets, recycled billets, or a blend. Primary billets give the most consistent properties. However, recycled billets can be acceptable if the scrap is well-sorted and remelting is properly controlled. Also ask about billet homogenisation — this heat treatment before extrusion improves extrudability by 20 to 30 percent and gives better surface finish.

Quality Control Documentation

A proper extrusion supplier should provide mill test certificates with every shipment, showing the alloy, temper, tensile test results, and hardness values for each heat number. If a factory hesitates to share this documentation or says they do not do tensile testing on every batch, walk away. Moreover, dimensional inspection reports for critical dimensions are equally important — especially for profiles that mate with gaskets, hardware, or other components.

Why Choose NA-VIEW as Your Aluminium Extrusion Partner

NA-VIEW has been manufacturing aluminium profiles for 11 years. Our factory in Foshan, China runs 6 extrusion lines with press capacities ranging from 600 to 2,500 tons. Consequently, we have the flexibility to produce everything from small glazing beads to large curtain wall mullions. In addition, we extrude 500 plus profiles daily with dimensional accuracy held to plus or minus 0.5 millimetres.

ISO-Certified Quality Systems

Our quality system is ISO 9001 certified, and every production batch undergoes tensile testing, hardness verification, and full dimensional inspection before shipping. Moreover, we maintain detailed process records for every extrusion run — billet temperature, ram speed, quench rate, ageing cycle — so you can trace any profile back to its production parameters. If you need custom profiles requiring aluminium door and window profiles with specific wall thicknesses or thermal break cavities, our tooling engineers design dies in-house with a 7-day turnaround. We also provide aluminium profile surface treatment including anodising, powder coating, PVDF, and electrophoresis in our integrated finishing lines.

Global Export Experience

We export to 30+ countries including markets in the Middle East, Southeast Asia, Africa, and South America. Our standard lead time for new die development is 7 days, and we deliver free profile samples in 3 days for your evaluation. For production orders, expect 25 to 35 days from deposit to container loading, depending on profile complexity and surface treatment requirements. Meanwhile, every shipment is packed in export-grade wooden crates with protective film on visible surfaces, and we provide full mill test certificates and dimensional inspection reports with each order.

Fast Response and Free Samples

We offer free samples for profile evaluation. Therefore, send us your drawings or cross-section sketches — our engineering team responds with a feasibility assessment and quotation within 24 hours.

[IMAGE: naview-aluminium-extrusion-factory-overview.jpg | Alt=”NA-VIEW aluminium extrusion factory with 6 production lines in Foshan China”]

Frequently Asked Questions About the Aluminium Extrusion Process

What is the minimum wall thickness for extruded aluminium profiles?

The practical minimum wall thickness for 6063 alloy is 1.0 millimetre for small profiles and 1.5 millimetres for profiles wider than 50 millimetres. Going below this increases the risk of die breakage and profile tearing during extrusion. However, 6061 alloy requires slightly thicker minimum walls — typically 1.5 to 2.0 millimetres — due to its higher extrusion pressure requirement.

How long does it take to produce custom aluminium extrusion dies?

Standard solid dies take 5 to 7 working days. Hollow dies and semi-hollow dies take 7 to 12 working days. Moreover, complex multi-cavity dies with tight tolerances may take up to 15 days. At NA-VIEW, we produce dies in-house and provide a 3-day sample turnaround after die completion for your approval before starting production.

What aluminium alloys are best for architectural profiles?

6063-T5 is the standard choice for most architectural applications including window frames, door frames, and curtain wall profiles. It offers a good balance of extrudability, surface finish, corrosion resistance, and moderate strength. In addition, 6060 alloy is occasionally used where better surface finish after anodising is critical. Meanwhile, 6061-T6 is used for structural applications requiring higher strength, such as load-bearing mullions and transoms in high-rise curtain walls.

What surface treatments can be applied to extruded aluminium profiles?

The four main options are anodising (10 to 25 micron oxide layer, excellent corrosion resistance), powder coating (60 to 80 micron polyester or polyurethane layer, wide colour range), PVDF coating (25 to 35 micron fluoropolymer, best UV and weather resistance), and electrophoresis (transparent or coloured glossy finish over anodising). For more details, refer to our aluminium profile surface treatment comparison guide.

What is your MOQ for custom extruded aluminium profiles?

Our standard MOQ is 500 kilograms per profile design. However, for smaller trial orders, we can work with 300 kilograms. Die costs are amortised over the first production order. Moreover, for larger projects with multiple profile designs, we offer consolidated die development and discounted tooling packages.

What payment and shipping terms do you offer?

We accept T/T bank transfer (30 percent deposit, 70 percent before shipment), irrevocable L/C at sight, and PayPal for sample orders. Standard shipping terms are FOB Shenzhen or Guangzhou. In addition, we offer CIF and DDP to major ports worldwide. All profiles are packed in export-grade fumigated wooden crates with protective film on finished surfaces.

How do you ensure profile tolerances are maintained across large production runs?

We perform dimensional inspection at three checkpoints: first article inspection after die setup, in-process random sampling during extrusion, and final inspection before packing. Critical dimensions are measured with calibrated callipers and go/no-go gauges. Therefore, our standard tolerance is plus or minus 0.5 millimetres for most dimensions, with tighter tolerances available for precision applications. We also monitor die wear — when a die approaches its service life limit, we refinish or replace it before it produces out-of-tolerance profiles.

Ready to Source Custom Aluminium Profiles?

Whether you need standard aluminium window and door profiles or complex custom extrusions for an industrial application, NA-VIEW has the press capacity, tooling expertise, and quality systems to deliver. Therefore, send us your profile drawings or project requirements today. Our engineering team responds with a feasibility analysis and quotation within 24 hours — and we will ship free profile samples within 3 working days so you can inspect the quality before committing to a production order.

Contact NA-VIEW Aluminium to start your extrusion project.