Aluminum Extrusion
Also: extrusion, aluminium extrusion, extruded aluminum, custom aluminum extrusion, aluminum profiles, extruded profiles, hollow extrusions, T-slot extrusion, heat sink extrusion, architectural extrusion
Aluminum extrusion pushes a hot billet through a steel die into long, constant-profile shapes: low die cost, 6063 and 6061, cut to length and machined.
186 shops tagged Aluminum among 575 extrusion companies in the Noramark directory
A cylindrical aluminum billet is heated to about 450-500 °C (840-930 °F) and pushed by a hydraulic ram through a hardened steel die with the profile cut through it. The shape leaves the press as one long piece, is quenched at the press exit by air or water spray, stretched about 1-3% to straighten it and relieve stress, cut to length, and aged in an oven: to T5 after an air quench, or to T6 after a water quench at the press or a separate solution heat treatment. Solid profiles use a flat die. Hollow profiles such as tubes and multi-void shapes use a porthole or bridge die, which splits the metal around a mandrel and welds it back together inside the die, leaving longitudinal seam welds.
Extrusion dies are cheap by tooling standards, typically a few hundred to a few thousand dollars, and are made in 2-4 weeks, so a custom profile pays off quickly. Rails, tracks, frames, heat sinks, enclosures, handles, trim and tubes are extruded, and many brackets and blocks are sliced from a profile instead of machined from plate. The size of a profile is described by its circumscribing circle diameter (CCD), the smallest circle that encloses the cross-section, which decides the press, the billet and the price. Tolerances follow the Aluminum Association standards (ANSI H35.2): good enough for assembly, snap fits and screw bosses, with machining kept for bores, flatness and fits.
6063 is the extrusion alloy: it flows fastest, fills thin walls and sharp detail, and anodizes to the best appearance, at moderate strength. 6061 is stronger and structurally qualified but extrudes slower, needs thicker walls and anodizes less evenly; 6005A and 6082 sit in between. 2024, 7075 and 7050 are extruded for aerospace at a fraction of the speed and at a premium. The profile is the same along its whole length, so holes, notches, pockets and end features come from secondary fabrication: precision sawing, CNC machining, punching, bending and welding, then anodizing or powder coating. Most extruders offer these in-house or through partners.
At a glance
| Typical tolerances | Standard Aluminum Association (ANSI H35.2) tolerances scale with the dimension, the CCD and whether a dimension is across metal or across an open space: roughly ±0.15-0.2 mm (±0.006-0.008") on thin walls and small metal dimensions, about ±0.3 mm (±0.012") near 25 mm (1"), and wider on large dimensions, open spaces and hollow walls. Straightness about 1 mm per meter (0.0125" per foot); twist, flatness and angles per the same tables. Precision (tighter than standard) tolerances by agreement with the extruder at a cost. Cut length ±1.5 mm (±1/16") off the press saw, ±0.25 mm (±0.010") on a precision saw. Machined features ±0.05 mm (±0.002"). |
|---|---|
| Size limits | CCD from about 12 mm (1/2") to 250-300 mm (10-12") at most custom extruders, 500-600 mm (20-24") on large presses and more at a few heavy presses. Minimum wall about 1 mm (0.040") in small 6063 profiles, 1.5-2 mm (0.060-0.080") in 6061 and larger CCDs, and more in 2024 and 7075. Mill lengths typically 3.7-7.3 m (12-24 ft), with longer lengths by arrangement; parts are cut to shorter lengths at the press or in fabrication. Weights from under 0.1 kg/m to tens of kg per meter. |
| Surface finish | Mill finish about 0.8-1.6 µm Ra (32-63 µin), with faint longitudinal die lines that show under a clear anodize; 6063 gives the smoothest surface. Anodizing (clear, color or hardcoat), powder coating, painting, brushing, polishing and bright dipping (6463) are the usual finishes. Seam welds in hollow profiles can show as faint stripes after anodizing, and 6061 anodizes grayer and less uniform than 6063. Machined features 1.6-3.2 µm Ra (63-125 µin). |
| Lead time | New dies in 2-4 weeks, first samples in 3-5 weeks; production runs in 4-8 weeks, sooner from an existing die. Standard shapes (angle, channel, tube, T-slot) ship from distributors in days. Machining, anodizing and fabrication add 1-3 weeks. |
Typical of U.S. job shops; confirm with the shop for your part.
Materials
This record covers aluminum. 6063-T5 and T6: architecture, trim, heat sinks, enclosures and furniture, with the best surface and anodized finish and the thinnest walls. 6061-T6: structural frames, T-slot rails, fixtures, marine and truck parts, roughly 30% stronger in yield than 6063-T6 but slower to extrude. 6005A-T6 and 6082-T6 come close to 6061 strength with better extrudability. 6463 for bright-dipped trim; 1100 and 3003 for heat-exchanger tube. 2024, 7075 and 7050 for aircraft stringers, spars and fittings, in heavier walls and simpler shapes. Most 5xxx alloys, including 5083, extrude only in thick, simple shapes. Brass and copper are extruded by copper mills, and plastic profile extrusion is a separate trade.
What drives the cost
- Die charge, typically $500-2,500 for small solid profiles and more for hollows, multi-void shapes and large CCDs
- Metal by weight: the price per kilogram tracks the aluminum market (LME plus the regional premium) plus the extruder conversion charge
- Profile difficulty: thin walls, hollows, deep narrow channels and wide flat sections slow the press and raise scrap
- Alloy: 6063 runs fastest, 6061 slower, and 2024 and 7075 at a fraction of the speed
- Minimum run: most extruders set a minimum of a few hundred kilograms per run or a minimum charge
- Tolerances tighter than the Aluminum Association standard, and cosmetic requirements on anodized surfaces
- Secondary fabrication and finishing: precision cutting, machining, punching, bending, anodizing and powder coating
When to use it
- Long parts with a constant cross-section: rails, tracks, frames, channels, handles, trim and tubes
- Heat sinks with many fins, and enclosures with integral screw bosses, card guides and snap features
- Brackets and blocks sliced from a profile instead of machined from plate, saving machine time and material
- Volumes from a few hundred meters a year up, where a custom die pays back against machining
- Aluminum structures that will be anodized or powder coated
When not to
- Cross-sections that change along the length: machining, casting or forging
- Very small quantities when a standard shape plus machining will do
- Tolerances tighter than the extrusion standard across the whole profile, unless the critical features are machined
- Very wide, thin, flat profiles and deep narrow slots, which distort and break dies; sheet metal or a bonded assembly may be better
- Thin, complex shapes in 7075 or 2024, which extrude slowly and at a premium; consider 6061 or machining from plate
Design tips
- Keep wall thickness as uniform as possible; adjacent walls within about 2:1 of each other extrude evenly and hold tolerance.
- Radius every corner, inside and out, by at least 0.5 mm (0.020"); sharp corners wear the die and tear the metal.
- Keep open channels no deeper than about three times their width in 6063, and less in 6061; deeper slots deflect and crack the die tongue.
- Use the smallest CCD that fits the function: it decides the press, the die price and the running cost.
- Prefer open or semi-hollow shapes to true hollows when the function allows; hollow dies cost more and leave seam welds.
- Design in screw bosses, grooves, snap fits and alignment features; they cost nothing on the extrusion and save assembly and machining.
- Mark the exposed (significant) surfaces on the drawing for anodized or painted parts, and add small grooves or a texture to hide die lines on large flat faces.
- Specify the alloy and temper (6063-T5, 6063-T6, 6061-T6), the tolerance basis (Aluminum Association standard, with any exceptions listed), the length and the cut tolerance.
Frequently asked questions
- How much does a custom aluminum extrusion die cost?
- Typically $500-2,500 for a small solid profile and $1,500-5,000 or more for hollows, multi-void shapes and large CCDs. Dies are made in 2-4 weeks and some extruders waive or refund the charge against volume. That low tooling cost is the main reason extrusion beats machining from plate for long, constant-section parts.
- 6061 vs 6063 aluminum extrusion: which should I use?
- Use 6063 unless you need the strength. It extrudes faster, fills thinner walls and finer detail, and anodizes to a better finish, so it is cheaper and looks better. 6061-T6 is roughly 30% stronger in yield and is the common structural choice, but it needs thicker walls and costs more to extrude.
- What is the minimum wall thickness for aluminum extrusions?
- About 1 mm (0.040") in small 6063 profiles, 1.5-2 mm (0.060-0.080") in 6061 or in profiles over about 100 mm (4") CCD, and more in hard alloys such as 7075. Minimums rise with the CCD, for hollows and for walls far from the profile center; ask the extruder with the drawing.
- What is circumscribing circle diameter (CCD) in extrusion?
- The diameter of the smallest circle that fully encloses the profile cross-section. It decides which press and billet size can run the shape, drives the die cost, and sets the tolerance class in the Aluminum Association tables. Keeping the CCD small keeps a profile cheap.
- What is the minimum order for custom aluminum extrusions?
- Most extruders set a minimum run of a few hundred kilograms (roughly 500-1,000 lb) or a minimum lot charge, because each run means hanging the die and pushing full billets. Smaller needs are met by distributor stock shapes, or by extruders that run small lots at a premium.
