How aluminum window frames are made
Aluminum carries heat so well that window frames are split in two and rejoined by a plastic strip.
- stations
- 9
- things upstream
- 83
- raw sources
- 24
- steps from the ground
- 10
The short version
Heated aluminum billets are forced through steel dies into long profiles, which are aged and then powder coated or anodized. To stop heat crossing, wheels knurl and crimp inner and outer profiles onto a polyamide strip. Saws then miter the pieces at 45 degrees, corner cleats lock them into a rigid rectangle, and a glass unit goes in.
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Extrude the profile
Aluminum logs are cut and preheated until malleable, then forced through a precision steel die under hydraulic pressure. Long hollow sections come out the other side, usually in 6063 or 6060 alloy.
750 to 970°F, 800 to 2500 tons
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Age for strength
The profiles get a T5 heat treatment to strengthen them before any finish goes on.
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Coat the surface
Dry powder is sprayed on electrostatically and cured under heat, typically to 60 to 120 micrometers. Anodizing is the costlier alternative, thickening the metal's own oxide in an acid bath.
60 to 120 micrometers
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Knurl the pockets
A knurling wheel cuts tiny teeth, 0.15 to 0.30 mm long, into a pocket on the inner and outer profiles. Later they will bite into the strip.
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Insert the polyamide strip
Special equipment feeds a rigid polyamide strip into the pockets. It joins the two pieces of metal and keeps heat from passing straight between them.
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Crimp the assembly
Three sets of wheels roll the metal onto the strip, applying over 1300 pounds of pressure in stages. The result carries load as one composite, and samples are shear tested now and then.
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Miter the lengths
Saws cut the composite profile to length, with each end at 45 degrees.
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Cleat the corners
A corner cleat of aluminum or steel slides into the hollow chambers of two neighboring pieces and is fixed with screws, crimping or adhesive.
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Set the glass
A sealed glass unit is set into the finished rectangle against compressed gaskets.
Goes in
Worth repeating
- An anodized layer can crack but will not peel, unlike a coat of paint.
- A rival thermal break is made by pouring liquid polymer into a channel in the extrusion, letting it harden, then cutting away the metal under it.
Back to the ground
Follow every input upstream and aluminum window frame starts as these 24 raw sources.
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Sources
- Extrusion
- Anodizing
- Aluminum Extrusion Assemblies Provide a Thermal Barrier, Aluminum Extruders Council
- A Guide to Powder Coated Aluminium Windows Frame, HTS
- Extruded Aluminum Window Framing, Lucent Doors
Cite this page: "How aluminum window frames are made." Assembly Line, 2026-11-03. https://assemblyline.org/make/aluminum-window-frame