Key Terminologies in Aluminum Extrusion

Aluminum Extrusion

The manufacturing process where an aluminum billet is forced through a die to create a long, continuous object with a specific cross-sectional profile.

Direct Extrusion

The standard method where the billet is pushed through a stationary die by a moving ram.

Indirect Extrusion

A less common method where the die moves and pushes against a stationary billet. Reduces friction and required pressure.

Extrusion Press

The main machine that performs the extrusion, characterized by its tonnage (e.g., a 2,000-ton press).

Container

The thick-walled, high-strength steel cylinder that holds the billet and withstands the immense pressure during extrusion.

Ram

The large, hydraulically-driven piston that applies force to the billet.

Stem

The part that connects the ram to the dummy block.

Dummy Block

A reusable disc placed between the stem and the billet. It seals the container and prevents aluminum from flowing backward.

Billet

A solid, cylindrical log of aluminum alloy that is the starting material for extrusion. It is cast from molten aluminum.

Alloy

A specific blend of aluminum and other elements (e.g., Magnesium, Silicon, Manganese) that determines the material's properties. Common extrusion alloys are in the 6xxx series (e.g., 6061, 6063).

Temper

A designation indicating the mechanical properties achieved through thermal and/or mechanical treatment. Key tempers for extrusion include:
• T5: Cooled from an elevated temperature shaping process and then artificially aged.
• T6: Solution heat-treated and then artificially aged. Offers higher strength than T5.

Homogenization

A pre-extrusion heat treatment of the billet to create a uniform microstructure, improving extrudability and surface quality.

Extrusion Ratio

The ratio of the cross-sectional area of the container to the cross-sectional area of the extruded profile. A high ratio indicates more severe deformation.

Die

The tool steel disc with a shaped opening that determines the profile's cross-section. It is the most critical and custom part of the process.

Die Stack

The assembly consisting of the die itself, the backer, and the bolster, which work together to withstand extrusion pressure.

Die Orifice / Bearing

The final, shaped opening in the die. The length of this opening (bearing length) is critical for controlling metal flow.

Solid Die

A die used for producing solid profiles (profiles with no enclosed voids).

Hollow Die

A die used for producing hollow profiles (profiles with one or more enclosed voids). Requires a mandrel.

Porthole Die

A type of hollow die where the metal is split into streams that flow around bridges (which hold the mandrel) and are then welded back together inside the die chamber before exiting.

Bridge

The part of a porthole die that supports the mandrel. It creates weld lines in the final profile.

Mandrel

The core component of a hollow die that forms the inner surface of a hollow profile.

Feeder Plate

A plate used in conjunction with a die to help control metal flow for complex shapes.

Profile

The final, extruded product. Also called a shape or section.

Solid Profile

A profile with no enclosed voids.

Hollow Profile

A profile with one or more completely enclosed voids (e.g., a tube or rectangular pipe).

Semi-Hollow Profile

A profile that partially encloses a void but has a narrow, open gap that makes it less rigid than a true hollow.

Cross-Section

The two-dimensional shape of the profile when cut perpendicular to its length.

Tongue

A narrow, protruding feature in the die that forms a recess in the profile. Tongues are susceptible to deflection and breakage.

Wall Thickness

The thickness of the material in the profile. Maintaining uniform minimum wall thickness is a key design constraint.

Circle Size

The smallest circle that can fully enclose the profile's cross-section. This is a key parameter for pricing and press capacity.

Butt

The portion of the billet that remains in the container after extrusion. It contains oxides and impurities and is discarded for recycling.

Breakthrough

The moment when the aluminum first emerges from the die orifice.

Extrudate

The hot, soft aluminum as it exits the die.

Runout Table

The conveyor system that supports the extrudate as it exits the press.

Quenching

The rapid cooling of the extrudate using air (air quench) or water (water quench) to achieve the desired temper.

Stretching

A post-extrusion operation where the profiles are stretched (0.5-3%) to straighten them and align the grain structure, improving strength.

Die Lines

Fine, longitudinal lines on the profile's surface, caused by minor imperfections in the die bearing.

Pick-Up

Surface defects where small particles of aluminum adhere to the die bearing, causing scratches on the profile.

Weld Lines / Seam Welds

Longitudinal lines in a hollow profile where the metal streams were re-welded after flowing around the bridges in a porthole die. A potential weak point if not done correctly.

Age Hardening (Artificial Aging)

A heat-treatment process where extruded profiles are heated for a specific time to increase their strength (achieving T5 or T6 temper).

Anodizing

An electrochemical process that thickens the natural oxide layer on the aluminum, providing superior corrosion resistance and allowing for coloring.

Powder Coating

A dry finishing process where electrostatically charged powder is applied to the profile and then cured under heat to form a durable, colored coating.

Fabrication

Secondary operations performed on extruded profiles, such as cutting, drilling, milling, tapping, and welding.

Mitering

Cutting profiles at an angle for assembly at corners.