Metal extrusion

An ideal 100 mm diameter container feeding one 50 × 30 mm hollow profile with 3 mm walls uses 444 mm² of metal area, giving 17.69:1 extrusion ratio. Two identical openings give 8.84:1 using total outlet area. Use the metal area of the cross-section and validate force, die life and the integrity of hollow seams separately.

Direct or indirect describes tool and billet motion. Hot, warm or cold describes the thermal route. Specify both when they affect the product and its downstream processing. SME, study guide DV04PUB12, undated, Bonnell Aluminum, process description, undated

This reference uses aluminum producer examples for profile design and acceptance. Their temperature, die, temper and tolerance guidance should not be transferred unchanged to steel, copper, magnesium or another metal.

Identify the route and delivered form

Bonnell defines the first two arrangements. SME describes warm and cold extrusion separately from hot working and identifies force, material and geometry as process-selection variables. A route label alone does not define the lubricant, temperature or pressure schedule. Bonnell, SME

Hollow does not mean seamless

AEC distinguishes solid, hollow and semi-hollow profile categories. A hollow section completely encloses a void in cross-section. Semi-hollow classification concerns a partially enclosed region; not every open cavity is necessarily classified identically for tooling purposes. Ask the extruder to confirm the category rather than deciding solely from a casual view of the drawing. AEC, extrusion design tips, undated

Hydro's pipe and tube brochure, revision August 2023, describes seamless production using a die-and-mandrel press with a hollow billet or a piercer press with a solid billet. It contrasts these with porthole/bridge production: the metal separates into longitudinal streams and rejoins through the die, leaving longitudinal weld seams. An invisible seam is still a route characteristic. Specify seamless manufacture when it is required, not merely “extruded tube.” Hydro, seamless versus structural products

This distinction is not a blanket rejection of die-welded profiles. AEC notes successful structural use and distinguishes longitudinal die welds from billet-to-billet weld material that may require process planning or removal. Agree the relevant route and acceptance with the supplier for the service, forming and finishing requirements. Do not assume that a subsequent drawing operation changes the original extrusion route into seamless manufacture. AEC, extrusion FAQs, undated

Profile, tooling and press limits

Uniform walls, smooth thick-to-thin transitions and suitable radii generally improve the feasibility of an aluminum profile. AEC identifies die-tongue breakage, distortion and surface defects among concerns associated with unfavorable geometry, and notes that wide thin sections can be difficult to straighten. Its rules are design guidance, not universal minimum wall or corner dimensions for every alloy and press. Complex exceptions should be reviewed with the extruder. AEC, profile design guidance

Bonnell describes shape, alloy, ratio, tolerance, finish, temperature, speed and pressure as interrelated. A press with adequate nominal force does not automatically qualify a profile with thin projections or difficult flow balance. Confirm the complete die and process rather than approving a design from circumscribing diameter or press tonnage alone. Bonnell, factors affecting extrusion

SME defines extrusion ratio using the container-liner cross-sectional area divided by the total area of the die openings. Ratio is one contributor to ram-force requirements; billet material/condition, section dimensions, complexity, length and temperature also matter. It is not a standalone force equation. SME, DV04PUB12

Original ratio and length example

Assume an invented 100 mm diameter container feeding one 50 mm × 30 mm rectangular hollow section with uniform 3 mm walls, ignoring corner radii:

• Container area = π × 100² / 4 = 7,853.98 mm².
• Product metal area = 50 × 30 − 44 × 24 = 444 mm².
• Extrusion ratio = 7,853.98 / 444 = 17.69:1.

For two identical openings, use 888 mm² total outgoing area in the denominator.

For a hypothetical 400 mm usable billet length, ideal volume conservation gives 7.076 m from one opening, or 3.538 m per strand from two equal openings. These are geometric upper bounds excluding butt scrap, cropping, losses and temperature-related volume changes. They do not predict feasible force, die life, welding integrity or production yield. No ratio in this example is a recommended operating limit.

Temper and downstream operations

AEC distinguishes alloy from temper and lists, for example, T5 as cooling from an elevated temperature followed by artificial aging, and T6 as solution heat treatment followed by artificial aging. Do not order an alloy number alone when mechanical condition matters, or infer that an as-extruded profile has the properties of an aged product. Confirm the actual alloy-temper designation and the applicable product-property limits. AEC, alloys and tempers, undated

AEC's process description places quenching, mechanical treatment and aging after the profile leaves the die. Therefore, the die-exit shape is not necessarily the delivered state. Identify cutting, straightening, thermal treatment, machining and surface finishing in the agreed supply route, and define when critical dimensions are accepted. AEC, extrusion process

Specify acceptance for the product and service

ASTM B221-21, active on the publisher's page and updated October 29, 2021, covers specified aluminum/alloy extruded bars, rods, wire, profiles and tubes. Its scope directs pressure-related seamless pipe/tube applications to other specifications and warns that its general-purpose tube coverage may not address pressure-service manufacturing and integrity verification. A B221 designation is not by itself a pressure rating. Use the appropriate alloy, temper, product and service specification; B221M is the separate metric companion. ASTM B221 scope

AEC identifies industry and precision tolerance tables but also emphasizes designer/extruder agreement on the actual requirements. Specify cross-sectional dimensions, wall thickness, straightness, twist, flatness, cut length and functional datum relationships as applicable. A nominal section drawing or a single wall measurement does not establish the whole profile's conformance. AEC, tolerances, undated

The handoff should include the drawing/model revision, material/temper, route restrictions such as seamless construction, functional surfaces, finish and downstream operations. Agree sample qualification and inspection coverage for the delivered condition. The original calculation above is an area/volume model, not evidence that the illustrated profile is production-qualified.