Hot Metal Extrusion

Hot metal extrusion forces heated metal through a die to create long, constant-profile shapes with good formability, high throughput, and moderate dimensional control.

Overview

Hot metal extrusion pushes a heated billet through a shaped die to produce continuous lengths with a constant cross-section. Heat lowers flow stress, so it works well for tougher alloys, larger reductions, and more complex profiles than cold extrusion, while keeping grain flow aligned with the profile for solid mechanical performance.

Choose it for medium-to-high volume production of bars, tubes, channels, and custom profiles where per-part cost matters and you can live with “extrusion-level” tolerances. It’s common when parts will be cut to length and then finish-machined at critical features.

Tradeoffs: hot processing means scale/oxidation, more die wear, and dimensional variation from thermal effects and quench/stretch steps. Expect straightness, twist, and surface finish to drive secondary operations. Very thin walls, sharp corners, and tight tolerances typically require conservative designs or added machining.

Common Materials

  • Aluminum 6061
  • Aluminum 6063
  • Magnesium AZ31B
  • Copper C110
  • Titanium Grade 2
  • Steel 4140

Tolerances

±0.005" to ±0.015" (profile-dependent; tighter on small simple sections, looser on large/thin-wall shapes)

Applications

  • Aluminum heat sink profiles
  • Structural T-slot and custom aluminum rails
  • Tube and pipe hollows for hydraulic systems
  • Copper busbar profiles
  • Window and curtain wall mullions
  • Automotive crash management extrusions

When to Choose Hot Metal Extrusion

Hot metal extrusion fits parts with a constant cross-section made in long lengths that you can cut to size and finish-machine where needed. It’s a strong choice for medium-to-high volumes, tougher alloys, or larger section changes where cold forming loads would be excessive. Plan for process variation and include secondary operations if critical dimensions or cosmetic surfaces matter.

vs Cold Metal Extrusion

Choose hot metal extrusion when the alloy is hard to cold form, the section is larger, or the profile complexity/reduction ratio would drive cold extrusion forces, tooling risk, or cracking. Hot extrusion trades tighter tolerances and surface finish for better formability and broader material/process window.

vs CNC machining

Choose hot metal extrusion when the part is primarily a constant profile and you need low cost per foot with high throughput. Use machining after extrusion for localized tight-tolerance features (holes, pockets, sealing faces) rather than machining the whole shape from billet.

vs Roll forming

Choose hot metal extrusion when you need solid sections, thick walls, or non-sheet geometries (including hollows) that roll forming can’t make. Extrusion also supports more 3D cross-section complexity in a single profile versus progressive bends in strip.

vs Closed-die forging

Choose hot metal extrusion when the geometry is a long constant cross-section rather than a discrete 3D shape. Extrusion is usually more economical for continuous lengths and profile families, while forging better fits localized thick features and non-constant sections.

vs Casting

Choose hot metal extrusion when you need better mechanical properties from wrought grain flow and consistent density along a profile. Extrusion also delivers higher throughput for long constant sections, while casting fits complex non-constant shapes but may require more property/porosity management.

Design Considerations

  • Keep the cross-section constant; push lengthwise features (ribs, grooves, channels) instead of cross-section changes
  • Use generous internal corner radii and avoid sharp re-entrant features to improve metal flow and die life
  • Control wall thickness and avoid extreme thin-to-thick transitions to reduce distortion, twist, and scrap
  • Call out which dimensions are critical and where machining stock is acceptable; don’t tolerance the whole profile tightly by default
  • Specify straightness, twist, and camber requirements explicitly; these often drive stretching, fixturing, and secondary ops
  • Define alloy, temper, and post-extrusion heat treat/quench requirements early because they affect distortion and achievable tolerances