Cold Metal Extrusion

Cold metal extrusion forces room‑temperature metal through a die to create near-net, high-strength constant profiles with excellent surface finish at high volumes.

Overview

Cold metal extrusion plastically deforms metal at or near room temperature by pushing a slug or billet through a hardened die. It produces near-net-shape parts with constant or near-constant cross sections, excellent surface finish, tight dimensional control, and high material utilization. Cold working increases strength and hardness, often eliminating secondary heat treatment.

Choose cold extrusion for high to very high production volumes of axisymmetric or prismatic parts such as shafts, splines, bushings, and thin-walled tubes. It excels when you need consistent cross sections, good fatigue performance, and minimal machining. Tradeoffs: very high press forces, expensive tooling, and process development mean poor fit for low volumes or very complex, non-uniform geometries. Tooling wear and die stresses also limit extremely hard or low-ductility alloys. Expect some constraint on wall thickness ratios, corner radii, and feature transitions to keep flow uniform and avoid cracking.

Common Materials

  • Aluminum 6061
  • Aluminum 1070
  • Low carbon steel 1018
  • Alloy steel 4140
  • Copper C110
  • Brass C360

Tolerances

±0.002" to ±0.004"

Applications

  • Automotive transmission shafts and gear blanks
  • Spline shafts and serrated hubs
  • Bushings and bearing sleeves
  • Hollow fasteners and rivet blanks
  • Aerosol and collapsible aluminum cans
  • CV joint and drivetrain components

When to Choose Cold Metal Extrusion

Use cold metal extrusion for high-volume parts with constant or near-constant cross sections that benefit from work hardening, good surface finish, and excellent material utilization. It fits axisymmetric or simple prismatic geometries where you want to minimize machining and achieve consistent, repeatable dimensions from coil or slug stock.

vs Hot Metal Extrusion

Choose cold metal extrusion when you need better surface finish, tighter tolerances, and higher final strength without a separate heat-treat step. It is ideal for ductile alloys and smaller cross sections where high press forces are manageable and dimensional accuracy is critical.

vs CNC machining

Choose cold metal extrusion when the cross section is mostly constant and volumes justify tooling, so you can form rather than cut material. This drastically reduces material waste and cycle time for shafts, bushings, and splined profiles that would be slow and expensive to machine from solid bar.

vs Metal stamping

Choose cold metal extrusion when you need thick sections, significant plastic flow, or 3D axisymmetric shapes that flat stamping cannot achieve. It works well for deep, thick-walled features and closed-end tubes where stamping would require multiple draws and still leave more variability in wall thickness.

vs Cold forging

Choose cold metal extrusion when the primary requirement is a controlled constant cross section or long length-to-diameter ratio, not just heading or upsetting. Use it for shafts, tubes, and profiles where metal must flow through a die land rather than just into a localized head or flange.

vs 3D printing (metal)

Choose cold metal extrusion when you need millions to tens of thousands of identical, relatively simple profiles at low part cost. It delivers far higher throughput and better surface finish than metal AM when the geometry is extrusion-friendly and up-front tooling investment is acceptable.

Design Considerations

  • Keep cross sections as uniform as possible along the length to promote even flow and reduce required press tonnage
  • Use generous internal and external corner radii; sharp corners increase die stress and risk of cracking
  • Avoid extreme wall thickness ratios and sudden section changes; taper transitions to control metal flow
  • Specify realistic tolerances and surface finishes for formed features, reserving tight tolerances for truly critical dimensions
  • Define maximum allowable grain direction and work hardening effects if the part is fatigue-critical
  • Call out any critical machining stock and datum features so the shop can design dies and trimming operations appropriately