Aluminum Profile Extrusion Die Processing Equipment

An aluminum profile extrusion die is usually a stack: a die body with the bearing and orifice, a backer or bolster, sometimes a mandrel for hollow sections, and a set of support plates. The die body takes the wear. The backer takes the load. If the backer face is not flat and parallel to the die face, the die flexes under press load and the bearing opens unevenly.

Machining order follows that load path. Rough the die body, stress relieve, then finish the mating faces before you cut the orifice. Cut the orifice before the bearing, because the bearing is the last feature that controls metal flow. Changing the bearing after the orifice is cut is normal. Changing the orifice after the bearing is cut means starting over.

For a simple solid profile, one die body and one backer are often enough. For a hollow profile with two or more cavities, expect a mandrel, a mandrel holder, and a porthole or bridge design in the die body. Each added plate adds a flatness requirement.

• 1
  One-piece diesSolid shapes, low volume, fastest to machine.
• 2
  Porthole or bridge diesHollow sections; the billet splits and re-welds.
• 3
  Semihollow diesNearly closed shapes that still need a mandrel.
• 4
  Multi-cavity diesTwo or more identical profiles per press stroke.

Die blanks arrive as H13 or a similar hot-work tool steel block, typically pre-hardened to 44–48 HRC after heat treatment. Before hardening, the blank is sawn to size and rough machined. A programmable band saw handles this well. The AMADA HFA700C2 class of machine cuts up to roughly 700 mm stock and runs a programmed cut list, so repeat blanks come out the same length.

Rough milling removes most of the volume. A 3-axis mill with a 500 × 500 × 450 mm envelope covers most single-cavity dies. Larger multi-cavity blocks need more travel. At GreatLight we run 27 three-axis machines and 12 four-axis mills for this kind of work, plus 16 five-axis centers when the die has angled faces or deep pockets that would need multiple setups otherwise.

Leave 0.5–1.0 mm of stock on every surface that will be finish machined after heat treatment. More than that wastes cutter time later. Less than that and scale or distortion from hardening will not clean up.

After heat treatment, the die is hard. Milling will not cut it cleanly at 44–48 HRC, so the orifice and bearing are cut by electrical discharge machining. Wire EDM handles through-features with straight walls and tight corner radii. Sinker EDM handles blind pockets, draft angles, and porthole bridges where a wire cannot reach.

Wire EDM holds position well, but the surface it leaves is a recast layer. That layer is brittle and must be removed before the die goes into the press. A light grind or polish on the bearing removes it. Skip this step and the bearing spalls early, which shows up as lines on the profile.

Sinker EDM electrodes are the real cost driver. A porthole die with four ports and a complex bridge may need several electrodes per cavity, and each electrode is machined on a 3-axis or 5-axis mill before it ever touches the die. Electrode count, not die size, often sets the lead time.

• 1
  Wire EDMStraight walls, tight corners, through cuts.
• 2
  Sinker EDMBlind pockets, draft, bridge geometry.
• 3
  Electrode machiningOften the longest single step.
• 4
  Recast removalGrind or polish before first run.

The orifice profile sets the extruded shape. The bearing length sets the flow balance. A bearing that is 0.05 mm too long on one side of the profile will starve that side and push metal to the other, and the extruder will spend the first shift adjusting the die instead of running it.

For most profiles, bearing width is held within a few hundredths of a millimeter, and the die and backer faces are ground parallel. At GreatLight we machine die components to ±0.005 mm where the drawing calls for it, and we hold Ra 0.2–0.8 μm on bearing surfaces that see metal flow. Rougher surfaces drag and cause pickup.

Flatness is the quiet one. A backer face that is 0.02 mm out of flat will not show up on the CMM report as a profile problem. It shows up as a die that runs fine at low ram speed and drifts at production speed.

Not every die needs the full chain. A short-run die for a simple trim profile can be milled, hardened, ground, and hand-finished. There is no EDM step and no electrode cost. That is the right call when the profile has generous tolerances and the run is under a few hundred meters.

The full chain earns its cost when the profile is hollow, has thin walls, or will run for years. Porthole dies, multi-cavity dies, and profiles with tight wall thickness all need EDM and a controlled bearing. Add nitriding or a similar surface treatment when the alloy is aggressive or the run is long.

One more decision: who polishes the bearing. Hand polishing by an experienced die finisher still beats automated methods on flow surfaces, because the operator can feel the transition at the bearing entry. That transition is where most flow marks start.