China Refreshes the Largest Recording in Heavy Extrusion Machines

Heavy extrusion pushes a billet through a die at high reduction ratios, and the metal does not flow evenly. The outer shell moves slower than the core because of friction at the container wall. That speed difference creates internal shear, and shear is what sets the real limit on how large a section you can produce in one pass.

A press rated at higher tonnage gives you more force. Force alone does not fix an uneven flow front. Tooling stiffness, container alignment and billet temperature uniformity decide whether the profile exits straight or comes out with twist and internal cracking.

When a country refreshes the largest recording for a heavy extrusion machine, the practical gain is a longer stroke and a stiffer container. Longer stroke means fewer billet welds in one length. Stiffer container means the die stays centered under load, so wall thickness variation across a 400 mm wide profile stays inside the drawing.

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  Reduction ratioAbove roughly 30:1, flow lines start to fold instead of running straight.
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  Billet temperatureA 15 °C spread across the billet is enough to bend a long profile.
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  Die bearing lengthShort bearings cut friction but lose wall thickness control.

Aluminium is the easy case. Alloys such as 6061, 6063, 6082 and 7075 extrude well at 400–500 °C, and the press tonnage needed scales with the cross-section area. A 7075 profile with thin walls is harder because the alloy has a narrow working window; too cold and it tears, too hot and it exits with a rough surface.

Magnesium AZ31B and AZ91D run at lower temperatures and lower ram speed. The metal is lighter, so the same tonnage produces a longer billet, but the fire risk during handling means the press line needs inert gas and clean chip control.

Copper and brass sit at the other end. C27400 and C36000 need much higher pressure and a heated container. Tool life drops fast, and most shops run these on smaller presses with shorter billets rather than chasing a tonnage record.

Titanium and Inconel do not belong here at all. They are worked by forging, rolling or machining, not by pushing a billet through a die. If a drawing calls for a Ti-6Al-4V profile with a hollow section, the realistic route is machining from plate or bar, not extrusion.

A heavy extrusion line is not just the press. The die stack, the container liner, the dummy block, the shear blade holder and the run-out table all carry load and all need machined fits. These parts are large, heavy and often made from 4140 or 4340 steel that has already been heat treated.

Cutting hardened 4140 is a different job from cutting 6061. We run it on 5-axis centers with through-spindle coolant and keep depths conservative. A 4,000 × 400 × 150 mm travel envelope covers most container liners and dummy blocks without repositioning, which matters because a second setup on a 300 kg part is where the error creeps in.

Die backers and bolster plates need flatness more than they need a fine finish. We hold ±0.005 mm on the seating faces and leave the non-critical surfaces as machined. Measuring a 2 m long plate for flatness takes time, and we do it before shipment, not after the customer finds a gap.

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  Container linersBore concentricity and a hard inner surface; often nitrided after machining.
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  Dummy blocksFlat face against the billet, relief behind, threads for the ram connection.
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  Die holdersPocket fit and dowel positions decide whether the die stays centered.
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  Shear bladesTool steel, tight clearance to the container bore, edge kept sharp.

Size changes how tolerance behaves. A ±0.005 mm callout on a 100 mm bore is routine. The same callout on a 3,000 mm plate is a statement about the machine, the fixturing and the temperature of the shop. We hold it, but we plan the setup around it rather than assuming it.

Thermal drift is the main enemy on long parts. A part that measures correctly at 8 a.m. can move by the afternoon if the shop warms up. We rough, let the part settle, then finish. On steel parts that have seen heat treatment, we check for movement between operations and correct it before the final cut.

Inspection on large parts is not a caliper job. We use CMM where the part fits and portable arm measurement where it does not. Every shipment gets a raw material check, in-process monitoring and a final inspection. Reports go out on request, and dimensional reports are standard for anything feeding a press.

Surface finish matters mostly where parts slide or seal. Sealing faces on a container liner run at Ra 0.8–1.6 μm. Structural plates can stay at Ra 1.6–3.2 μm, and there is no reason to pay for finer work on a face that only touches a shim.

The extrusion record gets attention because it signals capability. For a buyer, the useful question is narrower: can the shop that machines my die holder hold size on a heavy part, and can it prove it? A press record says nothing about that.

Ask about machine travel first. A shop with a 4,000 mm bed and a Ø400 mm rotary table can handle a container liner in one setup. A shop that must reposition the part will fight alignment all day.

Ask about heat treatment sequence. Large steel parts should be rough machined, heat treated, then finished. If a supplier finishes before hardening, the part will move and the tolerance on the drawing becomes fiction.

Ask about inspection records. For press tooling, the seating faces and bore concentricity are the numbers that matter. A supplier who cannot produce those numbers on paper is asking you to trust the machine operator's eye.

GreatLight has been machining since 2011, with 127 high-precision CNC machines across three plants and 150 technicians. We take parts from one prototype to 10,000+ runs, and uploads stay confidential with an NDA available on request.