Aluminum Extrusion Cooling Bed: How It Works and How to Specify One

2026-09-24 11:40:14

An aluminum extrusion cooling bed — often called a cooling table or run-out table — is the long conveyor that receives the hot profile from the haul-off machine after the quench and carries it while it cools to handling temperature. Its job sounds passive, but the bed quietly decides whether your sections end up straight, hard and scar-free or warped and soft.

What the cooling bed does after the quench

Straight from the die the profile is 500–600 °C. The quench (air or water mist) strips most of that heat in seconds, but the metal is still too hot and too soft to cut or stack. The cooling bed supports it on a flat, moving surface and finishes the cooling while keeping it straight.

Because the profile is fully supported and conveyed, you avoid the sag and twist that happen on a static rack. The bed also buffers the line: while one length cools, the next is already arriving from the puller.

Belt-driven vs chain cooling beds

Two conveyor families dominate. The choice trades surface care against load capacity.

Belt-driven roller beds

Continuous belts or fabric-over-roller surfaces cradle the profile, spreading support and avoiding point loads. They run quietly and protect anodised or painted surfaces — the default for architectural and doors-and-windows lines.

Chain-type beds

Heavy slat or chain conveyors tolerate high heat and heavy sections. They are the rugged choice for large industrial shapes and rail-transit profiles, though they need more maintenance.

Cooling length and airflow design

Length is not arbitrary. It is set by your maximum pull speed and the dwell time the alloy needs to stabilise. A typical 6xxx line uses a bed of 30–90 m. The quick formula is bed length ≈ pull speed × dwell time + buffer. If you push 1,800 mm/s and need 40 s of cooling, you are already past 70 m before the buffer.

Airflow matters as much as length. Forced-air fans across the bed strip heat evenly and stop one edge cooling faster than the other. Uneven cooling is the silent cause of post-cut warpage, especially on asymmetric hollow sections.

Table speed and its effect on hardness and straightness

Bed conveyors usually run 5–30 m/min. That speed is a balancing act:

• Too fast — the profile reaches the saw while still hot, giving soft spots and trapped stress that bends it later.

• Too slow — you waste floor and starve downstream stations, killing throughput.

• Just right — the section exits near ambient, uniform, and already straight.

Hardness tracks cooling uniformity, not just final temperature. A profile cooled evenly at a steady table speed reaches its target Brinell value with minimal residual bow.

Layout with the puller and the saw

The bed sits between two partners. The puller feeds it at a matched, constant rate; the saw pulls finished lengths off the far end. A good layout keeps the pull speed, bed speed and saw cadence in one control loop so nothing queues or starves. Air quenches are often mounted at the bed entrance, with the bed acting as the cooling and metering stage.

Temperature targets and maintenance

Aim for below 60 °C at the saw infeed. Large or complex sections may need staged cooling to avoid quench cracking. Daily maintenance is light but regular:

1. Clear aluminium fines from belts, rollers and chain guides each shift.

2. Check belt tension and chain alignment weekly.

3. Verify fan operation and clean intake filters monthly.

4. Inspect support surfaces for weld spatter or dents that mark profiles.

Selection checklist

Frequently asked questions

What is the purpose of a cooling bed on an extrusion line?

It receives the hot profile from the puller after the quench and lets it cool uniformly to handling temperature while being conveyed and supported, so the metal gains hardness without warping.

Belt-driven or chain cooling bed — which is better?

Belt-driven beds protect surface finish and run quieter, suiting anodised and painted profiles. Chain beds carry heavier loads and resist heat better, suiting large industrial sections.

How long should a cooling bed be?

Length is set by line speed and the cooling time your alloy needs. A typical 6xxx line uses 30–90 m; multiply your maximum pull speed by the required dwell time, then add a buffer.

Why does table speed affect hardness and straightness?

Too fast and the profile leaves before it is uniformly cooled, causing soft spots and residual stress that bends it later. Too slow wastes floor space and throughput. Speed must match the quench and alloy.

What temperature should profiles reach before the saw?

Generally below 60 °C at the saw infeed so cutting and handling will not induce thermal distortion. Large sections may need staged cooling to avoid quench cracking.