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Direct vs Indirect Aluminium Extrusion


Aluminium extrusion is a process of creating customised profile components for various metalwork industrial solutions. Discover the difference between direct and indirect extrusion, alongside joining methods and manufacturing capabilities.

In 2019, the value of the global aluminium extrusion industry was $77.8 billion, with a 5.6% CAGR prediction taking it to $118.7 billion in 2027.

While aluminium extrusions can produce countless results, two main methods are applied in the industry:

  • Direct extrusion
  • Indirect extrusion

Read on to discover the difference between both aluminium extrusion solutions and learn which method best serves your business.

Aluminium extrusion creates specific profile components for industrial solutions. Discover if direct or indirect extrusion is the best method for you.

What is Aluminium Extrusion?

Aluminium extrusion is the process of applying powerful hydraulic pressure to force a block of aluminium (billet) through a die to create aluminium lengths of a specific cross-section profile.

The process is applied across various industries, such as automotive, aviation, and construction, creating complex cross-section components of incredible strength while still offering a smooth finish.

As a simple comparison, imagine a tube of toothpaste with a customisable cap. When you force the toothpaste out, it takes the specific mould of whatever design is given to the cap. Aluminium extrusion works like this but at almost 1000ºF while using blocks of aluminium.

Due to most extrusion machinery generating 15,000 tons of pressure, as the ram forces the billet through the die, aluminium extrusion can create any cross-sectioned shape imaginable.

After heating the furnace to temperatures between 750-925ºF, the pressure of the hydraulic ram combines with the sheer heat of the furnace, transforming the billet into whatever shape on the die.

Finally, when the extruded products are removed and left to cool, they are delivered to a stretcher, where they get straightened.

How Are Aluminium Extrusions Made?

Two methods can be used during the extrusion process, direct or indirect extrusion. Both these methods have different benefits while still creating various cross-section designs upon the billet.

What is Direct Aluminium Extrusion?

Direct extrusion involves moving the aluminium billet with a hydraulic ram through a stationary die. During the process of direct extrusion, more friction is forced upon the aluminium, demanding added pressure and heat from the machinery. 

The Benefits of Direct Aluminium Extrusion

It’s the most common form of extrusion and comes with several advantages, including:

  • Extruding longer aluminium lengths
  • Increased operational flexibility
  • Lower cost per component
  • Modifications after extrusion are easy when aluminium is still hot
  • Smooth surface finishes

Simple in process, direct extrusion can produce more intricate shapes at less cost, which is why direct extrusion can be favoured over indirect extrusion in manufacturing.

What is Indirect Aluminium Extrusion?

For indirect extrusion, instead of the billet moving, it stays stationary while the ram moves the die. Less heat and pressure are required during the indirect aluminium process, allowing higher ram speeds and improved extrusion ratios

The Benefits of Indirect Aluminium Extrusion

Indirect extrusion, also known as backward/reverse extrusion, has multiple benefits, including:

  • Decreased extrusion loads
  • No temperature increase affects the billet surface
  • Uniformed metal flow leads to fewer defects or coarse grain ring zone
  • No friction between the billet face and the tolling leads to a longer tolling lifespan
  • Consistent extrusion during constant exit temperatures
What Are Aluminium Extrusions Used For?

Aluminium extrusion is utilised across various industries, mostly to create solid bars, rods, or hollow/semi-hollow tubes. The general demand for extrusion solutions is attributed to the strength and precise design capabilities they can generate.

Typically, we see the three following extrusion shapes:

  • Solid – No voids or openings
  • Hollow – Large voids or openings
  • Semi-hollow – Partially enclosed voids or openings

But within these three general specifications, shapes can conform to any design given to the die. Various aluminium extrusion shapes are used for numerous purposes, including:

The high strength-to-weight ratio makes extrusion ideal for:

  • Engine blocks
  • Roof panels
  • Car chassis
  • Train, car, and boat structural components

Aluminium extrusion resists distortion from weather and building movement. Extrusion components can also spring back from the shock of impact while still retaining their strength and flexibility.

Common in construction includes variations of t-slot and v-slot aluminium extrusion, while you can purchase specific sizes of extruded components such as 4080, 4040, or 2020. 

Aluminium extrusion has high density and reflective characteristics, so it works well to protect things from light, radio waves, and radiation. Applying an electrochemical process will also add durability and prevent corrosion.

Aluminium extrusion is utilised across various industries, mostly to create solid bars, rods, or hollow/semi-hollow tubes.

Aluminium Extrusion Joining Methods

Aluminium extrusion methods can range in complexity and size for creating structures, involving the flowing solutions:

  • Screw port
  • Snap-fit
  • Nut crack
  • Corner cleat
  • Hinge
  • Interlocking

Each aluminium extrusion joining method is unique to the specific design of the extruded profile. When producing aluminium extrusion profiles, directly or indirectly, it’s worth creating one or two extrusion profiles that you can join together later.

Speak to an Expert Manufacturer in Aluminium Extrusion

Barton International is proudly founded upon over 100 years of combined experience from Midlands-based manufacturing while utilising the best global and low-cost partners to supply our metal formwork solutions.

We offer expert aluminium extrusion services for our clients, with specialist support and advice provided throughout the process.

So, if you’re interested in our aluminium extrusion solutions, get in touch today. Your enquiry will be handled by a designated project manager, offering you technical support and guidance throughout the process.

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