Prototyping Aluminium Extrusion Profiles with 3D Printing

As one of the most established fabrication techniques, it’s not strange to find aluminium extrusion applications all around, from every-day-life to high-end uses.

Releasing an aluminium extrusion part into the market encompasses a multistage development process, typical of mass production manufacturing processes. Therefore, experienced developers strongly recommend prototyping from the early stages to enable a smooth flow between design, tooling, and final production.

For this reason, aluminium extrusion companies are increasingly engaging FDM machines in their prototyping processes to provide more confidence in the design before committing to tooling costs.

This article will point out some of the basic concepts surrounding the development of aluminium extrusions from design throughout mass production. Then, we’ll evaluate why and under what conditions it is worth investing in 3D printing as a prototyping tool.

What is Aluminium Extrusion? Why Use It and Where?

Aluminium extrusion is a forming process where an aluminium billet is pushed past a die mould with immense pressures to shape it into a part with a characteristic cross-sectional profile.

As a material, aluminium has one of the highest weight-to-strength ratios among metals. Its extraordinary ductility makes it an incredibly friendly material to work with in forming, casting and cutting processes. Additionally, aluminium alloys are non-magnetic, and their properties excel at corrosion resistance, high electrical and thermal conductivity and recyclability. For these reasons, aluminium alloys have been one of the favourite options in engineering applications for several decades.

Extrusion processes are highly demanded, given their low costs and fast turnaround times for custom and mass production requirements. The resulting profiles can meet precisions for applications with tolerance requirements as tight as +- 0.1 mm.

Some of the best-known applications for aluminium extrusions are:

• Structural: Widely employed for all kinds of structural frames, common in architectural and industrial settings. Given aluminium’s excellent strength-to-weight ratios, these frames are fundamental in aircraft and land vehicles. It is also worth mentioning that these structures ar common in 3D printer frames!
• Heat sinks: Common in HVAC, electrical and electronic devices
• Highly corrosive environments, namely in the marine and chemical industries

The Aluminium Extrusion Process

Once initial investments are met, this process is relatively low cost and straightforward. Let’s quickly overview its core stages.

1. Preheating: Around 400 to 500 C, but it can alternatively be a cold process
2. Extrusion: An hydraulic ram pushes the billet throughout the die at extreme pressures until the material achieves enough plasticity to flow throughout the cavities (As toothpaste would from a tube)
3. Quenching, cutting, stretching and ageing: At controlled rates to achieve optimal mechanical strengths, relieve internal stresses and achieve higher temper grades.
4. Inspection: Extrusions commonly undergo inspection processes to verify tolerances
5. Post-processing: Extrusions are friendly to many additional techniques like grinding, polishing, painting, powder coating, anodisation and welding.

Die Tooling

Considering the high pressures and temperatures, plus the numerous cycles die tools must bear, they are naturally made of alloys like H13 steel. These tools consist of a stack of round plates with cavities. There’re two kinds of plate arrangements: Solid profile dies and hollow profile dies.

Solid profile dies consist of a feeder plate to control the flow of aluminium, followed by the die plate containing the profile and a backer and a bolster plate to support and protect the other plates from failure. Alternatively, an additional mandrel-cap die set is necessary to produce hollow profiles. Processes like turning, CNC milling, wire EDM and grinding are commonplace in die plate production.

Aluminium extrusion dies offer favourable fabrication costs, ranging between £400 and £4000, within a few weeks lead times. In comparison, tooling costs can generally cost above £10000 and take several months to complete.

An extrusion die receives thousands of tons of pressure, which takes a toll on the die and ultimately leads to failure—having the correct design decisions optimally balances your die’s cost and life.

Design Considerations for Aluminium Extrusion

So, what should you consider in your profile design before submitting it to manufacturing? Thankfully, the range of possibilities for extruded profiles is wide. However, having a clear understanding of design for manufacturing rules is key to a successful and cost-effective product. Before starting an aluminium extrusion production, the following design considerations are essential to know.   

Standard vs Custom

The aluminium extrusion process enables enough versatility to produce many shapes, from the standard profiles (i.e. rod, tube, square, L, T, I, C shapes) to complex custom designs. As designs grow in complexity, developers and manufacturing shops face challenges, escalating risks of failure and increased tooling and extrusion costs.

Solid vs Hollow

As stated before, an additional mandrel-cap plate is necessary to produce hollow features. In terms of costs, solid die costs are around £400-2000, while a hollow one can cost from £1000.

Moreover, there’s a third semi-hollow classification. An excellent example of this is the fin features of a heat sink, and the hollow space between each fin is called a tongue. The tongue ratio is the relation between the length and the thickness of that void area. Issues arise as this number increases. Since we must consider the extreme pressures a die must undergo, the higher the tongue ratio, the result becomes prone to:

• Wavy surfaces

• Die breakage, or at least a shorter life
• The extrusion might have to go slower

An ideal tongue ratio must go below 4:1.

Symmetry

Designers must strive for as much symmetry as possible. The more asymmetric the shape, the higher the unbalanced weight distribution, ultimately causing:

• Die breakage at large mass sections
• Pushing the material slower is also necessary
• Difficulties in holding dimensional tolerances
• Runout surfaces can’t hold flatness specifications
• Bowing in the centre

Wall thicknesses

Some considerations regarding wall thickness are:

• Strive to avoid thin walls
• Wall thickness should be +- 10% of nominal thickness
• Look for walls as uniform as possible. Variable wall thicknesses lead to variable velocities as the material flows through the die.
• Sharp corners are not ideal, but, if needed, budget costs might rise

Tolerances

Tolerance specification is needed because no dimension or measurement is exact, and it depends on machinery design and human factors. For this reason, international standards exist to control deviations and potential manufacturing errors.

The following standard guides enable a clear framework regarding design and tolerance decisions for aluminium extrusion:

• The BSI BS EN 755 standard
• Aluminium association’s Aluminum Standards and Data
• AEC’s Aluminium Extrusion Manual

In some cases, custom designs require to achieve precisions beyond the standard tolerances. For instance, profiles intended to fit interlocking features must deal with tighter requirements. Fortunately, this is possible to achieve. However, it comes with additional corrections, costlier and more time-consuming inspection tasks, slower extrusions and increased rejection rates. In other words, as a design’s customisation level increases, not only does a project become costlier, but also your process becomes highly uncertain.

At the end of the day, communication is vital when it comes to dimensions and tolerances. Unclear communication between designer and workshop leads to costly misunderstandings. Beyond avoiding incomplete drawings and inconsistent dimensioning, it’s highly beneficial to transmit the big picture regarding intended functionality and how the extrusion interacts with other parts so that manufacturers can be on the same page.

Other Considerations

Although alloys are beyond the scope of this article, it’s worth mentioning that alloys composition and temper designations also affect tolerances, extrusion rates, costs and the process in general.

Lastly, the profile size is a crucial factor to take into account. The diameter of a circumscribed circle determines the size of a profile, thus tolerancing and costs.  

How Does a 3D Printer Help?

Knowing the many variables involved throughout the aluminium extrusion development process, it is clear that accuracy is a major concern as the complexity of the design increases.

Investing in prototypes early in the design process enables decision making clarity and smooth bridging into manufacturing. For more information on prototyping, click here.

Prototypes can help you answer the following questions:

• Will my design work the way I thought it would?
• Can I lower my extrusion costs through a design change?

A 3D printed profile is a great way to assess your design and verify whether it’s going to work. Having a physical representation of your design at hand enables you to visualise and quickly identify if any adjustments are necessary before any tooling commitments.

Making assertive changes to the design early on is a great way to prevent tolerancing issues as you go forward. With a 3D printed profile, you can actually feel and test in a real-life setting potential problems that can be unpredictable on paper, such as weight distribution and fits.

Again, communication is of utmost importance. Having a tangible representation of an intended profile is an excellent way of communication between all the parts involved in production.

Recommended Printers for Aluminium Extrusion Prototyping

Thankfully, it’s possible to prototype extrusion profiles with almost any FDM machine. However, investing in a high-quality printer is a must to avoid potential and costly errors. Since tolerances are vital under this context, an ideal printer must excel at dimensional accuracy, repeatability and ease of use.

The following three examples are among the best and most reliable professional 3D printers currently available in the market.

Raise3D Pro 2 Plus

As a larger version of the Raise3D Pro 2 , this machine is designed to run continuously with 24/7 reliability. The Raise3D Pro 2 Plus is equipped with multiple fail-safe systems, such as:

• An integrated battery keeps your print paused and ready to restart after a power brake
• Fast and reliable electronic lifting nozzles
• Best in class 32-bit controller enables fast, smooth and precise movement

Specs:

• Build volume:  305×305×605 mm
• Nozzle: 0.2/ 0.4/ 0.6/ 0.8/ 1.0 mm
• Accuracy: 5 μm repeatability
• Price: £4,499.00 ex. VAT

Bigrep Pro

This machine is all about bulk and size. Equipped with industrial-grade components, the Bigrep Pro can print large parts with outstanding speed and precision. Some of its most notable features are:

• A state-of-the-art Bosch CNC control system
• The Metering Extruder Technology (MXT®) enables further speed and precision
• An enclosed build chamber and temperature-controlled filament chambers

Specs:  

• Build volume:  1020 x 970 x 985 mm
• Nozzle:  0.6 mm, 1.0 mm
• Accuracy:  ±0.2mm or ±0.002mm/mm
• Price: Request quote

BCN3D Epsilon W50

Besides their reliability, BCN3D printers are best known for their IDEX technology, an independent dual extrusion system that enables duplication and mirror mode printing, doubling productivity for the same price. The Epsilon W50 is at the top of BCN3D products. Some of its most notable features are:

• IDEX Technology
• Bondtech Extruder: High-tech dual drive gears
• Hotends optimised and manufactured by E3D

Specs

• Build volume: 420mm x 300mm x 400mm
• Nozzle: Brass: 0,4mm/ 0,6mm/ 0,8mm/ 1,0mm
• Resolution: 1,25μm/ 1,25μm/ 1μm
• Price: £6,575.00 ex. VAT

The team of experts at Solid Print is here to help you. For further information on 3D printed prototypes for aluminium extrusions, please call Solid Print at 01926 333 777 or email info@solidprint3d.co.uk.