Aluminum Extrusion Design Guide

Aluminum Extrusion Design Guide

Aluminium is forced through a die (a specialised tool used to shape material) that has been designed and manufactured to create the desired cross-section. Extrusion can be performed at high temperatures (350°C+) to reduce work hardening or at room temperature to improve surface finish and strength. 

Specifications

Press sizes: 450T ~ 3000T

Minimum order volume: 0.5 ton aluminum for smaller machines, 1.0 ton of 6063 aluminum for larger machines.

Tooling lead time: 2 weeks for small molds, 4 weeks for larger molds.

Post-machining: Full service CNC cutting, threading, slotting, face milling, etc.

Aluminium Extrusion End-to-end Steps

The die is first manufactured from tool steel, typically using CNC machining and/or Electrical Discharge Milling.

A billet of aluminium alloy is heated. The normal temperature range will be 420°C-500°C.

The billet is loaded into the extrusion machine with lubricant to reduce friction in the process.

A high-pressure ram forces the aluminium billet through the machine towards the die.

Nitrogen is introduced and allowed to flow through the die sections creating an inert atmosphere. This increases the lifespan of the die.

The extruded aluminium exits the die in the required shape and passes onto a runout table, followed by a cooling table.

Once cooled, the extrusion is then cut to the required length, typically this is achieved through a sawing process. However, at Get It Made we choose to use wire EDM to ensure a clean cut.

Finally, the extrusions undergo any further processing or finishing if required.

Uniform wall thickness

Keeping the wall thickness consistent ensures a more efficient extrusion, as this will reduce production time and create a cost-efficient product. Varying thicknesses can be achieved but it will add time and complexity to the overall process. Although increasing part cost, by varying the wall thickness you can adjust the mechanical performance of your extrusion in specific locations. It is important to keep in mind that during cooling, variation in wall thickness will result in uneven part cooling, causing potential deformation.

Geometry

When designing a part, try to use simple geometric patterns since the more complex a shape is, the more difficult it will be to force material through an extruder. Having symmetry in the design is also highly recommended, as this decreases peak die stress as the forces are evening distributed. Furthermore try to avoid cavities in your design as cavities significantly increase the die complexity, cost and lead time.

Corners

Adding radii to sharp corners simplifies the extrusion process, since sharp internal and external corners are very difficult to achieve, sometimes requiring additional machining. Corners without radii can slow down production and increase the risk of imperfections. In short, rounded corners will make it easier for the part to be extruded. We recommend adding a radius of 0.5mm to 1mm on all sharp corners.

Occasionally, however, there are times when a corner interfaces with another part and you might therefore need a sharp corner. In these instances, we recommend adding a dogbone style corner, as shown in the image below on the right. This essentially removes a small circle of material from the corner to allow the mating part to interface correctly with the extrusion. We recommend a circle with a minimum radius of 0.5mm.

Channel Ratios

With profiles that have channels (sometimes called pockets or tongues), a basic rule applies in which the ratio between the height and width of the channel should approximately be 3:1, to ensure the die strength is not compromised. The higher the channel ratio, the more difficult it will be to extrude the part.

When using large radii at the channel’s opening, and a complete radius at the base of the channel, an increased ratio of 2:1 can be adopted.

Minimum Wall Thickness 

It is also critical to ensure the wall thickness is not too low. Insufficient wall thickness can cause issues during extrusion such as distortion, incomplete extrusion and increased tool wear.

The minimum wall thickness for aluminium extrusion depends on several factors, however, the most notable factors are the cross-sectional shape and size and the aluminium alloy chosen. The graph below indicates the recommended wall thicknesses for several common profiles based upon the circumscribing circle.

Visual Surfaces

It is recommended to make essential visual surfaces known to the manufacturer, so the part can be created with minimal visual imperfections. Do also consider adding a pattern to these surfaces, as this has the advantage of hiding potential imperfections during the machining and handling of the part.

What Grades Of Aluminium Can Be Used For Extrusion?

The common grades of aluminium used for extrusion at Get It Made are tabulated below. We recommend asking an experienced manufacturer such as ourselves if you are unsure as to the best grade for your project. Below we will compare a few different aluminium grades.

Common Grades    Other Grade    

Aluminium 6063    Aluminium 1060    

Aluminium 1050    Aluminium 3003    

Aluminium 6082    Aluminium 5083    

Aluminium 6042    

Aluminium 6060    

Aluminium 6061    

Aluminium 6262    

Aluminium 7180    

Al6063

This is the most popular aluminium extrusion grade, its fine grain structure allows for complex profiles to be extruded with a smooth surface suitable for anodising. It has good mechanical properties but parts requiring higher strength should use Al6082 or Al6061. It is typically used in architectural applications due to its ability to extrude intricate profiles. 6063A is a variation of 6063 with greater mechanical properties but still retains the smooth surface finish and anodising ability. This alloy is used in road transport, rail industry and more extreme sports equipment.

Al1050

This is a commercially pure grade and is popular in the electrical industry due to its excellent electrical conductivity, corrosion resistance and workability. Its moderate strength, high ductility and reflective finish make it a popular choice for manufacturing heat sinks. It can also be found in the food industry for containers due to its corrosion resistance properties.

Al6082

This is the highest strength 6000 series alloy with great corrosion resistance, often used for structural purposes. However, it is difficult to produce thin-walled, complex extrusions and leaves a less smooth surface finish compared to other 6000 series alloys. It is commonly used for high-stress applications such as bridges, trusses and cranes. This alloy should not be used for decorative extrusions.

Common defects with Aluminium Extrusions 

Conclusion

For more information on Aluminum Extrusion Design Guide, Contact IDEAL whenever you need help assessing the manufacturability of your product designs.