Knowledgebase

On this page, you can find all kinds of general and specific information about aluminium and the associated standards and options.

What is aluminium?

Aluminium is one of the most widely used metals in the world and is characterised by a number of favourable properties:

• It is lightweight, yet strong at the same time. This helps to reduce CO2 emissions in, for example, the transport sector.
• It is very malleable and therefore offers unique design possibilities.
• It is easy to make corrosion resistant.
• It is suitable for (highly) decorative applications.
• It is easy to process mechanically (machining, deforming, joining).
• It has good conductivity of heat and electricity.
• It is 100% recyclable.
• It is present in large quantities. About 8% of the Earth’s crust contains aluminium.

Although aluminium is produced in a number of different product forms, such as cast products and rolled products, ALUDEX focuses almost entirely on extrusion products, i.e. aluminium profiles.

Extrusion

Aluminium profiles are extruded. In this extrusion process, part of an aluminium pole, the so-called billet, is pushed through an extrusion die with great force; also called pressing. The desired aluminium profile is made on the basis of the openings that have been created in the relevant die.

The manufacturability and price of your aluminium profile mainly depend on these factors:

• The size of the profile (see our press diagram)
• The number of enclosed rooms in the profile
• The chosen aluminium alloy
• The desired surface treatment
• The desired profile tolerances
• The quantity per order and per year

Below you will find a brief overview of our extrusion options:

Press diagram

We are happy to help you with your design choices so that you always achieve the optimal result.

Extrusion dies

Aluminium profiles are made by pressing an aluminium pole, the so-called billet, through an extrusion die. Let’s call it: “the spaghetti principle”. In this process, in addition to this billet, the die plays a crucial role.

The extrusion die is a large tool steel disc (or discs) in which the cross-section of the aluminium profile to be made has been cut out using spark erosion. We distinguish between 2 die types here:

• Solid        meaning there are no enclosed chambers (e.g. an L profile)
• Hollow      meaning there are one or more enclosed rooms

To make a hollow profile, the aluminium must first be guided over a core via a bridge, before it passes through the disc with the outer contours.

The enormous diversity of design options when making aluminium profiles has resulted in the demand for profiles increasing enormously in recent years.

Did you know that…?

Extrusion die costs are one-time

• In other words, as soon as you have had a die made by us, the costs for follow-up dies will be for our account. A subsequent die will be created as soon as the existing die approaches the end of its technical life. This means that the profile is reaching the maximum tolerances, due to the wear of the die.
• In some cases, there are no extrusion die costs at all. This is especially in the case of large purchases and with standard profiles.

You have the exclusive right of use

• If you have had an extrusion die made by us, then that is your die. That is to say: you have the exclusive right to use the die in question. No extrusion is allowed on this die for anyone else.
• However, the physical property remains with ALUDEX. So, unfortunately, you can’t take the die with you, because they are made specifically for our presses and because we want to keep certain technical features in-house. As an aside, this is standard practice for all extruders.

The price for an extrusion die is determined by:

• The size of the profile. A large profile is made using a large die, which needs more tool steel and therefore has a higher cost.
• Which press is used to extrude the profile? A large press requires a large extrusion die and vice versa.
• The number of enclosed rooms in the profile. An enclosed chamber means a core in the die. The more cores, the higher the cost of the extrusion die.
• The complexity of the profile and thus of the die.
• The technical and economic lifespan of the die.
• Is it a so-called multi-cavity die or not? If a profile is (very) small, or rather: light, it may be necessary to have several profiles come out of the die at the same time. As a result, several openings (cavities) have to be created, which increases the cost of the die.

Alloys

By far the most common alloys used for aluminium profiles come from the so-called 6000 series. This range of alloys contains silicon and manganese as alloying elements, making the material ideally suited for extrusion.

The composition of the alloying elements determines the properties of the aluminium profiles. The amount of the elements silicon and iron is decisive here. The more of these elements in the alloy, the stronger and harder the alloy will be, but also the lower the productivity will be and the less the profile will be suitable for decorative anodising (see surface treatment).

The composition of the various aluminium alloys is laid down in the standard EN 573-3:2019.

Source: EN 573-3:2019

The corresponding mechanical properties are as follows:

Anodising

Anodising is the application of an oxide layer on the aluminium surface by means of an electrolytic process. This oxide layer is not a coating but is part of the aluminium (profile) itself.

What does anodising do?

• An increase in corrosion resistance..
• An increase in scratch resistance.
• Creating a beautiful, even and decorative surface.
• Creating an electrically insulating surface.

During anodising, an aluminium oxide skin is applied in an electrolytic manner. This anodised layer not only provides a hard and wear-resistant surface but also gives the aluminium an even, decorative colour. Because we optionally offer sandblasting for anodising or extruding with liquid nitrogen, we can also provide you with a (high) decorative surface quality. In addition, colour anodising or hard anodising is an option.

In order to obtain extra high surface quality, there are a number of mechanical pre-treatments to ensure that the aluminium to be anodised has virtually no irregularities or gives it a certain look (such as the stainless steel look).

In addition to obtaining the desired “finish”, the surface quality or look, the layer thickness is important. The rule of thumb is:

Our anodising lines meet the highest quality requirements, including Qualanod.

Qualanod is an international quality label that has extensively laid down the process and product requirements. The product requirements include:

• Layer thickness
• Sealing test
• Acid test
• Visual test (structure, colour)
• Light reflection
• Corrosion test
• Hardness test
• Scratch hardness
• Electrical conductivity
• …and other tests

Process requirements include:

• Cleaning
• Pickling
• Anodising
• Sealing
• …and other processes

A copy of the Qualanod standard can be downloaded here

Powder coating

Powder coating is the application of a polyester or epoxy layer on the aluminium surface by means of an electrostatic process. It is therefore not part of the aluminium (profile) itself, but it is an applied plastic layer.

In this electrostatic process, the object to be coated is electrically grounded and the powder paint is sprayed (atomised) onto the object via an air mixture. The powder is electrostatically charged as it leaves the spray gun. These powder paint particles can now be attracted to the grounded object, settle on it and stick to it, as it were. The object with the powder coating then enters an oven set at 140°C to 220°C. During the heating phase, the solid powder coating particles first change to a liquid (paint) form, after which it becomes viscous at increased temperature and finally hardens into a solid paint film.

The processing of a metallic, flakes, chrome look, blank, candy and hammertone is also possible with powder coating.

Our coating lines also meet the highest safety and quality requirements, such as Qualicoat. Qualicoat is an international quality label that has extensively laid down the process and product requirements. The product requirements include:

• Layer thickness
• Adhesion
• Bend test
• Impact test
• Salt spray test
• Filiform corrosion test
• Scratch hardness
• …and other tests

Process requirements include:

• Storage materials
• Pre-treatment
• Coating
• Drying
• Handling
• …and other processes

You can download a copy of the Qualicoat standard here