The Process of Aluminium Extrusion Explained Step by Step

aluminum extrusion manufacturingThe aluminium extrusion process is the heating of aluminium and applying enough force to it using a hydraulic ram placed within a shaped opening in the die. Once the extrusion is done, the output aluminium must be cooled, straightened, quenched, and then cut. Extrusion allows the metal to emerge as a longer and lengthier piece without losing its properties.

Are you still not clear about the extrusion process? Well, let’s take an example from everyday life. 

You certainly brush your teeth regularly. To make it happen, you have to squeeze a small amount of toothpaste from the tube into your brush. The focus applied to this squeezing process can be compared to the aluminium extrusion procedure. The constant streaming of the paste creates a round-tip based shape. Similarly, the aluminium extrusion takes a certain die-like shape. Simply changing the die or tip and helps achieve different extrusion profiles. Using a hydraulic pressing mechanism, aluminium can be easily extruded into any type of shape you may imagine.

The Most Common Types of Shapes

Although any type of imaginable form can be achieved through the aluminium extrusion process, the most commonly available variants include:

  • Solid shapes like squares, circles, rectangles etc. to produce rods and bars with cross-sections
  • Semi-solid shapes like channels and angles or anything that comes with partial openings
  • Hollow shapes like squares, rectangles, circles, etc to produce tubes with several cross-sections

Types of Aluminium Extrusion procedures

The aluminium extrusion process can be direct or indirect, depending on the requirement.

  1. Direct Aluminium Extrusion

It is the most popular of the two. Here, a preheated walled container is used for placing the heated aluminium. Using a ram, the aluminium is forced carefully through the die. Remember, strong pressure must be exerted to ensure that the targeted shape is produced.

A dummy material block is placed between the aluminium and the ram during the extrusion process. This is extremely necessary to ensure that both the elements are not being able to make contact with each other.

The process is also known as the Forward Aluminium Extrusion process. The main reason is that the aluminium and ram are moving forward in the same direction during the extrusion process. Once the ram starts to apply pressure, the aluminium starts to get squeezed through the die hole. When done, the heated aluminium output is then cooled down (water quenched), stretched, and then sawn to the required length.

  1. Indirect Aluminium Extrusion 

The functioning of the indirect extrusion press is slightly different compared to the direct procedure. Here, in the indirect extrusion process, the ram and die remain intact in their actual position while the aluminium billet and the container keep on moving together. Remember to use a stem of greater length than the container while using this process. Since the die remains stationary, this approach is the only way to push the aluminium billet through the same. This results in producing less friction compared to direct press.

The indirect procedure ensures better heat controlling capacity due to the production of less amount of friction. The output is also more consistent in terms of product quality due to the steadiness of the pressure being exerted. It also results in achieving better mechanical and structural properties. But that said, the major problem with indirect extrusion press is the limitation in size and less availability of extruders who can manage this process effortlessly.

Direct or Indirect aluminium extrusion process – which one is better?

Of the two procedures for aluminium extrusion, the direct process is more popular. However, the other option proves to be more efficient but not without flaws.

The indirect process is perfect for the extrusion of large-sized aluminium at a faster rate without much wear and tear. So naturally, the chances of die cracking due to production is less. The consistency level is higher and this results in minimal extrusion defects.

But then again, the indirect procedure is not simplistic compared to the direct options available. With the help of direct extrusion, it is possible to produce more numbers of complex shapes. This makes the direct process a more popular option of the two.

Step by step process of aluminium extrusion

The extrusion process may vary from one project to another, based on the specifications. But then again, the basics remain the same. Here are the basic procedures followed:

Step 1: Understanding the profile of the project

This is the first step where customer requirements are discussed. The customer will explain the profile through drawing for the best of the idea. Once the drawing is produced, the extrusion provider will examine the same and see whether it is possible to produce the design while meeting tolerance level and specifications. Once the design is approved, the extrusion company starts preparing the die.

Step 2: The aluminium cutting process

Aluminium metal must be cut into billets for the extrusion process. Billets are nothing but cylindrical blocks of metal.

Step 3: The role of dye

Without the dies, the extrusion process will not commence. So, it is necessary to get the dies produced at the earliest to commence with the extrusion process.

Step 4: Heating the billets

This is a very crucial stage. The aluminium billets are heated in the range of 850 – 925 degree Fahrenheit. Preheating the metal under such a temperature setup results in softening them. However, this heat temperature will not let the metal melt into a liquid state. But do keep in mind that the operating temperature must be static and should not vary throughout the process. An inconsistent operating temperature will challenge the uniformity of the end product.

Step 5: Transferring of the billets

After the heating of the billets, they are carefully placed on the loader and then lubricated to ensure that they do not stick to the extrusion equipment.

Step 6: The final extrusion  

Once the billets are placed at the loader, they undergo the final extrusion process (most commonly, direct extrusion). In this process, one end of the billet is pushed by the ram to ensure that the other end is forcefully extruded through the die. Once the entire billet is pushed through the die, they are cooled down before sending for additional processing steps like straightening, heat treating, surface finishing, stretching, work hardening, and cutting.

What's the future holds in store for the aluminium extrusion industry? 

Aluminium extrusion is an extremely popular and effective way to reshape the material for use in different industries. There are limitless possibilities available in regards to the utilization of the extruded aluminium alloy in the manufacturing of different industrial and commercial applications. Therefore, it can be said that the future holds bright prospects for this industry and the process of extrusion will only improve with time.