In recent years, aluminum extrusion has been a key aspect of product innovation and production. It's an important part of our daily lives, as manufacturers use this process to create various components for homes, workplaces, and more.
Although extruded aluminum parts are used everywhere, they are rarely noticed by many. Due to its remarkable properties, aluminum extrusion technology is used in various industries. This article discusses aluminum extrusion technology, its techniques, advantages and disadvantages, and important extrusion design considerations. Let's start!
What is aluminum extrusion?
In the aluminum extrusion process, aluminum alloy is heated and pressed through a die with a prefabricated cross-section shape. A solid ram pushes the aluminum through the die and pulls it along an exit table during the process. Typically, you can change the die opening to create different shapes and sizes according to your product specifications.
This process is a simple technique; It's easy to understand on a basic level. The force used in aluminum extrusion is similar to that used to squeeze a tube of toothpaste with your fingers. Furthermore, the extruder nozzle has a similar function to opening a toothpaste tube. The extrudate is a long, solid extrudate because the opening is a solid circle.
Various aluminum extrusion techniques
There are two main techniques for aluminum extrusion: direct and indirect extrusion.
Aluminum direct extrusion
This is the most commonly used technique for aluminum extrusion. The aluminum extruder places the heated billet/aluminum into a container with heated walls while a moving ram forces the metal through the die opening. This step creates high pressure.
Additionally, machinists typically place blocks of material between the heated aluminum (the block) and the ram to prevent them from coming into contact. Most suppliers and manufacturers refer to this technique as a forward/forward extrusion process because the aluminum and ram advance in the same direction.
Indirect Aluminum Extrusion
Indirect or reverse extrusion is completely different from the direct technique. In this process, the heated aluminum and the container move simultaneously while the die remains in the same position. Machinists often use a “stick” for this process. The length of the rod must be greater than the length of the container. Therefore, the rod pushes the aluminum block through the stationary die.
Reverse extrusion creates less friction compared to the forward extrusion technique. It has better heat regulation. This result may be due to the applied force being relatively constant. Furthermore, the constant temperature guarantees better grain structure and better mechanical properties. Therefore, the product quality for indirect extrusions is generally reliable.
What shapes can be extruded?
The aluminum extrusion process offers unlimited possibilities in terms of formats, available in different specifications and sizes. Extrusion is an essential part of several industries; therefore, it is very difficult to list all the species. The main extrusion categories include:
- Hollow molds : Shapes such as tubes or profiles with different cross-sections (i.e. rectangles, circles, squares, etc.)
- Semi-solid shapes : These shapes include channels, angles, and other partially open shapes.
- Solid Shapes : This includes solid rods and rods with different cross-sections (i.e. squares, circles, rectangles, etc.).
- Custom aluminum extrusion profiles : These types of shapes often have multiple extrusions. They can also be interlocking shapes with various color profiles. These shapes correspond exactly to the designer's specifications.
A step-by-step guide to the aluminum extrusion process
Step 1: Prepare the extrusion nozzle
The first step is to make a round die or use an existing one if available. Preheat the die to exactly 450-500°C before starting the extrusion process. This ensures the metal passes through evenly and maximizes die life. After the preheating process, you can insert the die into the extruder.
Step 2: Preheat the aluminum block
Next, the cylindrical block is cut from a stretched log of material and then preheated in an oven to 400-500°C. This technique prepares the block and makes it malleable for the process. She guarantees that it didn't melt.
Step 3: Move the block to the extruder
After preheating, transfer the block mechanically to the press. However, add lubricant before loading the block into the press. Also, be sure to apply a release agent to the press ram. This helps prevent the pad and stamp from sticking together.
At this point the moldable block is ready in the extruder. Here the hydraulic cylinder can exert a pressure of exactly 15,000 tons. This pressure presses the malleable block into the container. The aluminum material expands until it fills the walls of the container.
Step 4: Press the extruded material against the die
The aluminum material that fills the walls of the container is pressed against the extrusion die. You must continually apply pressure to the material. Therefore, the extruded material exits the die opening fully formed.
Step 5: Temper Extrusion
A puller grabs the profile and holds it in place after it comes out of the press. It protects the profile when leaving the press while the alloy goes through a “tempering” process as it passes through the table. The profile cools evenly in a water bath or with a fan.
Step 6: Cut the extrusion to the length of the table
Once the aluminum profile reaches the entire length of the table, cut it with a hot saw. However, keep in mind that temperature is critical at every step of the extrusion process. Despite the tempering process, the profile does not always cool completely.
Step 7: Let the extrusion cool to room temperature
After the shearing process is complete, the profiles are taken from the delivery table to a cooling level. The profiles remain there until they reach room temperature. Once they reach room temperature, stretching begins.
Step 8: Transfer the extrusions to the stretcher and stretch them in the correct orientation
At this stage you will discover certain kinks in the shape of the extruded aluminum that need to be corrected. It would be helpful if you had a tensioner to fix these kinks. Manually hold each profile at different ends while pulling until it is completely straight. This process helps adapt the extrusion to the desired specification.
Step 9: Transfer the extrusion to the target saw and cut to length
Now that the extrusions are completely straightened and hardened, you can place them on the saw table. Then cut the extrusions to the desired length. These lengths are generally between 2.4 and 6.4 meters. After the sawing process is complete, place these extrusions in the oven so that they reach the correct hardness (T6 or T5).
Step 10: Perform secondary operations (heat treatment, manufacturing and surface finishing)
After the extrusion process has been completed, it is possible to improve the properties of these profiles through heat treatment. After heat treatment, consider manufacturing extrusions if dimensions need to be corrected. Additionally, adding surface finishes helps improve the aesthetic appearance and corrosion resistance of extruded aluminum.
What factors affect extruded aluminum?
Although the extrusion steps of the aluminum extrusion process explained above seem simple and automated, these steps can be very complicated. The extrusion process is quite complex and depends on the relationship between numerous parameters that need to be managed. This includes the following:
1. Extrusion speed
In general, the extrusion speed is directly proportional to the temperature in the container and the pressure of the metal. To maintain a stable process and provide a consistent extruded segment, speed, temperature and pressure must be properly correlated.
2. Extrusion ratio
The extrusion rate of a mold is an indicator of the amount of mechanical work performed during the extrusion process. When the extrusion rate of a section is relatively low, the minimum mechanical work is performed in those areas of the mold where the greatest mass of metal is involved. On the other hand, if the extrusion rate is high, more pressure will be required. Pressure is used to push the metal through small openings.
3. Billet temperature
Optimal billet temperature ensures proper surface conditions and acceptable tolerances. It also guarantees the shortest possible cycle time. It is always preferable to have the lowest possible temperature for ingot extrusion. Very high temperatures cause the metal to flow more freely. Metal can resist entry into tight areas. Therefore, mold dimensions may be outside of specified tolerances. Likewise, high temperatures can cause metal to crack at thin edges and sharp corners.
4. Extrusion press
Due to variation in extrusion, weight per foot plays an important role in aluminum extrusion. As expected, extrusion of lighter parts requires smaller presses. However, larger capacity presses may be necessary for other reasons.
A common example is a larger, thin-walled hollow mold. Despite the low weight per foot, the required pressing force of the extruder can be higher. The effect is similar to that of extrusion rate. A higher factor makes the part more difficult to extrude. This, in turn, has an impact on press production.
5. Extrusion molding
The shape determines the complexity and cost of extruding a component. The aluminum extrusion process can produce a variety of shapes, but it has some limitations. For example, simple solid shapes can be extruded much more easily, quickly and economically than semi-hollow shapes. The more complicated the shape, the more difficult and expensive the extrusion will be.
After successfully completing the extrusion and tempering processes, you must also carefully and accurately monitor these parameters:
- Product dimensions and tolerances
- Macrostructure of bars/tubes/profiles
- Surface Finish
- Mechanical properties
- Other special quality aspects
Post-treatment options available for extruded aluminum
Post-treatment options for extruded profiles help improve their properties. These are some of these possibilities:
Heat treatment process for metals
To improve tensile strength and yield strength, you can heat treat aluminum alloys of the 5000, 6000 and 7000 series. To do this, you need to place these profiles in furnaces where they age quickly.
Mechanical machining
Machining extruded aluminum is not a one-size-fits-all process; is a series of methods that help improve the surface of extruded aluminum. This includes cutting, polishing, sanding and grinding. Unlike chemical applications, you must use abrasives to apply mechanical force to the aluminum surface and smooth it. This helps improve the surface and prepare it for another finishing operation.
Surface treatment
Aluminum bars can be subjected to different surface treatments. This can improve the appearance of these extruded profiles and their corrosion resistance.
●Anodizing
Anodizing is a process that strengthens the naturally existing aluminum oxide layer. This is done by improving its corrosion resistance. Additionally, anodizing aluminum makes the metal more wear-resistant, strengthens surface emission, and creates a porous surface that can absorb various dyes.
●Painting
Manufacturers often paint extruded profiles for aesthetic reasons. However, this also helps to extend the service life and reduce maintenance costs. You can also paint extruded aluminum profiles in different colors to protect them from corrosion.
● Rays
Sandblasting helps remove residue and scale that remains on a machined component after heat treatment. This process adds texture to the surface while removing other contaminants that may remain after heat treatment. Blasting facilitates other work steps, such as processing and painting, and gives your extruded aluminum profiles an aesthetic, matte finish.
Advantages and disadvantages of extruded aluminum profiles
Most manufacturers prefer the aluminum extrusion process over other production methods because it offers an exceptional combination of strength and light weight. However, from an industrial point of view, the aluminum extrusion process offers additional advantages. Here are some of those benefits:
- Extruded aluminum is typically stiffer and stronger.
- Low industrial costs.
- High flexibility of use.
- They generally represent an economical and competitive manufacturing option for machining complex cross sections.
- Extruded products have a perfect surface finish and are more stable than those made from cast aluminum.
However, it is important to note that despite its enormous advantages, the aluminum extrusion process also has some disadvantages.
- Aluminum extrusions are generally limited by the capacity of the extrusion press' steel container.
- The extrusion die is often exposed to harsh working conditions such as high temperatures and friction, causing rapid wear. This often affects the strength and life of the mold.
Applications of Extruded Aluminum Parts
The material's properties make aluminum extrusion an effective and efficient manufacturing process for many industries. The material's tensile strength and strength-to-weight ratio make it perfect for extrusion of transmission housings, vehicle chassis, engine blocks and many other important parts.
Aluminum extrusion plays an important role in the production of nuclear reactors, cooling devices in electronics, air conditioning systems and condenser tubes. Extruded aluminum has non-magnetic properties and is therefore suitable for residential cables, coaxial cables and aluminum housings.
Furthermore, this aluminum material is ideal for outdoor applications due to its resistance to corrosion and rust. It is important to note that aluminum profiles have high reflective properties. This makes them ideal for protecting products against infrared radiation, light and radio waves.
Custom Extruded Aluminum Parts in Small Quantities at WayKen
Concluding
Aluminum extrusion is an economical production process that can produce various products with different shapes. This process can be used to produce various simple or complex shapes with excellent product properties. You can create 8- to 25-foot profiles that can be fabricated, heat-treated, and finished with finishing options to best meet your product specifications. However, for best results, you must carefully follow the extrusion steps and design tips.
Common questions
Which aluminum alloys are suitable for extrusion?
6063 aluminum is ideal for the extrusion process. However, 6061 is generally stronger. Therefore, if strength is a key requirement for an application, the 6061 is the appropriate choice between the two.
What factors affect the cost of aluminum extrusion?
The crucial factors that affect the cost of aluminum extrusion are die and tooling costs, ongoing aluminum costs, labor and production costs, surface finishing and secondary operations, and production volume.
Which aluminum is best for extrusion between 6061 and 7075?
Both aluminum alloys are suitable for extrusion because they are heat treatable. 6061 aluminum is best suited for extrusion due to its high thermal conductivity. Although 7075 is much stronger than 6061, it melts quickly at lower temperatures.
