Aluminum extrusion -similar to plastic extrusion, injection molding, is one of the most popular manufacturing ways for the manufacturing industry. As a traditional on-demand part manufacturing company, we accumulate huge experience in profile extrusion. In the following guide, we are going to go through everything about this manufacturing process. It will help you when you want to look for customized aluminum extrusion specialized knowledge or services. If you have a solid project and want to talk to a supplier, then you can talk to RapidDone. We are willing to serve with efforts to provide all the solutions to meet your expectation.
Extruded aluminum profiles are shaped depending on their application, and the most common shapes to be manufactured are as below seven types.
At RapidDone, we are able to make all of these types due to our stronger customized manufacturing capabilities.
This extruded profile consists of a solid circular shape and it’s usually manufactured with small diameters with a maximum of 3,5 inches, the die used is very simple, which makes this a relatively easy and low-cost process.
Solid profile shaped as a rectangle or a square that is easy to manufacture. Its main application is to provide smaller aluminum pieces to minor industries.
aluminum round tubing is very popular in the construction and power industry. It consists of a circular (or oval) hollow shape. A wide variety of inside and outside diameter combinations can be found.
Same as the round tube but it has a rectangular hollow shape that may or may not have rounded edges. It is used in structural applications and as machine component support.
A T-slotted profile is a rectangular or squared profile that is optimized for maximum rigidity while being as light as possible. Some of the most popular T-slotted profiles are the 80/20 and the 40/40 which are used in industrial applications and as a frame part for CNC equipment, 3D printers, work tables, and many others.
Angles are very popular for industrial applications and they come with sharp and round edges and a wide variety of degrees, it all depends on the design specification.
Also known as the double angle profile, zee bars are used in construction applications for both indoor and outdoor environments. These profiles are also found as part of various frames and machine components.
Extrusion dies for aluminum are thick disks usually made of steel that contain one or more openings shaped like the desired profile. The steel they’re made of is heat-treated to withstand the high pressures needed for an efficient extrusion process.
Since extrusion dies are designed to support immense loads, they are built to be durable but need a constant inspection to ensure the optimal tolerances of the extruded profile. A direct inspection routine, as well as constant measurement of the profiles extruded, is needed to maintain the highest quality in the extrusion process.
The die used to obtain a solid profile is different from the one used for the manufacturing process of hollow profiles.
A solid profile die is composed of four parts or plates. The feeder plate, located at the front of the die, has two orifices to control the flow of aluminum.
The following part is known as the die plate, which contains the profile shape and behind it, the backer plate is located, which is thicker than the two firsts and has a similar pair of orifices that prevent the failure of the created profile during long extrusions.
The bolster plate is located at the end and it’s the thickest of all four because its purpose is to support all the pressure needed in an extrusion process.
Hollow and semi-hollow profile dies are composed of three plates.
The first one is known as the mandrel controls the flow of metal and it generates the inner features of the profile.
The second plate is known as the death cap and it has the shape of the profile.
The last one is the thick bolster plate, which is responsible for supporting the extrusion load.
Aluminum is one of the most used materials in the extrusion process because of its convenient mechanical properties. Aluminum is not a hard material, this characteristic reduces the force required at the piston, making it possible to use smaller machinery that consumes less power.
For extrusion, the favorite alloys to be extruded are part of this 6XXX series, including aluminum 6061 and aluminum 6063. Its composition has higher percentages of magnesium and silicon, enhancing aluminum’s mechanical properties.
These series have high strength, and corrosion resistance, and are very popular because they are heat-treatable, meaning that their mechanical properties could be improved after the extrusion process.
After the extrusion process, aluminum profiles are most likely to be heat-treated inside an oven to increase their strength.
To run a proper extrusion process for aluminum alloys these eight steps need to be taken into account at RapidDone.
Before starting an extrusion process, the correct die (usually made of steel alloy) is selected or designed to match the customer’s cross-sectional requirements. After the selection phase, the die is then placed at the end of the container.
Since extrusion is a mass-production technique, it’s crucial to periodically inspect the condition of the dies to ensure the quality of the product.
Each aluminum alloy needs to be configured depending on the cross-section desired. Piston force, also known as ram force, and its correct displacement must be selected to obtain a better product.
In a direct extrusion process, the ram forces are higher due to the friction effect between the billet and the container walls. For aluminum alloys, piston forces range between 800 and 2000 tons.
Large cylinders of aluminum, known as billets are placed inside the container. These billets come in different diameters ranging from eight to sixteen inches.
The alloy must be chosen before starting the process and, in the case of hot extrusion, its temperature needs to rise inside a hoven until it reaches aluminum’s crystallization point (between 450 and 500 °C for most aluminum alloys).
When the heating process is over, and the aluminum has reached a plastic state that allows it to easily flow through the die, the billet is fed to the extruder.
To reduce friction and avoid the creation of aluminum slag, a lubrication system applies fluid to the cylinder. When hot extruding, glass may be used as a lubricant, in other cases, oils and grease are used.
Selecting the proper lubricant, it’s important to avoid excessive pressure levels and residual stresses on the final product.
After everything is ready, the extrusion process begins. The piston pushes the aluminum billet into the die (direct extrusion) plastically deforming it to obtain the required cross-section.
The entire process is monitored using the latest technologies to increase its efficiency of the process. Monitoring extrusion data allows us to create extrusion recipes saving time and money in future projects involving the same alloy and die.
After exiting the extruder, billets are grabbed by the puller, guiding the profiles through the run-out table, where a series of fans will start to cool them.
In some cases, water quenching techniques need to be applied to improve the mechanical properties of the profile. Water causes the aluminum to shrink, so an additional stretching process is performed to achieve the proper dimensions and tolerances.
The long aluminum profiles are then cut into pieces of 20 ft. or less using an automated table saw. They are stacked and loaded into carts to continue with the aging process if needed.
After the cooling process, aluminum is in a T4 tempered state. In some cases, when better mechanical properties are required, the aluminum is sent back into an artificial aging oven, where the aluminum gets a T5 or T6 temper hardness.
There are several processes that could follow aluminum extrusion, the most remarkable are:
Probably the most common secondary process, cutting is achieved by using a metal saw or an EDM process to match the length of the profile to the one specified based on its application, this is done because most profiles are extruded to standard lengths that might be longer than what is needed.
A grinding process is done to change the appearance of the profile or to remove any superficial imperfection.
Profiles are frequently welded together, especially when working in the construction, naval and automotive industries.
CNC machining is less likely to be performed on extruded profiles. Drilling and tapping are the most common of all CNC processes but mills and CNC punch presses are also used, it all depends on the pattern required and the profile’s application.
At RapidDone, we hold some precision CNC machines including 3-axis CNC machining and 5-axis CNC machines, we can take post-processing operations precisely according to your exact specifications. Please talk to our CNC manufacturing team if you have customized requirements.
Tolerances are the deviation or variation limits in which a part can be produced and are usually agreed upon by both manufacturer and designer before starting the manufacturing process. Specification of tolerances is needed because no dimension or measurement is exact, and it depends on both machinery design and human factors. These deviations are controlled by international standards to diminish manufacturing errors.
The extrusion processes are known for their close tolerances, which have been previously approved by international technical committees. Since the process involves the use of a matrix or die, the latter can be designed with a specified tolerance so that, after the aluminum flows through it, its shape has the same tolerances as the die. In an extrusion process tolerances as close as +-0.004 are achieved.
Being able to adjust tolerances to such a minimal value allows for better designs focused on weight and cost reduction.
At RapidDone, we follow the standard general NADCA tolerances. However, if you have a high precision requirement for your customized project, you can talk to our team, and our service team can come back to you quickly.
For most applications, a surface finish must be applied to extruded aluminum parts to enhance their duration and reduce the risks of suffering from corrosion. Surface finishes may also be applied to hide extrusion stripes generated by friction, which in most cases are seen all over the surface of an extruded profile, especially when the die needs to be replaced.
It includes techniques such as grinding, polishing, and tumbling. These surface finishes are used to improve the surface quality and to obtain even the closest tolerances if needed.
This anodizing process increases the aluminum oxide layer present on extruded surfaces. The main objective of the anodization is to enhance corrosion resistance but it makes the surface more durable, provides electrical insulation, and may also provide a decorative glossy finishing with a lot of different colors.
It is the most popular finishing for extrusion parts. At RapidDone, more than 80% of extrusion parts are with anodizing finishing. Therefore, we have rich experience in this for getting a good anodizing project.
Powder coating is used to apply any color desired to the surface and it also improves corrosion resistance, UV rays protection for outdoor applications, and also increases abrasion and impact resistance.
Other secondary surface finishes may be applied such as screen-printing and reflective coating, the surface finishing selection depends on the application of the extruded profile.
No manufacturing process is perfect; they all have their flaws. Based on our manufacturing experience, we list out typical defects below for these processes.
The extrusion process requires compressive forces and relies on friction to re-shape the aluminum and if excessive forces are applied small blisters tend to appear on the profile’s surface, affecting its mechanical properties and its overall performance.
When these blisters appear the extrusion is classified as deficient and the process needs to be checked to adjust its settings.
Another flaw related to the extrusion process is surface streaking, which affects corrosion resistance and mechanical properties. There are plenty of reasons pointing for the presence of streaks in aluminum profiles but one of the most common is “carbon marks” which caused an increase in friction related to a worn-out extrusion die.
Excessive lubrication, aluminum oxide on the container wall, and differences in cross-sectional wall thickness are also related to the existence of surface streaks.
One way to avoid the appearance of streaks is maintenance. Changing the extrusion die before it wears considerably, checking the lubrication system, and cleaning the extruder after a series of extrusions prevent surface streaking. In most non-extreme cases, anodizing will remove streaks and other surface damages.
The high stresses supported by the aluminum billet cause are the main cause of center burst, which is perceived as the billet’s internal cracking. Centerburst is an imperfection less likely to occur on aluminum extrusions due to the low hardness of the material and its ductility.
Ultimately, extruded aluminum may also suffer from thermal distortion. Distortion is also a consequence of friction, especially when the profile has thin hollow features. Like most metals, aluminum expands due to temperature rises, and not providing an adequate cooling environment are the main cause of thermal distortion.
Extruded aluminum is often heat-treated to enhance mechanical properties and one of the most common heat treatments applied is water quenching, which causes the metal to shrink. An improper water quenching process, when applied to long extrusions, will most likely cause distortions that are mechanically treatable with an additional stretching process.
To improve the aluminum extrusion, and process any profile, we recommend following the next tips:
1. Inspect the extrusion die constantly; a damaged die could result in poor surface finishes and tolerances for the profile.
2. Make sure of testing your machine configuration before starting the production process on a new profile, this will avoid damaging your equipment and reduces costs and manufacturing time.
3. Monitor extrusion data for each material and profile. Possibly you’ll need to extrude the same combination of profile and material, having a working configuration stored will reduce testing time
4. If you’re a customer, clearly specify the material and application of your extruded profile to the manufacturer. This is done to inform him if any surface finishing or heat treatment is needed.
5. To avoid distortion, try not using thin hollow sections and make sure that any heat treatment is properly applied by providing an adequate heat-transfer atmosphere.
Extrusion is a bulk deformation process in which the raw material, such as aluminum, is forced to flow through a die opening with the desired dimensions and cross-sectional shape. It is similar to what happens when we squeeze toothpaste out of a tube before brushing our teeth.
In this process, a gradual compressive force acts either on a piston or a cylinder. The cylinder contains the aluminum to form a larger version with its cross-section modified by the die. This process allows for obtaining both hollow and solid cross-sections.
To achieve the extrusion process different techniques are used. Two physical configurations allow us to classify extrusion as direct or indirect based on the location of the die.
When you place the die in the container the process is known as direct extrusion and, if the die is located on the piston, an indirect extrusion process is taking place.
Another way to classify it is as a cold, warm, or hot process based on the working temperature of the raw material.
Last but not least, aluminum extrusion is also classified as discrete and semi-continuous.
Discrete refers to impact extrusion, in which shorter pieces are created from a single piece of raw material applying an impact force. Semi-continuous refers to a process in which a constant force is applied to a large piece of raw material, and it is used to obtain larger profiles.
Extruded aluminum profiles are used in a wide variety of applications for their low weight, corrosion resistance, and decent mechanical properties. Also, extrusion is quite a simple process, making it easier for customers to obtain their product for a lower price, compared to other manufacturing processes.
The ability to create optimized cross-sections for structural members makes aluminum extrusion one of the favorite manufacturing processes for the automotive and aerospace industry where reducing weight and enhancing the mechanical behavior of a structure increases the overall efficiency of the design. Its corrosion resistance and the wide availability of surface finishes make it suitable for outdoor applications and those that involve direct contact with salt water, such as the marine industry.
Frequent applications for extruded aluminum are:
The answer to this question is mass production. When manufacturing for mass production, processes that assure quality are very important to maintain low costs, and even though the initial machinery costs for an extrusion process are high, production costs of extruded profiles are relatively low.
Extrusion and the procedures that follow, when correctly performed, assure the quality by creating profiles with a low dimension deviation percentage.
Another reason to use extrusion processes on aluminum it’s the close tolerances achieved. Fine tolerances are important when manufacturing profiles to be used as machine components.
Aluminum alloys offer a series of benefits and extruded aluminum profiles combine these benefits with the possibility of a complete manufacturing process that allows the creation of optimized cross-sections to lessen weight and exploit mechanical properties. Some of the benefits of extruded aluminum are:
Extrusion requires the employment of heavy machinery to achieve the large forces needed to push the aluminum through the die. The size of these machines and their cost are the main limitations of the aluminum extrusion process, reserving it for mass production processes in which the number of products generated achieves an economical balance.
Another limitation is that, so far, no changes in the cross-section such as enlargements or reductions are allowed. The cross-section of the profile remains constant, making it less suitable for some special applications where stress concentration requires a non-constant cross-section.
If you have any questions on Aluminum Extrusion Service, Custom Parts Manufacturing. We will give the professional answers to your questions.