Production Process of Custom Aluminum Extrusion

Custom aluminum extrusion is a process whereby a manufacturer takes aluminum and shapes into different sizes and shapes with cross-sections that meet the exacting specifications of clients’ applications.

Typically, the manufacturer speaks with the clients and gets a comprehensive list of specifications then selects an aluminum alloy and prepares it into a billet ready for heating and pressing through a mold opening to give it a profile the client will find useful.

Upon extrusion, the profile is cut to desired lengths and then put through post processing including machining, finishing and quality control to ensure it meets clients’ specifications and universal standards for tensile strength, hardness, corrosion resistance and other properties.

Therefore, the production process of custom aluminum extrusion takes raw aluminum and turns it into a client-specified shape with a uniform cross-section as required by their application.

Steps Involved in Custom Aluminum Extrusion

Here’s a look at the key steps manufacturers use to turn aluminum into specific shapes with desired cross-sections.

Design and Engineering

Most aluminum extrusion shops provide ready-made pieces for various construction and engineering activities. However, there are some who also offer custom extrusion services.

They welcome requests from clients and develop computer models or technical drawings of the shapes as specified by the client. These designs help capture the dimensions, tolerances, finishes and other special features as described by the client.  

Technical drawings and CAD models also allow the manufacturer to perform technical feasibility tests to check if the profile you have in mind is structurally stable and meets safety standards.

Once they are done with the tests, they’ll optimize their extrusion process, based on the design, to ensure efficiency and reduce production costs.

Die Assembly

Most extrusion presses come with ready-made dies, meaning if your specifications match any available die the manufacturer can begin making your aluminum extrusions right away. However, if your profile is too complex for the available die assembly, one will be created from steel or aluminum material just for the project. Dice crafted from high-quality steel are the most durable and best for dimensional accuracy.

Alloy Selection

Aluminum metals come in alloys where aluminum is the primary metal intimately mixed with elements such as zinc, copper, silicon, tin, magnesium and manganese.  Some alloys are stronger than others, for example, 6061 is stronger than 6063 making it popular for use to make beams and frames.

Additionally, different alloys have different ductility, corrosion resistance, electrical conductivity, and thermal conductivity. Therefore, the manufacturer will select an alloy based on your specifications.

Advantages of aluminum material include:

lHigh Strength to weight ratio making it strong yet lightweight and advantageous in applications where one needs to create strong structures without making them too heavy. These include beams, frames, and aircraft parts.

lMalleability.  Aluminum is soft making it easy to bend and shape it into custom profiles with desired cross-sections. Architects and engineers can turn it into eye-catching decorations, force it around curves and angles to optimize space or join different pieces without welding thus saving money.

lCorrosion Resistance. Upon exposure to air, aluminum reacts with oxygen forming a thick protective layer of oxide on its surface. That way, it will not react with elements further unless the layer is removed.

lDurable. Some alloys of aluminum withstand wear and tear just as well as steel. For example, 7068 has a tensile strength comparable to that of steel.

lThermal and electrical conductivity. Aluminum conducts heat and electricity well making it useful in the manufacture of electrical and electronic equipment, heat sinks, radiators, HVAC channeling systems etc.

lHigh scrap value. Aluminum is recycled to a high degree. In fact, three out of every four aluminums in use today are from recycled scrap. This saves energy and spares the environment from excessive mining activities.  

Heating

It’s important to control temperature throughout the extrusion process. The three important stages of temperature control are at the press loading, during the extrusion and at the lead-out table.

The manufacturer starts by preheating the die to about 500 degrees Celsius in what’s usually a five-hour task and the aluminum to between 400–500°C to make it molten but not flowing like a soup.  This way, the aluminum won’t lose heat when it makes contact with the die during pressing.

Extrusion

The manufacturer picks the billet from the furnace once it’s malleable enough for extrusion and mechanically loads it onto the extrusion press ready to force it through the die opening with the help of a powerful ram.

Depending on the setup, this can be a direct or indirect process, in direct extrusion, the ram forces the aluminum onto and through the die. On the other hand, indirect extrusion involves forcing the die onto the aluminum such that it gives in to pressure and passes through the ring opening.

Each method has its own advantages and disadvantages. In particular, the direct method is easy to understand and set up but generates a lot of friction when the ram makes contact with the aluminum.

Friction implies heat meaning the manufacturer has to keep an eye on things to ensure the heat doesn’t impact the final profile of the piece. On the other hand, the indirect method is complex but doesn’t generate significant friction and heat control issues and therefore results in precise pieces.

In any case, it’s also important to monitor the pressure and ram speed. Applying too much pressure or speed can force the aluminum out before it conforms to the desired shape. It can also damage the extrusion die.

On the other hand, wasting too much time can create problems if the die and the aluminum lose heat with the latter hardening and forcing the operator to use extra pressure. Extrusion processes run on fuel; extra pressure means extra fuel costs. Under immense pressure, the softened aluminum is forced through the die opening, taking its shape as it emerges.

Quenching

When the aluminum passes through the die opening it assumes a profile matching the cross-section. On the other side, a puller gras and guides it onto the lead-out table which is usually a setup comprising fans or a water bath to quench the extruded piece. Different alloys have different quenching time requirements.

Straightening

Once the piece has been quenched it’s maneuvered onto the runout table for further cooling and straightening. Manufacturers perform cooling before any post-processing steps just to harden the piece and improve mechanical properties.

Next, a stretcher grabs the piece on both ends and pulls it to remove stress and unwanted kinks.

Post-Processing

Depending on your stipulations regarding lengths, finishing and other special features, the manufacturer may take the extruded piece through the following processes:

Cutting

This is where the manufacturer uses saws and shears to cut the extruded pieces to length as per your precise stipulations.

Heat Treatment

The resized extrusions can be tempered in special ovens for several hours to boost hardness and mechanical properties. This is usually performed at temperatures ranging from 300 to 420 degrees Celsius, depending on the aluminum alloy used.

Punching

The manufacturer will then punch holes and other special features into the tempered profiles to help assemble structures and also improve functionality.

Machining

Manufacturers may also perform additional machining to give the pieces nuanced details or simply make the dimensions precise.

Finishing

The manufacturer may give the extruded aluminum pieces surface treatment such as powder coating, painting, anodizing, electroplating, and ceramic coating depending on your preferences.  Surface finishing bestows benefits such as:

lImproved protection from elements beyond what the natural oxide layer provides.

lThermal insulation to make aluminum surface highly emissive or reflective and reduces heat transfer in aerospace applications, pipes and other industrial components.

lImproved hardness making the pieces more resistant to abrasion and heat, in high friction environments such as when used in aircraft landing gear, medical equipment, and machining operations

lImproved lubricity leading to reduced stickiness of aluminum with heat exposure.

lImproved UV resistant leading to reduced fading when used to make automotive parts and outdoor furniture.

lImproved antibacterial properties by making surfaces smooth, or giving them nano-porous topographical patterns to scare off bacteria and reduce adhesion and contamination when used to make food and medical equipment.

lImproved appearance. Surface treatment smoothens surfaces and removes sharp edges to create aesthetically pleasing pieces.

Quality Control and Inspection

The manufacturer will perform quality control checks and inspections to ensure the final pieces meet established standards and adhere to your stipulations for dimensions, surface finishing and other features. Typical tests include tensile strength tests, hardness tests, impact absorption tests and corrosion resistance tests.

Tensile strength testing involves a series of experiments to measure the tensile strength, yield strength and elongation of aluminum frames. The manufacturer will apply a tensile load and then measure the depression resulting from the force.

On the other hand, hardness testing involves the use of a known force to measure the level of indentation and establish just how rigid the extruded pieces are.  Additionally, engineers may want to know the piece's performance against impacting forces, they’ll bump a weight against each piece and measure the amount of energy each one absorbs.

Meanwhile, corrosion resistance tests involve a simple exposure of the profiles to elements to establish how well they perform in harsh environments.

However, before final inspections and tests, manufacturers will use strict quality control protocols to ensure your designs align with established standards for tensile strength, hardness, impact absorption and corrosion resistance.  They will guide you through the alloy selection process, thickness measurements and even design optimization to reduce the cost of the final product.

In conclusion, custom aluminum extrusion is an efficient and flexible way to shape aluminum alloys just the way clients want them to look for specific applications.