The beauty of cold aluminium extrusion bending
what is aluminum bending?
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What is Aluminum Profile Bending?
The aluminum profile can be extruded and bent (cold bending aluminum) to specified tolerances or to standard dimensional tolerances. While a product’s dimensions and bend angles can be methodically measured and re-measured, the end product will only be as precise as the aluminum profile bending machine or method used.
Understanding Aluminum Before Bending
Before we dive into the techniques for cold bending aluminum, it is essential to understand the properties of aluminum. Compared to other metals, aluminum is relatively flexible, ductile, and lightweight. These properties make cold bending aluminum easier than bending a stronger, heavier metal like steel. When selecting an aluminum alloy, it’s essential to choose the correct material based on the final application to ensure that it can withstand environmental or structural stress.
Preparing the Aluminum for Cold Bending
- Cleaning the aluminum: The first step in preparing aluminum for cold bending is to remove any dirt, dust, or other impurities. Use a solvent-based cleaner to wipe down the surface of the aluminum and ensure that the surface is as smooth and blemish-free as possible.
- Marking the aluminum: Marking the aluminum with the desired bend point helps to ensure accuracy and consistency in bending. Use a measuring tape and marking pen to mark the aluminum before you begin, ensuring that the mark is clear and visible.
3 Important Key Parameters Of Aluminum Profile Bending
Several factors should be considered when choosing which bending process is appropriate for a certain product. Aluminum profile bending engineers can provide crucial input on the bending, shaping, and forming of aluminum during the design phase of a project. Deformation of the inside or outside radii can be a design issue and can also determine which forming process to use.
- What tolerances, or deviations, are expected on the inside radius, the outside dimension radius, and the overall length of the part?
- What surface areas are critical for appearance?
- What mechanical strength is required?
The product’s alloy, temper, and cross-section also are important considerations.
Once these factors are determined, aluminum profile bending manufacturers can begin the bending process using one of the following five common bendings and forming methods.
Four Tips for Successful Cold Bending of Aluminum
- Use the correct aluminum alloy: Choosing the right aluminum alloy for your application is essential. Different alloys possess different ductility and strength, which can affect the success of aluminum cold bending.
- Minimize the force: As aluminum has low ductile properties, it is important to avoid applying too much force during the cold bending process. Applying excessive force could lead to deformation or cracking.
- Preheat the Aluminum: Some thicker pieces of aluminum require preheating before the bending process. Heating increases the ductility of the material, making the bending process easier.
- Work slowly: Aluminum cold bending is not fast-paced work. Take time to move the metal piece through a sequence of movements that are both predictable and steady.
What are the 5 methods for COLD bending aluminum?
Roller and roll bending
Aluminum roll bending is used to form aluminum profiles. BIT’s PBA Aluminum Bending Machine and PBH Section Bending Machine can perform this mission, as an angle roll machine manufacturer, we are used to calling it a profile bending machine.
Cold roll bending is a specific type of roll bending used in the metalworking industry that has many benefits, particularly when it comes to aluminum.
Top 3 pros of roll bending aluminum
- One significant advantage of cold roll bending aluminum is that it produces smooth, uniform bends with minimal deformation or distortion, preserving the material’s physical properties. Cold rolling exposes the aluminum to compressive forces gradually, forming the bends over an extended period, preserving the material’s strength. As such, it is ideal for projects that require high precision and accuracy, such as aerospace or architectural projects.
- Another advantage of cold roll bending is that it can create curves and angles that are challenging to create using traditional bending techniques. The process requires progressively applying pressure to the aluminum, producing a smooth and continuous bend, even on thinner aluminum as it does not require heating.
- Cold roll bending is also faster than other metalworking techniques that involve considerable heat treatment or extensive tooling. As there is no heating process involved, the aluminum bar can be bent quickly and efficiently, reducing production time and overall project costs.
Cold roll bending is a popular method for bending aluminum because it provides accurate, uniform bends that preserve the metal’s physical properties, creates unique curves and angles not achievable by traditional bending methods. It is also faster and more efficient than other types of metalworking processes.
Read More: Profile Bending Machine: 5 Things Before Buy, 6 Steps to Bend
What is the Best Aluminum Bending Machine?
Choosing the best aluminum bending machine depends on several factors, including the specific needs of the project, the thickness and diameter of the aluminum being bent, and the budget. Here are some things to consider when looking for the best CNC aluminum bending machine:
- Capacity and Durability: A high-quality aluminum bending machine should have the ability to bend aluminum of varying thicknesses and diameters. It should also be built with durability in mind, capable of withstanding the pressures and forces applied during the bending process.
- Features and Options: Different aluminum bending machines come with various features such as adjustable speeds and roll tension, repeatability, automatic or manual set-up, and the ability to perform different types of bending.
- Ease of Use: The best aluminum bending machine should be easy to set up and use, with clear instructions and user-friendly controls. A good CNC machine design will help users to spend less time configuring or troubleshooting the machine, and more time working on the project.
- Safety Features: Safety should be a priority when considering an aluminum bending machine, especially when it comes to CNC automation. Ensure that the machine has the required safety switches and guards to keep users safe while operating the machine.
In fact, when a customer proposes to buy an angle roll machine for aluminum bending work, we will recommend the PBA series profile bending machine, which is widely used in various industries such as building doors, windows and curtain walls, decoration, automobile industry, high-speed rail, bathroom, ship, advertising, and other industries. It can bend various shapes (including C shapes, U shapes, circles, ellipses, multiple radius combinations, etc.), which is an ideal aluminum bending machine for bending arc processing by professional aluminum bending companies.
What is the working principle of an aluminum bending machine?
Aluminum bending is used to form aluminum profiles.
3-roll bending pushes an extrusion around three different rolls placed in a triangular shape. The rolls are adjusted to form a precise angle, up to a 360-degree rotation, that can roll horizontally or vertically. As the extrusion is slowly moved across the power-driven rollers, it begins to curve and bend.
Extrusions are limited to a single bend per cycle, meaning a higher angle of the bend would take longer to reach the desired angle. Though it may take longer, the maximum bend radius is unlimited. Symmetrical profiles are preferable for roll bending.
It is the forming of aluminum profiles in one axis by a multi-roll aluminum bending machine. If the semi-finished product is not moved during the bending process, the distance between the rollers, their diameter, and the depth of immersion determine the bending radius. To produce particularly large bends, the material is pulled through the roller bending machine and moved alternately. The distance between the rollers is gradually adjusted.
Why use an aluminum profile bender to bend aluminum?
Aluminum is a light metal with good-natured bending behavior. To permanently bend it into a new shape, only lower forces are required than for other metals with the same cross-section. This makes its processing so simple that many adjustments can be made by hand at the installation site. However, professional processing machines promise the best results in consistent quality when bending aluminum.
In most cases, roll bending is the most flexible and cost-efficient bending method. A profile is guided between three adjustable bending rolls and gradually bent in the desired radius.
Roll bending is the ideal bending method for profiles with complex designs and different radii. BIT’s CNC profile bending machine has become specialized in 3D aluminum profile bending machines.
What are the models of the Aluminum Bending Machine?
Roll bending is the forming of profiles or sheets in one axis by a multi-roll aluminum bending machine. If the semi-finished product is not moved during the bending process, the distance between the rollers, their diameter, and the depth of immersion determine the bending radius.
To produce particularly large bends, the material is pulled through the roller bending machine and moved alternately. The distance between the rollers is gradually adjusted. Roller bending machines with narrow rollers are used to form aluminum profiles. Roller bending machines work according to the same principle. They are used for the gentle, one-dimensional forming of aluminum sheets.
Ram or Push Bending
Ram or Push Bending is ideal for components such as boat gunnels, portable structure supports, wheelchair frames, and medical beds.
Ram or push bending, as the name implies, uses a ram to force the extruded metal piece on a bending die. A die pushes the extrusion onto the pressure dies, forcing the extrusion into your desired bent form. With programmable bend angles, this form of bending allows close proximity to multiple planes bends, though only one radius can be bent at a time. Ram bending offers inexpensive tooling and good bend precision with a low per-bend cost.
In intension bending, an aluminum profile is clamped on both sides and stretched during the bending process. It is a gentle process that reduces the formation of cracks or pressure points at the bending point.
During stretch forming, an extrusion is placed along a rounded, fixed bending die and clamped in place on each end. The machine begins to swing the clamped ends downward to angles up to 180 degrees, and the extrusion is bent around the die to reach the desired form.
The bend radius is unlimited with this method. A stretch forming machine can bend, twist and lift an extrusion simultaneously to create unique, specified shapes and angles for parts up to 25 feet long. This method also offers the most accurate and consistent bending through elongation control. Because of the way the rounded, fixed bending die pushes on the extrusion, stretch forming has the least amount of surface distortion and traffic marking on the extruded piece.
Stretch forming is commonly used for parts with a larger bend radius, as the minimum bend radius is generally two to three times greater than other forming/bending methods.
Hydraulic Rotary Draw Bending
In the hydraulic rotary draw bending process, manufacturers place extruded aluminum onto a bender and hold it in place with a stationary or sliding pressure die and clamping block. The round bending die, powered by hydraulics, is rotated up to 90 degrees, bending the extrusion as it rotates. With this method, an extrusion can only be bent one radius at a time.
Incorporating a mandrel or other tool component to grip the rotary die can prevent creasing or misshaping of the product, though its use isn’t required. The single axis-controlled revolution can bend within one-tenth of a degree for extremely precise bend angles.
Hydraulic bending is often used when forming round tubes or pipes for applications such as handrails and is ideal for extrusions with a large diameter, such as building signage.
ElectricRotary Draw Bending
The electric rotary draw method is best for applications that require multiple bends per part in close proximity to each other, or different radii bend for each part.
Electric rotary draw bending uses the same process as the hydraulic method but allows faster setup. The bends also are more accurate and easily repeated because angles and rotations can be automated in a machine’s programmable logic controller. Rotations of the extruded aluminum also can be mechanized for variable plane bends.
Each of these bending methods has various benefits. Designing for success and determining the best method ultimately comes down to an end product’s desired tolerance, appearance， and strength.
Which aluminum alloy profile bends best?
Aluminum is a good-natured material that is easy to bend. Once bent into shape, the sheet or profile retains its bending condition permanently. Provided no mistakes were made during bending, the formed semi-finished product remains in the desired position.
Formability of aluminum profile
- Series 1xxx are Aluminum alloys with 99.00% pure aluminum. They have little structural value. They are very ductile in the annealed condition and have excellent corrosion resistance.
- Series 2xxx are the Aluminum – Copper alloys. These alloys have excellent machinability, limited cold formability (except in the annealed condition), and less corrosion resistance than other alloys, which is why they are anodized prior to usage.
- Series 3xxx are the Aluminum – Manganese alloys. With an addition of 1% Manganese, these alloys have no significant loss in ductility, good corrosion resistance, and very good formability. This series is one of the most preferable for forming applications.
- Series 4xxx are the Aluminum – Silicon alloys. This series has the addition of silicon, thus lowering the melting point and for this reason, it is used entirely for manufacturing welding wire.
- Series 5xxx are the Aluminum-Magnesium alloys. They exhibit a very good combination of high strength, resistance to corrosion, formability, and good weldability.
- Series 6xxx are the Aluminum-Magnesium – Silicon alloys. These heat-treatable alloys exhibit great strength, good corrosion resistance, and ease of formability. They are mainly used in architectural applications.
- Series 7xxx are the Aluminum – Zinc – Magnesium and Aluminum – Zinc – Copper alloys. They exhibit very high strength, making them very difficult to form.
Thickness and bending radius of aluminum profile bending
Another factor to consider is that during the process of bending, the metal hardens and strengthens by reason of the working effect. Apart from alloy selection, thickness and bend radius are also critical factors that must be considered. The table below shows the permitted bend radii for 90o bending.
Percentage of aluminum profile bending elongation
A third factor to be considered is that the formability of a specific alloy can be found in the percentage of elongation and the difference between yield strength and ultimate tensile strength.
This rule states that the higher the elongation value (the wider the range between yield and tensile strength), the better the forming ability of the alloy.
From the aforementioned descriptions of alloys and the data shown in table 3 (below), it is quite obvious that the best series for forming, and thus for bending, are series 3xxx, 5xxx, and in some cases 6xxx. Series 2xxx and 7xxx are not to be considered and thus should be avoided due to being extremely strong. They are difficult to form in any way.
Top 3 Aluminum Alloys For Bending
- 3003：This would be the best solution for most applications. This alloy exhibits medium strength, the best cold workability together with high elongation such as 25%, and one of the biggest differences between yield and tensile strength of 14 Ksi (Kilo-pound of force per square inch) at 0 temper – annealed, followed by the H14 temper which is partially annealed and strain hardened.
- 5052：5052 is a close second. At the annealed temper, it has an elongation of 20% and the difference between yield and tensile strength of 21.5 Ksi. It is the highest strength alloy of the more common non-heat treatable grades. It has excellent corrosion behavior and in the annealed condition has better formability than 3003 or even 1100 alloys, with 21.5 Ksi of difference between yield and tensile strength and up to 20% of elongation.
- 6061： This is one of the most versatile of the heat treatable family of alloys. In the annealed condition, it can be used for bending since the difference between yield and tensile strength is 10 Ksi and elongation is up to 18%. When moving up to T4 and T6 tempers, however, bending ability tends to decrease. Bending these tempered alloys is not impossible, but requires great caution and probably larger bending radii to avoid cracking.
7005 and 2024 alloys are not recommended for bending, since they are both alloys with great strength and forming capabilities which are very limited even in the annealed conditions.
Five tips for aluminum extrusion dimensioning and tolerancing
In today’s fast-paced manufacturing industry, it can be difficult to set aside time to define tolerances for a new aluminum extruded component design. Pressed for time, OEM design engineers often default to title block tolerances. This might save a little time, but it risks adding unnecessary cost to the part due to poor fit and function.
On the other hand, a print filled with too many tight tolerances may cause extruders to not quote the part or excessively price a part that has tighter tolerances than needed for its function.
Below are five tips to help manufacturers successfully engineer proper dimensioning and tolerance when designing aluminum components. These tips can help achieve optimal manufacturability and keep costs competitive.
Choose the critical dimensions.
Adding tight tolerances on non-critical dimensions is a major source of hidden costs. Many times manufacturers will include tighter tolerances that do not affect the form, fit or function of the final product. These tight tolerance features can result in requests for print deviations, longer setups, reruns, costly die trials, unnecessary tooling alterations—all of which can lead to costly, late or rush deliveries, and ultimately price increases. Manufacturers can reduce those costs by identifying only the critical product dimensions, which can then reduce setup and inspection time. Some dimensions may not require tolerances at all—just a visual inspection to ensure a part has its intended shape.
Understand which tolerances are achievable.
Once manufacturers have identified the most critical product dimensions, their next step is to understand which tolerances are achievable based on the specific manufacturing process. Tolerances are affected by multiple extrusion factors, including press size, billet temperature, extrusion speed, die shape and type, cooling time, amount of post-stretch, air temperature, and multiple die copies, just to name a few. This is why having discussions with your aluminum extruder in the design/quoting stage to agree on tight tolerance features is important.
To help manufacturers, the Aluminum association has developed industry-standard tolerances for extruded products. These tolerances try to encompass most of the variables in the extrusion process. While you should use the Standards Book as a guide, know that it cannot cover every possibility of design creation. Having discussions with your extrduer in the design/quoting stage is key to mutual tolerance agreement and establishing a tolerance hierarchy.
Manufacturers can use these standards – as well as the information showing how differences in features or size can affect tolerances – as a reference guide when designing a product. Some extruders can hold tighter tolerances than the standards—another good reason to discuss tolerances with the extruder beforehand.
Establish critical dimensional product measurement (CpK) values
Establishing the CpK value to be used is a critical element in determining the capability of dimensional tolerances. Some CPK requirements will necessitate a capability study to determine the extent to which the extrusion process can meet specified dimensions. Although this is an added cost it will allow the extruder to understand process capability and repeatability. For example, a 1.33 CpK requirement, in effect, reduces the tolerance band to 75 percent. Likewise, requiring a 1.67 CpK reduces the tolerance band to 60 percent.
It is important to verify the extruder’s ability to control their processes to attain specified CpK values. This can eliminate many future complications when the product goes into production.
Understand Geometric Tolerancing.
Geometric Dimensioning and Tolerancing (GD&T) is becoming the internationally recognized language of the manufacturing world. GD&T is being used more often on customer prints throughout industries globally.
For more complex component extrusions, geometric tolerancing may be necessary to maintain precise shapes and forms.
When discussing the flatness of the whole surface, as defined with geometrics, make sure that your extruder understands the difference between GD&T “flatness” and “straightness” compared to traditional standard extrusion terminology of “flatness” and “straightness”. The General flatness of extrusion in standard extrusion terminology refers to the cross-sectional flatness of the profile and straightness refers to the bow in the length of the part.
Some geometric tolerances, such as the profile of a surface, can lead to increased inspection time and add significant cost to the part. A best practice is to use the profile of a line on the cross-sectional profile as well as noting twists and straightness to achieve the desired profile of a surface (Exhibit #2). This allows the extruder to verify the extrusion prior to machining to ensure its functionality.
Another point pertaining to Figure #2, is the use of symmetric ID grooves. When designing a symmetrical shape, add an identification mark to allow proper orientation. This reduces tolerance variance that is characteristic of the extrusion process.
Design for both functionality and manufacturability.
Designing tight tolerance features without taking into account manufacturability, can increase costs and frustration. Take for instance a part that has an acceptable saw cut tolerances, but machined features, and their tolerances are set from both ends of the part. This could cause you to have to add milling processes, multi-clamping, or touch probing operations, which can add costs.
Keep the dimensioning format as simple as possible by using the traditional primary, secondary and tertiary datums whenever possible. This can help reduce process variation and keep costs down by reducing excess machining operations, re-clamping, and handling operations.
These five dimensioning and tolerance tips offer manufacturers an alternative to defaulting to block tolerances. By partnering with your extruder early in the design process, manufacturers can productively design for both function and manufacturing goals, and improve their organization’s competitiveness.
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