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How to bending aluminum without cracking it?

Aluminum breaking after bending can be a significant issue in various applications: The aluminum sheet or aluminum extrusion is easy to break after bending, or it will crack after anodizing bending. Many aluminum alloy processing companies are confused about this. Understanding the main reasons for this problem and implementing preventive measures is essential for achieving successful aluminum bending without failures. So, how to bend aluminum without breaking it? 9 main reasons and 6 tips for preventive measures for aluminum to break after bending.

Aluminum Bending Basics: Three Factors Affecting The Bending Of Aluminum Alloy

Freeform Aluminum Tube Bending Without Cracking It

Normally, higher strength means the aluminium alloy will be more difficult to bend, due to the tradeoff between strength and elongation – ductility. As one increases, the other decreases.
So what points and factors affecting can help you identify the right alloy for bending? And what alloys are best for bending?
Then we can know the answer from three aspects: Formability, thickness, bend radius, and the percentage of elongation of aluminum profiles.

What points can help you identify the right alloy for bending? And what alloys are best for bending?

Formability of aluminum

Formability is a critical property of aluminum, especially in applications involving bending, shaping, and forming. Formability refers to the material’s ability to undergo permanent deformation without experiencing cracking or tearing during the forming process. It is one of the most useful characteristics of aluminum due to its versatility and ease of manipulation.

Here are some key points to understand about the formability of aluminum:

6 key points

  • Strength and Ductility Tradeoff: Typically, there is a tradeoff between strength and ductility (elongation) in aluminum alloys. Higher-strength aluminum alloys tend to be less ductile, making them more challenging to bend or form without cracking. Lower-strength alloys may have higher ductility, making them more forgiving when it comes to shaping.
  • Alloy and Temper Selection: The choice of aluminum alloy and temper is crucial for achieving the desired formability. Different alloys and tempers offer varying levels of strength and ductility. Selecting the right combination is essential for the specific application, balancing the need for strength with the requirement to prevent cracking during forming.
  • Relative Nature of Formability: Formability is a relative term and not a specific numerical value. It depends on multiple factors, including the applied force, the shape of the part, the thickness of the starting material, and the specific characteristics of the aluminum alloy and temper.
  • Standardized Tests: To assess and rank the formability of different aluminum alloys, standardized tests, such as ASTM E2218 (Standard Test Method for Determining Forming Limit Curves), are available. These tests help establish a formability “ranking” for different sheets of alloy, providing insights into their baseline formability characteristics.
  • Process Variables: The formability of aluminum is influenced by process variables. These include the equipment used for bending, the method of force application (gradual bending is preferred), and the monitoring of the bending process to ensure uniform deformation.
  • Shape and Thickness Considerations: The shape of the part being formed and the thickness of the starting material significantly affect the required force for successful forming. Thicker materials may require more force for bending, and complex shapes can pose challenges in terms of achieving uniform deformation.


Formability is a vital property of aluminum, especially in applications where shaping and bending are required. The choice of alloy and temper, understanding the relative nature of formability, adherence to standardized tests, and careful consideration of process variables are all essential factors for achieving successful bends and forms without cracking. Formability is a key factor in harnessing the full potential of aluminum’s versatility in various industrial and manufacturing applications.

Click for the chart of tensile strengths for aluminum and stainless steel to compare with mild steel

Thickness and bend radius of aluminum bending

How to bend aluminum tubing (Stretch forming and other 3 methods)

The thickness and bend radius of aluminum are crucial factors to consider when working with this versatile material, especially in bending and forming applications. These parameters directly impact the success of the bending process and the quality of the final product. Here’s a closer look at the significance of thickness and bend radius in aluminum bending:


  1. Material Thickness: The thickness of the aluminum sheet or extrusion is a fundamental factor to consider. Thicker materials typically require more force to bend and may have different minimum bend radii to avoid cracking.
  2. Minimum Bend Radius: Each aluminum alloy and temper has a recommended minimum bend radius that should be followed to prevent cracking and ensure the desired bend angle. Thicker materials generally have larger minimum bend radii to accommodate the increased thickness.
  3. Aspect Ratio: The aspect ratio is the ratio of the material’s thickness to its width. It can influence the ease of bending. Higher aspect ratios may require larger bend radii and more force for successful bending.

Bend Radius

How to bend T5 aluminum extrusion without cracking it
  1. Minimum Bend Radius: The minimum bend radius is the smallest radius a bend can have without causing cracking or deformation in the aluminum. This value varies depending on the alloy, temper, and thickness of the material. Smaller radii may lead to increased risk of cracking.
  2. Alloy and Temper Impact: Different aluminum alloys and tempers have varying minimum bend radii. For example, softer alloys and tempers are more forgiving in terms of bend radius, while harder alloys and tempers require larger radii to prevent issues.
  3. Die and Tooling Selection: The choice of die and tooling plays a significant role in determining the bend radius. Using the appropriate tooling ensures that the desired radius is achieved and minimizes the risk of cracking.
  4. Aspect Ratio: The aspect ratio of the material can also influence the minimum bend radius. Materials with higher aspect ratios may require larger radii to accommodate the increased thickness.


In practice, it’s essential to consult the manufacturer’s recommendations and guidelines for the specific aluminum alloy and temper you are working with. These guidelines will provide information on the appropriate minimum bend radius and other considerations to ensure successful bending without cracking or deformation.

Proper equipment, tooling, and technique, including the application of gradual force during bending, are essential to achieve precise bends and maintain the integrity of the aluminum, especially when working with various thicknesses and bend radii.

Read More: Minimum Recommended Bend Radius Chart of Aluminum and Steel Profiles

Percentage of elongation of aluminum

The percentage of elongation is a measure of a material’s ability to deform plastically (stretch) before it reaches its breaking point. It is typically expressed as a percentage and is calculated by comparing the original length of a material to its length after it has been stretched to the point of failure. The formula for calculating percentage elongation is as follows:

Percentage Elongation=(LfLi​​)/Li× 100%


What the best way to bending aluminum
What is the best way to bend aluminum extrusion?
  • Percentage ElongationPercentage Elongation is the percentage of elongation.
  • Lf​ is the final length of the material after stretching.
  • Li​ is the initial length of the material before stretching.

For aluminum, the percentage of elongation can vary depending on factors such as the alloy, temper, and the specific conditions of the stretching or tensile testing. Generally, aluminum alloys exhibit good elongation properties, which means they can be stretched or deformed significantly before breaking. This characteristic makes aluminum a desirable material for many applications, including those that involve forming, bending, and shaping.


The elongation percentage can be an important mechanical property to consider when selecting an aluminum alloy for a particular application. It is often used to assess the material’s ability to withstand deformation without cracking or failure. Different aluminum alloys and tempers will have different elongation percentages, and these values can be found in material specifications and data sheets provided by aluminum manufacturers.

Why Are These 4 Alloys Important?

Despite their different properties, these alloys are excellent examples of bendability in aluminum alloys. They demonstrate that even though some aluminum alloys feature better formability and percent elongation for a given bend radius and thickness, they each serve a unique purpose and a wide variety of applications.

Even with slightly lower bendability, the strength of alloy 6061 makes it one of the most widely used aluminum alloys. In the same way, alloy 3003 has multiple uses in applications that require superior bendability. Meanwhile, alloy 5052 is commonly used thanks to its balance in terms of bendability and strength.

aluminum extrusion bending machine
aluminum extrusion bending machine

PBA-CNC Aluminum Bending Machine.

Up to 15 independent controllable servo axes; Automatic CNC systems; Three-dimensional bending. Accuracy is as high as ≤0.01mm. which is the standard and optional equipment of the PBA Series CNC Profile Bending Machine.

Click here to get the details of the PBA aluminum bending machine

The aluminum sheet is easy to break after bending, or it will crack after anodizing bending. Many aluminum alloy processing companies are confused about this. So, how to bend aluminum without breaking it? 8 main reasons and preventive measures for aluminum to break after bending.

9 main reasons and preventive measures for aluminum to break after bending

Teflon Strip Takeout Machine For Bending Aluminum
  • Thickness: The too-thick aluminum plate is not easy to bend. Everyone knows they should use the thinnest possible sheet of aluminum.
  • Hardness: The aluminum plate is too hard and easy to break. The choice of aluminum sheet mainly depends on the grade and condition of the aluminum. Usually, T1, T3, and T5 are used. T6 and T7 series are too hard and need to be annealed to 0 tempers before bending.
  • Textured direction: The bending direction should be perpendicular to the textured direction of the aluminum plate and cannot be parallel. For aluminum sheet parts that need to be drawn, if processing allows, it is best to process them after bending, otherwise, the possibility of bending fracture will increase.
  • Bending angle R: The larger the R angle, the higher the success rate, so try to increase the bending R angle as much as possible.
  • Cracks after the bending of aluminum profiles are caused by high tensile force and unsatisfied laying stress. The edge of the aluminum profile is not in place, which will cause wrinkling. This can be solved by improving the cross-sectional area of the profile or adjusting the tension.
  • The depression of the curved surface mainly occurs on the aluminum cavity profile. Before stretching and bending this material, it is necessary to fill the curved portion of the cavity with filler. Open cavities can be stacked with spring steel sheets or filled with Teflon, while closed cavities are usually filled with sand.
  • According to the position generated by the vertical marks on the side, properly adjust the mold gap and improve the mold material, which can effectively prevent the surface of the aluminum profile from being scratched.
  • Heat the aluminum: Heating the aluminum(we call it softening or annealing) can make it more malleable and easier to bend without cracking. However, be careful not to overheat the aluminum, as this can weaken its structural integrity.
  • Avoid sharp bends: Sharp bends can put too much stress on the aluminum and cause it to crack. Use gentle curves instead.

Heat the aluminum Aluminum heating bending process: softening and annealing

Six tips for bending aluminum without cracking it

Aluminum Profile Bending Machine bends 3 specifications of T5 aluminum C-Channel in two ways

Tips 1#: Pay attention to the grade

For aluminum, the harder the grade, the greater the amount of spring back that you will need to deal with; very soft aluminum may exhibit no spring back at all.

Bending aluminum without encountering cracks while addressing spring back is a skill that requires attention to detail, especially when dealing with different aluminum grades and tempers. The grade of aluminum you choose has a significant impact on the bending process, and understanding the characteristics of various grades can help you achieve precise and crack-free bends.

Aluminum Grades and Their Impact on Bending

Aluminum alloys come in a wide range of grades, each offering unique properties. The grade of aluminum you select for your project can influence its formability, ductility, and susceptibility to cracking during bending. Some grades are more malleable and less likely to crack, making them ideal choices for bending applications.

The Role of Spring Back

The concept of spring back is crucial when bending aluminum. Spring back refers to the tendency of a material to return to its original shape after being bent. The harder the grade of aluminum, the greater the amount of spring back you will need to manage. However, very soft aluminum may exhibit no spring back at all. Understanding spring back is essential for achieving the desired bend angle and minimizing defects.

Tips 2#: Bending Aluminum Without Cracking: Choosing the Right Aluminum Alloy

Some aluminum alloys are more malleable than others and can withstand bending without cracking. 6061 and 5052 aluminum alloys are good options for bending.

Certainly, when bending aluminum without cracking it, the grade and temper of the aluminum are crucial considerations.

Choose the Right Alloy and Temper

Pay careful attention to the aluminum alloy and temper selection. Some alloys are more ductile and suitable for bending without cracking.
For example, 3003 and 6061 aluminum alloys are often chosen for their good bendability. T6 temper of 6061 is a popular choice for its balance of strength and formability.

Temper is as important as alloys.

Look at tempers when it comes to optimizing the bending ability of the aluminum alloy.

For non-heat-treatable 3xxx and 5xxx alloys, O-temper is the easiest temper to bend in.

  • 6xxx, 7xxx and 2xxx heat-treatable alloys should if possible be bent in the T4 condition, as this has a lower yield strength. However, there is a drawback. The yield strength in the T4 condition varies over time, due to natural ageing, a slow hardening process that occurs over time.
  • Although the variation in yield strength is small over short times, this might cause spring-back variation in some bending processes. So, in some cases, bending in T6 could be a better option. There are also special heat treatments that stop natural aging and allow the material to be heat-treated to T6 after bending, which could be considered.
  • T4 temper is moderate to bend, with low yield strength, however, for some bending processes, spring-back variations might occur
  • T6 temper is the most difficult to bend, but there is no spring back variation

Avoid High-Strength Alloys in Certain Temper States

High-strength aluminum alloys like 2024, 7075, or any in the T3 or T8 temper states are generally less ductile and more susceptible to cracking during bending. Avoid using these alloys unless necessary.
Annealing for Greater Ductility:

Consider annealing the aluminum before bending if it’s a heat-treatable alloy. Annealing softens the material and increases its ductility, reducing the risk of cracking.
Follow the manufacturer’s guidelines for proper annealing procedures to avoid overheating and ensure a uniform result.

Temper and Bend Radius Considerations

Consult material specifications and guidelines to determine the recommended bend radii for the specific aluminum alloy and temper you’re working with.
Be aware that different tempers within the same alloy may exhibit varying levels of ductility. For example, O (annealed) temper is more ductile than T6.

Proper Tooling and Equipment

Choose the appropriate bending equipment and tooling for the grade and temper of aluminum. Equipment such as hydraulic press brakes or specialized aluminum bending machines can provide precise control.
Ensure that the bending equipment is set up correctly with die and punch selection, pressure settings, and backstop adjustments tailored to the specific aluminum grade and temper.

Understanding Aluminum Alloys

Aluminum alloys are composed of various elements to enhance their specific properties, such as strength, corrosion resistance, and formability. When it comes to bending, the malleability and ductility of an alloy play a crucial role. Some alloys are more forgiving and less likely to crack during the bending process, making them ideal choices for such applications.

Properly document the grade, temper, and bending parameters used for each project to aid in quality control and traceability.

Tips 3#: Bending Aluminum Without Cracking: The Art of Marking Your Bend Lines

Mark your bend lines: Before bending, use a straight edge and a pencil to mark the exact points where you want the aluminum to bend. This will help you achieve the desired angle and prevent any mistakes.

Bending aluminum can be a delicate process, and achieving the desired angle without cracking or deformation requires precision and careful planning. One crucial step in this process is marking your bend lines accurately. By following this essential practice, you can ensure that your bends are precise, your angles are correct, and the risk of mistakes or cracking is minimized.

Helical Spiral Bending Aluminum Tubing

The Importance of Marking Bend Lines

Marking your bend lines serves as a visual guide that provides several advantages in the bending process:

  1. Precision: Accurate markings help you achieve the exact angle you desire, ensuring that your aluminum part meets your project’s specifications.
  2. Consistency: Consistent bend lines across multiple pieces or throughout a single piece are crucial for uniformity and the overall quality of your work.
  3. Mistake Prevention: By marking your bend lines before bending, you reduce the likelihood of making incorrect bends, which can lead to wasted material or additional work.
  4. Cracking Prevention: Precise bends reduce the stress on the aluminum, minimizing the risk of cracking or deformation.

How to Mark Bend Lines

  1. Choose a Straight Edge: Use a reliable straight edge, such as a ruler, a combination square, or a dedicated marking tool. The straight edge ensures that your bend lines are perfectly straight and consistent.
  2. Use a Pencil or Scribe: A pencil or scribe is the ideal marking tool for aluminum. It provides a clear, easily visible mark without damaging the material’s surface.
  3. Measure and Mark: Measure the desired distance from the edge of the aluminum to the point where you want the bend to start. Place your straight edge along this measurement, ensuring it is perfectly aligned with your reference point.
  4. Mark the Bend Line: Carefully draw a straight line along the edge of the straight edge using your pencil or scribe. This line represents the point where the bend will begin.
  5. Repeat as Needed: Depending on your project’s requirements, you may need to mark multiple bend lines. Ensure each line is measured and marked accurately.

Tips 4#: Bending Aluminum Without Cracking: The Art of Gradual Bending

Bend gradually: When bending, it’s best to apply gradual pressure rather than trying to bend the aluminum all at once. This will help prevent cracking and ensure a smoother bend.

Bending aluminum is a delicate process that requires careful attention to detail to ensure a successful outcome without any cracking or deformation. One crucial technique in achieving precise bends is to apply gradual pressure during the bending process. This method not only helps prevent cracking but also ensures that the aluminum undergoes uniform deformation, resulting in a smoother bend.

The Significance of Gradual Bending

  1. Crack Prevention: One of the primary reasons for cracking during bending is the sudden application of excessive force. Gradual bending minimizes stress concentrations and reduces the risk of cracking.
  2. Uniform Deformation: Gradual bending allows the material to deform uniformly along the entire bend line. This ensures a smoother and more consistent bend without distortions or deformations.
  3. Control: Gradual bending provides greater control over the bending process, allowing you to adjust the pressure as needed to achieve the desired angle.
  4. Safety: Gradual bending is a safer approach that reduces the risk of accidents, injuries, or damage to the material or equipment.

In conclusion, the practice of gradual bending is a fundamental technique when working with aluminum. It promotes crack prevention, uniform deformation, control, and safety. When combined with proper equipment, secure clamping, and careful monitoring, gradual bending ensures that you achieve precise and smooth bends in your aluminum projects without the risk of cracking.

Tips 5#: Bending Aluminum Without Cracking: The Crucial Role of Avoiding Creasing

Watch out for creasing along the bend line: Aluminum generally loses its integrity if the material is creased. If you make aircraft parts with that crease along the bend line, that alone will make the parts unacceptable.

Aluminum is a widely used material known for its lightweight, corrosion resistance, and formability. When it comes to bending aluminum, achieving precise and clean bends without any cracking or deformation is of utmost importance. One critical aspect to watch out for during the bending process is creasing along the bend line. This article explores the significance of avoiding creasing in aluminum bending and the techniques to ensure high-quality results.

The Significance of Avoiding Creasing

Creasing is a structural flaw that occurs when aluminum is bent so sharply that it forms a permanent, often sharp-edged indentation along the bend line. This crease compromises the material’s structural integrity and can lead to its failure, making it an unacceptable outcome, especially in critical applications such as aircraft parts manufacturing.

In conclusion, avoiding creasing along the bend line is a fundamental practice when bending aluminum. Creasing can compromise the structural integrity of aluminum components, rendering them unacceptable for critical applications. By using proper tooling, suitable bend radii, gradual pressure application, and maintaining uniform deformation, you can achieve high-quality results in aluminum bending while preventing creasing and ensuring the integrity of the final product.

Tips 6#: Mastering Inside Bend Radius in Aluminum Bending: A Crucial Factor in Preventing Cracking

Inside bend radius: When bending aluminum, know that the smaller your inside bend radius, the larger the chance that cracking will occur in the part. Also know that, for the best results and fewer cracks on the outside of the bend, the bend line should go across or diagonal to the material grain when and where possible.

Bending aluminum is a precise art, and achieving clean bends without cracking or deformations is a top priority, especially when working with this versatile material. One of the critical factors that directly impacts the success of the bending process is the inside bend radius. Understanding the importance of inside bend radius and its relationship with cracking is essential to ensure high-quality results in aluminum bending.

The Significance of Inside Bend Radius

The inside bend radius refers to the tightness of the curve on the inner side of the bend. It plays a pivotal role in the bending process, and its size has a direct impact on the likelihood of cracking in the aluminum part. Smaller inside bend radii are associated with an increased risk of cracking, making it a critical parameter to consider.

Additional Considerations

For critical applications like aircraft parts manufacturing, adherence to industry-specific guidelines and standards is vital to maintain the highest quality and safety standards.

When working with aluminum of different thicknesses, the inside bend radius may need to be adjusted accordingly. Thicker aluminum typically requires larger radii to prevent cracking.

In summary, mastering the inside bend radius is a fundamental practice when bending aluminum. Understanding the relationship between inside bend radius and cracking, following recommended guidelines, and aligning the bend line with the material grain are crucial steps in achieving high-quality results and preventing cracks in aluminum bending projects.

Ideally, part designers should know that when it comes to aluminum grades, 3003 and 5052 will bend, and 6061 will not. This is generalizing, of course, as there are ways to form 6061. The aluminum series’ ability to bend tends to decrease as you move down the list of tempers, from annealed to T4 and T6. Bending these tempered alloys is not impossible, but it is very difficult and will most likely require large bend radii to avoid cracking on the outside of the bend. If you’re not careful, you can completely fracture the bend line.

Read PDF: How To Bending Aluminum

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