Bending Basics for Sheet Metal Fabrication

Materials Suitable for Sheet Metal Bending

Almost all engineering materials are available in sheet form and can be bent to some extent. However, the suitability of a material for sheet metal bending depends on its inherent properties, such as ductility, strength, and thickness. Common materials used for sheet metal bending include:

• Mild Steel: Known for its excellent ductility and strength, it is a popular choice for various applications.
• Aluminium: Lightweight and corrosion-resistant, ideal for aerospace and automotive industries.
• Stainless Steel is highly resistant to corrosion and is suitable for medical and food processing equipment.
• Copper: Highly ductile and conductive, often used in electrical components.
• Brass: Combines good strength with excellent corrosion resistance and is used in decorative and plumbing applications.
• Titanium: Known for its high strength-to-weight ratio and corrosion resistance, used in aerospace and medical implants.

Each material has its unique characteristics, and the choice of material depends on the final product’s specific application and desired properties. Understanding these properties is crucial for selecting the right material for your sheet metal bending project.

Design Considerations for Sheet Metal Fabrication

Practical sheet metal fabrication relies not just on proper technique and equipment but also on meticulous design considerations. Key design factors include:

• Bend Radius: The material thickness and type determine the minimum bend radius. A smaller radius can cause cracking, while a larger radius may not achieve the desired shape.
• Material Thickness: The thickness of the material affects the bending process and the properties of the final product. Thicker materials require more force to bend and may have different spring-back characteristics.
• Bend Length: The length of the bend influences the bending process and the properties of the final product. Longer bends may require specialized equipment to ensure uniformity.
• Springback: The material’s tendency to return to its original shape after bending must be considered. Compensating for spring back is essential to achieve accurate angles.
• Processing Tolerances: Variations in sheet metal composition, thickness, and processing can affect the final product’s accuracy. Ensuring tight tolerances is crucial for high-quality fabrication.

Considering these factors during the design phase, you can optimize the bending process and ensure that the final product meets the desired specifications.

Common Metal Bending Techniques

Depending on your application, there are many available variations of metal bending, known as different bending methods, such as rotary bending, roll bending, and press brake bending. Selecting the right bending machine for each application is crucial for achieving high precision and the desired shape. It is important to calculate and apply the correct bending force based on material type, thickness, flange length, and bend angles to ensure proper bends without deformation.

Accurate placement of bend lines is essential for achieving precise bend angles and avoiding internal stress or cracking. Bend relief should be incorporated near edges or flanges to prevent tearing during the bending process. The process of making bends involves considering factors like bend allowance, bend radius, material behavior, and springback. Strategically placing bends and ensuring they are adequately spaced helps avoid fitting issues, especially when dealing with successive bends. When successive bends are unavoidable, the intermediate part should be longer than the flanges to ensure proper fitting on the die. Partial bending is a technique that allows for a range of angles and easier adjustment due to springback. Achieving the desired angular shape in bent parts and bent sheet metal parts requires careful technique selection and attention to detail.

Edge bending is used to shape edges without causing damage, improving both appearance and safety. Maintaining minimum flange length and proper flange length is critical in design to avoid deformation and ensure structural integrity. Designing bends in the same direction can reduce costs and minimize deformation. Here are some of the most common techniques you might use.

V-bending

The v bending method involves pressing the metal sheet between a top tool, the punch, and a V-shaped bottom tool, the die, resulting in a precise v shape. Punch presses play a crucial role in this process by applying force through the punch to form the desired angle and shape.

A press brake, or press brakes in general, are essential machines for performing V-bending, allowing for accurate control over the bend. The die and punch settings determine the inner radius and inside bend radius of the bend, and typically, the inside bend radius should match the sheet metal thickness to prevent cracks and maintain structural integrity.

The technique offers quick setup changes, making it ideal for projects with varying specifications. However, the depth of the bend can be limited by the machinery and the chosen die width. Springback is a frequent challenge, requiring compensation. Bottom bending generates less springback and creates more accurate angles compared to air bending, making it a preferred choice for precision work. CNC bending processes require less manual labor and can often be performed by unskilled workers.

U-bending

This technique forms a ‘U’ shape, pressing the metal sheet similarly to V-bending but with a U-shaped die. A hydraulic press is often used in U-bending to achieve deep channels or structures where a V-bend might be insufficient. When designing U-shaped bends, it is important to consider the curl radius to maintain structural integrity and ensure proper spacing for safety.

However, this method requires precise tooling for consistency and, like V-bending, is subject to springback.

Coining

A high-tonnage method that does more imprints a clear, sharp line on the bend. This is useful for applications that demand specific, tight bends, like certain electronic components or intricate decorative pieces.

Coining requires much force, thus consuming more energy. It works by applying force that exceeds the material’s yield strength, causing plastic deformation—permanently shaping the metal. It’s less versatile compared to V and U bending.

Rotary Bending

This method uses rotating dies or rollers to bend the metal. This eliminates direct, forceful contact between the tool and the metal. It’s useful for projects requiring consistent, repeated patterns or long, sweeping bends. Rotary bending is less suitable for very tight bends and might require more setup time for specialized bends. Various types of sheet metals can be processed using both rotary and roll bending techniques.

Roll bending, on the other hand, focuses on creating curved shapes such as tubes and cones. It utilizes roller sets and machinery that allow for multiple bends and various cross-section profiles, making it ideal for both large radius bends and intricate designs. Rolling machines are specialized equipment with multiple rolls that deform the sheet metal as it passes through, enabling the formation of precise curved shapes or cylinders.

Air bending

Instead of pressing the metal fully into a die, as with V or U bending, the sheet is floated above, making contact only at the bend point. This is ideal for situations where the angle is simple enough and when versatility is needed. The air bending method is the most commonly used brake press bending method due to its adaptability and efficiency.

Compared to wipe bending, which uses a wipe die and a pressure pad to guide the sheet and achieve precise bends, air bending relies on minimal contact and offers greater flexibility for partial bending. However, air bending is less precise in terms of the resulting angle due to variable springback, but it allows bending with a single set of tooling.

Common Challenges in Metal Bending

While bending sheet metal seems straightforward, some issues can arise. Fortunately, MakerVerse’s fully-vetted supply chain and in-house experts ensure the quality of your part. Sheet metal bending eliminates the need for specialized tooling, leading to shorter lead times and faster production cycles. Checking the flat pattern in CAD helps verify that designs can be produced without issues during bending. Laser cutting is often used to prepare flat patterns for bending, providing high accuracy and enabling complex shapes, which improves both efficiency and fabrication quality.

Managing material costs is a significant factor in sheet metal bending projects, as it directly impacts overall project expenses and the quality of the final product. Careful selection and optimization of materials help ensure cost-effective and high-quality fabrication.

Sheet Metal Design Tips:

• Always account for springback by slightly over-bending.

• Avoid sharp internal corners to reduce cracking risk.

• Use consistent material thickness for predictable results.

• Design with appropriate bend radii to prevent deformation.

• Collaborate with experts for feedback on manufacturability.

Springback: When metal is bent, it tends to bounce back a little toward its original shape once the bending pressure is released. This phenomenon is called springback. Predicting the amount of springback and adjusting the bend angle accordingly is crucial to fix this. This might involve over-bending the material slightly so that it springs back to the desired angle. Thicker materials generally require larger bend radii to prevent deformation.

Cracking: If bent too sharply, some metals, especially those that are brittle or not ductile enough, may crack at the bend. Using a larger bend radius or annealing the metal beforehand can reduce the risk. Proper material selection is also essential. Our experts are happy to help with design feedback and material selection. Parts should be designed to avoid sharp internal corners, as they increase internal stress and risk cracking.

Warping: Uneven stresses during the bending process can cause the metal to warp or deform undesirably. Ensuring even force distribution, proper tool alignment, and consistent material properties can help mitigate warping.

Surface Damage: The physical pressure during bending, especially with certain techniques, can mar the surface of the metal, leading to aesthetic and structural issues. Using films or coatings during bending, opting for less abrasive bending techniques, or post-process finishing can keep the surface pristine.

Inaccurate Angles: Achieving the desired angle is challenging, especially when dealing with variable material properties or machine inaccuracies. Regular machine calibration, using advanced tooling with angle feedback, and compensating for known material behaviors can increase accuracy.

Material Thickness Variations: Inconsistent material thickness can lead to unpredictable bending results. Quality checks of raw material and selecting high-grade sheets can ensure consistent thickness, leading to more predictable bends.

Tool Wear: Repeated bending, especially with harder metals, can lead to tool wear. Worn tools might not produce clean bends and can introduce defects. Regular maintenance, wear-resistant tooling materials, and rotating tools can prolong tool life and ensure consistent results.

The Future of Metal Bending

From the simple bends in a paper clip to the intricate curves of architectural marvels, bending shapes our world. It’s only getting better. Recent advancements in sheet metal bending processes are improving efficiency and quality, allowing manufacturers to achieve more precise and consistent results. The ability to accurately bend sheet metal remains crucial for meeting modern manufacturing needs. Advances in robot-assisted bending, better software, and more eco-friendly practices all make this critical component of sheet metal fabrication increasingly useful. Consistent bend radii help reduce costs and improve production efficiency, further enhancing the practicality of modern bending techniques. Using common tools for standard bends reduces tooling costs significantly.

You’re in the right place if you want access to sheet metal fabrication services. With lead times starting at 14 days, we can get you your parts quickly and with the highest quality.