"Bending" is the most commonly used method in stamping and sheet metal processing. It is a metalworking technique applied to many things around us, such as shelves, furniture, appliances, automobiles, and building components.
In this article, we will explain the "bending process" that transforms a piece of metal sheet into complex products. We have summarized everything from the basics of bending to its applications and how to ensure its accuracy, so please use it as a reference.
What is Bending (Forming) in Sheet Metal Processing?
Bending is a machining technique that involves bending metal materials into specific angles and shapes. It requires precision equipment and specialized skills and is crucial for enhancing the functionality and aesthetics of products.
Metal materials with high plasticity are used for bending. Plasticity refers to the ability of a material to change shape due to external forces and retain the new shape after the forces are removed.
Bending is actually applied in many products around us, such as car body components, appliance casings, and structural steel for buildings.
Bending creates specific shapes and structures that are suitable for their intended environment and purpose, making it a fundamental and essential technique in modern manufacturing.
Materials and Processes Used in Bending
Bending requires not only operating machinery but also skills and experience. It requires precision and careful consideration from material selection to manufacturing processes. Starting from here, we will explain the "Materials Used" and "Bending Processes" in bending.
1. Using stainless steel, aluminum, brass, etc.
The materials used for bending are typically metals such as cold-rolled steel, stainless steel, aluminum, copper, and brass. Each material has its own strength, weight, corrosion resistance, and workability.
For example, aluminum is chosen for its lightweight and ease of processing, while stainless steel is renowned for its high strength and corrosion resistance. For products requiring high strength, certain grades of steel can be chosen, and when electrical performance is crucial, copper materials can be selected.
Choosing the right material is crucial to ensure the product's lifespan, performance, and safety. Therefore, the material selection process requires a deep understanding of the overall goals and requirements of the project, as well as familiarity with the properties and advantages of each material.
2. Bending Process
The bending process is carried out precisely following the steps below:
Design Material Preparation Bending Quality Verification Precision Finishing/Assembly
2.1 Design
Firstly, create a product blueprint that clearly defines the required materials, dimensions, bending angles, etc. Comprehensive planning considering the functional requirements of the product and manufacturability is crucial.
2.2 Material Preparation
Next, cut the selected material into appropriate sizes and shapes. It is essential to maintain the quality of the material while ensuring the desired dimensional accuracy during this process.
2.3 Bending
Load the material into the bending machine and perform precise bending according to the programmed specifications. Several factors need to be adjusted in this step, including bending angles, pressure, and the method of material fixation.
2.4 Quality Verification
The bent parts undergo quality inspections for dimensions, angles, surface conditions, etc. Accuracy and consistency in accordance with the design specifications are crucial at this stage.
2.5 Precision Finishing/Assembly
Lastly, the parts are surface-treated as required and assembled with other relevant components. The functionality, durability, and visual quality of the finished product are ultimately ensured at this stage.
Each step directly influences the quality and performance of the bent workpiece. With collective efforts, the final product is guaranteed to meet the required specifications and standards.
Types of Bending
Bending comes in different types, ranging from V-bending to U-bending. Each bending type has unique advantages and is optimized for specific materials and product designs. I will explain the details.
1. V-Bending
V-bending is one of the most common bending methods, as the name suggests, it is the technique of bending a metal sheet into a V shape. The metal sheet is placed on top of a V-shaped die, and a punch is pressed down from above, generating the desired angle and shape.
V-bending is characterized by its simplicity and efficiency. The technique is compatible with metal sheets of various thicknesses and hardness. However, precise calculations considering the material type, thickness, and springback are crucial to achieve the correct angle and shape.
2. U-Bending
U-bending is the process of bending a metal sheet into a "U" shape. It is mainly used for manufacturing box-shaped components and casing parts, particularly suitable for items that need to accommodate other parts internally, such as the casing of electronic devices or small mechanical parts.
This process typically involves placing the metal sheet inside a bending machine and using a U-shaped die and punch to bend the metal. It is important to calculate the dimensions of the metal sheet before bending. This is because the elongation rate of the material in the bending area must be taken into account to ensure that the internal dimensions of the finished part align with the design.
U-bending requires high precision to achieve accurate angles and dimensions, and careful inspections during the processing are crucial.
3. L-Bending
L-bending is the method of bending a metal sheet at a 90-degree angle to form an "L" shape. It is crucial for applications that require right angles, such as shelf brackets and machine frame structures.
By pressing the metal sheet against a die, the precise "L" shape is formed. However, L-bending also presents its unique challenges. Internal stresses generated during metal bending can cause material distortion or deformation. The solution requires detailed planning and precise measurements of the part to be bent before processing.
4. Z-Bending
Z-bending is a specialized technique of bending a metal sheet into a Z shape, usually accomplished through multiple bending steps. It is the preferred choice for places that require structural strength and stability, such as joints and mounting brackets.
It typically involves two right-angle bends, resulting in the final product forming a "Z" shape. Ensuring accurate bending requires careful attention to bending machine settings, material placement, and bending angles.
The major advantage of Z-bending is the high rigidity and strength of the processed parts. This is because the Z shape provides additional structural support to the part.
5. Hat Bending
Hat bending is a technique of bending certain metal parts into a shape with a protruding center. It is used when additional structural strength or rib support is required.
Hat bending is achieved by bending the metal sheet at multiple points, often using a bending machine. Hat bending also requires precise calculations of material characteristics, bending angles, and bending locations. This technique enhances the durability and strength of the parts but requires the right tools, accurate data, and bending experience.
The Importance of Bending Accuracy and Dimension
In the field of bending, accuracy and dimension are crucial. Accurate calculations, precise workmanship, and fine adjustments are essential to ensure that the bent parts meet strict specification requirements.
Below, we will explain specific methods to ensure accuracy and the importance of dimension calculations.
To guarantee bending accuracy, the following points need to be understood and controlled.
Point 1: Elastic Recovery (Springback)
Elastic recovery, also known as springback, is the tendency of a material to partially return to its original shape after bending. By anticipating and considering the appropriate amount of over-bending, you can get closer to the desired angle and dimension.
Point 2: Material Uniformity
Inconsistent material quality can lead to unexpected deformations and uneven stress distribution during the bending process, affecting the accuracy of the final product. Therefore, maintaining consistent material quality is crucial.
One solution is to use high-precision steel sheets. Precision sheet materials often have consistent chemical composition and internal structure. They exhibit minimal thickness variation and excellent surface smoothness, reducing the risk of surface defects during bending.
They also help maintain dimensional consistency between parts, improving fit and functionality during assembly. However, high-precision sheet materials often come at a higher cost compared to regular sheets. You should consider factors such as your budget and specific requirements.
Point 3: Bending Radius
The bending radius refers to the inner curve radius when metal or other materials are bent. The smaller the radius, the higher the stress the material experiences, increasing the risk of cracking and failure.
Choosing the correct bending radius based on the material type and thickness can prevent these issues and improve product quality and lifespan.
Additionally, bending at the correct location is crucial. It helps maintain dimensional tolerances of the parts and prevents issues during the assembly process. Incorrect positioning can lead to deformation, resulting in component failures and assembly issues.
Point 4: Machine Accuracy
The accuracy of the machine directly affects the quality of the bending process. High-precision equipment ensures dimensional accuracy, repeatability, and predictable results, minimizing processing errors.
However, this requires regular calibration and maintenance. Compromised accuracy can result in non-compliant product dimensional tolerances and inconsistent performance, leading to increased rework and waste.
Point 5: Influence of Temperature during Processing
Temperature can affect material properties and may result in variations in processing accuracy. Specifically, higher temperatures soften the material, while lower temperatures make it harder. Maintaining an appropriate working environment temperature is crucial.
By understanding these points and managing them appropriately, bending accuracy can be ensured.
Calculations and Formulas for Bending
Accurate calculations are crucial for maximizing bending accuracy. Specifically, when predicting the final dimensions and shape of bent parts, calculating the flat pattern size is essential.
Bending calculations use the following formula:
L = A + B + (R + t + λ) × 2π × θ/360
L = Flat pattern size
A/B = Length of the part without bending stress
R = Inner bending radius
t = Thickness of the sheet (in millimeters)
θ = Bending angle
λ = Neutral axis shift rate (%)
This formula is used to calculate the accurate length of the part during the bending operation. In particular, the value of λ highly depends on the material type and other processing conditions, making accurate calculations and years of experience crucial.
Executing this calculation accurately ensures that the bent parts have the designed dimensions and shape, thereby improving the quality of assembly and the final product.
Considerations during Bending
Bending is a process that requires skill and experience, and there are several points to consider when using it. I will explain the details of each.
Springback Issue
During the bending process, the phenomenon of "springback" is considered a significant preventive measure. Springback refers to the elastic recoil that occurs when a metal partially returns to its original shape after bending. Stresses within the metal may cause the finished part to differ from the designed dimensions and shape.
Springback varies depending on the metal type, thickness, and bending angle. The impact of this phenomenon is particularly pronounced when high-strength metals or large bending angles are involved.
To address this issue, accurate calculations of material properties and springback amount must be made before bending. This often involves using experimental data or specialized software. Technicians also employ techniques such as over-bending to achieve the correct angle and dimensions.
Note the Material's Front and Back Side
During bending, it is essential to correctly identify the front and back side of the material being used and handle it appropriately. The material has characteristics known as "droop" and "burrs" during compression. These features significantly affect the quality of processing.
Burr refers to sharp points on the material's edges that, if present on the outer side of the product, increase the risk of material fracture during bending. Large burrs not only have a negative impact on product safety and quality but can also pose hazards during use.
Additionally, droop is a directional pattern found on the material's surface that can cause issues during processing. Specifically, unexpected distortion may occur if the bending direction does not align with the droop pattern.
Before bending, a thorough understanding of the material's characteristics and careful differentiation between the front and back side are necessary. This helps ensure product quality and reduces potential risks.
Requires Skill and Experience
Bending requires advanced techniques and extensive experience.
For example, in V-bending, when the material is bent along a straight line, compressive and tensile stresses act on the material. This causes the material's internal portion to compress and protrude while the external portion stretches, forming a "tilted shape."
This phenomenon results in mismatched external dimensions and the inability to achieve the expected external radius size, among other issues. Successfully managing and predicting these challenges requires an understanding of the bending process and the ability to accurately read the material's response.
This knowledge and skillset develop over time, and you may encounter complex issues that only experienced technicians can handle. That is why technical expertise and experience are crucial for ensuring bending quality. Understanding this complexity and taking appropriate measures will enable us to consistently deliver products that meet expected performance standards.
