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Bending is a processing technology that bends metal materials into specific angles and shapes. It requires precision equipment and expertise, and is essential for enhancing the functionality and aesthetics of products.
Metallic materials with high plasticity are used for bending. Plasticity is the ability of a material to change shape in response to an external force and to retain the new shape when the force is removed.
Bending is actually used in many products around us, such as automotive body parts, appliance housings, and steel for construction.
Press brake bending creates specific shapes and structures that are functionally suited to the environment and purpose for which they are used, making it a basic and essential technique in modern manufacturing.
Bending requires not only the operation of machines, but also skill and experience. It also requires precision and thought, from the choice of materials to the manufacturing process. From here on, we will explain the ‘materials used’ and the ‘bending process’ for bending.
Materials used for bending are usually metals such as cold rolled steel, stainless steel, aluminium, copper and brass. Each has its own strength, weight, corrosion resistance and workability.
For example, aluminium is chosen for its light weight and ease of machining, while stainless steel is known for its high strength and corrosion resistance. Certain grades of steel can be chosen for products that require high strength, and copper can be chosen when electrical properties are important.
Choosing the right material is critical to ensuring product longevity, performance and safety. The material selection process therefore requires an in-depth understanding of the overall objectives and requirements of the project, as well as familiarity with the properties and benefits of each material.
The bending process is carried out precisely according to the following steps.
Design, Material preparation, Bending, Quality Verification and Finishing/Assembly
Firstly, a product blueprint is created that clearly defines the required materials, dimensions, bending angles etc. Comprehensive planning that takes into account the functional requirements and manufacturability of the product is essential.
The selected material is then cut to the appropriate size and shape. During this process, it is important to maintain the quality of the material while ensuring the required dimensional accuracy.
The material is loaded into the bending machine and bent precisely according to the programmed specifications. Many factors need to be adjusted during this step, including the bending angle, pressure, and the way the material is held in place.
The bent part undergoes quality checks for dimensions, angles and surface condition. Accuracy and consistency of design specifications are important at this stage.
Finally, the parts are surface finished as required and assembled with other related parts. The functionality, durability and visual quality of the finished product is finally assured at this stage.
Each step directly affects the quality and performance of the bent workpiece. Everything works together to ensure that the final product meets the required requirements and standards.
There are different types of bends, from V-bends to U-bends. Each type of bend has unique advantages and is optimised for specific materials and product designs. I will explain the details.
V-bending is one of the most common bending methods and, as the name suggests, it is a technique where a sheet of metal is bent into a V-shape. The sheet metal is placed on top of a V-shaped die and a punch is pressed down from above and the pressure from the punch produces the desired angle and shape.
V-bending is characterised by its simplicity and efficiency. The technique is compatible with metal sheets of various thicknesses and hardnesses. However, accurate calculations that take into account the type of material, thickness and elastic recovery are essential to achieve the correct angle and shape.
U-bending is the process of bending sheet metal into a ‘U’ shape. It is mainly used in the manufacture of box-shaped components and shell parts, and is particularly suitable for the manufacture of items that need to accommodate other parts inside, such as the shell of electronic equipment or small mechanical parts.
This process usually involves placing a sheet of metal in a bending machine and using a U-shaped die and punch to bend the metal. It is important to calculate the dimensions of the sheet metal before bending. This is because the elongation of the material in the bending area must be taken into account to ensure that the internal dimensions of the finished part are as designed.
U-bends require a high degree of precision to obtain accurate angles and dimensions, and careful inspection during the process is essential.
L-bending is a method of bending sheet metal at a 90 degree angle to form an ‘L’ shape. It is critical for applications that require right angles, such as shelf supports and machine frame construction.
By pressing the sheet metal onto a mould, a precise ‘L’ shape is formed. However, L-bending has its own unique challenges. The internal stresses created when bending metal can cause the material to twist or distort. This solution requires detailed planning and precise measurement of the part to be bent prior to processing.
Z-bending is a special technique for bending sheet metal into a Z-shape, usually done in multiple bending steps. It is preferred where structural strength and stability are required, such as joints and mounting brackets.
It usually involves two right-angle bends to create a ‘Z’ shape in the final product. Ensuring accurate bends requires careful attention to bending machine settings, material placement and bending angles.
The biggest advantage of Z-bending is the stiffness and strength of the part being machined. This is because the Z-shape provides additional structural support for the part.
Hat bending is a technique for bending certain metal parts into a shape with a protruding centre. It is used when additional structural strength or rib support is required.
Hat bending is accomplished by bending sheet metal at multiple points, usually using a bending machine. Hat bending also requires precise calculations of material properties, bending angles, and bending positions. This technique improves the durability and strength of the part, but requires the right tools, accurate data, and bending experience.
In the field of bending, accuracy and dimensions are critical. Accurate calculations, precision work and fine adjustments are essential to bending parts to meet exacting specifications.
Below, we will explain specific ways to ensure accuracy and the importance of dimensional calculations.
To ensure bending accuracy, the following points need to be understood and controlled.
Elastic recovery (rebound) is the tendency of a material to partially return to its original shape after bending. By thinking back and considering proper overbending, you will get closer to the desired angle and size.
Inconsistent material quality can lead to unexpected deformations and uneven stress distribution during the bending process, which can affect the accuracy of the final product. It is therefore very important to keep the material quality constant.
One solution is to use high-precision steel plates. Precision plate material tends to have a consistent chemical composition and internal structure. It has very low thickness variation and excellent surface finish, reducing the risk of surface defects during bending.
It also maintains dimensional consistency between parts, which improves fit and function during assembly. However, the cost of high-precision sheet tends to be higher than regular sheet. You should consider your budget, purpose, etc. in a comprehensive manner.
Bending radius is the radius of the inner curve of a metal or other material when it is bent. The smaller this radius is, the more stress is placed on the material, which increases the risk of cracking and failure.
Choosing the correct bending radius for the type and thickness of the material prevents these problems and improves product quality and service life.
It is also important to bend in the correct position. This maintains the dimensional tolerances of the part and prevents problems during assembly. Inaccurate positioning can lead to distortion, which can result in part failure and assembly faults.
The accuracy of the machine directly affects the quality of the bending process. High-precision machines minimise machining errors by ensuring dimensional accuracy, repeatability and predictable results.
However, this requires regular calibration and maintenance. Impaired accuracy can lead to product dimensional tolerance violations and inconsistent performance, resulting in increased rework and waste.
Temperature affects material properties and can lead to differences in machining accuracy. In particular, materials soften when temperatures are high and harden when temperatures are low. It is important to maintain an appropriate working environment temperature.
By understanding these points and managing them appropriately, bending accuracy can be assured.
Accurate calculations are essential to maximise bending accuracy. In particular, the calculation of unfolding dimensions is critical when predicting the final size and shape of a bent part.
Bending calculations are performed using the following formula:
L = A + B + (R + t + λ) × 2π × θ/360
L = Unfolding dimension
A/B = Length of part without bending stresses
R = internal bending R (radius)
T = Plate thickness in mm
θ = bending angle
λ = neutral axis movement (%)
This formula is used to calculate the exact length of the part during the bending operation. In particular, the value of λ is highly dependent on the type of material and other processing conditions, so accurate calculations and years of experience are very important.
Performing this calculation accurately ensures that the bent part has the designed dimensions and shape, thus improving the quality of the assembly and the final product.
Bending is a process that requires skill and experience, and there are a few things to keep in mind when using it. I will explain the details of each one.
The phenomenon of ‘springback’ is considered an important precaution during the bending process. Springback is 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 be different in size and shape than designed.
Rebound varies depending on the type of metal, thickness and bending angle. The effects of this phenomenon are particularly noticeable when high strength metals or large bending angles are required.
In order to solve this problem, material properties and springback must be accurately calculated prior to bending. This usually involves the use of experimental data or specialised software. Technicians also use techniques such as overbending to obtain the correct angles and dimensions.
When bending, the front and back of the material used must be correctly understood and handled appropriately. Pressed materials have features called ‘sags’ and ‘burrs’ that greatly affect the quality of the process.
Burrs are sharp points on the edge of the material that, if located on the outside of the product, increase the risk of material breakage during bending. Large burrs not only have a negative impact on product safety and quality, but can also be dangerous during use.
In addition, ‘sag’, a directional pattern found on the surface of the material, can also cause problems during processing. In particular, if the direction of bending does not match the direction of bending, unexpected distortions may occur.
Before bending, it is important to fully understand the properties of the material and take maximum care to distinguish between positive and negative surfaces. This helps to ensure product quality and minimise potential risks.
Bending requires advanced skills and experience.
For example, in V-bending, compressive and tensile stresses are applied to the material as it bends in a straight line. This causes the inside of the material to compress and protrude, while the outside is stretched to form a ‘sloping shape’.
This phenomenon can lead to problems such as mismatched external dimensions and the inability to obtain the desired external radius dimensions. Successfully managing and anticipating the challenge requires an understanding of the bending process and the ability to accurately read the material response.
These knowledge and skills develop over time, and you may encounter complex problems that only experienced technicians can handle. That’s why skill and experience are critical to ensuring quality bending. Understanding this complexity and taking the appropriate steps will enable us to consistently deliver products that meet expected performance standards.
