Sheet metal bending refers to the process of changing the angle of a sheet or panel, which may involve forming it into various shapes, such as V or U shapes.
Related Reading: V and U Shaped Bending Strength Calculator
Generally, there are two methods used for sheet metal bending: die bending and press brake bending. Die bending is suitable for sheet metal parts with complex structures, low production volumes and high-volume processing. On the other hand, press brake is ideal for sheet metal structures with larger sizes or lower yields.
Both bending methods have their own distinct principles, characteristics and areas of application.
I. Common Materials and Metals
Sheet metal bending is a process widely used in the manufacturing industry. The choice of material greatly affects the final product. This section will discuss the most common metals used for sheet metal bending, including their properties and applications.
Steel
Steel is a widely used and versatile material, composed of iron and carbon. It exhibits desirable properties such as strength, durability and economy. There are several types of steel available for sheet metal bending, including:
- Mild steel: Low carbon content allows for easy bending; Commonly used in automotive parts and construction.
- Stainless steel: Corrosion resistant due to the presence of chromium; used in a variety of industries including food processing and medical equipment.
Aluminum
Aluminum is a lightweight, corrosion-resistant metal that offers excellent formability and electrical conductivity. Its advantages include:
- Good strength/weight ratio
- High resistance to rust and corrosion
- Compatible with various finishing processes
Common applications include aerospace components, transportation equipment, and electronic enclosures.
Copper
Copper is a highly conductive metal that is easily bent and shaped, making it the perfect choice for electrical and electronic applications. The main characteristics of copper include:
- High electrical and thermal conductivity
- Naturally antimicrobial
- Recyclable
Copper is widely used in the electrical industry for wiring, circuit boards and transformers, as well as in plumbing and decorative applications.
Brass
Brass, an alloy of copper and zinc, is a popular choice for sheet metal bending because of its ease of manufacture and attractive appearance. It offers several benefits, including:
- Corrosion resistance
- Low friction
- Excellent machinability
Brass is commonly used in decorative and architectural components, musical instruments, and hardware accessories.
II. Bending Techniques
airbending
Air bending is a technique widely used in sheet metal processing. The process involves placing the sheet metal in a die with a V-shaped opening. The punch then applies pressure to the material, causing it to bend. The final bending angle depends on the penetration depth of the punch and the characteristics of the material. The advantages of air bending include:
- Low tooling costs
- Greater flexibility as multiple bending angles can be achieved with the same tool
- Reduced die wear
Minting
Coining is a technique that uses significant force to force a sheet metal into a die, creating a bend. During the coining process, the punch and die are pressed together with sheet metal sandwiched between them, causing the material to precisely conform to the shape of the die. The benefits of coining are:
- High precision and repeatability
- Reduced springback effects
- Increased material strength due to work hardening
Three-point push-up
Three-point bending is a versatile technique used to determine the bending properties of sheet metal. In this method, the metal sheet is supported at two points, with a force applied at a third point between the supports. This approach allows:
- Even distribution of stress and strain
- Better insights into material behavior under bending loads
- Testing various materials and thicknesses
V-folding
V-die bending is a common technique in the sheet metal industry. The metal is placed between a punch and a V-shaped die, which apply pressure to form the desired bend angle. This method offers:
- High precision and accuracy
- Consistency between different items
- Wide range of radii and bend angles possible with various die sizes
III. Bending equipment
Press the brake
The press brake is a piece of equipment widely used for bending metal sheets, offering high precision and accuracy in producing the desired shapes. It consists of a punch and a die, which apply force to the metal sheet to produce the bend. Press brakes come in various styles such as hydraulic, mechanical and electrical to meet different needs and requirements. The capacity of a press brake is determined by factors such as working length, tonnage and type of control system.
- Hydraulic : Uses hydraulic cylinders to apply force to the metal sheet.
- Mechanical : Employs flywheels and eccentric gears to apply force.
- Electric : Uses servo motors and ball screws for precise bending operations.
Folding Machine
Press brakes, also known as bending machines or bending brakes, are another essential piece of equipment in sheet metal bending. They clamp sheet metal between an upper and lower beam, bending it to the desired angle using a bending blade. This equipment is suitable for a variety of materials such as aluminum, stainless steel and carbon steel and provides an efficient way to produce large volumes of bent parts. Press brakes can operate in manual or automated modes, depending on the complexity of the job.
- Manual : Operated by skilled workers for simple or small-scale projects.
- Automated : Equipped with CNC controls for complex, high-volume tasks.
Bending Dies
Bending dies are crucial components of sheet metal bending equipment as they determine the shape, angle and radius of the finished bend. They are available in a variety of materials such as hardened steel, stainless steel and tungsten carbide to withstand the forces and friction involved in the bending process. Bending dies come in several types, including V-shaped dies, rotary bending dies, and cleaning dies, each with its unique features and applications.
- V-die : Most common type, used for air bending and bottom bending processes.
- Rotary bending dies : Minimizes friction, ideal for sensitive and scratch-prone materials.
- Clean Dies : Employ a wiping motion to create narrow-radius curves in sheet metal.
4. Standards and Certifications
ISO standards
Sheet metal bending operations must adhere to specific international standards to ensure quality, safety and consistency. The International Organization for Standardization (ISO) develops and maintains these regulations. For sheet metal bending, relevant standards include:
- ISO 9013: This standard specifies requirements for thermal cutting methods, including laser cutting and plasma cutting, which are often used in sheet metal bending processes.
- ISO 16630: This standard defines the mechanical testing methods used to verify the structural integrity and mechanical properties of sheet metal materials.
Adherence to ISO standards ensures that sheet metal bending operations produce reliable, high-quality products for various industries and applications.
ASTM Standards
The American Society for Testing and Materials (ASTM) also plays a crucial role in the sheet metal bending industry by establishing and maintaining standards. Relevant ASTM standards for sheet metal bending include:
- ASTM A6/A6M: This standard describes general requirements for rolled steel sheets, profiles, sheet pilings, and bars used in a variety of applications, including sheet metal bending.
- ASTM A480/A480M: This standard specifies general requirements for heat-resistant stainless steel flat-rolled sheets, plates, and strips used in sheet metal bending.
- ASTM E290: This standard defines the methodologies for carrying out flexural tests on metallic materials, to evaluate ductility and formability.
Compliance with ASTM standards ensures that sheet metal bending operations meet industry requirements and maintain a high level of quality in their products.
V. Mold Bending
Manufacturers typically consider using die bending as a processing method for structural parts that have an annual capacity of more than 5,000 pieces and are relatively small in size, usually around 300 x 300.
1. Common bending mold
Figure 1-17 displays commonly used bending dies. To increase the longevity of the mold, it is advisable to incorporate rounded corners into the design of the pieces.
Figure 1-17 Special Forming Mold
Using a bending die with very small flange height is not ideal for forming. Normally the height of the flange should be L ≥ 3t, considering the wall thickness.
2. Stepped push-up method
Z-shaped steps made of sheet metal with a lower profile are commonly bent using simple dies on punch presses or hydraulic presses for small batches. For larger batches, a stepped die on a press brake can be used, but the height (H) should normally be between 0 and 1.0 times the wall thickness
