Bending is one of the most common operations in sheet metal fabrication. Also known as press bending, flanging, die bending, folding, and edge bending, this method is used to deform materials into angled shapes. It is achieved by applying force to the workpiece, and this force must exceed the material’s yield strength to achieve plastic deformation. Only then can you obtain lasting results in the form of bends.
This article serves as an introduction to sheet metal bending, covering the fundamentals of bending, common bending equipment, types of sheet metal bending, and technical considerations.
What is sheet metal bending?
Sheet Metal bending is a process by which a metal sheet can be deformed when applying force to the subject, which causes it to bend at an angle and form the anticipated shape, which often results in it being in V shapes, U shapes, or channel shapes. it is commonly used in rapid metal prototyping and low-volume manufacturing combined with other machining processes.
Sheet Metal Bending Tools
A press brake is a machine used for bending sheet metal and metal plates, using a moving punch and a corresponding die. During the bending operation, sheet metal is placed on the die and the punch is moved with force into the metal, forcing it into the die opening. Depending on the shape of the die, a press brake can be used to make V bends, U bends, and other shapes.
Metal rollers, also called sheet metal rollers or metal roller benders, can create a wide array of arcs, bends, cylinders, and circular objects. Types of metal rollers can be divided into 2-cylinder, 3-cylinder, and 4-cylinder rollers.
Rotary benders consist of a foundation block, often referred to as the saddle. The saddle has a spring-loaded V-shape component called the rocker. This rocker rotates about its centerline and performs the bending action. It acts as both a holding pad and a bending mechanism.
Types of sheet metal bending
According to the sheet metal bending tools, we have the following type of sheet bending method.
- press brake bending
- Roll bending
- Rotary bending
Press brake bending, V-shape
Sheet metal is bent when it is forced between two tools by the press brake: an upper tool (known as a punch) and a bottom tool (known as a V-die). The press brake controls the movement of either the punch or the die and provides the press force using hydraulic rams or electrical servo motors
Air bending—also called partial bending—is not as accurate as coining or bottoming. It is susceptible to springback. In this process, a punch applies pressure to the sheet metal part in the die cavity. During the bending process, the metal part doesn’t touch the die bottom necessitating the use of a press brake.
During the bottoming process, the punch forces the sheet metal fully into the die, creating a bend that corresponds to the geometry of the inside of the die. It is used to make V-shaped bends. Bottoming overcomes the spring back problem by punch and die force and shapes the metal part permanently.
Coining is a more expensive type of press brake bending in which a punch is lowered with much greater force at the sheet metal and into the die, creating a permanent deformation with no spring back. This is because the coin penetrates the sheet metal at a small radius, creating a dent present on a coin to distinguish sheets from another.
Press brake bending, U-shape
U-bending closely resembles the V-bending technique. It involves employing a U-shaped punch and a U-shaped die. The primary distinction between V-bending and U-bending is that the resulting sheet takes on a U shape rather than a V shape.
Press brake bending, Wipe bending
In wipe bending, a pressure pad holds the sheet metal against a wipe die. Subsequently, the punch applies force to the sheet’s edge extending beyond the die and pressure pad, prompting it to bend over the end of the die.
Roll bending is used to create different shapes of pipes or cones. If needed, it can also be used to produce large radius bends. Depending on the machine’s capacity and number of rolls, multiple bends can be carried out simultaneously or in a single pass.
The rotary bending technique is utilized when bending angles greater than 90 degrees are needed. While it shares similarities with V-bending, the resulting output is more uniform and aesthetically pleasing. This method uses a metal sheet bending machine that doesn’t scratch the sheet’s surface, contributing to a smoother finish.
Best materials for sheet metal bending
Sheet metal materials vary in their suitability for bending operations. Generally, the most suitable materials for bending are those that exhibit malleability and lack brittleness. Here are some commonly used materials for sheet metal bending:
- Mild Steel: Easily bendable at any temperature.
- Alloy Steel 4140: Can be bent after annealing.
- Spring Steel: Becomes bendable after annealing.
- Aluminum 5052: Highly bendable, particularly when compared to other aluminum alloys.
- Copper: Exhibits high bendability.
Benefits of Sheet Metal Bending
- Enhanced Precision: By precisely determining k-factors and bend allowances, the metal bending process achieves exceptional accuracy.
- Heightened Efficiency: Bending minimizes the need for complex tooling and supports automation, enabling swift operations and high-volume production.
- Streamlined Processes: Unlike sheet metal cutting, bending often eliminates the need for secondary procedures, such as welding, simplifying the overall manufacturing process.
- Cost-Effective Tooling: The bending process relies on straightforward tooling, resulting in cost savings compared to more complex methods.
- Material Efficiency: Bending allows the transformation of a single piece into the desired shape, reducing the need for numerous components in an assembly.
- Weight Optimization: Bending provides the desired part stiffness and strength without adding unnecessary weight to the component.
Guideline for Bending Sheet Metals
The bending height in sheet metal should be at least twice the thickness of the material plus the bend radius (H > 2t + R). A too-low bending height can lead to deformation and distortion during bending, resulting in an undesirable shape and size.
To ensure bending strength, the bend radius should be greater than the material’s minimum bend radius.
When sheet metal is bent, it’s advisable to bend it as perpendicular as possible to the direction of the metal fibers. Bending parallel to the fiber direction can lead to cracks at the bend point, resulting in reduced strength and potential fracture.
Avoiding Bending Failures
During sheet metal bending, problems often arise when other features are too close to the bending area, preventing proper material compression and resulting in bending failure or severe deformation. To prevent this, ensure that there are no obstructions within at least a distance of 2 times the sheet metal thickness plus the bend radius above the bending area.
Maintaining Bending Clearance
Due to sheet metal bending tolerances, a certain bending clearance should be maintained in the direction of the bending motion to prevent interference-related bending failures.
Ensuring Bending Strength
To maintain bending strength, it’s preferable to have long and narrow bends rather than short and wide ones. Therefore, sheet metal bends should generally be positioned along the longer edge.
Reducing Bending Steps
More bending operations increase tooling costs and decrease bending precision. Hence, sheet metal designs should aim to minimize the number of bending steps.
Avoiding Complex Bends
Complex sheet metal bending operations can lead to higher tooling costs, reduced precision, and material wastage. In cases of intricate bends, consider breaking them down into two separate components that can be assembled using methods like riveting, self-riveting, or spot welding
Include also sheet metal cutting and sheet metal welding, KUSLA is a leading sheet metal forming services provider from China. We offer high-quality bending services to our customers serving a broad range of industries. In addition, combined with our other manufacturing capabilities (like 3D printing and CNC machining), we can provide you with an all-encompassing manufacturing solution.