Sheet Metal Bending: Techniques and Best Practices

Sheet metal bending is one of the key fabrication methods used to produce various items across industries. It involves deforming the metal pieces into specific angles or shapes. There are many sheet metal bending techniques, each with a unique mechanism and capabilities. Most of the techniques involve placing the work in a die with a specific bending angle and pressing it with the punch. 

Furthermore, this article will elaborate on the fundamentals of bending,  different techniques, press break dies, and bending examples.

The Fundamentals of Sheet Metal Bending

Bending is achieved using equipment such as press brakes, which utilize dies and punches to create precise angles and shapes.  It can be performed using V-bending, U-bending, roller-bending, and other methods. 

• Deformation Process: The sheet metal is inserted in the chosen die and aligned perfectly with the punching tool(press brake). Then, force is applied with a punch, causing it to deform.
• Tooling Control: Accurate control of the punch and die, along with proper tooling, ensures the desired angle and radius are achieved.
• Force Calculation: The bending force must be precise to prevent cracking or other defects in the worksheet.

Compression on the inner and tension on the outer side can cause defects on bent parts. So, localized stress can be managed with proper tooling and force control.

What are the Common Sheet Metal Bending Techniques?

Bottoming, air bending, U-bending, V-bending, roller bending, and edge bending are common sheet metal bending techniques. Here is their brief elaboration;

1. Bottoming 

Bottoming or press brake dies involves bending the sheet metal by placing it in the die of a specific shape and punching it to the bottom of the die surface. As punch is applied at the end of deformation, it reduces the spring-back effect and ensures higher bending precision. The inner surface of the worksheet gets pressed until the last point, which allows it to exert as much force as possible so the final bending angle becomes accurate. Typically dies can be U or V-shaped. 

2. U ad V-Bending 

Both types of sheet metal bending techniques are similar, except the die shapes are V and U. The punch presses the sheet metal in the v or U-channel and deforms into the corresponding shape. Additionally, the bending angle can be changed by adjusting the die sections. These dies are common in bending applications as they can simply bend the sheets into U or V-shaped parts or varying angles. 

3. Air Bending 

As the name suggested, the punch creates the bends without touching the bottom of the die. It means the punch remains in the air before returning to the initial position.  We can say it is the opposite of bottoming. Subsequently, air bending is also flexible, with bending angles of 30°, 60°, 90°, 120°, and 135°.  One drawback of air bending is the spring-back effect. The punch does not hold the surface of the worksheet to the last location(bottom). So, there is the risk of bending angle deviation.

4. Roll or Roller Bending

This bending type produces curvature bends like cones,  tubes,  and pipes. It involves three rotating rollers, two drives, and one adjusting roller. Two driving rollers at the top and bottom rotate opposite directions, whereas the material is clamped between the top roller and the two bottom rollers. 

The bending force is exerted by the top roller pressing down on the material, while the bottom rollers provide resistance and shape the material as it passes through. The bending radius can be controlled by adjusting the position of the top roller and the spacing between the bottom rollers.

5. Rotatory Draw Bending

The rotatory draw bending involves clamping the workpiece or sheet and rotating around the bending die. Meanwhile, external supports(pressure die) are provided outside the surface to avoid flattering. This types of sheet metal bending techniques can achieve consistent, repeatable bends without any surface defects. Additionally, rotatory bending is also used in bending stainless steel tubing or other cylindrical components. 

6. Edge Bending

This applies where edges are unsuitable for reaming due to their large size. In the edge bending, work is attached tightly in a clamp or die, and then punched exerts the force to deform it. 

7. Folding 

This bending technique bends the sheet metal along a straight line, for example, a simple 90-degree bend, flanges, etc. It is a simple and quick process that costs significantly less than other bending types. Folding is widely popular in fabricating boxes and similar shapes.

The Press Brake Dies

Press brake tooling is essential in sheet metal bending, not for each technique, but for all bending types that involve placing the sheet in a die and pressing with the punch.

Press brake dies consist of two main parts: punch (upper die) and Die ( lower die). The punch is attached to the ram of the press brake machine and moves down to apply force to the sheet metal. Meanwhile, the die is connected to the bed of the press brake machine. It supports the sheet metal and forms the desired angle or shape when the punch applies pressure.

For strength, toughness, and durability, press brake dies are made with materials like tool steel, hardened steel, and carbide.

Which Materials Can Be Bent Using These Techniques? 

Sheet metal Bending is compatible with many metal alloy grades, such as steel, aluminum, copper, titanium, etc. However, allowable thickness and bending radius can be different based on individual material properties. The table below shows the common bending materials, their key properties, and popular grades.

Conclusion

There are many sheet metal bending techniques. Some of them use press brake and die setup to craft bending parts, whereas others might involve another mechanism like rollers or folding bars. All of the processes deform the sheet metal from a specific position into different angles. Meanwhile, V and U-shaped dies are most common among the bending dies.

At ProleanTech, we have facilities for all of these bending techniques, advanced CNC bending machines, custom die and tooling approaches, expert engineers, and more than a decade of experience in Sheet Metal Bending Services across the globe. So, if you need bending or other fabrication parts, please request a quote for cost and other technical details.

FAQ’s

What are the sheet metal bending techniques?

Sheet metal bending techniques include air bending, bottoming, roll bending, and folding.

Does bending affect the original properties of sheet metal?

Yes, bending can affect the original properties of sheet metal, causing changes in its mechanical properties like hardness and flexibility due to internal stresses.

Which one is better, air bending or bottoming?

Air bending is more flexible and requires less force, which makes it suitable for higher precision and consistency for specific angles.

What does it mean by U and V-shape dies for bending?

These are the most common die sets, creating U and V-shaped angular bends in sheet metal workpieces. It is ideal for U and V-shaped channels and profiles.