Bending (sometimes called flanging or bending) is one of the most important and widely used techniques in sheet metal fabrication.

Sheet metal bending allows a manufacturer to turn a straight piece of sheet metal into an angled part, which is more cost effective than welding or fixing two separate parts together.

Sheet metal bending typically works by applying forces to the sheet metal in a way that causes permanent deformation. However, there are many different bending methods and bending machines that can be used to achieve the best results.

What Is Sheet Metal Part Bending

Sheet metal bending is a metalworking technique used to turn flat sheet metal parts into V, U or channel shapes.

It is an important and convenient manufacturing process because it is much cheaper to bend a flat sheet of metal into a new shape than to machine a V, U or channel shape from a solid part or to cast it in a foundry. In addition, bending produces a part that is stronger than, for example, a part made by welding two flat pieces of metal into a V shape.

Many types of sheet metal bending involve the use of machines called brakes, sometimes called bending machines or sheet metal folding machines. Forces can be applied manually or using, for example, hydraulic devices.

Sheet Metal Part Bending Equipment

The most important sheet metal bending equipment is the brake, which comes in several different forms.

A gable brake is a simple bending machine - and the most widely used brake in manufacturing - that clamps a sheet of metal to a flat surface and then uses force to make straight bends or simple creases through the movement of a movable bending blade.

A bending machine is a type of bending machine that uses a moving punch and corresponding dies. In this process, the sheet metal is placed on the die and the punch is forced to move into the metal, forcing it into the die. Depending on the shape of the die, bending machines can be used to create V-bends, U-bends and other shapes.

Box brakes (also known as finger brakes) are another type of bending machine that uses a row of metal "fingers" to make multiple custom bends. As the name implies, box brakes are typically used to make custom-sized boxes.

A bar folding machine is a small and simple bending machine with a handle that grips a sheet of metal and bends it in a single motion.

Types Of Sheet Metal Part Bending

There are different types of sheet metal bending used to achieve different bends in different ways. Three of these bending methods (air bending, priming and embossing) use bending machines, while the other bending methods use various machines.

1. Air Bending

Air bending is a method of bending bending in which the punch presses the sheet metal into the die, but not so far that it touches the walls of the die.

This method is not as accurate as the others, but it is very flexible: it can be used to make V, U and other shapes of bends. This is partly because the die geometry does not need to correspond exactly to the desired sheet metal bend, since there is no contact between the two surfaces.

2.Underbending

Underbending is another bending method. During underbending, the punch presses the sheet metal completely into the die, creating a bend that corresponds to the geometry inside the die. It is used to make V-shaped bends.

3.Stamping

Stamping is a more expensive type of bending bending in which the punch is lowered with greater force in the sheet metal and die, resulting in permanent deformation with little springback.

4.Folding

Folding can be done on machines such as gable brakes or rod folding machines. The sheet metal is clamped in place before the clamping beam is raised to bend the metal around the profile. Folding achieves a V-bend and allows for positive or negative bending angles.

5.Wiping

Wiping (or edge bending or wipe-bending) is another bending method applied to machinery such as gable brakes and steel folding machines (and in some cases, bending machines). It is faster than folding, but causes more damage to the sheet metal surface.

6. Roll Bending

Due to the machinery used, roll bending is probably the most unique sheet metal bending process. The roll bending system has three cylindrical rollers that bend the sheet metal into a curved shape, so it can be used to make pipes, tubes and other round parts.

7.Step Bending

Step bending (sometimes called dimple bending) is a method of bending using a bending machine to approximate smooth bending (e.g., bending by roll bending). By performing several small V-shaped bends in succession, step bending can produce bends that look like curves.

Rebound After Sheet Metal Part Bending

When sheet metal is bent into a new shape, it will naturally spring back to some degree after the bending force is removed. This is called "springback".

Rebound occurs due to the compressive strength of the bent sheet metal. When sheet metal is bent, one side is stretched in tension and the other side is compressed; however, because the compressive strength of the material is higher than the tensile strength, the compressed side successfully resists deformation and decompresses itself when the force is removed.

Rebound is not a major problem, but it means that the manufacturer must compensate for the expected rebound by over-bending the sheet metal. If the metal is intentionally slightly over-bent, a small amount of natural springback will result in the correct angle.

Of course, calculating springback is far from simple, and several variables affect the severity of springback, including the type and gauge of the material. In addition, a larger inside radius will result in greater rebound.

Sheet Metal Part Bending Allowance

When a sheet of metal is bent, the outer side of the bend is stretched and therefore its dimensions change. This means, for example, that the total length of the two legs of a V-bend will be longer than the original length of the sheet.

So, if the dimensions change, how do we accurately design a part to ensure that it fits together with the other components? How do we decide how long the flat sheet of metal must be? To compensate for the dimensional change, we must consider the bending allowance: the difference between the length of the unfolded sheet and the sum of the lengths of each leg of the finished bent part.

The bending allowance calculation will take into account factors such as sheet metal thickness, bending radius and bending angle. The bending factor required for a sheet metal part can be calculated using the bending factor calculator.

Optimal Sheet Metal Part Materials And Gauges For Bending  

Some sheet metal materials are better suited for bending than others. In general, the best bending materials are ductile rather than brittle.

Common materials used for sheet metal bending include

Mild Steel: Can be bent at any temperature.

Spring Steel: Can be bent after annealing.

Alloy Steel 4140: Can be bent after annealing.

Aluminum 5052: Highly bendable compared to other aluminum alloys.

Copper: Highly bendable.

Materials that are more difficult (though not impossible) to bend include aluminum 6061, titanium, brass and bronze.

How Grain Orientation Affects Sheet Metal Part Bending

The orientation of the sheet metal grain - the direction in which the metal's tiny crystals are elongated due to the sheet's original roll - affects the way it bends.

Grain orientation makes the sheet metal stronger in one axis and weaker in the other. Bending along the grain (longitudinally) increases the likelihood of cracking, tearing or orange peel peeling; bending against the grain reduces the chance of these problems.

However, while bending against the grain reduces the chances of breakage, it also requires more force because the sheet metal is stronger. As a result, it may cause more springback and require greater compensation in this regard.