Indispensable Methods of the Bending Sheet Metal Processing

Posted on : May 31, 2022 By  GREFEE

Bending (sometimes called flanging or bending) is one of the most widely used technologies in sheet metal-making.

Sheet metal bending allows the manufacturers to turn a straight sheet metal part into one with angles. This is more cost-effective than welding the two single parts together or fixing them together.

Sheet metal bending works in a permanent deformation method to apply the force to the sheet metal. However, many different bending options and mechanics are used to achieve the optimal effect.

 What is sheet metal bending?

Sheet metal benign is a metal processing technology, used to transmit the flat sheet metal material into V, U shaped or the groove.

This is an essential and convent manufacturing process because it is cheaper to bend a flat metal plate to form a new shape than to make a solid part into a V, U-shaped, or channel-shaped one or cast in a die casting factory. Besides, the bend parts are more sturdy than those which weld the two flat metal plates together.

Many types of sheet metal bending involve the use of an arrester. Sometimes it is called the bending machine or sheet metal folding machine, which allows you to apply force manually or with the hydraulic pressure device.

 Sheet metal bending equipment

The essential sheet metal bending device is the arrester, which includes different types.

The cornice brake is a simple folding machine and the one that is the most widely used machine. It clamps a metal plate on a plane and then moves with the movable bent blade to make force it straight bends or simple creases.

A bending machine is a bending machine using a movable punch head and the related molds. In this process, the metal plate is placed on a mold, and the punch head is forcedly moved into the metal so as to enforce its move into the mold. According to the shapes of the mold, we can use the bending machine to make the V & U shaped and other shapes.

Box brake (also known as finger brake) is another bending machine that uses an array of metal fingers to achieve multiple custom bends. Obviously, the box brake is often used to manufacture customer-sized boxes.

A bar folding machine is a small-scale and simple bending machine with a handle that can be used to clamp the metal plate and bend it in a single action.

Types of sheet metal bending

Different types of sheet metal bending are used to achieve various bending in different ways. Three bending methods (air bending, backing, and embossing) need a bending machine, whereas the other bending methods employ different mechanics.

(1).  air bending

Air bending is a bending method in which the punch head presses the metal plate into the mold but not too far to make it contact the walls of the mold.

This method is not as accurate as other methods but is very flexible, which can make U, V, and other shapes bend. This partly results from the mold geometry does not need to correspond exactly to the required sheet metal bending because there is no contact between the two surfaces.

(2). backing

The backing is another type of bending method. During the process, the punch head presses the metal plate into the mold completely to form a bend corresponding to the internal geometry of the die. It is used to make V-bend.

(3). punching

Punching is a more expensive bending type in which the punch head drops with a higher force in the sheet metal and molds to produce permanent deformation and mild rebound.

(4).  folding

Folding can be processed on the cornice brake, rod folding machines, and other types. Before the clamping beam lifts to surround the contour to bend the metal, clamp the sheet metal firmly and fold it to obtain the V-bend and positive or negative bending angle.

(5).  wiping

Wiping (or edge bending and wipe bending) is another type of bending method which suits mechanics, such as the cornice brake and steel bar folding machine (in some situations is a bending machine). It is faster than the folding speed but will lead to more server damage to the metal surface.

(6).  roll bending

Due to the used mechanics, the roll bending might be the most unique sheet metal bending technology. It has a three-cylinder roller that can bend the metal plate into an arc, so it is used to make pipes and other circular parts.

(7). Step bending

Step bending (sometimes is called uneven bending）is a type of method that using a bending machine to approximate smooth bending (such as bending by roll bending). By continuously performing several small v-bending. The step bending can produce parts bends that look like bends.

Springback of sheetmetal after bending

When the sheet metal is bent into a new shape, it will naturally rebound to a certain extent after removing the bending force.

Due to the compressive strength of the bent metal plate, the metal will rebound itself. When the sheet metal bends, one side is in tension, and the other is in compression. However, the compressive strength of the material is higher than the tensile strength. So, the compression side successfully resists deformation and decompresses itself when the force is removed.

Springbank is not the primary issue, which means that the manufacturers must compensate for the expected rebound through the over-bending metal plate. If the metal is slightly excessive bending, s small amount of natural rebound will lead to the correct angle.Of course, it is easy to calculate the springback. Some variable quantities will affect the springback to a large extent, including the material types and specifications. Moreover, the larger inner radius will lead to a larger springback.

 Allowance of sheet metal bending

When a metal plate bends, the outside of the bend will be elongated. Thus, the size will be changed, too. This means that, for example, the whole length of the two legs that are v-bend is longer than the original length of the board.

So, what if the size is changed? How to we properly design a part and make sure it fit and work perfectly with other accessories?

The bending allowance calculation needs to consider the thickness of the sheet metal, the radius of bending, bending angle, and other factors. We can use the bend factor calculator to obtain the needed coefficients that the sheet metal part requires.

Best sheet metal material and gauge for bending

Some sheet metal materials suit the bending better. Generally, the best bending material is malleable rather than brittle.

Common materials of sheet metal bending include:

（1）Low carbon steel: bend under any temperature

（2）Spring steel: bend after annealing

（3）Alloy steel 4140: bend after annealing

（4）Aluminum 5052: it has high flexibility compared with other aluminum alloy.

（5）Copper: high flexible

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

How does grass direction affect sheet metal bending

The direction of the grain of the metal plate —— the direction in which the tiny grains of metal are stretched due to the original rolling of the plate —— will affect the way it bends.

The direction of grains will make the sheet metal stronger on one axis and make another one weaker on another axis. Bending along the textures (longitudinal) will increase the possibility of cracking, tearing, or peeling orange peel. Bending against the texture reduces the occurrence of these issues.

However, although bending along the texture decreases the damage rates, it needs a higher force because the metal is tougher. Thus, it might lead to more springback and more compensation on this aspect.

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