What Is Sheet Metal Bending?

Air Bending

During this process the work piece comes into contact with the outside edges of the die, as well as the punch tip. The punch is then forced past the top of the die into the V-shaped opening without touching the V.

Air bending is the type of bending where the least amount of contact is made. The equipment only touches the material at 3 points: the punch, tip and the die shoulders.  Seen as though the tonnage doesn’t produce the bend, you don’t need as much as you would do when using the coining method.

Air bending is the most widely used type of metal bending and it’s not difficult to see why, as there are many advantages to this technique. Because the punch tip doesn’t need to be pushed past the surface of the metal, much less weight is required to bend in comparison to bottom bending and coining.

Bottom Bending

The difference between air bending and bottom bending is that there is a difference in radius between the two. It differs from coining as the punch and the tie don’t make full contact with the material, and there isn’t enough tonnage to make an imprint into the metal.

Bottom bending has many advantages, such as greater accuracy and less spring back when using the tooling, which makes it a safer option when considering metal bending techniques.

Coining

Coining is a bending process in which the punch and the work piece bottom on the die. This produces a controlled angle, which leads to little spring back. There is more tonnage required on this type of bending than in air bending and bottom bending.

The advantages of coining are that, in order to produce outstanding results, accuracy is essential and that is precisely what the coining method can provide. Along with being accurate, repeating the results is also an easy task when it comes to using this technique.  Spring back is also less common when using coining, meaning that the metal is less likely to return to its original state.

Folding

The metal folding technique involves folding the surface part of the sheet metal to form the desired bend. Folding uses clamps, which hold the metal piece in place and apply force to fold the metal at a specified angle to create the sheet metal bend.

Clamping beams will hold the longest part of the metal sheet. As the beam rises and folds the sheet metal, the bending beam can move up or down the workpiece.

Benefits: What’s useful is that, with the folding method, it is possible to create several folds in the same piece of metal, creating a two-sided channel or a square or rectangular hollow tube.

The finalised bend angle is influenced by the folding angle of the beam. This process can handle large sheets of metal and offers a very limited risk of damaging the sheet.

Wiping

The method of wiping involves applying force to the metal, which bends the workpiece into an angular shape by holding it between a pad and a die, then sliding the wiping flange downwards.

Similar to the folding technique, it is a plastic deformation of sheet material. Wiping enables you to round the workpiece that is being bent, which can be done by adding angle tangents from the radius to both the die and the flange.

Benefits: The method of wiping offers some advantages for sheet metal bends, such as excellent precision and limited surface damage, when compared to other methods. The applied force is spread evenly across the workpiece’s surface, and you are able to bend a workpiece multiple times in one run.

Important to note: The method is one of the more expensive techniques. It doesn’t support bending angles over 90° because of the geometry of the wiping flange, bent workpieces tend to create a moderate spring-back effect, and curved shapes require custom tooling.

Joggling

Joggling is a process where a machine bends the metal in both directions creating an ‘S’ or ‘Z’ shape.

Joggling involves shaping a sheet metal section by section through the use of stringers and formers. This method has been found to be particularly helpful for when you need to bend an extended workpiece in a periodically repeated pattern.

The process pushes a sheet metal workpiece into an equipment unit or a brake.

It bends the metal by 20 to 30 degrees, using the formers. The part should be released, turned over and bent again until the joggle is achieved.

Benefits: The benefits of the joggling technique are that it is very versatile in creating different shapes, has low production costs, and also has minor spring-back effects.

In terms of weaknesses, it might cause deterioration of a workpiece’s surface.

Rolling

Mostly used for manufacturing large workpieces in the construction sector, rolling is the method used for making tubes or cones in different shapes or bigger radius bends, using a rolling machine.

Metal rolling machines have the capability of feeding sheet metal between two rollers, which leads to the sheet emerging into a curve.

To increase the shape of the curve, the operator of the machine will reverse the rollers and then run the metal back through the rollers in the opposite direction. This process is repeated until the desired bend is achieved.

Rotary Bending

Rotary bending is a complex process of sheet metal bending. The process tends to create pipes, which can offer a variety of central line radiuses. The process involves bending a tube with a mandrel inserted inside so that it fits the exact outside diameter.

Benefits: Rotary bending can rotate a tube to a maximum of 180°, making it highly versatile. With this, the method can bend the workpiece several times in one run, from different angles. As well as this, the method shows limited spring-back effects.

However, some weaknesses of rotary bending include: being expensive, deterioration of a workpiece’s surface, and complexity of the overall process.