What Is Sheet Metal Bending?
Sheet metal bends are formed using metal bending. Metal bending is a process by which metal 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 a ‘V’ or a ‘U’ shape.
A press brake is a tool used in order to bend sheet metal and uses a punch and die to do this. Although press braking may seem straight forward, it can be quite difficult to remain accurate throughout the process. There are several types of press brakes which deliver different levels of force applied, such as mechanical, pneumatic, hydraulic and CNC to name a few examples.
Due to this press brakes design, it isn’t a suitable option for air bending. The two major benefits of a mechanical press brake are speed and accuracy, however other press brakes are safer and easier to use, such as the CNC press brakes.
A compressor is used to supply air power for bending the metal sheets. This type of press brake is often used when less pressure is needed. A pneumatic press brake is also best used for bending small parts of metal.
Hydraulic press brakes often have the latest technology incorporated within them and are best used for precise bending of metal sheet, which makes them a popular choice for sheet metal bending.
Computer Numerically Controlled (CNC)
Salamander Fabrications has 4 CNC press brakes, including a 4.2 metre bed with 180 tonne capacity. These machines produce very accurate result and are able to bed sheet metal work from just a few millimetres across to sections which are metres long on some of the larger machines.
Types of Metal 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.
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 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.
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.
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 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.
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 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.
Tips for Bending Sheet Metal
Whilst bending sheet metal is a useful strategy for many different types of projects, sheet metal bends can be easy to mess up if you get the technique wrong. To ensure you create the professional bend you are after, follow these helpful tips.
Tip 1: Choose the Right Materials
Due to some metals being more malleable than other metals, you need to be aware of the use of heat, and if it is necessary to reduce any cracking and weakening of the material.
Materials That Work Well for Sheet Metal Bends:
- Galvanised steel: A resilient and corrosion-resistant metal. If you bend galvanised steel, it can be moulded into the appropriate shape for your project. The bending process is usually quite simple, and in most cases, galvanised steel will be more malleable than shaped stainless steel forms.
- 5052 Aluminium: With high workability as well as low weight, aluminium is easy to bend as it is extremely malleable. This makes cracking rare.
- Stainless Steel: Mostly used for manufacturing within the food and medical industries, it has corrosion resistance, with some grades excelling at resistance. Different grades of stainless steel will perform differently but it can be prone to work hardening.
- Spring steel: Can be malleable when annealed but, once the work has hardened, it tends to require heat in order to bend again.
- Copper: This tends to be very malleable. Its antimicrobial benefits also give copper an added edge.
- Mild steel: No heat tends to be required for mild steel, making it very malleable.
Tip 2: Avoid Bending to a Sharp Internal Corner
It’s important to avoid bending to a sharp internal corner when producing sheet metal bends because it could cause cracking or weakening of the metal. This can be avoided by having a radius on your tool.
PRO TIP: The thickness of the material you’re producing should be the same as the inside bend radius.
Tip 3: Use a Press Brake
Brakes are extremely useful for creating a clean bend, as the metal won’t be wavy or even warped.
The two biggest advantages of a mechanical press brake have to be the speed and accuracy it offers when bending sheet metal.
Tip 4: Protect the Surfaces
Take care of the appearance of your metal by avoiding scratching its surface.
PRO TIP: The best way to avoid scratches is to use masking tape anywhere that might come into contact with something hard. Similarly, you could also use wood blocks to protect the section when bending.
Tip 5: Bend Allowance
Bending metal involves pushing, pulling, or stretching the material. Therefore, you need to calculate the bend allowance because this will offer you reliable numbers to work from when you lay out a flat sheet.
Certain factors need to be considered with this, such as material thickness and internal radius size.
Bend allowance is compensation for what happens to the material when it is stretched and formed from a flat pattern into the desired bend. By working out this bend allowance, you can figure out how much of a flange will remain when you’ve made the desired bend.
Benefits of Sheet Metal Bending
- Accuracy: Programmed laser cutters and CNC bending machines with high-quality software, as well as top-notch equipment, can produce accurate bends.
- No tooling investment: The laser cutting and sheet metal bending processes don’t require specialised tooling, as common tools usually can produce the desired bends. This means limited tooling investment.
- Speed of manufacture: Sheet metal parts can be produced fast, enabling big quantities of components to be produced in a short space of time.
- Fewer parts required: Making a workpiece from one piece of material instead of multiple, through the use of joints, reduces time, errors, complexity, and failure points.
- Less weight: There is a complex range of bends available. Strength can be achieved without the need for too much material. This reduces weight, which is an advantage for every step in the supply chain.
- Lower costs: CNC cutting, laser cutting and bending cut down on the manual labour required, and parts can therefore be made by less-skilled workers, leading to lower-end costs.
Quality Sheet Metal Bends with Salamander
Salamander Fabrications is a full-service sheet metal fabrication company. Our expert team works with organisations all over the country to create high-quality fabricated metal products with an exceptional customer experience.
Salamander provides a complete range of CNC machining services, and we pride ourselves on our ability to offer both full-service sheet metal fabrication and sub-contracting services.
It’s no wonder we have been the UK’s chosen choice for sheet metal fabrication solutions for over 50 years, with an expert team providing end-to-end machining services.
To learn more about the work we do or to get started with your next project, please don’t hesitate to get in touch with our friendly team on 01484 843599 or at firstname.lastname@example.org.