Metal bending is a common way to make finished products out of metal. It might look like a simple task, but it takes a lot of different skills and complicated tools to do it right. One such tool is the press brake, which can bend and shape even the biggest sheets of metal. However, various press brake bending techniques exist to fit the ever-changing bending requirements.
In this article, we will look into techniques involving different types of bending machines. We will also discuss the basics of press brake bending, along with safety tips to help you avoid any hazards.
What are the Components and Principles of Press Brake Bending?
The upper or lower die of a press brake machine applies pressure to metal sheets, which causes them to stretch and then shrink. This is called press brake bending.
To understand this technique better, we first need to go through the components and principles involved. Let’s do that!
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Basic Components
A press brake is mainly made up of c-shaped frames, a top die or punch, a bottom die, and a hydraulic system. The flow of fluid that moves the top die is controlled by the hydraulic system. This system has tanks, pumps, motors, valves, and pipes. They all work together to move the top die.
The press brake’s main body is the c-shaped frame, which holds up the top and bottom dies.
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Bending Principles
At the start of bending, the sheet is free to bend. It is put on the bottom die, and the top die bends the metal sheets by applying pressure. The bending force arm and radius of curvature get smaller as the upper or lower die presses on the plate. This makes the plate slowly fit into the V-groove of the lower die.
At the end of the stroke, when the upper and lower dies are fully touching, they make a V-shape. This is basically called bending. Multiple aspects of bending need your attention, and one key principle is checking the straightness and indentation.
To get rid of indentations, operators increase the shoulder radius of the lower die. This process uses an anti-indentation film or an indentation-free lower die. On the other hand, the rigidity of the machine frame (frame design, choice of steel, etc.) determines how straight the bent products are.
Press Brake Bending Techniques
There are four different ways to bend metal sheets: air bending, bottoming, coining, and three-point bending. Each type follows its own process and has different advantages and applications. Let’s discuss them in detail.
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Air Bending
Air bending is a popular method in metalworking that doesn’t require the metal to directly touch the die. Instead, a punch pushes the metal into the die without fully contacting its bottom.
This technique uses an air gap beneath to bend metals by placing them on top of a v-shaped die. The depth of the punch determines bend angles. There is not much direct force needed for this process because it works better with leverage.
This method is praised for its adaptability. That’s because it permits varying bending angles using identical tools. That means decreased tool change times and boosted productivity. Additionally, air bending requires less power compared to other techniques, and that can extend the life of machinery.
Due to its flexibility, air bending is used a lot in hydraulic press brakes. This characteristic is important when different bends are needed.
Air bending can handle different metals and small to medium production sizes in many fields, such as aerospace and automotive construction. These industries appreciate not having to constantly switch out tools while still achieving diverse component designs.
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Bottom Bending
Bottom bending is a process where metal sheets are completely pressed into the bottom of v-shaped dies. Here, the punch makes the metal take on the shape of the die by pressing it fully against both sides and top.
This method differs from air bending as it involves full contact, although it uses less pressure compared to coining. Due to this lower pressure, achieving an exact bend angle like that of the die can be challenging.
A noticeable aspect of bottom bending is “rebound.” After metals have been bent and then released, they tend to spring back slightly towards their original form. This slight return can disrupt precision efforts.
Punches may overbend materials in order to address rebounding issues effectively. You might also use specially designed dies with sharper angles before setting the correct final angles. These changes are very important when accuracy is the goal.
Bottom bending has the capability of providing uniform parts with minimal variation among them. Hence, it’s an ideal option for projects needing consistent outcomes and precise dimensions, such as electronics manufacturing.
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Coining
Coining is a method that uses intense pressure to press metal sheets into specific shapes. The metal deforms, bends, and thins out to fit the mold perfectly through this powerful process. Originally, the process was developed for creating coins, hence the name “coining.” This technique requires strong machinery and detailed tool designs. That’s because it’s used for making high-precision parts.
Let’s think about coin making, where blank plates of metal are squeezed between two dies at very high pressure. In this way, the design of the dies is transferred accurately to the metal plate. This creates a coin with complex patterns.
The technology behind coining enables capturing even small details during shaping processes. This is possible thanks to the incredible force applied to metals using specially designed presses and tools.
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Three-Point Bending
This is a fairly new way to bend things. Some people think of it as a unique form of air bending.
For this method, you need a special die with a servo motor that lets you precisely change the height of the bottom tool. Over the bend radii of the die, the sheet bends until it touches the bottom. As the depth of the die bottom grows, the bend angle drops.
Addressing the differences in sheet thickness, a hydraulic cushion is used to make adjustments between the ram and the upper tool. This makes it possible to set the height of the bottom die to within ±0.01 mm. Because of this, the process can carefully bend angles that are less than 0.25 degrees.
The benefits of three-point bending are that it is very flexible and can make precise bends. But there are problems, such as high costs and a small selection of tools. Hence, this method can only be used in niche markets with a lot of demand right now.
Advanced Technologies in Press Brake Bending
The press brake uses advanced and improved technologies, including CNC (Computer Numerical Control). With CNC, manual operation is minimized because tasks are preprogrammed. This allows operators to set precise parameters on a computer for the machine to follow.
Let’s look at the advantages of incorporating CNC into press brakes
- Improved accuracy can be achieved since the technology precisely controls bending for consistent results.
- There’s also repeatability; programmed operations ensure uniform outcomes across all productions.
- Automation reduces manual labor and speeds up complex bends, increasing output.
- It is also easier to change the bending settings to meet different job needs, which increases flexibility.
- Setup times are shorter because machines can use stored programs instead of having to be reconfigured for each new piece. This makes switching between tasks faster.
- Furthermore, precision greatly lowers mistakes, which means less waste and lower costs.
Safety Tips
As an operator, you need to follow some basic safety rules for the press brake. Here are some of them:
- Prior to using your press brake, make sure you carefully read the instructions.
- Wear personal protective equipment (PPE) at all times.
- Perform a test run on the machine to ensure it is free of any dirt or other impurities.
- There are some press brakes that come with front and rear light curtains for safety. If these sensors find a blockage, they stop the machine from working. Keep an eye out for them.
FAQ
Q. What is the Rule for Bending Metal?
Ans. Bending metal depends on a few things, like the material, how thick it is, and the shape you want. Usually, the inside bend should match how thick your metal is. So, if your sheet is ⅛” thick, use a bending tool with a ⅛” radius for the best results. Similarly, for a thin sheet of 0.020”, use an equal radius.
The smallest bend you can make without breaking the metal depends on its flexibility and strength against cracks. People who sell these things usually write this information down in guides. They’d talk about safely shaping the metal to avoid issues. Likewise, they’ll also suggest minimal bends based on what kind of material you’re working with.
Remember to check whether you need to fold along or across any texture (like grains) because that matters, too.
Q. At What Temperature Does Metal Start to Bend?
Ans. Warm the thick sheet up to 200 to 300 degrees Fahrenheit before you shape it. This is especially important if you want to bend it to at least 0.75 inches. However, finding the right bending temperature requires knowing the chemical makeup, surface and edge states, and thickness of the material.
Conclusion
In simple terms, when you use press brakes to bend metal sheets, you put pressure on them to make them stretch and then shrink. However, to get the desired outcome, you need to adjust parameters like the straightness of the sheet.
There are different types of bending techniques for press brakes. They differ mostly based on the position of the workpiece and how it’s pressed. Besides, the intensity of the pressure and the range of tasks the process can cover also differ.
The hydraulic systems of a press brake mainly conduct the bending process. And, of course, the quality of the press brake defines the end result. And if you need the best press brakes, Fab-Line Machinery is here. Contact us today to find the press brake that suits your needs.