Press Brake Bending Basics: Everything You Need to Know for Efficient Bending

1. What are the basics of press brake bending?

1.1 Definition of press brake

A press brake is a common metalworking machine that bends metal sheets into a desired shape. Using different tools, it can achieve different shapes and bends.

1.2 Types of press brakes

1.2.1 By drive method: mechanical, hydraulic, and electric servo

Due to different drive methods, press brakes are categorized as mechanical, hydraulic, and electric servo.

1.2.2 By control method: manual, semi-automatic, and CNC

Due to different control methods, press brakes are categorized as manual, semi-automatic, and CNC.

2. Bending Methods and Techniques

2.1 Air Bending

2.1.1 Definition

This is a commonly used method for metal processing, which does not allow the metal to directly contact the tool. The punch will press the metal in the direction of the die, but will not contact the die. The die here is usually a V-shaped die, and due to the different depths of the punch, the bending angle is different. This technology not only has low power, but also can extend the service life of the machine.

2.1.2 Advantages and disadvantages

This method saves a lot of work time by using the same set of press brake tools for different bends, and requires relatively low machine power, which can extend the machine’s usage time. But it will cause rebound after bending, so manual bending is needed to achieve the desired bending angle, which is why this technology cannot achieve particularly accurate angles.

2.1.3 Typical usage scenarios

Air bending is widely used due to its flexibility. It is suitable for various fields such as automobile manufacturing, aerospace, and is generally used for small and medium-sized enterprises because it does not require frequent tool replacement, making it more suitable for this method.

2.2 Bottom bending/bottom mold bending

2.2.1 Definition

This method involves completely adhering the metal sheet to the die, and then using a punch to press the metal completely into the die, resulting in a shape that is exactly the same as the die.

2.2.2 Advantages and disadvantages

This method can better control the bending angle, reduce the number of angle adjustments, and also reduce rebound.

2.2.3 Typical usage scenarios

This technology is the best choice for items with the same results and precise dimensions, generally used in the manufacturing of parts.
Co2 is mainly suitable for cutting some non-metallic materials and relatively thin metal materials. The cutting quality of non-metallic materials is not as high as that of fiber laser cutting machines. Therefore, CO2 laser cutters generally cut wood, acrylic, glass, plastic, paper, leather, paper, foam, etc. “

2.3 Bending

2.3.1 Definition

This method involves applying strong pressure to push the metal downwards, causing it to deform, bend, thin, and then bend into the same shape as the die.

2.3.2 Advantages and disadvantages

After this method of bending is completed, there is almost no rebound, and it can make the bending angles of multiple components the same, thus producing high-precision bending. However, due to the need for strong pressure, there are significant requirements for press brakes, punches, dies, etc., which generally lead to damage to these instruments.

2.3.3 Typical usage scenarios

This method was originally used to produce coins. During the production process, a metal plate is pressed between two dies under strong pressure to ensure that the metal can completely fill the dies.

2.4 Three point bending

2.4.1 Definition

The three-point bending die requires a servo motor to accurately adjust the height of the bottom die. This method can only bend within the radius of the die, and as the depth increases, the bending angle will become smaller and smaller until it reaches the bottom of the die.

2.4.2 Advantages and disadvantages

This method has high flexibility, can automatically adjust the height, and also has high accuracy, which can control rebound. But this approach will increase equipment costs and there are not many tools to choose from.

2.4.3 Typical usage scenarios

This method is generally applied to the manufacture of high-precision instruments and tools, and can be used for multi size and multi angle plates.

Related technical reading : The Complete Guide to Press Brake Techniques:11 Types of sheet metal pressing process Explained

3. Press Brake Workpiece Preparation and Operation Process

3.1 Material loading, alignment, and fixation

The brake press first places the metal sheet on top of the machine die to ensure that the sheet is aligned with the die, in order to avoid tilting during the bending process, which ultimately leads to inaccurate bending. Then align the sheet metal and use fixtures or automatic backstepping to secure the metal, in order to ensure that the sheet metal does not move during the entire bending process.

3.2 Tool Settings

After the material is fixed, it is necessary to make correct settings, including knowing the type, thickness, length, and bending radius of the material, in order to select suitable tools and punches. Then, by inputting these parameters into the controller, the 3D mode of the required graphics can be calculated. If it is a manual or semi-automatic press brake, the bending angle needs to be manually adjusted. Then press the foot pedal to run, and bending can occur.

3.3 Bending process monitoring and parameter control

High end press brake equipment, equipped with a real-time monitoring system, can automatically repair the bending angle, while ordinary models require manual adjustment of the angle.

Due to the different pressures required for different materials, it is necessary to use CNC systems to automatically allocate reasonable pressures. Some materials require excessive pressure, which may cause damage to the tool and machine, so pressure control is necessary. In the entire travel monitoring, the Y-axis is an important factor, and its repeated positioning accuracy is particularly high.

3.4 Bending operation

After all the preliminary work of the brake press is set up, the bending operation can be carried out.

Firstly, force is applied to the metal plate through a punch, and then the metal plate is pressed into the tool so that it fits perfectly with the tool. Finally, the desired shape can be formed. If you have a press brake CNC system, you can program these parameters in advance. The advantage of doing so is to prevent errors caused by manual operation, and it is relatively safe.

3.5 Inspection and adjustment after bending

After the bending is completed, take off the board for inspection to see if the required bending effect has been achieved. If the effect has not been achieved, perform a second bending to ultimately achieve the desired effect.

4. Bend Calculation

4.1 How to Calculate Bend Allowance

Bending deduction amount=total length of flat parts – bending amount
The external indentation refers to the length beyond the bending angle, the K coefficient is determined by the material properties and thickness, T refers to the material thickness, and A is the required bending angle.

4.2 How to Calculate Bend Allowance

Bending allowance=bending angle x (π/180) x (inner bending radius+(K factor x total material thickness))
The K factor refers to the neutral layer, which is neither stretched nor compressed during the bending process of the sheet metal. The K value represents the ratio of the distance from the center layer to the inner surface of the sheet metal to the total thickness of the material.

5. Basic terms for bending

5.1 Bending radius

The bending radius refers to the radius formed on the inside of the material during the bending process, and its radius is determined according to the thickness of the material, generally speaking, the radius is 3 times the thickness of the material. If the radius is too small, cracking will occur, and if it is too large, it will affect the effect of bending.

5.2 Bending angle

The bending angle refers to the angle formed by the plate after bending, and the general angle is 90° or 180°. Effective bending angles must be precisely set in combination with practical use.

5.3 Rebound

Springback refers to the elasticity that occurs after the material is finished, which will lead to a larger bending angle. The thinner the material, the greater the rebound amplitude, and the bend angle is usually pre-set in advance to offset the rebound.

5.4 Definition of V-shaped bend and U-shaped bend

5.2 Recommendations and best practices to avoid these mistakes

V-shaped bending refers to the use of V-shaped dies, which are mainly suitable for relatively hard metal plates, and are generally suitable for mass production of plates and standard parts that can manufacture sharp angles. The die used in U-shaped bending is a U-shape, generally a combination of two or multiple bends, it is more suitable for brackets and other shapes, usually requires high die accuracy.

6. Important factors affecting bending accuracy

6.1 Press brake material Characteristics

The characteristics of materials play a very important role in the bending process. Generally, materials with high strength may require greater pressure, and press brakes also have ductility, where ductility determines the magnitude of springback during bending. If the ductility is low, it is easy to break during bending.

6.2 Press brake material thickness

Thicker materials tend to require greater pressure, which can affect the machine’s settings. If the pressure is too high, it may cause damage to the tool and machine, as well as cracking and other damages to the required materials.

6.3 Material Hardness

Due to the fact that the hardness of the material can affect the bending effect, the choice of impulse and tool will also be different. If it is a harder material, greater pressure is required, and excessive pressure can cause cracking. If it is a softer material, less pressure is required, but it is easy to leave marks on the surface.

6.4 Selecting the correct punch and die

Due to the fact that the punching angle and radius must be kept the same as the required bending angle and radius, it will affect the radius of internal bending, thereby affecting the final bending quality. In general, wider dies are easier to bend with thicker sheets, while narrower dies are more suitable with thinner ones.

6.5 Rebound phenomenon

Rebound is a process in which elasticity is restored due to the release of pressure after bending occurs. Due to different materials, rebound may occur differently. Generally, harder materials experience more rebound, and different bending methods can also lead to different rebound effects. The most obvious is air bending, which does not forcefully press the material into the die, so rebound will be greater.

7.Common errors and avoidance strategies

7.1 Angle deviation caused by cornering

Excessive or insufficient bending angle may lead to over bending. The main reason for this phenomenon is the failure to select suitable dies and punches based on the characteristics and thickness of the material. To avoid this situation, it is necessary to repeatedly check the compatibility between the die and the material.

7.2 Inaccurate operation alignment and error superposition

If the material is not aligned with the centerline of the bending machine worktable and the rear material system, it will result in errors. If not corrected in a timely manner, small errors will accumulate on multiple products, leading to inaccurate bending.

7.3 Preventive measures for surface indentation, scratches, fractures, and other issues

Molds not only need to be well preserved, but also regularly cleaned. If there are debris on the surface of the tool, it will cause the tool surface to become rough. In the process of selecting boards, sometimes the boards are too hard and prone to breakage, so it is necessary to choose suitable boards.

More about bending problem technology recommended reading: 10 Press Brake Bending Problems and How to Fix Them in Sheet Metal

8. Safety and maintenance recommendations

8.1 Training of operators, equipment certification, and compliance with standards

In order to ensure the safety of the bending machine during operation, it is recommended that all press brake operators receive comprehensive safety training, which should include the operation of the bending machine, knowledge of all contents of the control panel, knowledge of common faults and solutions, as well as training on safety precautions for operators.

8.2 Common PPE (protective goggles, gloves, etc.) and use of protective devices

When operating the bending machine, operators not only need to wear protective goggles to avoid eye injuries, but also need to wear protective gloves to prevent their hands from being cut and ensure their safety. They also need to wear protective clothing to avoid being cut by the machine and to avoid safety hazards caused by static electricity.

Recommended reading for related press brake maintenance technologies: Ultimate Guide to Hydraulic Press Brake Maintenance: Top Tools, Schedules & Expert Tips

9. Conclusion

From the above article, it can be seen that brake presses are indispensable in the metal manufacturing process and have many applications in our daily lives, such as industrial manufacturing, aerospace, automotive manufacturing, and other industries that play a crucial role.

CNC press brakes are the most widely used among all press brakes in daily life. They not only improve work efficiency, but also provide greater protection for operators.

Raymax is a press brake manufacturer with over 20 years of factory experience. If you are interested in our press brakes, please click on the homepage to communicate with us.

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