How Does a Press Brake Work? A Quick Guide

I. What Is A Press Brake

Press brake is a versatile machine tool used in industries and fabrication shops for bending sheet metal to a desired angle and shape. The sheet metal bending process is accomplished by applying force on the point of the bend. The metal sheet is placed between the punch and the die on the press brake machine. The punch is the upper component, and the die is the lower component.

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The press brake machine exerts force on the metal sheet through the punch, causing it to bend or deform according to the shape of the die. As the punch forces the metal into the die, the material bends. The force applied by the punch, and hence the bending, can be mechanical, pneumatic, hydraulic, or servo-electric, each having a specific use-case and advantages.

It drives punches and dies through different driven sources to bend repeatable sheet metal and form profiles. Materials of different thicknesses and lengths require different bending forces. Simply put, press brake forming is a process used to bend and shape sheet metal.

Bending force, measured in tonnage, is the force exerted by the press brake. Tonnage determines the press brake's load limit. If a press brake has a higher tonnage, it can bend thicker and longer sheet metal. Different types of press brakes produce tonnage in different ways. The hydraulic press brake machine is suitable for bending with large tonnage, while driven sources are generally divided into mechanical, hydraulic, electric, and pneumatic types.

The name of the press brake is determined by the driving method. For example, the pneumatic bending machine drives the ram through air pressure, while the servo-electric press brake drives the ram using a servo motor. The servo-electric press brake offers very high precision and speed.

II. How does A Press Brake Work

Modern common type of press brakes can be mainly divided into mechanical and hydraulic press brakes. At present, the modern press brake has developed into the advanced Computer Numerical Control (CNC) hydraulic press brake. Using CNC press brake can handle all kinds of complex and mass workpiece-forming tasks.

Here is a detailed comparison of different types of press brakes (hydraulic, mechanical, CNC) along with their respective advantages and disadvantages:

The mechanical press brake drives the flywheel through the motor. The operator operates the clutch to control the flywheel, and the crank drives the movement of other parts. The operation of a press brake is relatively simple, and it can handle large tonnage bending.

The hydraulic press brake is driven by the synchronous movement of the hydraulic cylinder. There is a hydraulic cylinder on each side of the uprights, and the hydraulic cylinder is connected to the ram through the piston rod.

The movement of the hydraulic cylinder drives the ram up and down. The movement modes of the hydraulic press brake are divided into up-moving and down-moving. The back gauges accurately position the workpiece through the movement of different axes. The hydraulic press brake has the advantages of high speed and high precision. However, the tonnage of bending is limited, which is a disadvantage.

The CNC press brake is a hydraulic press brake equipped with a CNC control system that controls the movement of each part with modular programming functions and high precision. The operator can set parameters through the control system. For example, bending angle, plate thickness, flange length, cycle time, stress, etc.

Additionally, the CNC press brake is also equipped with an automatic feeding system that accurately controls the position of the workpiece through the movement of the ram and back gauge. Synchronous movement of the motor drive axes of the back gauge and the ball screws. The back gauge can accurately measure the length of the flange being formed.

Adjust the bending angle by adjusting the ram movement through the control system. There are basically three bending methods: air bending, bottom bending, and embossing bending. The choice of bending method has a great relationship with the thickness of the plate.

Air bending is the most commonly used bending method, where the workpiece is not in full contact with the bottom die. It can be carried out with relatively small tonnage. Bottom bending and coining methods can also be used as needed.

During bending, the hydraulic cylinders drive the movement of the ram, which in turn drives the upper die to apply pressure on the lower die on the workbench. The sheet metal in the middle is formed into a specific angle through the extrusion of the die, and after repeated bending, the final profile is obtained.

The angle and shape of the metal plate are determined by the shape of the punches and dies, as well as the movement of the ram. The CNC press brake offers flexible numerical control and programming functions, making it operator-friendly.

III. How to set up a press brake?

First of all, it is critical to understand the drawing of the bending workpiece. Determine the material, length, and thickness of the workpiece, as well as the bending angle, bending radius, flange dimension, and tolerance of the workpiece. Secondly, choose the appropriate bending method and die.

Select the appropriate bending method based on the relationship between the bending radius and metal thickness, such as air bending, bottom bending, or coining. Choose a punch and die set that match the material of the bending workpiece. Thirdly, determine the tonnage according to the tonnage table.

Consult the corresponding tonnage estimation provided by the manufacturer. If it is air bending, you can refer to the tonnage chart to determine the tonnage. The tonnage of bottom bending is four to six times that of air bending, and the tonnage of coining is eight to ten times that of air bending tonnage.

Press brake tooling plays a crucial role in achieving precise bends. Install and adjust the press brake tooling, including checking the thickness and proportion of the upper and lower dies, adjusting the stroke of the ram, adjusting the upper limit point of the toolings to reserve the stay position of the ram, and setting an appropriate gap between the upper and lower dies.

Perform the program procedure of the press brake, familiarizing yourself with the functions of the CNC controller, programming offline, and using scrap plates for a bending test. If there is a problem with the bent workpiece, check and correct the program, and operate the press brake accordingly. These steps can save costs and improve efficiency.

IV. Cases and Application

1. Automotive Industry

Press brakes are widely used in the automotive industry to manufacture various car components such as brackets, chassis, body panels, and exhaust systems. Their high precision and consistency ensure the quality and safety of these parts. For example, press brakes can accurately bend metal sheets to meet the stringent specifications of car manufacturers, resulting in high-quality vehicles.

2. Aerospace Industry

In the aerospace industry, press brakes are used to produce critical components like aircraft frames, wing parts, and engine covers. Given the need for extreme precision and reliability in aerospace parts, press brakes ensure the structural integrity and functionality of these components. For instance, press brakes can precisely bend aluminum and titanium alloys to meet the rigorous requirements of aircraft and satellites.

3. Home Appliance Industry

Press brakes are used in the home appliance industry to produce refrigerator panels, washing machine housings, and air conditioner components. Their high precision and flexibility allow manufacturers to meet the specific design requirements of each appliance. For example, press brakes can accurately bend metal sheets to produce appliance housings and internal components that adhere to design specifications.

4. Construction Industry

In the construction industry, press brakes are used to manufacture structural components, beams, and other metal elements used in building and infrastructure projects. For example, press brakes can bend metal sheets to produce structural components like I-beams and metal decking that meet architectural design requirements.

5. Furniture Manufacturing

Press brakes are used in furniture manufacturing to produce metal frames, brackets, and decorative metal parts. For example, press brakes can bend metal sheets to create complex shapes and angles that meet furniture design requirements, enhancing both the aesthetics and functionality of the furniture.

6. Medical Equipment

In the medical equipment manufacturing industry, press brakes are used to produce high-precision and high-performance metal components. For example, press brakes can bend metal sheets to produce components that meet the stringent specifications of medical devices, improving production efficiency and product quality.

7. Electronics and Electrical Equipment

Press brakes are used in the electronics and electrical equipment manufacturing industry to produce precise metal housings and components. For example, press brakes can bend metal sheets to create housings and brackets that meet the design requirements of electronic devices, ensuring their functionality and safety.

8. Defense Industry

In the defense industry, press brakes are used to manufacture high-strength metal plates and alloy components such as ammunition storage containers, armored vehicles, and armor plates. For example, press brakes can bend metal sheets to produce components that meet the stringent requirements of military equipment, enhancing the durability and safety of the equipment.

V. Common Faults of Press Brakes and Solutions

VI. Conclusion

There are many kinds of press brakes, such as mechanical press brakes, CNC press brakes, hydraulic press brakes, etc. No matter how advanced the technology of the press brake is, its basic working principle is similar. The modern CNC press brake is more advanced than the previous press brake technology, and the bending accuracy and efficiency have been greatly improved.

ADH produces various CNC press brakes, NC press brakes and large press brakes. You can consult our product experts to learn more about our press brake or other machines.

I. Introduction to Press Brake Bending

Press brake bending is a common metal fabrication technology that bends metal into specific shapes. It is vital in metal fabrication industries and manufacturing. It involves a machine known as a press brake.

Types of press brake machines include manual press brakes, hydraulic press brakes, CNC press brakes, servo-electric press brakes, and mechanical press brakes. Each type has its own advantages and characteristics during press brake operation.

In the process of bending, the piece of sheet metal is placed on the press brake and can be bent into the required angles and shapes by exerting pressure.

In the bending process, the workpiece is clamped between the top punch and bottom die and can be bent by exerting pressure. The whole bending process is programmed and smooth. Knowing the press brake bending basics is vital to designing and producing sustainable, intelligent products.

II. Bending Process Overview

Steps in Press Brake Bending Machines

Material Loading, Alignment, and Securing

The first step in the bending process is loading the metal sheet onto the press brake machine. The material is typically placed on the machine's bed, ensuring it is aligned with the tool centerline. Proper alignment is critical to avoid any skewing during the sheet metal bending process, which could lead to inaccuracies in the final product.

Once aligned, the sheet metal is secured in place using clamps or a backgauge system. These systems ensure that the material stays in position throughout the bending operation, preventing any movement that might affect the bending accuracy.

Setting Up the Press Brake

After the material is secured, the press brake machine needs to be properly set up. This involves selecting the appropriate punch and die tooling based on the material type, thickness, and the desired bend radius. The machine operator also needs to adjust the bending angle, the stroke length, and the force applied by the press brake.

These parameters are crucial in achieving the desired bend with the right amount of precision. Additionally, the machine's control system may need to be calibrated for specific part dimensions, ensuring that the bend is produced within the specified tolerances.

Bending Operation

Once the setup is complete, the bending operation can begin. The press brake applies force through the punch, pressing the sheet metal into the die to form the desired bend. The amount of force applied is carefully controlled to avoid material cracking or improper bending.

Throughout the operation, the operator monitors the process to ensure that the bend depth and angle are achieved accurately. If the machine is CNC-equipped, the bending parameters can be pre-programmed, allowing the machine to automatically adjust for optimal results.

Post-Bending Inspection and Adjustments

After the bend is complete, the operator will inspect the part to verify that the bend meets the required specifications. Any adjustments to the machine or tooling can be made if necessary.

Depending on the complexity of the part, additional processes, such as finishing or trimming, may also be performed to refine the shape and ensure the part fits precisely into the final assembly.

Types of Press Brake Bending Techniques and Applications

There are different types of bending techniques for every press brake:

Process

Air bending is one of the commonly used technologies in metal bending, which will not make metal contact the die directly. The punch will press the metal sheets into the die to some depth without connecting the bottom.

The reason for bending is the metal sheet lies on the top of the v die at the bottom and utilizes the bottom air gap. The bending angle is determined by the depth at which the punch descends into the die. Additionally, air bending requires less power compared to other techniques, and that can extend the life of machinery.

Advantages

Air bending stands out for its versatility. Because the metals do not utterly fit the shape of the die, thus using the same set of tools is able to achieve a bending angle, which decreases the tool changing time and improves the efficiency. Compared with other methods, air bending needs less force, thus can prolong the machine's lifespan.

Considerations

• Springback: The material springs back slightly after bending, so you need to bend it slightly more to get the right angle.
• Angle Accuracy: Achieving precise angles may require additional adjustments due to springback.

Applications

Air bending is widely applied in the hydraulic press brake for flexibility, especially when multiple bending die angles are needed in the same work. It can be used to bend multiple metal materials and produce small-medium scale products.

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Many industries have benefited from this technology, such as automotive, aerospace, and construction. There is no need for these industries to replace the tool constantly, and can generate various components.

Process

In bottom bending, the metal sheets are utterly pressed in the bottom of the v-shaped dies. The punch forces the metal to form the same shape as the die. Unlike air bending, bottom bending forces metal to the whole contact with the top of the punch and two sides of the tooling.

However, compared with coining, the exerting pressure is relatively more minor. Thus, the bending angle is hard to match the die utterly.

Rebound

The apparent phenomenon in bottom bending is 'rebound'. When the metal sheets have been bent and released, they will shrink slightly to recover to their original shape. This elastic recovery may cause problems when the precision is paramount.

To offset rebound, the punch will bend the material excessively. Or the die with a finer angle can be pre-adopted to bend to ensure the final bending angle is accurate in case rebounding occurs. This method is applicable to bend parts with relatively simple geometry.

Advantages

• High Precision: Provides greater control over the bend angle, reducing the need for adjustments.
• Reduced Springback: Minimizes springback, ensuring consistent results.

Considerations

• Higher Force Requirements: Needs more tonnage than air bending, increasing wear on the machine and tooling.
• Tooling Wear: The increased force can lead to faster wear of the punch and bottom of the die.

Application

Under the circumstance of emphasizing consistency and precision, bottom bending is preferred. It is widely applied to the industry requiring minimum difference and uniform components, such as electronics.

Coining

Process

Coining is a technology that uses strong power to press the metal sheet and forces it to deform, bend, and thin to precisely fit the die shape. This process is renowned for its enormous power and will make people reminiscent of the coin's coining process.

It requires a higher-strength press brake and a more intricate tooling design and is mainly used for components requiring high-precision production.

Advantages

• Extreme Accuracy: Produces highly accurate bends with virtually no springback.
• Consistency: Ensures consistent bend angles across multiple parts.

Considerations

• High Tonnage: Requires substantial force, which can place considerable demand on both the press brake and the tooling.
• Tooling Stress: The intense pressure can lead to rapid wear and potential damage to the tooling.

Relation to coin production

'Coining' refers to the method of coin production initially. In the process of coin production, the blank metal plates will be pressed between the two dies under tremendous pressure, thus ensuring the metal flowing and die filling. A coin with a complex design will be produced. Similarly, the metal will be pressed in coining technology to capture each mini detail of the die.

III. Factors Influencing Press Brake Bending

Material Properties

The properties of the material being bent play a crucial role in the press brake bending process. Different materials respond differently to bending forces due to variations in their physical and mechanical properties. Understanding these properties is essential for selecting the appropriate bending parameters and ensuring optimal results.

Material Thickness

Thickness of the material is one of the most critical factors in press brake bending. Thicker materials require more force to bend, which can impact tooling selection and machine settings. The bending force must be sufficient to achieve the desired angle without causing damage, such as cracking or excessive deformation.

Additionally, thicker materials tend to exhibit less springback, making it easier to achieve accurate bends. Operators must consider the thickness in their calculations to ensure the press brake is capable of handling the required force efficiently.

Material Hardness

The hardness of the material also affects the bending process. Harder materials, such as high-strength steels, require more force to bend and are more prone to cracking if not handled correctly. Softer materials, such as aluminum, require less force but can be more susceptible to surface marking and denting.

The material's hardness influences the choice of punch and die, as well as the bending method (air bending, bottoming, or coining). Properly matching the tooling to the material's hardness helps in achieving consistent results without compromising the material's integrity.

Material Type

Different materials, including steel, aluminum, copper, and their alloys, have unique properties that affect their behavior during bending. For example:

• Steel: Known for its strength and durability, steel is commonly used in press brake bending. It typically requires higher bending forces and careful handling to avoid issues like cracking or excessive springback.
• Aluminum: This material is easier to bend than steel but is more prone to surface deformation. It has a higher springback tendency, requiring adjustments in bending angles to compensate.
• Copper: Copper and its alloys are ductile and formable, making them suitable for complex bends. However, they can be prone to surface damage, requiring softer tooling materials or protective coatings.

Tooling Considerations

Tooling is another critical factor in press brake bending, as the choice of punch and die directly impacts the quality and precision of the bends. Proper tooling selection and maintenance are essential for achieving consistent and accurate results.

Selecting the Correct Punch and Die

The selection of punch and die sets is paramount to the success of the bending operation. Factors to consider include:

• Punch Angle and Radius: The punch angle and radius must match the desired bend angle and radius. For sharper bends, a lower punch angle is required, whereas larger radii may necessitate different tooling. The punch radius also affects the internal bend radius, which can influence material flow and the final bend quality.
• Die Opening Width: The width of the die opening (V-width) should correspond to the material thickness and desired bend radius. A wider V-width allows for easier bending of thicker materials, while a narrower V die width is suitable for thinner sheets. The die opening must be carefully selected to avoid material damage and ensure accurate bends.
• Material Type of Tooling: The material of the tooling itself is important. For instance, harder tool materials like carbide are suitable for high-strength metals, while softer tool materials like aluminum or brass tools with protective coatings are ideal for avoiding surface damage on softer metals like copper or aluminum.

Tool Wear and Maintenance

Regular maintenance and inspection of press brake tooling are vital for maintaining precision and extending tool life. Tool wear can lead to inaccuracies and defects in the bending process. Key maintenance practices include:

• Regular Inspection: Tools should be inspected for signs of wear, such as cracks, chips, or deformations. Damaged tools must be repaired or replaced immediately to prevent compromises in bend quality.
• Tool Cleaning: Keeping tools clean from debris and buildup ensures smooth operation and prolongs tool life. Contaminants can cause uneven force distribution, leading to inaccuracies.
• Proper Storage: Tools should be stored in a manner that prevents damage and corrosion. Proper storage solutions, such as tool racks and protective covers, are essential for maintaining tool integrity.

Compatibility with Automation

With advances in CNC technology, press brake machines increasingly rely on automated systems for improved precision and efficiency. Tooling must be compatible with these systems to fully leverage the benefits of automation.

CNC-compatible tooling allows for quick and accurate tool changes, reducing setup times and improving production throughput. Additionally, advanced tooling systems may include sensors and feedback mechanisms to monitor and adjust bending parameters in real-time, ensuring consistent quality across production runs.

IV. Advanced Technologies in Press Brake Bending

Press brake bending is a widely used metal forming process involving the elastic deformation of the metal sheets under the pressure of press brakes' top punch and bottom die and plastic deformation.

CNC (Computer Numerical Control) Systems

The press brake adopts many advanced technologies, and CNC is the one. Through CNC technology, the press brake operation does not utterly rely on manuals. Instead, the preprogramming is advanced.

This means the construction and operators can design and input the specific parameters on the computer. The machine can be operated according to these instructions. The benefits of using CNC in press brake are as follows:

• Precision improved: the CNC technology can control the bending process precisely, thus achieving accurate and consistent bending.
• Repeatability: due to the machine being operated by pre-designed programs, each bending can achieve highly consistent results, regardless of the production quantity.
• Productivity improved: the automotive operation reduces the need for human manipulation. CNC machine tools can achieve intricate bending operations with high efficiency, decreasing production time and improving productivity.
• Flexibility: CNC technology allows the users to modify and adjust the bending parameters easily to adapt to the different task requirements.
• Setting time reduced: CNC machine tool can restore and recall bending programs without manual setting, reducing the transition time between the workpieces.
• Waste reduced: high precision and repeatability mean fewer errors and wastes, thus reducing materials and costs.

Laser Angle Measurement

Laser angle measurement systems provide real-time feedback on the bend angle, ensuring precise control and reducing the need for manual measurements and adjustments. This technology enhances accuracy and repeatability in bending operations.

Laser systems continuously monitor the bend angle, allowing for immediate adjustments. Precise measurements ensure that each bend meets the specified angle, reducing rework and scrap. Integrating laser measurement systems with CNC controls simplifies the bending process, making it easier for operators to achieve accurate results.

In the automotive industry, laser angle measurement systems help produce body panels with precise bends, ensuring that parts fit together correctly and meet design specifications. An automotive manufacturer reported a 15% reduction in rework and a 10% improvement in production speed after implementing laser angle measurement systems.

Advanced Backgauge Systems

Advanced backgauge systems enhance the positioning accuracy of the metal sheet, ensuring that each bend is made at the correct location. These systems can be CNC-controlled, providing automated and highly precise positioning.

Advanced backgauges offer accurate and repeatable positioning of the workpiece. CNC-controlled backgauge systems automate the setup process, reducing manual intervention. These systems can handle a wide range of sheet sizes and thicknesses, accommodating various bending tasks.

In large-scale manufacturing operations, advanced backgauge systems improve efficiency and accuracy, enabling the production of complex components with tight tolerances. A manufacturing plant reported a 20% increase in production capacity and a 15% reduction in scrap rates after integrating advanced backgauge systems.

These advanced technologies utterly transform the press brake bending process, making various industries more efficient and cost-effective.

V. Press Brake Bending Calculations

Bend Allowance

Bend allowance (BA) is the length of the arc through the bend area, which must be accounted for to maintain accurate part dimensions after bending. It is the additional material needed to accommodate the bend. Bend allowance is calculated using the following formula:

Where: A - Bend angle, R - Inside radius, K - K factor, T - Material thickness.

Bend Deduction

Bend deduction (BD) is the amount subtracted from the total length of the flattened part to account for the bend. It reflects the difference between the sum of the flange lengths and the initial flat length. The formula to calculate bend deduction is:

Where: OSSB - The outside setback (the length of the part that extends beyond the bend angle). R - Bend radius, K - K-factor (determined by material properties and thickness), T - Material thickness, A - Desired bend angle in degrees.

VI. FAQs

1. Why does springback occur during press brake bending, and how can it be controlled?

Springback occurs due to the elastic recovery of the material after the bending force is released. It is more pronounced in materials with higher yield strengths.

Factors influencing springback include:

• Material properties: Harder materials exhibit more springback.
• Bend radius and angle: Tighter radii and sharper angles increase springback.
• Bending method: Air bending, which does not force the material into the die, shows more springback compared to bottoming or coining.

Strategies to control springback:

• Over-bending: Slightly bending beyond the required angle to compensate for springback.
• Material selection: Choosing materials with lower springback tendencies.
• Precision-ground tools: Utilizing tools designed to account for springback.
• CNC adjustments: Modern CNC systems can dynamically adjust the bending parameters in real time to counteract springback.

2. What is the difference between air bending and bottoming in press brake bending?

Air bending and bottoming are two distinct methods used in press brake bending, each with unique characteristics and applications.

Air Bending involves positioning the workpiece over a die and using a punch to bend the metal without pressing it completely into the die. The material is not forced into the exact shape of the die, allowing for some degree of springback. This method is versatile and can handle a range of material thicknesses and bend angles using the same tooling. One of the primary advantages of air bending is its cost-effectiveness and flexibility, though it tends to be less precise compared to other methods due to the influence of springback.

Bottoming, also known as "bottom-dead-center bending," pushes the material all the way into the die, forcing it to conform closely to the die's shape. This method provides more precise control over the bend angle and results in higher accuracy and consistency. Bottoming requires more force than air bending and is generally used for applications where exact bends are critical. However, the increased force can lead to more wear on the tooling.

VII. Conclusion

Nowadays, press brake bending is indispensable for metal manufacture. This process is renowned for its long history, advanced technology, and widespread use, which makes it pivotal in various industries like aerospace, automotive, and construction.

The applications of CNC technology make the press brake bending significantly improved. It is essential for you to choose experienced manufacturers to delve into this technology and its back mechanical manufacturing.

As a leading company with over 40 years of press brake manufacturing experience, ADH Machine Tool can provide you with the most professional solutions and consultation.

If you want to inquire about the machine's price or want to learn more about the press brake knowledge, you can browse our product website or contact us directly. Let us work together for the future of manufacturing.

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