What is a Press Brake and How Does It Work?

Press brakes are powerful machines used to bend sheet metal into various shapes and angles. From the sleek curves of a car body to the sturdy frame of a refrigerator, press brakes play a crucial role in manufacturing across many industries.

Operating Principle: How Does a Press Brake Work?

Imagine a giant sandwich maker. The bottom slice of bread is the die, a sturdy, precisely shaped mold. The top slice is the punch, a matching shape that presses down on the sheet metal. The press brake applies immense force, causing the metal to bend permanently into the desired shape.

Key Components of a Press Brake

Ram

This is the moving part of the press brake that houses the punch. It travels vertically, applying the bending force. It runs vertically along the Y axis and is positioned by numerical control at specific positions according to the operation to be performed. There are independent Y1 and Y2 axes that regulate the possible unbalance of the machine’s main ram (in a hydraulic press these are the different strokes that the cylinders can perform).  

Bench

The bench or bed is the fixed part under the beam where the dies are installed. It can contain a crowning system to compensate for the crossbar deformation, especially in machines two meters/6’ wide and up. Such a system can be found in a variety of versions which embrace different design philosophies among manufacturers or are based on specific machine types or families. Excellent results are possible through the use of a hydraulic crowning system. In this case, a number of high pressure and low flow rate cylinders are inserted within the machine bench to compensate for the frame deformation during the pressing phase by producing a counterforce from underneath.  

Lateral Frames

Represent the side plates or shoulders that define the width of the machine frame. These can also be different: for example, machines with synchronized hydraulics almost always have a gap, called throat, so a sheet that is wider than the distance between the shoulders or columns can be inserted into the machine frame.  

Punch

This tool replicates the desired bend profile and makes direct contact with the sheet metal. Punches come in various shapes and sizes to accommodate different bend angles and materials.  

Die

The die is the stationary counterpart to the punch, providing the form for the bend. It can be a simple V-shaped die for basic bends or a more complex shape for specific profiles.  

Clamping System

This mechanism securely holds the sheet metal in place during the bending process, ensuring accuracy and preventing slipping.  

CNC

The CNC (Computer Numerical Control) is the core of the machine. The operator interface device used to program the sequence of machine movements through direct input of parameters/programs or off-line programs, which are normally created by the technical department as directed by the production management. Very often the CNC allows several setting/input options such as numerical mode or graphic mode: the former requires the operator to enter the data for the desired part directly in the appropriate fields on the program screen; the latter is more user-friendly, especially for a non-expert operator, and requires the use of 2D or 3D graphics showing the shape of the desired end product as well as the bending sequence.  

Sheet Metal Supports

These are very often optional accessories. If fixed and sliding on a guide, they only serve to support heavy and/or bulky workpieces during processing. If mobile (followers), they serve to “accompany” or follow, the sheet metal as it swings due to the bend forming process. They work during both upward and downward sheet movements.  

Rear Backgauge

This device ensures that the bend is positioned correctly in the part to be produced. It usually consists of a beam on which two or more "finger stops" (backgauges) are mounted. They are able to move sideways to find the correct position.

Choosing a press brake: first, the basics!

Here are some key terms to familiarize yourself and to for accurately determining bend parameters for your sheet metal:

Tonnage: the force required to perform the bend.

Inside radius: the inner curvature of the bend. The smaller the inside radius, the tighter the bend. This value is crucial in sheet metal working because it affects the strength of the bend, the aesthetic appearance of the finished part, and the choice of tools to use.

Minimum flange length: the shortest possible length of the flange to prevent breakage. Imagine folding a sheet of paper. If you fold it too sharply, it will tear. The same applies to sheet metal. The minimum bend length represents the point beyond which the material can no longer be bent without risk of breaking or excessive deformation. It's like a "strength threshold" that every material has.  

Our online calculator is your ideal tool for accurately determining bend parameters for your sheet metal. Try it now: vicla.eu/en/calculators/bend-parameter-calculator

When Was Press Brake Invented?

Press brakes, while a relatively modern invention, have a history dating back to when the first patents were filed. Early press brakes were labor-intensive affairs, relying heavily on manual operations. To create a bend, a mold was first crafted to match the desired shape. Sheet metal was then placed on the mold and surrounded by a mixture of sand and lead shot. Workers would then use a T-stake to pound on the metal, forcing it into the mold's shape. This process, while effective, was slow and often resulted in straight, simple bends.

What are the differences between old press brakes and modern press brakes?

If we compare a modern press brake to one from fifty years ago, on the outside it seems that little has changed. However, the truth is that they are two completely different machines; the external elements may also have remained stationary with the typical design that we all know, but mechanics and electronics have evolved in a silent and inexorable way.

Conceptually, between a bending machine from the past and a modern one, there are no changes in the process; both, in fact, share the same purpose: to bring a punch to a matrix up to a certain altitude in the most precise and repeatable way possible. 

Yet, the modern press brake is the result of constant evolution. Just as happened with cars, which from a simple and almost rudimentary means of transport have become truly high-tech machines, the bending machine is also now a concentration of technological and mechanical innovation. However, both in the case of the car and the press brake, the basic mechanical components have remained the same, but over time they have been improved and refined.

Types of Press Brakes: Powering Up Your Bends

Press brakes come in various configurations, each suited for specific applications and production needs. Here's a breakdown of the most common types:

Mechanical Press Brakes: A Look Back at a Once-Dominant Technology

While mechanical press brakes once reigned supreme in metalworking shops, they've largely been replaced by safer and more precise alternatives like hydraulic and electric models. Despite their diminished role, these machines played a significant part in the history of metal fabrication.

How Mechanical Press Brakes Work

These robust machines utilize a flywheel to generate the powerful force needed to bend sheet metal. As the flywheel spins, it builds up momentum that drives the punch up and down. A clutch system engages and disengages the gear shaft, allowing for controlled movement.

Key Advantages of Mechanical Press Brakes

• Speed and Power: Mechanical press brakes are renowned for their speed and impressive force, capable of handling challenging bending tasks.
• Simple Operation and Maintenance: Their straightforward design makes them relatively easy to operate and maintain.
• High Load Capacity: These machines often exceed their rated tonnage, offering unexpected power reserves.

Why Mechanical Press Brakes Have Become Obsolete

• Safety Concerns: The inherent nature of their operation presents significant safety risks.
• Limited Control: Mechanical press brakes offer limited control over punch speed and movement, impacting bend quality and accuracy.
• Advancements in Technology: The emergence of hydraulic and electric press brakes, with their enhanced safety features, precision, and energy efficiency, has made mechanical models less desirable.

Notable Manufacturers

Brands like Mariani and Omag were once highly regarded for their innovative mechanical press brake designs.

RG Promecam Hydraulic Press Brakes: A Legacy of Innovation

The RG Promecam hydraulic press brake, a brainchild of Italian-French inventor Roger Giordano, stands out for its distinctive low-profile design and compact footprint. Unlike conventional press brakes that lower the upper beam to bend the metal, RG Promecam machines ingeniously raise the workbench using a central hydraulic system. This innovative approach offered simplicity and reliability, significantly impacting the evolution of Italian press brake technology.

A Unique Approach to Bending

The unique design of RG Promecam press brakes allowed for the bending of large, closed profiles. The low-profile structure enabled these profiles to be "embraced" by the upper part of the machine, facilitating efficient bending operations.

A Historical Perspective

In the post-war era, RG Promecam press brakes gained significant popularity. They represented a groundbreaking innovation in metal fabrication, offering a compact and efficient solution for many bending applications.

Safety Considerations

While historically significant, these machines no longer comply with modern safety standards. They lack features like adjustable bending speeds and advanced safety mechanisms. To remain operational, significant safety upgrades are necessary.

Hydraulic Press Brakes with Torsion Bar: Early Steps Towards Synchronization

These press brakes represent a significant step in the evolution of modern synchronized press brakes, sharing a similar visual appearance. They operate by utilizing a hydraulic system to drive the downward movement of the main beam.

Typically, these machines incorporate two or three primary axes of movement:

• X-axis: Controls the horizontal movement of the rear carriage.
• Z-axis: Controls the vertical positioning of the rear carriage.
• Y-axis: Controls the vertical descent of the main beam.

A key characteristic of these press brakes lies in the mechanical connection between the two main hydraulic cylinders, facilitated by a torsion bar. This linkage ensures synchronized movement of the beam throughout the bending cycle, up to the lower dead center, guaranteeing consistent and accurate bends. The lower dead center, or the final position of the beam at the end of its stroke, is adjustable. Two nuts, positioned on the cylinders, allow for precise adjustments to the end-of-stroke height, providing flexibility in bending operations.

Control systems for these press brakes were relatively basic compared to today's sophisticated CNC systems. They were often equipped with simple positioners, lacking the internal memory and advanced programming capabilities found in modern machines.

Synchronized Hydraulic Press Brakes: The Pinnacle of Bending Precision

Hydraulic press brakes revolutionized metal bending by replacing mechanical systems with precise hydraulic control. Utilizing two oil cylinders to drive the punch, these machines offer significantly enhanced bending capabilities and accuracy compared to their mechanical predecessors.

Advantages and Challenges of Hydraulic Press Brakes

While offering superior performance, hydraulic press brakes come with increased complexity. They require skilled operators and can have higher maintenance costs due to the intricate nature of their hydraulic systems. Maintaining strict adherence to the machine's rated tonnage is crucial to prevent damage. Additionally, potential fluid leakage from the hydraulic cylinders remains a concern.

The Rise of CNC Hydraulic Press Brakes

The advent of CNC technology has significantly advanced hydraulic press brake capabilities. CNC-controlled machines feature automated systems that precisely control movement and timing, enhancing both accuracy and efficiency. Synchronized hydraulic press brakes represent the pinnacle of press brake technology. They employ two independent hydraulic cylinders and proportional valves to regulate the movement of the upper beam. This sophisticated configuration offers greater versatility, allowing operators to adjust each cylinder individually to compensate for variations in sheet metal thickness or irregularities.

Electric press brakes or servo press brakes

Electric press brakes, the latest innovation in press brake technology, remain a specialized solution for certain applications. While they offer speed, repeatability, and energy efficiency, they often lack the versatility of synchronized hydraulic press brakes, especially on large formats.

Two primary methods are used to operate electric press brakes: ball screws and special belts.

Servo press brakes utilize servo motors to power the punch. These motors, also known as servo-electric press brakes or electric press brakes, transfer mechanical energy to the punch via a pulley and belt system.

Servo motors offer precise control over punch movement due to their numerous adjustment options. This translates to accurate bends and a quieter workplace. Eliminating hydraulic or pneumatic systems also prevents leakage issues.

However, servo press brakes have a lower force capacity compared to other options. This limitation restricts their use in industries requiring higher tonnage.

CNC press brakes

CNC press brakes, versatile and automated machines, utilize computer numerical control (CNC) systems to deliver exceptional precision and repeatability. By incorporating CNC technology, businesses can significantly boost productivity, efficiency, and accuracy while reducing labor costs.

Ideal for a diverse range of industries, including aerospace, automotive, construction, and electronics, CNC press brakes offer a powerful solution for various applications.

To learn more about the specific benefits and capabilities of CNC press brakes, explore our in-depth article, "CNC Press Brakes: A Comprehensive Guide"

Hybrid Press Brakes: A Technological Advance in Metal Bending

Hybrid press brakes represent a significant advancement in press brake technology, offering a compelling combination of efficiency, precision, and versatility. Unlike traditional hydraulic press brakes, which rely solely on hydraulic power, hybrid models incorporate electric motors to drive the bending process.

Key Advantages of Hybrid Press Brakes:

• Enhanced Precision: By minimizing oil usage and reducing the impact of oil temperature fluctuations, hybrid press brakes achieve a high degree of precision and repeatability in bending operations.
• Energy Efficiency: Hybrid systems significantly reduce energy consumption compared to traditional hydraulic models, leading to substantial cost savings.
• Versatility: Hybrid press brakes offer greater flexibility in bending operations compared to some electric models, particularly those using belt systems.

How Hybrid Press Brakes Work:

Hybrid press brakes utilize a combination of electric motors and a reduced hydraulic system. This approach minimizes oil volume, leading to a more compact and efficient design.

Key Features of Hybrid Press Brakes:

• Reduced Oil Usage: Minimizes oil volume, leading to reduced heat generation and expansion.
• Electric Motor Drive: Utilizes powerful electric motors to drive the bending process.
• Precise Control: Enables precise control over bending parameters.

Hybrid press brakes represent a cutting-edge technology in metal bending, offering a compelling balance of precision, efficiency, and versatility. By combining the strengths of hydraulic and electric systems, they provide a significant advancement over traditional press brake designs.

Applications: Bending Across Industries

Press brakes are incredibly versatile machines, used in a wide range of industries:

Automotive: car bodies, engine components

Aerospace: aircraft parts

Construction: roofing, cladding, ductwork

Appliance manufacturing: Refrigerators, washing machines

Electronics: enclosures, chassis

Advantages and Disadvantages: Weighing the Options

Each type of press brake has its own set of advantages and disadvantages:

Choosing the right press brake depends on your specific needs. Consider factors like production volume, required bend precision, material thickness, and budget.

Bending Force Calculation: Bending with Confidence

Calculating the bending force required for a specific bend is crucial to ensure successful and safe operation of the press brake. Here's a simplified formula for estimating the bending force (F) for a V-bend:

F = T * L * S

Where:

F is the bending force (in tons or Newtons)

T is the material thickness (in millimeters or inches)

L is the bend length (in millimeters or inches)

S is the material's tensile strength (in MPa or psi)

Note: This is a simplified formula, and several factors can influence the actual bending force required. It's recommended to consult the material manufacturer's data and use more sophisticated bending force calculation methods for precise results.

Maintenance and Safety: Prioritizing Care and Caution

Proper maintenance and safety practices are essential for ensuring the longevity and safe operation of a press brake:

• Regular Inspections: Conduct routine inspections of all components, including hydraulic lines, electrical systems, and safety guards.
• Lubrication: Regularly lubricate moving parts according to the manufacturer's recommendations.
• Tool Maintenance: Properly maintain and store punches and dies to prevent damage and ensure accurate bending.
• Safety Guards: Ensure all safety guards are in place and functioning correctly.
• Operator Training: Provide comprehensive training to all operators on safe operating procedures, including lockout/tagout procedures and emergency stop procedures.
• Personal Protective Equipment (PPE): Always wear appropriate PPE, including safety glasses, hearing protection, and steel-toed shoes.

Conclusions: Mastering the Art of Bending

Press brakes are essential tools in metalworking, enabling the efficient and precise bending of sheet metal into a wide variety of shapes. By understanding the principles of operation, the different types of press brakes available, and the importance of safety, you can effectively utilize these machines to achieve your manufacturing goals.

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