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Modern technologies of metal working
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Sheet metal bending
+48 95 762 08 61
Laser beam cutting
Laser cutting of tubes and sections
Robotic welding
Sheet metal bending
Sheet metal bending using press brakes is one of the most important operations in metal plastic forming. This process enables flat sheet metal to be given various three-dimensional shapes, which is essential in the production of structural elements, equipment housings, automotive body components, and many other industrial components. The press brake, also known as a hydraulic press brake or folder, is a fundamental tool in sheet metal workshops and manufacturing facilities worldwide.
The bending process in a press brake is based on the principle of plastic deformation of the material. During the operation, the sheet metal is placed between two tools: the lower one (die) and the upper one (punch). The upper tool, driven by hydraulic, pneumatic, or mechanical force, exerts controlled pressure on the sheet metal, causing its deformation along a specific bending line.
When force is applied, the material's yield strength is exceeded, resulting in permanent deformation. A key aspect is controlling the depth of punch penetration, which determines the final bending angle. Modern press brakes are equipped with numerical control (CNC) systems that enable precise process control and achievement of repeatable results.
Hydraulic presses constitute the widest group of machines of this type. They are characterized by high pressing force, smooth speed regulation, and the ability to precisely control bending force. Hydraulic systems also enable programming different speed profiles for optimal bending processes of various materials.
Mechanical presses use crank-rocker mechanisms to generate bending force. Although they have limited regulation compared to hydraulic presses, they are characterized by high efficiency and are particularly useful in series production of elements with standard parameters.
Electromechanical presses combine the advantages of mechanical and hydraulic systems, offering high precision at relatively low operating costs. Servo drive systems provide excellent position and speed control.
The punch is the upper tool of the press and has direct contact with the bent sheet metal. Its geometry significantly affects bending quality and process characteristics. The most important punch parameters are:
Tip radius - determines the minimum bending radius achievable. A punch that is too sharp can lead to material cracking, while a radius that is too large prevents achieving small bending radii.
Punch angle - standardly 90°, but punches with different angles are available for special applications. Sharp-angled punches enable bending elements with limited accessibility.
Working width - must be adapted to the bending length and material characteristics. Narrower punches require less force but may cause greater local stresses.
The die is the lower tool that determines the final bending shape. Key die parameters include:
Opening width (V) - is one of the most important parameters affecting bending force, minimum bending radius, and material springback. The general rule states that the opening width should be 6-12 times the sheet thickness, depending on the material and quality requirements.
Die angle - standardly 90°, but dies with different angles are available. Dies with larger angles (e.g., 120°) are used to compensate for springback in high-strength materials.
Radius - affects the bending radius and surface quality in the bending zone. Dies with larger radii reduce stress concentration and cracking risk.
Hemming tools enable creating edge folds that increase structural rigidity and improve product aesthetics.
Multi-operation bending tools allow several bends to be performed in one machine cycle, significantly increasing production efficiency.
Segmented tools consist of multiple elements, enabling bending of complex shapes and elements with protrusions or recesses.
Calculating the required bending force is fundamental for proper press and tool selection. The force depends on many factors:
F = k × σ × s² × L / V
where:
This formula provides a basic approximation, and actual force may differ depending on additional factors such as tool surface condition, process temperature, or bending speed.
The minimum bending radius depends on material properties and process parameters. For most structural materials, the minimum internal radius is:
where s denotes sheet thickness.
Springback is the phenomenon of partial return of the material to its original shape after load removal. The amount of springback depends on:
Springback compensation requires overbending the material by an angle greater than the target. Typical springback values are:
This is the most commonly used method, where the sheet is bent by partially pressing the punch into the die. The sheet has contact at three points: the punch tip and two die edges. This method is characterized by:
Advantages:
Disadvantages:
In this method, the punch presses the sheet into the die with sufficient force to achieve contact with the die bottom. Characteristics of this method:
Advantages:
Disadvantages:
The most accurate but most demanding method, where material is plastically deformed under very high pressure. The punch presses the sheet with force 3-5 times greater than in air bending.
Advantages:
Disadvantages:
Carbon and low-alloy steels are the basic material in sheet metalworking. They are characterized by good formability but require attention to the material grain direction. Bending across the grain can lead to cracking, especially in hot-rolled sheets.
Technological recommendations:
Austenitic steels (e.g., 304, 316) are characterized by high ductility but also greater work hardening during deformation. They require greater bending forces and particular attention to springback.
Process specifics:
High-strength steels (HSLA, UHSS) require a special technological approach. They are characterized by large springback and tendency to crack.
Process requirements:
Aluminum is characterized by good formability and low springback. However, some alloys (2xxx, 7xxx series) may be prone to cracking.
Characteristics:
Cracking can occur on the outer or inner side of the bend and has various causes:
External cracking:
Internal cracking:
Causes:
Prevention:
Causes:
Solutions:
Contemporary press brakes equipped with numerical control systems offer:
Offline programming - ability to prepare programs away from the machine using specialized CAM software.
Compensation systems - automatic consideration of springback, press beam deflection, and other factors affecting accuracy.
Online quality control - measurement systems integrated with the machine enable dimensional control during production.
Modern systems can adjust process parameters in real-time based on:
Integration with robotic systems enables:
Light curtains - optoelectronic systems stopping the press when the light beam is interrupted.
Safety mats - pressure sensors placed on the floor around the machine.
Two-hand control - requiring simultaneous pressing of two buttons to start the cycle.
Lockout/Tagout (LOTO) systems - procedures for safely shutting down machines during maintenance.
Material feeding systems - facilitating manipulation of heavy sheet metal.
Adjustable table height - adapting the workstation to operator height.
Noise reduction systems - sound-absorbing enclosures and damping systems.
Dimensional control - using templates, protractors, and coordinate measuring machines.
Bending angle control - specialized instruments for measuring angles with 0.1° accuracy.
Bending radius control - radius templates and optical measurement systems.
Flatness control - checking deformations of flat element surfaces.
Statistical Process Control (SPC) - real-time process parameter analysis using control charts.
First and last parts - quality control procedures at the beginning and end of production series.
Process documentation - complete registration of process parameters for each element.
Bending process optimization requires consideration of many variables:
Material analysis - detailed characterization of mechanical and technological properties.
Numerical modeling - using finite element method (FEM) to predict bending results.
Design of experiments - systematic investigation of process parameter effects on product quality.
Energy recovery systems - energy recovery from hydraulic systems during punch lowering.
Adaptive control - adjusting drive power to current process requirements.
Work cycle optimization - minimizing auxiliary times and downtime.
In the automotive industry, press brakes are used to produce:
Requirements for high surface quality and dimensional precision require the use of modern tools and control systems.
Special requirements regarding:
Production of structural elements requires:
Integration of press brakes with fourth-generation industrial systems includes:
Internet of Things (IoT) - remote monitoring of machine operating parameters.
Artificial Intelligence - learning systems optimizing process parameters.
Cloud computing - storage and analysis of production data.
Augmented reality - operator support in programming and machine operation.
Development of new materials poses new challenges for bending technology:
Ultra-high strength steels - requiring special bending techniques.
Metal-ceramic composites - combining properties of metals and ceramics.
Shape memory materials - enabling reversible deformations.
Nanomaterials - with unique mechanical properties.
Ecological aspects play an increasingly important role:
Energy efficiency - reducing energy consumption per production unit.
Material recycling - using waste and scrap as raw material.
Tool longevity - increasing durability through better materials and coatings.
Emission reduction - air filtration and purification systems in production halls.
Sheet metal bending using press brakes remains one of the most important metal plastic forming technologies. Continuous technological development, including advanced control systems, new tool materials, and intelligent monitoring systems, enables achieving increasingly higher quality while improving production efficiency.
The key to success in this field is deep understanding of process theory, proper selection of technological parameters, and application of modern quality control methods. As Industry 4.0 develops and artificial intelligence technologies are implemented, we can expect further automation and optimization of bending processes, which will translate into even better product quality and greater production flexibility.
The future of this technology is also related to growing ecological awareness, which means the necessity of developing even more energy-efficient processes and better utilization of raw materials. Investments in research and development of new materials, tools, and bending methods will be crucial for maintaining competitiveness in a dynamically changing industrial environment.