Machine for bending sheet and plate material
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A press brake bending a sheet of steel
A press brake is a type of brake, a machine used for bending sheet metal and metal plate.[1] It forms predetermined bends by clamping the workpiece between a matching top tool and bottom die.[2]
Bending process
A high-tonnage hydraulic press brake
Liwei CNC T 12M Heavy Duty model
Typically, two C-frames form the sides of the press brake, connected to a table at the bottom and on a movable beam at the top. The bottom tool is mounted on the table, with the top tool mounted on the upper beam.
Types
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A brake can be described by basic parameters, such as the force or tonnage and the working length.[1] Additional parameters include the stroke length, the distance between the frame uprights or side housings, distance to the back gauge, and work height. The upper beam usually operates at a speed ranging from 1 to 15 mm/s.
There are several types of press brakes including nut-stop hydraulic, synchro hydraulic, electric and hybrid.
Hydraulic presses operate by means of two synchronized hydraulic cylinders on the C-frames moving the upper beam.[3] Servo-electric brakes use a servo-motor to drive a ballscrew or belt drive to exert tonnage on the ram.
Historically, a mechanical press entailed with energy that was added to a flywheel with an electric motor. A clutch engages the flywheel to power a crank mechanism that moves the ram vertically. Accuracy and speed are two advantages of the mechanical press.[3]
Until the s, mechanical brakes dominated the world market. The advent of better hydraulics and computer controls have led to hydraulic machines being the most popular.
Today's press brakes are controlled by two types of controls, NC (Numeric Controlled) or CNC (Computer Numeric Controlled). NC is a basic controller where the CNC is the high-end controller. Although the initial outlay might be more than with an NC , a CNC controller can be more effective, keeping cost down in the long run.
Pneumatic and servo-electric machines are typically used in lower tonnage applications. Hydraulic brakes produce accurate, high-quality products; are reliable; use little energy; and are safer because, unlike flywheel-driven presses, the motion of the ram can be easily stopped at any time in response to a safety device, e.g. a light curtain or other presence sensing device.
Back gauge
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Recent improvements are mainly in the control and a device called a back gauge. A back gauge is a device that can be used to accurately position a piece of metal so that the brake puts the bend in the correct place. Furthermore, the back gauge can be programmed to move between bends to repeatedly make complex parts. The animation to the right shows the operation of the back gauge, setting the distance from the edge of the material or previous bend to the center of the die.
Press brakes often include multi-axis computer-controlled back gauges. They allow operators to position material correctly and sequence the bends step-by-step until completed. Optical sensors allow operators to make adjustments during the bending process. These sensors send real-time data about the bending angle in the bend cycle to machine controls that adjust process parameters.
Dies
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Press brakes can be used for many different forming jobs with the right die design. Types of dies include:[3]
- V-dies&#;the most common type of die. The bottom dies can be made with different-sized die openings to handle a variety of materials and bend angles.
- Rotary bending dies&#;a cylindrical shape with an 88-degree V-notch cut along its axis is seated in the "saddle" of the punch. The die is an anvil over which the rocker bends the sheet.
- 90 degree dies&#;largely used for bottoming operations. The die opening dimension depends on material thickness.
- Acute angle (air-bending) dies&#;used in air bending, these can actually be used to produce acute, 90 degree, and obtuse angles by varying how deeply the punch enters the die by adjusting the ram.
- Gooseneck (return-flanging) dies&#;The punch is designed to allow for clearance of already formed flanges
- Offset dies&#;a combination punch and die set that bends two angles in one stroke to produce a Z shape.
- Hemming dies&#;two-stage dies combining an acute angle die with a flattening tool.
- Seaming dies&#;There are a number of ways to build dies to produce seams in sheets and tubes.
- Radius dies&#;A radiussed bend can be produced by a rounded punch. The bottom die may be a V-die or may include a spring pad or rubber pad to form the bottom of the die.
- Beading dies&#;A bead or a "stopped rib" may be a feature that stiffens the resulting part. The punch has a rounded head with flat shoulders on each side of the bead. The bottom die is the inverse of the punch.
- Curling dies&#;The die forms a curled or coiled edge on the sheet.
- Tube- and pipe-forming dies&#;a first operation bends the edges of the sheet to make the piece roll up. Then a die similar to a curling die causes the tube to be formed. Larger tubes are formed over a mandrel.
- Four-way die blocks&#;A single die block may have a V machined into each of four sides for ease of changeover of small jobs.
- Channel-forming dies&#;A punch can be pressed into a die to form two angles at the bottom of the sheet, forming an angular channel.
- U-bend dies&#;Similar to channel forming, but with a rounded bottom. Spring back may be a problem and a means may need to be provided for countering it.
- Box-forming dies&#;While a box may be formed by simple angle bends on each side, the different side lengths of a rectangular box must be accommodated by building the punch in sections. The punch also needs to be high enough to accommodate the height of the resulting box's sides.
- Corrugating dies&#;Such dies have a wavy surface and may involve spring-loaded punch elements.
- Multiple-bend dies&#;A die set may be built in the shape of the desired profile and form several bends on a single stroke of the press.
- Rocker-type dies&#;A rocker insert in the punch may allow for some side-to-side motion, in addition to the up-and-down motion of the press.
See also
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References
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Further reading
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If you are looking for more details, kindly visit Hydraulic Bending Press.
- Benson, Steve D. Press Brake Technology: A Guide to Precision Sheet Metal Bending. Society of Manufacturing Engineers, . ISBN 978-0--483-1
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.
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:
TypeAdvantagesDisadvantagesHydraulic Press BrakeHigh precision and control
Suitable for various materials and thicknesses
Capable of handling heavy materials
Even force distributionHigh cost
Complex operation
Cannot exceed rated tonnageMechanical Press BrakeHigh precision and consistency
Suitable for thin to medium-thickness materials
Quick setup and tool change
Ideal for forming complex shapesRequires frequent tool changes and setups
May lock into a complete cycle
Requires skilled operationCNC Press BrakeHigh precision and automation
Easy to operate, reduces labor intensity
Suitable for various shapes and angles
Increases production speed and efficiency
Programmable, suitable for multi-step operationsHigh cost
Limitations with highly reflective or brittle materials
Requires specialized training and maintenance
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
Fault PhenomenonPossible CausesSolutionsNo pressure or insufficient pressure in the hydraulic system1. Incorrect forward or reverse rotation of motor and pump
2. Blocked spool of overflow valve
3. Blocked spool of solenoid valve
4. Internal leakage of pressure control valve1. Check the rotation direction of motor and pump
2. Clean the spool of overflow valve
3. Clean the spool of solenoid valve
4. Check the pressure control valveSlow or jerky descent of ram1. Worn or damaged cylinder
2. Worn or non-vertical guide rails
3. Low oil level in tank
4. Fast forward speed, insufficient oil supply
5. Stuck and not fully open filling valve1. Check the cylinder
2. Check the guide rails
3. Check the oil level
4. Adjust the fast forward speed
5. Clean the filling valveOil leakage in the hydraulic system1. Loose connecting screws and pipe fittings
2. Damaged seals1. Tighten screws and fittings
2. Replace sealsUnbalanced bending on both sides1. Uneven wear of dies
2. Non-parallel ram1. Adjust the hexagonal tube to correct the angle difference
2. Adjust the parallelism with eccentric sleevesLoud noiseLoose connections, worn bearings, damaged partsAdjust the ram, replace dies if necessaryElectrical faultsLoose wiring, sensor failure, damaged circuitsCheck wiring, replace sensors or circuitsOverheatingBlocked radiator, cooling system failureClean the radiator, repair the cooling systemRam cannot descend slowly, weak bending force1. Failure of 4/2-way valve
2. Stuck filling valve1. Check the 4/2-way valve
2. Clean the filling valveSlow return speed of ram, high return pressureFilling valve not openCheck the filling valve
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.
Contact us to discuss your requirements of How to Choose a CNC Machine Center. Our experienced sales team can help you identify the options that best suit your needs.
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