Press brake

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 (in working mode) and up to 200 mm/s (depends of the type) in idle mode (approach and return).

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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• Benson, Steve D. Press Brake Technology: A Guide to Precision Sheet Metal Bending. Society of Manufacturing Engineers, . ISBN 978-0--483-1

The increased demand for custom-made products prompted research that showed sheet metal to be a versatile material that can be transformed into various shapes. The transformation is accomplished by using simple sheet-forming processes like metal bending to shape the sheet metal into the desired shapes required for various production purposes. Numerous techniques are involved in achieving this, and learning how to bend sheet metal requires a basic understanding.

This article will look at the significance of sheet metal bending, how it is done and its role in sheet metal fabrication processes. It also includes some helpful bending tips for bending steel plates.

What Is the Meaning: Sheet Metal Bending?

The process of bending or shaping metal sheets to create a product with a specific geometry is called metal bending. With the aid of a sheet metal bender, force is applied to a workpiece to change its geometry and produce the desired shape. Performing a sheet metal bending procedure is not as easy as it seems; the many requirements are checking the product&#;s material, calculating the k-factor, determining the metal&#;s shape, and many more. The metal is particularly unique in bending operations because of its malleability.

A variety of machines does the bending work for manufacturing industries. To accomplish the same task, a single machine can employ multiple bending techniques. The same procedures, which will be covered in more detail later in this piece, are used for all products whose manufacturing process calls for bending. Let&#;s move right into the sheet metal bending process.

hydraulic CNC bending machine

How to Bend Sheet Metal?

A variety of machines are available for bending sheet metal. Typically found in small machine shops, the most popular type of device is the press brake machine. It can be operated manually or with computer numerical control (CNC) and a hydraulic system. Both machines work on the same principles, but the operator&#;s experience varies. The following procedure focuses on how a CNC press brake machine operates: 

• Determine the Parameters of Design

Determine the design parameters, such as the force needed, the bend line (the place where the force is applied), and the sequence of bends (if there are any), before using the press brake for sheet metal. There&#;s also the decision of which die to use for the bends. 

• Set Up the Press Bending Brake 

The CNC bender machine must be programmed with the calculated information to set up the press brake. Only then will it be able to determine the proper bend and the sequence to make the bends in the metal. The appropriate tool and die must be fastened to prepare the press and brake for bending. 

• Align the Part

Line up the metal about the die and tool. The metal sheet will be bent at the bend line by the operation of the machine. 

• Engage the Press Brake

Press the release button to apply the force parameters entered into the CNC press brake in the second step. The part can be taken out and prepared for the following stage of production after the press brake has bent the metal. 

Sheet Metal Bending Methods

Here are the standard sheet metal bending methods:

Rotary Draw Bending

The process of rotary draw bending involves clamping sheet metal to a revolving die and drawing the metal around the die to create a shape whose radius corresponds to the required bend radius. An internal supporting mandrel is frequently used in this technique to keep the bent sheet metal from wrinkling.

Roll Bending

Sheet metal can be bent into rolls, tubes, cones, or curved shapes using the roll bending technique. Sets of rollers are used in this special sheet metal forming process to feed and bend the metal stock into the required curvature. 

Metal sheets can be formed into various cross-section profiles with multiple bending curves using roll bending. It is beneficial for producing extremely long sheet metal components with widths of up to 20 inches and thicknesses ranging from 0.004 to 0.125 inches. The roll bending machine, for instance, can be used to make rapid prototyping parts like panels, tracks, and shelving, which are generally utilized in buildings for HVAC, lighting, and roofing applications.

Bottoming

A variation of v-bending known as &#;bottoming&#; or &#;bottom bending&#; also resolves the spring back problem. After bending, it entails exerting additional force through the punch tip to deform the sheet metal in the bend region.

Bottoming provides an accurate control over the bend angle, just like air bending does. However, it calls for a larger tonnage press than bottom bending.

Air Bending

Similar to the V-bending technique, air bending also uses a V-shaped punch and die to bend sheet metal. The punch in the air bending technique, in contrast to the traditional v-bending method, does not press the sheet into the cavity&#;s bottom. Unlike traditional v-bending, it allows for greater control over the bend angle because it leaves space (or air) underneath the sheet. 

For example, suppose you have a punch and die at a 90° angle. Bend angles can be achieved with the air bending method anywhere from ninety to eighty-one degrees. Because it experiences less spring back&#;a term that describes the partial recovery of a bent sheet metal part to its geometry before applying bending force&#;this method also guarantees a more accurate result. Irregular bends are caused by spring back, which is not desirable.

Wipe Bending

The wipe bending technique uses a pressure pad to hold the sheet metal against a wipe die. The edge of the sheet that protrudes past the die and pressure pad is then forced by the punch to bend over the die&#;s end.

You can create desired bends (and bend angles) with less force when using this method because it has a good mechanical advantage. Nevertheless, there might be better options for making sharp bend angles because that would need a more sophisticated piece of machinery that could apply horizontal force.

V-bending

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The most popular technique for bending sheet metal is V-bending. The v-bending method, as its name suggests, uses a punch and a v-shaped die to bend metal at desired angles. The sheet metal workpiece is forced into the die&#;s &#;v-shaped&#; groove by the v-shaped punch, creating sheet metal with various bend angles. For instance, depending on the v-shaped punch and die angle, you can achieve acute, obtuse, or 90° bend angles. 

What Equipment Is Needed to Bend Sheet Metal?

If you want precise and excellent outcomes when bending sheet metal, you must use specialized tools. The three common essential tools to bend sheet metal are hydraulic bending machines, manual bending machines, and shears.

Metal Bending Machines or Hydraulic CNC Folding 

A hydraulic bending machine is a more sophisticated tool for sheet metal bending. This machine has a hydraulic system that allows it to bend thicker and larger sheets. It also has a digital control system that allows different bends to be programmed and performed automatically. It is ideal for large manufacturing companies producing large sheet metal parts.

Hydraulic press braking bending machine

Manual Folding Machines

Sheet metal is typically bent using a manual bending (or folding) machine. The size of the tool varies based on the thickness of the sheet and is commonly utilized for straightforward bends. Small machining businesses and workshops frequently choose it because it is also reasonably simple to use and transport.

Shears

Sheet metal is broken into pieces using shears. Their functions include cutting precise geometric shapes out of metal sheets before they are bent; they can be either manual or electric.

What Are the Several Techniques for Bending Sheet Metal?  

Multiple tools imply a variety of metal bending techniques. To select the best method for your company, you must first understand the differences between the various approaches.

Laser Bending

Laser bending is a relatively new method that creates excellent bends by utilizing the accuracy of a laser beam. The benefits of press brakes and laser cutting are combined in a laser bending machine.

First, cut the metal sheet to the appropriate size and shape using the laser. Next, continue to use the laser to heat the bent area of the sheet to make the metal more pliable and thus easier to bend. A conventional press brake is used to bend the sheet after it has been heated.

The ability to quickly and precisely bend extremely thick sheets is just one of the many benefits of this bending technique. Additionally, it allows for the creation of bends with extremely sharp angles without running the risk of the sheet cracking or deforming.

Press Brake

The press brake is essential for producing structures involving sheet metal work. A metal sheet is bent by punching it into the desired shape against a die. You can bend sheets up to 20 mm thick with this machine. The mechanical and hydraulic press brakes are the two types of press brakes.

You can create U- or V-shaped bends with a press brake. When the metal is fully punched into the die&#;s shape, a V-shaped V-bend is made. This kind of bending is limited to sheets no thicker than 2 mm.

A press brake can also perform an air bend, in which the punch only presses the sheet to the required angle rather than fully into the die. A versatile tool, the press brake can bend sheets of various thicknesses in various ways. Get in touch with metal bending experts right away to find out more about its capabilities.

CNC press brake

Manual folding

You can bend metal sheets by hand if you don&#;t have a bending machine. To begin with, you must determine the sheet&#;s bending tolerance based on the kind of metal you are using. After that, use a marker to indicate the bend lines on your sheet and cut it to the proper size. Place the plate firmly within a vice grip with a wooden block as a guide for the form.

Next, gently pound the sheet against the wooden block with a hammer until the metal changes shape. Thicker sheets may break, so this method is only advised for sheets no wider than 2 mm.

While it may be quick and easy to do by hand, manual bending cannot match the precision and quality that a bending machine can provide. It is advised to use a bending machine for thicker sheets or more intricate bends to prevent breaking the sheet.

Which Materials Work Well for Bending Sheet Metal?

A bending machine cannot bend an elastic-plastic material. If attempted, it may also damage your machine. When selecting materials for sheet metal bending in the manufacturing process, special care must be taken. Let&#;s take a look at some of the best materials for sheet metal bending and forming.

• Copper

The strongest anti-corrosive material is also the least expensive. Copper is used to produce high precision sheet metal bending. Copper is a tried-and-true material that is widely used in many metal bending industries for a variety of applications.

Rolled copper sheets

• Stainless steel

When the resulting product requires robustness and greater metal strength, stainless steel is the first material that comes to mind. To shape the product, stainless steel also necessitates using a high-power sheet metal bending machine.

• Titanium

Titanium is a corrosion-resistant and high-strength material that is ideal for sheet metal bending techniques. If your product is medical or sporting equipment, titanium should be the most preferred material on your list.

• Aluminum

Aluminum is commonly found in lightweight applications. Bending the aluminum material requires special care to avoid collapsing or cracking in the corners. 

• Carbon Steel

Carbon steel is one of the most versatile and durable materials for sheet metal fabrication. Because this material is recyclable, it will also help to reduce carbon footprints.

These are some of the best sheet metal bending materials. Among the materials mentioned above, carbon steel is the most widely used. Many other metals can be useful in the bending process. However, before finalizing the material, make sure to conduct thorough research.

Top Tips For Bending Sheet Metal

Sheet plate bending

To ensure that your metal bending goes smoothly, we&#;ve provided a few tips to consider in your sheet metal bending techniques:

Avoid Bending to a Sharp Internal Corner

Internal stress is increased when inner corners bend sharply. Even if the metal is ductile and malleable, it is susceptible to cracking. This problem can be significantly reduced if the radius of the bending tool is considered. Working back and forth between your bend lines, gradually bend the sheet metal to the desired angle. 

Keep an eye on the inside bending radius, which must equal the thickness of the forming sheet metal. For example, if bending a 3 mm thick sheet of metal, the inside bend radius should also be 3 mm. The same is true for the bending angle, which must not be greater than the overall thickness of the metal sheet.

Use Heat for thick/heavy Bends

Some metals are prone to breaking or cracking when bent by force. Such metals necessitate heat rather than force to achieve the desired bend in sheet metal. Regarding bending with heat, two technical terms are used: hot forming and annealing. Annealing softens a metal, making it more malleable. Hot bending is simply heating the metal until it turns red and then using force to bend it. These techniques significantly reduce the likelihood of metal breaking and cracking.

Use Bend Allowance

Bend allowance is a property of metal that determines how easily it can be bent. We recommend that you perform bend allowance calculations to determine the sheet length required to make a specific angle and radius bend. Considering the bend allowance and bending force during the manufacturing process will help you achieve a neater product outcome. It will also assist you in producing an accurately flattened manufacturing model.

Applications of Bent Sheet Metal

In the metal processing industry, one of the most important processes is sheet metal bending. For instance, since automakers experiment with various forms to find the ideal car component that complements their design, this stage is crucial. Large engine parts can be produced using the process at an industrial level. 

However, it can also make small parts to replace worn-out engine components. All sheet metal bending methods consider standard procedures to ensure precision throughout the production process, even though numerous processes are involved.  

Application of sheet metal bending

Conclusion

To prevent failure during the manufacturing process, it is essential to adhere to the rules for sheet metal bending and possess proficiency in multiple functions. If the proper steps are taken, it may become manageable. Contact Zintilon sheet metal fabrication to find solutions for all of your sheet metal bending issues.

FAQs

How Can Laser Cutting Increase the Accuracy and Effectiveness of Sheet Metal Bending?

Since laser cutting takes less time to prepare the sheet metal for bending, it increases the efficiency of sheet metal bending. Tight tolerance edges are another benefit of laser cutting. If a press metal brake bending machine is being used, these edges can be utilized as data. The accuracy of the bend&#;s location would decrease with a decrease in the cut edge&#;s precision.

What Is Sheet Metal Bending Allowance?

The term &#;bend allowance&#; in manufacturing describes the space allotted to allow for the stretching and bending of sheet metal. Sheet metal undergoes physical dimension changes when bent from its original flat shape. The material compresses and stretches both inside and outside when it is forcefully bent.

The force of compression and stretching on the bend results in this deformation. This modifies the overall length of the sheet metal. The distance between the exterior under tension and the inner compressed surface, however, is still determined by measuring the thickness of the bend. A line known as the &#;neutral axis&#; serves as an indicator of this.

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