How to Reduce Springback in Press Brake Bending (SS/AL/MS Checklist)

ByFrancis Pan
Francis Pan

Francis Pan

Francis Pan is the Foreign Trade Manager of RAYMAX, with over 10 years of experience in sheet metal fabrication equipment and CNC machinery. He has worked closely with manufacturers worldwide on press brakes, fiber laser cutting machines, fiber laser welding machines, and practical production-oriented metal processing solutions.

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Quick answers

Press brake springback refers to the phenomenon in which the bend angle slightly opens after a sheet is formed on a press brake due to the sheet’s elastic recovery. Due to the simultaneous plastic and elastic deformation of metal during bending, once the pressure disappears, the partially plasticized parts will attempt to restore their original state. So this phenomenon is almost inevitable in bending.

How can we reduce springback? Common methods include overbending, selecting the appropriate punch radius and V-die opening, using bottoming or coining when needed, and using a CNC press brake equipped with angle compensation and crowning/deflection compensation.

It should be noted that there are differences in yield strength, springback law, and applicable processes among SS (stainless steel), AL (aluminum), and MS (low carbon steel), and the same set of empirical values cannot be applied. They should be controlled separately based on their material properties.

Introduction

In the sheet metal workshop, many people may mistakenly think that bending springback is just a small error when they encounter it for the first time during operation. However, after starting mass production, they realize that this “small error” can cause a lot of trouble. Specifically, it shows up as unstable bend angles, dimensional deviation, increased rework and scrap, and longer machine adjustment time. Many factories attribute these issues to operator skill problems, but the real reasons actually lie in materials, processes, and equipment, such as material fluctuations, incorrect tooling selection, incorrect process methods, and insufficient equipment compensation capabilities.

In this article, we will explain the definition of bending springback, how it is generated, methods to reduce springback in press brake bending, how to control the springback of SS/AL/MS, and when to consider higher-spec press brakes.

press brake springback mechanism diagram showing bend angle opening after unloading
Press Brake Springback Mechanism Diagram

What Is Press Brake Springback and Why Does It Happen?

What is springback

Springback is the phenomenon in which, after the punch presses the material into the lower die to complete the bend, the angle opens up again, the inside radius becomes larger, or the formed result deviates from the target value (attempting to return to the original shape) when the pressure is released and the punch is lifted due to elastic recovery.

How Springback Typically Shows Up on the Shop Floor

Here are some common scenarios:

  • Our target angle is 90°, but the measured angles after bending are 91° and 92°;
  • Under the same program, the batch of sheets bent yesterday had a correct angle, but after changing to another batch today, there was a drift in the angle;
  • The bend angle of the first part meets the target value, but after mass production, it was found that the angle became increasingly unstable;
  • When bending a long workpiece, it was found that the angle between the middle and both ends was not consistent.

Why does springback happen

The reasons for springback may be due to the following:

  • Material Yield Strength: The higher the strength of the material, the more pronounced the springback will usually be. That’s why stainless steel is often more prone to springback than ordinary carbon steel.
  • Material Thickness: Under the same process, thin plates usually exhibit more significant springback phenomena than thick plates. But we cannot just look at the thickness, we also need to judge it together with the inside radius and process method.
  • Inside bend radius: The larger the radius of the inner corner, the less plastic deformation the material produces, and the springback is often more pronounced. The inner corner radius, V-die opening, and punch shape are interrelated.
  • Bending method (Air Bending/Bottoming/Coining): Air bending is the most flexible method. It has the smallest contact area with the tooling and relies more on springback compensation. In bottoming, the material contacts the die more fully, which can significantly reduce springback. In coining, the material is pressed fully into the lower die, so springback is minimized, but this process requires much higher tonnage and stronger tooling.
  • Material batch and rolling direction: The same material does not necessarily mean the springback will be the same. Different batches, hardness condition, and rolling direction (whether the bending line is parallel or perpendicular to the grain direction) can significantly affect the springback angle and even cause cracking.
  • Equipment and tooling status: machine deflection, Y-axis synchronization status, and tooling wear can affect the actual forming angle and springback compensation effect; Back gauge repeatability and clamping stability mainly affect bend position accuracy, dimensional consistency, and repeatability in production.

The relationship between Springback and accuracy/repeatability

If springback remains stable, it mainly affects the accuracy of an individual part; But what really troubles factories is often springback variation caused by small fluctuations in material batches, hardness, thickness tolerance, and similar factors, which can result in significant differences in the angle performance between the first and 50th pieces.

How to Reduce Springback in Press Brake Bending

Method 1: Overbending Technique

This is the most common and basic method, as material springback can cause the actual angle to be slightly larger than the expected angle.

Therefore, when bending, we can make the actual inside bend angle slightly smaller than the target angle. For example, if our target internal angle is 90° and the material is expected to spring back by 2°, we can set the bending program to 88° so that after the pressure is released, the final angle of the material after springback is exactly 90°.

However, compensating for overbending angles is not necessarily better, as excessive or insufficient compensation can lead to unsatisfactory angles.

Method 2: Change to bottoming or coining

The air bending process we commonly use is the most flexible, but it relies more on springback compensation.

  • If customers have stricter requirements for the angle tolerance of the workpiece or if the material springbacks greatly, bottoming can be considered.
  • If the application requires extremely high precision, coining can be evaluated. But coining relies more on the high tonnage and frame rigidity of the press brake, and the load on the tooling is also greater.

Therefore, for materials with high springback and customers with extremely high precision requirements, the configuration of the press brake is also crucial. ( Compare air bending vs bottoming vs coining )

air bending vs bottoming vs coining springback comparison on press brake
Air Bending vs Bottoming vs Coining Comparison

Method 3: Choosing the Right Press Brake Tooling

Tooling is not just an accessory, but a key variable in springback control.

The radius of the punch tip, the angle of the lower die, the V-die opening, and the hardness of the tooling will all affect the springback of the material to a certain extent. The important thing is how to choose the appropriate tooling, for example, although a sharp punch can reduce springback, it also depends on whether the material is prone to cracking; For materials with high hardness such as stainless steel, choosing tooling with high hardness and wear resistance will be more suitable.

Method 4: Choose the Right V-die Opening

The V-die opening will directly affect the inner corner radius, tonnage requirements, indentation risk, and springback performance of the material, therefore, choosing the correct V-die opening is crucial.

In air bending, 8 times the plate thickness (8t) is usually the most common starting point for selecting V-dies for ordinary low-carbon steel, but this is only a common experience and not a universal law.

  • The V-opening is too large, and the inner corner radius of the material is larger, resulting in more obvious springback;
  • If the V-opening is too small, the required press brake tonnage will increase, which may increase the risk of cracking and indentation.
How V-Die Opening Affects Radius and Flange Length
How V-Die Opening Affects Radius and Flange Length

Method 5: Build a Material-Specific Bending Database

When bending, the angle cannot be controlled solely based on the experience and intuition of an experienced operator.

It is recommended to establish a material-specific compensation database based on your material grade, thickness, rolling direction, V-die opening, tooling combination, target angle, and actual compensation amount. The next time you bend the same workpiece, you can use those parameters directly, which can significantly reduce the number of trial and error times. This operation is the key to transforming springback control from relying on experience to being replicable.

Method 6: Using a Crowning System ( Deflection Compensation )

In the working conditions of long workpieces, thick plates, and large tonnage, it is easy to encounter inconsistent angles between the middle and both ends of the workpiece. Some customers may think that this is caused by springback, but in reality, it is caused by deflection of the machine table.

At this point, we need to use a deflection compensation system. Its function is not to directly reduce the springback of the material itself, but to compensate for the deformation of the machine tool and worktable under stress, so that the angle along the entire bend line is more uniform from left to right.

For long workpieces and high-precision production, CNC press brakes with mechanical or hydraulic deflection compensation are more capable of meeting machining needs.

Method 7: Improve Back gauge Repeatability and Clamping Stability

Although the backgauge does not directly determine the amount of springback, if the repeated positioning of the back gauge is not accurate, it will cause changes in the conditions of each bending, resulting in fluctuations in angle and flange size, indirectly affecting the amount of springback.

Similarly, if the quick clamping system cannot stably and firmly clamp the tooling, it may cause the tooling to shift, resulting in inaccurate angles and flange dimensions, and indirectly affecting the amount of springback. Backgauge stability and clamping stability are particularly important for multi-pass bending parts and parts with small flange dimensions.

Method 8: Utilize CNC Press Brakes with Angle Compensation

If relying solely on manual experience for angle compensation, efficiency and stability will be poor in the production of multiple varieties and batches. Modern CNC press brakes with angle compensation can reduce deviations caused by springback through material databases, program compensation, angle measurement systems, and adaptive control.

Our purpose of using CNC press brakes is not to completely eliminate the need for trial bending, but to minimize the number of trial and error times, improve first-piece pass rate and batch consistency.

Method 9: Run Test Bends Before Mass Production

No matter how experienced you are in operation or how advanced your press brake is, it is essential to do a trial bending before mass production. Especially for stainless steel, aluminum, new batch materials, and parts with extremely strict tolerance requirements, it is even more important.

A first-piece test bend is not a waste of time or material, but rather the lowest cost insurance measure to avoid rework or scrapping of the entire batch.

Specific Material Checklist for Springback Control: SS, AL, and MS

Mild Steel（MS）Checklist

Springback characteristics: Low carbon steel is usually the easiest material to establish standard parameters among these three categories. Its springback is relatively controllable and the angle is easier to predict, but it does not mean there is no springback.

Operation points:

  • It can serve as a benchmark material for establishing a bending database;
  • In most cases, it is suitable for conventional air bending;
  • Pay attention to the thickness differences of different boards and the material fluctuations of different batches;
  • When processing long workpieces, it is necessary to check whether the deflection compensation setting is correct;
  • Before mass production, it is recommended to conduct a bending test for confirmation.

Aluminum（AL）Checklist

Springback characteristics: Different grades of aluminum alloys also have differences in springback. For some aluminum alloys, the springback angle is not only difficult to predict, but also more prone to cracking, scratching, and indentation.

Operation points:

  • Do not directly copy the bending parameters of low-carbon steel;
  • More careful selection of punch fillet and V-die opening is needed to avoid using overly sharp punches;
  • Pay attention to the rolling direction and surface protection of the material;
  • A bending test must be conducted to confirm the compensation amount.

Stainless Steel（SS）Checklist

Springback characteristics: High yield strength, more obvious work hardening performance, resulting in more obvious springback, and higher requirements for angle compensation and equipment rigidity.

Operation points:

  • Usually requires greater bending force than low carbon steel;
  • The angle compensation for overbending is usually greater than that for low carbon steel;
  • Recommend tooling with higher hardness and greater wear resistance;
  • When surface quality requirements are high, it is necessary to find the most suitable bending method or bend angle while balancing mark prevention and springback control;
  • First piece bending and program verification must be conducted.

SS/AL/MS Comparison Table

Feature

MS

AL

SS

springback trend

Relatively controllable

Varies by alloy grade

More obvious

Main risks

Batch fluctuations

Cracking and surface scratches

hard-to-control springback, tonnage overload

Recommended method

Air bending

Air bending

Air bending, bottoming

Tooling recommendation

Standard tooling

Large radius punch

High hardness and wear-resistant tooling

Is test bending required?

Recommended

Must

Must

Need for advanced CNC support

Recommended

Recommended

Highly recommended

How to Estimate Springback Compensation

Why can’t we rely solely on experience to guess angles

Although experienced operators may be very familiar with how certain materials bend, the same material does not equal the same springback. Batch fluctuations and different suppliers may lead to differences in hardness, thickness, and rolling direction of the material, resulting in inconsistent springback. So, experience-based values can only serve as a starting reference. To achieve truly stable mass production, it is necessary to rely on bending testing and data recording.

Experience compensation and trial bending correction

We can set an initial compensation value based on experience and historical data; Second, perform a first-piece test bend; After the test bend is completed, use measuring tools to measure the actual forming angle; Then, the operator or the control system adjusts the compensation value based on the measured angle and fine-tunes the program; Finally, save the confirmed parameters to the database for future reference when bending the same workpiece.

Should K-Factor be mentioned?

The K-factor is mainly used to calculate the flat pattern length, helping us estimate the position of the neutral layer in the material, and it is not equal to the direct springback compensation value. The actual springback compensation still relies more on bending verification.

Common Mistakes That Make Springback Worse

Springback is always difficult to control, which may be caused by the following reasons:

  • Misunderstanding that the springback of the same material is always the same, without considering the possible differences between different suppliers and material batches.
  • Only blindly modifying the program without checking the tooling and V-die, ignoring the impact of tooling and V-die openings on springback.
  • The direct cause of batch rework or scrap is that the first piece was not subjected to bending verification before mass production began.
  • Using air bending to create workpieces with extremely strict angle tolerance requirements, but without using springback compensation methods.
  • Ignoring machine table deflection under long workpieces, thick plates, and high-tonnage conditions, and failing to apply crowning/deflection compensation.
  • Failure to check the accuracy of the positioning of the back gauge system and whether the clamping system is stably and firmly clamping the tooling.
  • Only focuses on whether the first piece is qualified, without conducting random inspections during mass production, ignoring the consistency of mass production.
  • Believes that a larger tonnage will definitely solve all problems, without considering the impact of tooling, V-dies, angle measurement, and deflection compensation on springback.

When Do You Need a Better Press Brake Instead of More Manual Adjustment?

These signs indicate that you should upgrade your press brake

  • Whenever there is a slight change in the grade or thickness of the material, it is necessary to repeatedly adjust the machine;
  • Under the same program, yesterday’s batch and today’s batch have different angles;
  • When bending a long workpiece, it was found that the angle between the middle and both ends was not consistent;
  • The angle control of bending relies too much on the operator’s experience;
  • The increasing number of high-precision orders makes it difficult for existing equipment to handle them;
  • Material changes and job changes are so frequent that the cost of manual compensation becomes too high.

Equipment configuration more suitable for springback control

  • A CNC control system with angle compensation;
  • Deflection compensation system;
  • Stable hydraulic system or hybrid servo system;
  • A back gauge system with high repeatability and positioning accuracy;
  • Tooling with high compatibility and support for fast clamping system;
  • Optional angle measurement function.
High-Precision CNC Press Brake
High-Precision CNC Press Brake

Why Machine Capability Matters

If your company processes stainless steel, aluminum or demanding parts over the long term, in addition to accumulating experience parameters, you should also pay more attention to the machine structure, control system, deflection compensation and tooling compatibility of the press brake.

Raymax can provide you with professional press brake machine and matching solution recommendations based on your workpiece length, thickness, material range, and accuracy requirements.

Conclusion

Material springback is an inherent physical property of metals, and we cannot completely eliminate this phenomenon during the bending process. However, it can be predicted and controlled through overbending, selecting appropriate tooling and V-die openings, choosing appropriate bending processes, establishing material databases, first-piece bending verification, deflection compensation, and angle measurement, in order to reduce material springback.

If you are troubled by angle fluctuations and bending springback of stainless steel, aluminum or low-carbon steel, please contact Raymax and send us your material type, thickness, target angle and accuracy requirements. Our team can recommend suitable press brakes and configuration solutions for you.

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Frequently Asked Questions (FAQs)

The elastic recovery of materials is the fundamental reason for springback. When the press brake bends, the punch presses down, causing elastic and plastic deformation of the material. When the pressure is released, the elastic deformation part of the material will attempt to restore its original state, resulting in a slight opening of the angle. The strength, thickness, inner corner radius, bending method, V-die opening, equipment condition, etc. of the material may all affect the magnitude of springback.

The most common methods are: overbending, selecting appropriate tooling and V-die openings, and using bottoming or coining if necessary. If higher precision is required for the angle, solutions such as angle compensation, establishment of material database, and bending verification can also be adopted.

The springback of air bending is usually more pronounced; Bottoming applies greater pressure to the material, resulting in less springback; And coining uses extremely high pressure to completely press the material into the lower die, making the material more fully plasticized and minimizing springback. But coining requires a very large amount of pressure, so it has extremely high tonnage requirements, tooling strength, and frame rigidity for the press brake. The specific process that is suitable also depends on the tonnage, tooling strength, material properties, and frame rigidity.

Normally, when using standard V-die openings, the springback of thick plates is relatively easier to control. But it still needs to be judged together with the inner corner radius, material strength, and process method.

Generally speaking, yes. Due to the high yield strength of stainless steel, work hardening is more pronounced, resulting in more pronounced springback. However, under different grades, states, and tooling conditions of materials, bending verification still needs to be conducted.

Yes, to a certain extent. Modern CNC press brakes with angle compensation can reduce deviations caused by springback through material databases, program compensation, angle measurement systems, and adaptive control. But the specific effect of compensation also depends on the control system, database, angle measurement, and equipment configuration.

Springback can vary from batch to batch because yield strength, thickness tolerance, hardness condition, and rolling direction may differ among material batches.

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