How to Improve Press Brake Bending Accuracy?

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I. Introduction

Errors that result in the failure of press brake bending accuracy can arise from various factors, including mechanical issues with the sheet metal bending machine, as well as external factors like bending tools, material thickness, and human operational errors.

In this article, we will examine the various factors that impact accurate bend and provide solutions for some of the common scenarios encountered. Before starting, let's watch the video first:

II. Machine Factors

There are several factors affecting bending accuracy of a press brake bending machine. These include:

  • Straightness of the Ram Opening: The clamping opening of the ram is straight in both Y and X directions. Repositioning accuracy and arbitrary positioning accuracy of the left and right ram. The accuracy of the ram opening in both the Y and X directions is crucial for precision of bending. If the ram opening is not straight, it will lead to deviations in the bending angle and position.
  • Clearance Between the Ram and Frame Guide Rails: The clearance between the press brake ram and the frame's linear guide should be reasonable. Proper clearance between the ram and the frame guide rails ensures the stability of the ram during movement, thereby improving bending accuracy of press brakes.
  • Perpendicularity and Inclination of the Frame: Perpendicularity and inclination of the frame. The perpendicularity and inclination of the frame affect the distribution of bending force during the bending process, which in turn ensure bending accuracy.
  • Connection Between the Cylinder and Ram: The connection between the cylinder and the ram must be consistent to ensure uniform bending force distribution during bending in press brakes.
back gauge system

There are also other factors affecting the precision press brake bending, like strength and accuracy of the frame and ram, repositioning accuracy of the back gauge system in both X and R directions, proper adjustment of the computer system, adjustment of the hydraulic system, matching between the hydraulic system and computer adjustment.

III. Tooling Factors

1. Precision of the Upper and Lower Dies:

The accuracy of the upper and lower dies is critical. Deformation, damage, wear, and other issues with the dies can impact all aspects of metal bending. If discovered, it should be promptly reported and corrected. So regular inspection and maintenance are necessary.

upper and lower dies

2. Die Alignment:

Misalignment between the upper and lower dies can result in deviation in the bending size. Ensure that the toolings are properly aligned during tool setting.

After the left and right positions of the back gauge move, the distance between the lower die and the back gauge changes. This can be measured using a vernier caliper and adjusted using the back gauge screw.

The accuracy and compatibility of the lower die compensation device should be verified, matching the design of the frame. The upper die fixture should be highly precise.

3. V-Die Opening Size:

The opening size of the V-shape die and the bending pressure are inversely proportional. When the plate length and thickness are fixed, the larger the opening, the lower the pressure required. Therefore, when working with different thicknesses, the appropriate V-shape die opening size should be used.

When processing with a unilateral load, such as at one end of the press brake, the bending pressure may be impacted, harming the machine. This is strictly prohibited. The middle part of the machine should always be stressed when assembling the tooling.

IV. Sheet Metal Factors

The straightness of the reference plane of the sheet metal must be checked. Ensure that the stress on the metal plate is uniform. Verify that the sheet metal thickness is consistent.

Inadequate parallelism between the workpiece and the lower die during bending can cause the workpiece to spring back after the upper die is pressed, affecting the bend size.

Springback refers to the phenomenon where the material tries to return to its original shape after bending. The tensile strength, thickness, tooling, and type of press brake all influence springback. Effectively predicting and evaluating springback is crucial for handling tight bends and thick, high-strength materials.

Material properties and thickness can impact the bending angle, so proper inspection and spot checking must be performed on each workpiece before bending.

The following are the material properties in detail:

  • Yield Strength: Yield strength is the maximum stress that a material can withstand before it begins to deform permanently. Understanding the yield strength helps determine the maximum force that can be applied during bending to avoid damaging the material.
  • Elastic Modulus: The elastic modulus indicates a material's stiffness and determines the amount of deformation under a given stress. Knowing the elastic modulus helps predict the amount of spring back after bending.
  • Material Thickness: The thickness of the material significantly affects the bending process. Thicker materials require more force to bend, and a larger bending radius is needed to avoid cracking or deformation.
  • Ductility: Ductility refers to a material's ability to undergo plastic deformation without breaking. Materials with high ductility are easier to bend and less likely to crack or tear during the process.

V. Bending Operation Factors

1. Consistency of Operator's Actions:

Check that the left and right forces are consistent when the press brake operators push the material to bend. Inconsistent bending force can lead to deviations in bending dimensions.

2. Adjustment of System Data:

Ensure that the system data error is properly adjusted when using the system. An insufficient primary bending angle can affect the secondary bend dimension. Accumulated errors in bending will increase the error in the workpiece's outline dimension.

The pressure required for bending varies with the length and thickness of the workpiece, and the length and thickness of the plate are proportional to the required pressure.

It is important to adjust the bending capacity accordingly when the length and thickness of the workpiece change.

press brake

VI. Case Study

1. Case Study 1: Automotive Industry

Company: A leading automotive parts manufacturer

Challenge: The company needed to produce highly precise body panels and structural components with tight tolerances to ensure proper fit and function in vehicle assembly.

Solution:

  • Advanced CNC Press Brakes: The company invested in CNC press brakes with automated tool changers and high-precision back gauge systems.
  • Material Consistency: They implemented strict quality control measures to ensure uniform material thickness and properties.
  • Operator Training: Operators received extensive training on machine setup, programming, and maintenance.

Results:

  • Increased Accuracy: Achieved bending accuracy within ±0.1 mm, significantly reducing rework and scrap rates.
  • Enhanced Productivity: Automated processes and quick tool changes reduced setup times by 50%, increasing overall production efficiency.
  • Cost Savings: Reduced material waste and labor costs, leading to a 20% decrease in production expenses.

2. Case Study 2: Aerospace Industry

Company: A manufacturer of aircraft components

Challenge: The production of complex, high-precision parts such as fuselage sections and wing components required consistent bending accuracy to meet stringent aerospace standards.

Solution:

  • Precision Tooling: Utilized high precision and quality punch and die specifically designed for aerospace applications.
  • Advanced Control Systems: Integrated CNC controls with real-time monitoring and feedback to ensure consistent bending angles and dimensions.
  • Springback Compensation: Implemented advanced algorithms to predict and compensate for material springback.

Results:

  • High Precision: Consistently achieved bending tolerances within ±0.05 degrees, meeting aerospace industry standards.
  • Improved Quality: Enhanced part quality and reduced the incidence of defects, leading to higher customer satisfaction.
  • Operational Efficiency: Streamlined production processes, resulting in a 30% increase in throughput.

VII. Conclusion

Various aspects need to be considered to improve the press brake accuracy of the bend. In addition to adjusting the bending machine's components, ensuring the accuracy and repeatability of the tooling, and implementing correct bending compensation, attention should also be given to the daily maintenance and upkeep of the press brake.

This will help to extend its lifespan and maintain efficient and precision bending. There are four ways of bending metal sheets: air bending, bottom bending, coining, and three-point bending.

Investing in a high-quality press brake is another effective way to guarantee productive press brake operations in metal fabrication. ADH Machine Tool is a trusted fabricator of press brake machines with two decades of expertise in the sheet metal industry.

Apart from modern press brakes like hydraulic press brakes, CNC press brakes, we also offer other machinery, like laser cutting machine, panel bender, etc.

Visit our press brake product page for more information or our contact us page for detailed product and pricing details. 

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