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Understanding Press Brake Tonnage Ratings and Their Influencing Factors

In the metal fabrication sector, it is common for press brakes to be rated in terms of their tonnage capabilities. Tonnage rating, as it is called, is derived from the maximum amount of force that the machine can generate to bend metals. Different press brake machines have different ratings assigned to them.

The efficiency and effectiveness of a press brake machine depend on its tonnage ratings. In this article, we discuss some of the common press brake tonnage ratings and the factors that influence them.

What is Press Brake Tonnage?

press brake

The press brake exerts a force on the metal sheet during the sheet metal bending process to shape it into the desired shape.

Since the metal bending process has several variables, the force that the press brake generates varies. In one example, different metals have different thicknesses. This is a factor that dictates the amount of force that is required to bend the metal. This is one of the reasons press brakes have different tonnage ratings to account for such factors.

The maximum force that a press brake machine exerts on a metal sheet is referred to as tonnage. This implies that every press brake has a limit to the amount of force it can generate to bend metals.

When a press brake has a high tonnage, it is capable of bending a wide variety of metals with various properties. For example, a 50-ton press brake can bend thin or thick metals, while a 10-ton press brake is only limited to thin metals.

Common Press Brake Tonnage Ratings

Standard ratings are used across the industry. However, press brake manufacturers are at liberty to design and assign ratings to the machines they produce. This is because these ratings are based on several aspects. Some of the common ratings include;

10-ton press brake

Any press brake with a rating between 0 and 10 tons is considered a low-tonnage machine. These press brakes are meant for light-duty work, including pressing thin sheet metals for non-industrial use cases. Most of these press brakes are manual.

30-ton press brake

At 30 tons, we start to get more capable machines. While 30 is still not a lot of tonnage, these press brakes are capable of handling diverse bending operations. This means they can handle metals with various mechanical properties. Similarly, 30-ton press brakes are mostly manual.

100-ton press brake

A press brake with a tonnage rating of 100 tons can handle bend metals into intricate shapes and fast. This means they can be used for industrial applications where accuracy and speed are a priority. Most of these machines use hydraulics to generate the force or pressure to bend the metals.

Hydraulics is the system used in hydraulic press brakes. This system is efficient at producing pressure due to the uniform pressure generated. This ensures that the machine produces perfect bends at all times.

500+ tons press brake

At this level, we start getting the most capable and advanced industrial press brake machines. Five hundred or more is a lot of tonnage for a press brake, provided that most metals can be bent with a force that is less than this.

However, most press brakes with this tonnage rating can handle any bending operation. They are mostly reserved for large-scale metal fabrication where precision and speed are a priority. Additionally, most of these are usually CNC press brakes.

How to Calculate the Required Bending Force

Tonnage is also known as bending force. This force is calculated using a specific formula where several variables are computed to determine the ideal tonnage for a specific press brake machine.

Tonnage calculation formula

𝑃=𝐾×𝐿×𝑇2 / 𝑉×𝐶

In this formula,

  • P is the tonnage
  • K is the K-factor of the material. 
  • L is the bend length
  • T is the material thickness
  • V is the V-die opening width
  • C is a constant known as imperial units

Computing these variables and constants helps technicians determine the ideal force to apply when bending sheet metal. As you will see later, using the right amount of force has several benefits.

The Benefits of Using Correct Press Brake Tonnage

Using incorrect tonnage when bending metal sheets has several negative implications for the process’s outcome. Some of the demerits associated with using low or high-tonnage press brakes include tool damage, incomplete bends, safety issues, and material waste.

The opposite of these disadvantages is the expected benefits of using the correct tonnage ratings. Critical press brake components such as the ram, punch, and die must remain in good shape for the machine to produce perfect bends. Also, using the correct tonnage ensures that the sheet metal is bent properly without wasting it.

Factors Influencing Press Brake Tonnage

Several factors determine press brake tonnage. They include;

Material thickness

The maximum force required to bend a material depends on its thickness. In essence, the thicker the metal, the higher the force requirements. This thickness is measured as the cross-sectional area of the metal’s width, expressed in millimeters.

Bend geometry

The geometry of the desired bend also influences the tonnage requirements. By bend geometry, we refer to the bend’s shape, width, depth, and angle. All these are factors that will dictate the ideal bending force required.

Strength of the material

Different metals have different strengths. For instance, aluminum is not as strong as other types of metals, which means it requires less force to bend. The strength is also influenced by factors such as the metal’s thickness, neutral axis, and k-factor.

Material properties

All metals used in sheet bending operations must exhibit certain properties, such as malleability and ductility. Still, these metals have other mechanical and chemical properties that define their molecular and physical structure. These aspects need to be considered when determining the ideal tonnage.

Accuracy requirements

How accurate do you need the bend to be? If you are looking for precise bends, you are better off using a press brake with a higher tonnage. The tonnage should also not be too high since it will result in more harm than good.

Die maximum bearing capacity

The die component of the press brake also has a predetermined bearing capacity. This is the amount of force the die can withstand without getting deformed. Technicians have to account for this to ensure that the die is not damaged by too much force from the ram and punch of the press brake.

Conclusion

Press brake tonnage ratings ensure the sheet metal bending process is efficient and effective. Without these ratings, technicians would be operating on guesswork, which is unreliable and prone to errors. These ratings are among the aspects that make press brake machines the top metal fabrication process.

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