Section bending machines, commonly referred to as profile bending machines, are integral components of the metalworking industry. These versatile machines specialize in cold bending various profiles, including tubes, bars, angles, “T” profiles, “U” profiles, and beams. By applying controlled forces, section bending machines deform the profiles, enabling precise bending perpendicular to the axis of the profile itself.

At the core of every section bending machine are its rolls, typically numbering three, which play a pivotal role in shaping the metal profiles. These rolls apply a combination of forces that induce deformation during the bending process. Understanding the working principles, configurations, and applications of these machines is essential for maximizing their utility in metalworking operations.

Working Principles of Section Bending Machines

The operation of a section bending machine can be broken down into several phases:

1. Loading: The profile to be bent is carefully inserted between the rolls, with any necessary support to minimize stress on the material.
2. Roll Movement and Pinching: The rolls are adjusted to achieve the pinching position, securely holding the profile in place. In double pinch machines, the top roll remains fixed, while the bottom two can move independently, offering enhanced flexibility in managing pinching and bending operations.
3. Working Phase: Pressure is applied to the profile, resulting in deformation as the rolls translate and adjust accordingly. This phase is critical for achieving the desired bend in the profile.
4. Unloading: Once the bending process is complete, the pressure on the profile is released, and the space between the rolls is increased to facilitate the extraction of the bent profile from the machine.

Three Types of Section Bending Machines

The choice of section bending machine depends on various factors, including the working principle/configuration, drive mechanism, dimensions, control system, and available accessories. Machines can be categorized based on the movement possibilities of the rolls:

• Double Pinch Machines: These machines offer the highest flexibility, with independently movable bottom rolls. They excel in both symmetric and asymmetric bending operations, making them ideal for a wide range of applications.
• Pyramidal Machines: Featuring fixed bottom rolls and a movable top roll, pyramidal machines are suited for symmetrical bending tasks.
• Single Pinch Machines: With only one of the bottom rolls capable of movement, single pinch machines are primarily used for asymmetrical bending applications.

Each configuration has its own set of advantages and disadvantages, which must be carefully evaluated based on factors such as production costs, flexibility, and the ability to execute pre-bending at the ends of profiles.

Types 1#: Double Pinch Section Bending Machines

The double pinch profile bending machine is a versatile and efficient tool in metalworking, renowned for its flexibility and performance. Unlike other configurations, this machine features a fixed top roll and two independently movable bottom rolls, allowing for precise control over bending operations. This design facilitates both symmetric and asymmetric bending, accommodating a wide range of profiles with ease.

Available in various capacities, the double pinch machine can be equipped with three or four rolls, often referred to as double-pinch pyramid section benders. The addition of an extra roller beneath the top roll in four-roll models ensures consistent and uniform bending throughout the process. This feature distinguishes it from three-roll machines, enabling pre-bending of both ends without the need for profile removal, thereby streamlining operations and enhancing productivity.

Furthermore, the double pinch machine offers advantages in cycle time compared to its counterparts. Three-roll machines typically require pre-bending of the leading end, followed by bending the workpiece and then addressing the trailing end. In contrast, four-roll machines can execute pre-bending of the leading edge, rolling the main body, and completing the trailing pre-bend simultaneously, resulting in quicker and more efficient processing.

While smaller models may utilize mechanical components, hydraulic systems are commonly employed for their superior power and precision. Overall, the double pinch profile bending machine stands out for its versatility, efficiency, and reliability, making it a valuable asset in various metal fabrication applications.

Types 2#: Single Pinch Section Bending Machines

Single pinch section bending machines, also known as single initial-pinch machines, are primarily suited for light-capacity applications in metal fabrication. These machines, which may utilize electromechanical or hydraulic systems, operate by pinching metal sections between two vertically opposed rolls while a third, offset roll (the bending roll), moves upward to bend the metal profiles. When the rollers rotate, the metal profiles exit the machine at a predetermined radius. By cutting the metal profiles to the appropriate length and positioning the bending roll correctly, the part can be rolled into a round shape.

In most cases, single pinch machines require the removal and reinsertion of the metal profile to prebend both ends. While they are cost-effective options, particularly for smaller-scale operations, they can be more labor-intensive in a production setting compared to modern double pinch machines.

One characteristic of single pinch machines is their asymmetrical operation. Unlike double pinch machines, where both bottom rolls can move independently, single pinch machines only allow movement in one of the bottom rolls. Consequently, they are suitable for asymmetrical bending tasks where only one side of the profile requires bending.

Types 1#: Pyramidal Section Bending Machines

Pyramidal section bending machines operate with fixed bottom rolls and a movable top roll, enabling only symmetrical bending. However, true pyramid machines, featuring three rolls with fixed lower rolls and a moving top or bending roll, are uncommon in modern manufacturing. These machines often leave a long unbent flat section and are less user-friendly compared to other rolling machine types.

Advantages and Disadvantages of Different Configurations

• Production Costs: Double pinch machines tend to be the most expensive due to their increased complexity and number of movable parts. Pyramidal and single pinch machines generally have similar production costs.
• Flexibility: Double pinch machines offer the highest flexibility, allowing for both symmetric and asymmetric bending operations. While single pinch machines can also accommodate asymmetric bends, pyramidal machines are limited to symmetrical bending tasks.
• Pre-bending Capability: Double pinch machines have the advantage of executing pre-bending on both ends of the profile without the need for removal. In contrast, single pinch machines require the piece to be removed, turned, and reinserted for pre-bending at the opposite end. Pyramidal machines lack the capability for pre-bending.

Machine Capacity and Considerations

Machine capacity is a crucial factor to consider, as it must match the material being processed. Section bending machine manufacturers typically rate their machines based on baseline material yield strengths, commonly ranging from 36,000 to 38,000 pounds per square inch (PSI). However, it’s essential to verify the actual yield strength of the material being used, as steel mills produce materials with increasingly higher yields.

Three-roll initial-pinch or single initial-pinch section bending machines are suitable for light-capacity applications and may be electromechanical or hydraulic. They operate by pinching metal sections between two vertically opposed rolls while a third roll moves upward to contact and bend the metal profiles. While cost-effective, these machines may require more labor-intensive operations in a production setting compared to their modern counterparts.

Double-pinch section bending machines are available in various capacities and configurations, with three or four rolls. These machines offer enhanced capabilities and can pre-bend both ends of a metal section without removal, unlike single pinch machines. Four-roll styles feature an additional roller underneath the top roll, ensuring constant pinching during rolling and improved efficiency.

In contrast, true pyramid machines are less commonly used in modern facilities due to their limited flexibility and user-unfriendly nature. These machines have three rolls, with both lower rolls fixed in position and the top roll moving up and down. While they may leave long unbent flats, they are not as versatile as other types of section bending machines.

Conclusion

Section bending machines play a crucial role in the metalworking industry, offering precise and efficient bending capabilities for a wide range of profiles. By understanding the working principles, configurations, advantages, and disadvantages of these machines, manufacturers can select the most suitable machine for their specific bending requirements. Whether it’s achieving symmetric or asymmetric bends, maximizing flexibility, or optimizing production costs, choosing the right section bending machine is essential for achieving high-quality results in metalworking operations.