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Profile Bending: 3 Roll Bending Process Guide

PBH 450 Profile Bending Machine
PBH 200 Profile Bending Machine

The 3-roll profile bending machine(aka angle roller or angle roll) is the profile bending industry workhorse. The profile bending machine has three hydraulically driven rolls in a triangular configuration. In a typical horizontal configuration, viewed from overhead, material is fed between the two top rolls and single bottom roll until the end of the material touches the far roll. The distance between the middle of the far roll and the middle of the bottom roll is called the grip length, which provides leverage to induce the force needed to create the bending moment. The greater the grip length, the more leverage you have. The downside: In most cases, the material within that grip length needs to be scrapped, which is the reason most profile bending machine request material that is a little longer than what’s required.

Read More: Profile Bending Machine: 5 Things Before Buy, 6 Steps to Bend

What profiles can be bent by cold roll bending?

Cold section bending is suitable for bending metal profiles

Profile bending machines (section rolling machines) use a technique called cold rolling, also known as ring rolling to produce quality curved sections in a cost-effective way.
Large sweeping curves, and varying radius curves, such as ellipses, tight bends, rings, and coils, can be achieved for a wide range of sections and material types.

How to bend metal profiles with a section bending machine

The profile roll bending (section rolling) of the section bending is used to conduct continuous three-point bending of the metal profiles to make the profile produce plastic deformation and reach the required bending radius. The curving of profile bending machine (also called section bending machine, section rolling machine, or section bender) shapes—angles, bars, beams, channels, tees, pipe, and tube, are all part of section bending.  Read More: Bending Wikipedia
How to bend a profile with an angle roll? The 3-roll section bending machine is the main force of the metal profile, the machine has two fixed rollers, while the upper vertical roller is positioned accordingly in order to complete the desired bending. By changing the relative position and rotating movement of the working roller, continuous plastic deformation is achieved in order for the workpiece to receive a predetermined shape.

Important reading:2021 update: Read before the operation of profile bending machine

Bending process of profile bending machine
Bending process of roll cold bending

Profile Bending Principle of Profile Bending Machine

While profile bending, the workpiece is positioned between the lower and up roll of the section rolling machine. After placing the metal profile (bar, angle, h beam, tube and pipe, u channel) between the lower rolls, the up roll is lowered to secure the workpiece, and at the same time, it has achieved sufficient pressure on the sheet, generating plastic bending. When rotating the roller there is friction between the metal profile and the roller, so the profile moves along its longitudinal direction. At the same time, the upper roller adds pressure to the workpiece.

When the roller crosses the lower limit of the upper roller (the roller deformation zone) in one turn and the pressure exceeds the bending limit, plastic deformation occurs and the sheet is folded to its desired dimensions by its entire length. By adjusting the relative position between the lower and upper rolls, the sheet can be folded to a diameter that is not less than the diameter of the upper roller.

In the picture right you can see the principle of the symmetrical circular section bending machine with 3 rollers.

Rollers 2 and 3 move in the same direction and at the same speed. Because of the friction between the sheet metal and the rollers, the workpiece moves in advance. By adjusting the position of the upper roller, the desired bending angle can be achieved. If the workpiece does not achieve the proper curvature after the first bending, it can be adjusted and started the process in the opposite direction until the desired shape is achieved.

How to reduce the end flat part of cold rolling profiles? Six Tips

  • What is the flat part of a cold rolling bending? After bending (section rolling) the position of the rollers on the workpiece inevitably remains a flat part at the ends of the metal profile. This flat part is approximately half the length of the gap between the centers of the lower rollers.
  • How to reduce it? Although the appearance of a straight part is considered to be a flaw of a symmetrical roller with 3 rollers, their simple structure, comfortable use, and low price still make them the most wanted model of roll metal section bending machines. In addition, there are methods which we can use in order to easily eliminate this problem. You can find some of them below:
  • Pre-bending: This solution involves bending the edges of the workpiece on a press brake or roll bender before the roll bending process. If the metal profile ends can be bent prior to rolling, then no extra material is required. This process is called “pre-bending.”
    Pre-bending can be done with a radius die in a press brake or done in a 3-roll or 4-roll section bending machine, plate roll. How thick a plate you can pre-bend is controlled by the maximum pressure that can be applied by the top roll of the machine.More specifically, the capacity of an angle roll machine is defined by the maximum thickness and the minimum radius combinations that can be pre-bent for a given profile of maximum width. Pre-bending saves time. You do not have to cut then roll, cut then roll, etc. Pre-bending also eliminates flat spots and material waste.
  • Adding a “base” for the workpiece during the pre-bending: This method involves the installation of a “base” together with a workpiece designed for bending and performing the edge pre-bending process on the circular bending machine itself. The application of this method should take into account the possibilities of the circular bending machine and calculate the strength of the applied force on the “base” and the workpiece. Leaving allowance at the ends – if you add appropriate allowance at plate ends before the bending, you can, after the bending, cut off those parts into a desired bending shape.
  • Asymmetrical model: Regarding the asymmetrical models of roll bending machines with 3 rollers, the position of the rollers is better adapted to eliminate the flat edges of the sheet, in which case the lower rollers can also be mounted vertically.
    Thus, in a model with an asymmetric position of the rollers, the lower rotating roller can be lifted up to the middle of the gap between the two rollers, while the other can be positioned in the appropriate position so that the starting part of the metal profile can be folded to form a circle. The flat edge can be eliminated on both sides by turning the rollers in half of the bending process by folding the back of the profile. Additionally, the workpiece can also be turned around after the completion of one bending cycle and then the back part will become the front and both flat edges will be eliminated.

5 points of attention for profile bending

  1. In the process of roll bending, the deformation mode of the metal profile is equivalent to that of free bending.
  2. The curvature of the roll bending part depends on the relative position between the rollers, the thickness of the metal profile, and the mechanical properties.
  3. Due to the existence of bending elastic recovery, the curvature of the roll bending part cannot be equal to that of the upper roller.
  4. The most important characteristic of the section rolling method is its strong versatility.
  5. Generally, there is no need to add process equipment to the section rolling machine, and only rollers suitable for different section shapes and sizes are needed for rolling bending of profiles.

How to choose the right profile bending machine

Before purchasing a new profile bending machine, must make a responsible assessment of their purchases. Adding new equipment obviously requires cost considerations. However, if the new equipment is not as productive as the old one, then the investment will be ruined. According to a study, a considerable part of the procurement is ignoring the production capacity of the equipment and the impact of equipment maintenance, so the newly added equipment cannot meet the production needs.

3 key points for choosing the right angle rolls/Angle rollers

You can into the following 3 points for reference in the procurement of profile rolling equipment:

  • Bending capacity: To determine the proper profile bending machine, it is critical that yield strength, thickness, and diameter (or radius) of the profiles are all considered because, for example, a higher yield or tighter diameter will require more pressure to form.
  • Application: When determining which section bending machine is best suited for the task one has at hand, it is important to research what each profile bending machine is designed to do, and to understand the materials that one will be working with. Manufacturers can usually provide detailed information about their machines, such as capacity, yield and The best application: such as aluminum or carbon steel; whether the control system is PLC or CNC.
  • Compare the parameters provided by the manufacturer: Compare the manufacturer’s information about how much force a machine can produce and what kind of metals it is designed to handle, and compare this to your site’s mill certificates or other relevant information to see which section bending machine best fits your needs. For example, under the same bending capacity, the volume, weight, and energy consumption of BIT’s machines are far lower than those of the peers, which means that the energy consumption and transportation weight are smaller, and the price-performance ratio under the same bending capacity is higher than that of the peers.

Read More: Angle Roll Machine, Angle Roller – CNC Complex Shape Bending

Of course, you can also choose a correct angle roller through the following methods:

Select the metal profile to be bent

At the same time, we also provide a combined table, which lists the bending capabilities of the PBH series profile bending machine for 9 kinds of metal profiles. It is worth pointing out that there are some profiles that will not be in our table or the following pictures, but You can provide us with its drawings and bending process drawings, and we can customize the machine you need for you.
Regarding the bending capacity, if you have enough large profiles and budget, we can produce extra large profile bending machines with a section modulus up to 1700m3 for you. Click here to get the PBH series profile bending machine bending capacity parameter table

Here, BIT provides the bending process of 9 profiles and the corresponding bending capacity parameters of the PBH series profile bending machine: Next, you will find relevant information, including the processing capabilities of different profile bending machines manufactured by BIT related to the project you care about.

Select according to the bending requirements of the metal profiles that need to be bent

Profile bending machine (Angle roll) with 4 rolls

profile bending machine
Four rollers, CNC control, more precise bending

In addition to machine tools for roll bending with 3 rollers, there are on-the-market machines for roll bending with 4 rollers. They offer quicker and easier management. Read More: Best Guide to 4 Roll Profile Bending Machines/Angle Rollers