An Introduction to Rolling Pipe Bending Machine

Posted on Apr 23, 2021

Rolling Pipe Bending Machine

The rolling pipe bending machine, which is also called pipe roll bender or roller pipe bending machine, can be used to process both bars and sheet metals. It is designed to force the pipes and tubes through a series of designed rollers that apply pressure to the steel parts, forming unique profiles.

What Is a Rolling Pipe Bending Machine?

A rolling pipe bending machine is designed to force the pipes and tubes through a series of designed rollers that apply pressure to the steel parts, forming unique profiles. Among the metal forming and bending methods, rolling pipe bending is greatly suitable for long strips like pipes and other long gentle bending applications. The rolling pipe bending machines only generate very little deformation to the product in the cross-section.

The rolling pipe bending machine, which is also called pipe roll bender or roller pipe bending machine, can be used to process both bars and sheet metals. When handling bars, the materials usually have a uniform cross-section, which can be other shapes other than rectangular, without any overhanging cliff feature. After the extrusion, where the bars are formed, the shapes and profiles can be further customized through this rolling pipe bending machine. The rolling pipe bending machines permit the users to build as well as repair the pipes of almost unlimited size easily. Rolling the steel pipes or tubes in place, the heavy parts can be formed with the best efficiency and accessibility.

Structure of Rolling Pipe Bending Machine

The rolling pipe bending machine is also called a 3-roll bending machine since it is typically equipped with 3 rollers which are specially designed for bending the metal bar to a circular arc. The rolls freely spin on the parallel axes, which are mounted with standard, horizontal spacing. Similar to the roll bending machines that are designed for bending sheet metals, the rolling pipe bending machine is better suitable for applications requiring large radius bends.

Among the three special rollers, the two lower rollers, which are also known as the end rollers, are typically immobile. Fixed in the position, the two lower rollers can realize the positive or reverse rotations, cradling the bottom portion of the steel pipes in the roll bender machines. These rollers which support the bottom of the materials have a matching contour. 

The inverse shape of the lower rollers can maintain the shape of cross-section and prevent excess deformation that affects the appearance and quality of the products. On the other hand, the upper roller can be moved vertically, upward and downward, to adjust the height. The upper roller presses on the top portion of the stocks. The roller also has a matching contour when forcing against the pipes.

With the arrangement, the back-and-forth movement between the three rollers gradually bends the pipes until obtaining the unique profiles. Rolling pipe bending machines are ideal for applications for coils of pipe and long bends that have a large radius. The gradual forming process causes little deformation in the cross-section, providing high quality and gentle bends. 

:: Read more: An Introduction to Automatic Pipe Bending Machine

Plastic and Elastic Deformation in Roll Bending Process

Rolling, or roll bending, is the classic forming method for metals that forces the stocks to pass through the rollers in order to obtain mechanical property, reduce or uniform the thickness. With the screw arrangement, the bar stocks can be formed against the rollers, and the process causes the pipes to undergo plastic and elastic deformation. During the roll bending process in a rolling pipe bending machine, the portion of the pipe among the rollers will accommodate the shape of a cubic polynomial and gradually become a circular arc.

As the rollers spin along and move the pipes, at a new position, the pipes will take on the shape of a cubic which will be affected by the conditions of adjacent areas of the materials. The force that is applied to the roller is gradually enhanced whenever the end of the bar is reached, and the shape of the pipes will be more ideal to be closer to a circular arc.

Throughout the forming process in many kinds and applications for rolling bending machines, plastic deformation is retained. To compare with, the elastic deformation will be reversed when a part of the material leaves the area among the rollers. The spring back caused by the elastic deformation should be aware of and compensated when adjusting the roll to obtain a required radius. 

The levels of the spring back depend on the inverse stiffness of the metal type with respect to the ductility. For instance, when roll bending the aluminum alloys, which have much greater ductility and elastic compliance compared to steels. As a result, aluminum parts are better suited for roll bending to form into arc than steel bar stocks.

Different Types of Modern Pipe Bending Process

There are more and more automatic pipe bending machines, like CNC rolling pipe bending machines in the market to provide reliable, clean, and efficient pipe bending production. In addition to roll bender machines, there are many types of pipe bending technologies for automatically and permanently forming pipes or tubing into customized shapes. Modern pipe bending methods can be classified to “form bound bending” or “free-from bending”. 

In form bounding type which includes press bending and rotary draw bending, the pipes are formed by a series of unique dies. Straight pipes or tubing can be processed through the bending machine which performs single or multiple bends, creating more complex shapes. These bending methods are generally available for a wide variety of ductile metal pipes. 

As for the free-form bending, which includes the focus of this article, the 3-roll bending, typically forms the products kinematically. Therefore, the bending profile does not depend on the tool geometry used in the pipe bending machine. The acceptable radius of the steel pipes is also larger.

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