4 Essential Modes Of Tube Bending

Every tube bending workshop has to focus on precision and detailing to ensure the result adheres to the initial design and specs. However, achieving the accuracy at such a granular level won’t be possible if proper attention is not paid to the tube bending workflow. Manufacturers usually divide the entire process into multiple phases, each dedicated to create the right bend angle needed as per the design measurements. What’s more is that bent tubes for different applications require multifarious bending techniques or modes. 

Not knowing these or implementing the processes will lead to material damage, improper bend designs, and tooling damage. Besides, it can also delay the entire delivery, causing a significant decline in customer experience and brand value. That’s why we have prepared a comprehensive illustration, highlighting the four major modes involved with tube bending process that you must know for successful project execution.

The first mode of tube bending process that is quite common in most manufacturing projects is that of compression bending. Its primary goal is to increase the output efficiency and process speed while decreasing the manufacturing cost involved with every workpiece. Usually, manufacturers don’t pay too much attention in attaining accuracy and perfection for the roundness of the bent structure and the bend angle. Instead, they implement this method to have a higher output and prevent any production delays.

Apart from this, compression bending does not require any mandrel, which is one of the many reasons for irregular bent structures. However, manufacturers should pay attention to the material thickness and mechanical hardness while choosing this tube bending mode. Without the use of a mandrel, it would be difficult to prevent any type of structural deformation if the material thickness isn’t high enough to counterbalance the compressive pressure. 

One of the major attributes of compression bending is that it can be applied for both symmetrical and asymmetrical bends, which further gives manufacturers more independence for different project requirements. However, one should ensure that the tubes to be bent using compression bending must have a centerline as twice its diameter to have proper bend structures.

One of the most common bending processes that most manufacturers rely on is that of rotary draw bending. It provides the operator absolute control over the bend angles and dimensions to be created in the workpiece, thereby helping them to exercise accuracy and precision. However, it is a complicated tube bending mode, which not only requires meticulous planning but a long list of toolsets properly arranged together

Usually, most rotary draw bending machine comprises of three mandatory and three optional tooling pieces, each serving a dedicated task. In this following section, we have described each mandatory tool and their function in tube bending process

• Bend die: It is the moving part of the entire rotary draw bending machine. The die is used to create the bends in the tubes by applying pressure on the external and internal radii, depending on the initial bend design. It continues to rotate in a circular motion to smoothen the bend part of the tube and prevent any deformation. 
• Clamp die: One of the most important parts of the entire bending machine is the clamp die. It is used to hold the tube in place during operation and prevent its dislocation by any means. The die’s opening can be adjusted according to the tube’s thickness and diameter. 
• Pressure die: Tubes usually have a tendency to attain their original straight shape after bending. The pressure die maintains a consistent force on the bent structure to prevent the springbuck action and retain the bend angle.
  

Now, if the tube’s material thickness is extremely low or the bent angle needs to be tighter, three additional tooling components need to be used for accuracy and precision. These are:

• Wiper die: Usually, with lower material thickness, the chances of ripples forming on the inner surface of the workpiece are quite high, owing to the high applied pressure. To prevent the rippling effect, a wiper die is attached to the machine. As the tube passes through the bending die, the wiper die continues to roll over the inner surface and keeps it smooth. 
• Mandrel: Depending on the bend angle and the material thickness, you need to decide the total number of balls that the mandrel should have. It will support the weak structure of the workpiece and prevent any form of physical deformation. 
• Collet: When multiple bends are to be created in a single workpiece, a collet is used to move the tube further and maintain a consistent speed for the bending die
  

When larger bend angles are to be created having the radius as colossal as eight to ten times of the tube’s diameter, roll or angle bending is preferred. Here, a series of rollers, usually three are used to create the bend and maintain its appropriate structure without creating any deformation. Furthermore, it is the central roller which accurately determines the bending angle to be created along the tubular structure.

One of the major benefits of angle bending is that it is applicable for different material types and thicknesses, thereby allowing manufacturers to use the same for versatile project requirements. Thanks to the use of multiple rollers, the process is quite fast and hence increases the production efficiency. For tight bend radii or complicated designs with larger bend angles, this is the perfect tube bending mode to go with.

Freeform bending is perhaps the most unique form of tube bending used when multiple radii bends are to be created in a single workpiece. The machine comes with a ceramic hole that can be adjusted based on the diameter of the tube or pipe. Its action is solely controlled using the CNC software, which is why accuracy and precision are maintained at the optimal levels. Minimal tooling is required in this bending mode, which is why you won’t have to worry about the expense or any other difficulty.

In this article, we have explained the four major types of tube bending that can be implemented at your workshop for different projects having versatile requirements. All you need to do is gather the design requirements and choose the most feasible bending mode. Remember that several variables will influence the aptness of your choice, including material thickness and type, bend structures, desired result, and many more.