Bending stainless steel tubing refers to the process of forming the tubing into a desired shape using a press brake or a bending machine. Stainless steel tubing can be bent to a variety of angles and radii depending on the specific application and the type of tubing being used. The process of bending stainless steel tubing typically involves the use of a mandrel to prevent collapsing of the tubing during the bending process. The mandrel provides support to the tubing and prevents it from wrinkling or deforming. Additionally, lubricants and cooling methods such as water or oil may also be used to aid in the bending process and prevent the cracking of the stainless steel.

In this blog, we will explore the techniques and methods used for bending steel tubing and how to achieve optimal results. Additionally, we will provide tips and tricks for getting the best outcome when working with steel tubing.

Use the right equipment: Use a hydraulic tube bender or a mechanical bender with enough capacity to handle the size and thickness of the tubing you are working with.

Use proper bending techniques:

Make sure to apply pressure evenly when bending the tubing to avoid kinks or crimps. It may also be helpful to use a bending mandrel to support the tubing while it is being bent and to prevent the walls of the tubing from collapsing.

Choose the right type of stainless steel:

Different grades of stainless steel have different levels of ductility, or the ability to be deformed without breaking. For example, austenitic stainless steels, such as 304 and 316, are more ductile and can be bent more easily than martensitic stainless steels, such as 410 and 420.

Consider the final shape of the tubing:

The final shape of the tubing will depend on the degree of bend and the radius of the bend. Bending the tubing to a smaller radius will require more force and may cause the tubing to become flattened or distorted.

Be aware of springback: Stainless steel tubing will have a tendency to "spring back" to its original shape after it has been bent. This means that the tubing may need to be bent slightly more than the desired final shape to compensate for this springback.

There are several techniques that can be used to bend stainless steel tubing, including:

Mandrel bending is a popular technique for bending stainless steel tubing, as it allows for tight-radius bends without compromising the structural integrity of the tubing. During the mandrel bending process, a mandrel is inserted into the tubing before the bend is made. The mandrel is usually made of a harder and more durable material than the tubing and is typically shaped like a cone or a ball.

The mandrel provides support to the tubing during the bending process, preventing it from collapsing or deforming. This allows for tight-radius bends without wrinkling or kinking, which can be especially important in applications requiring precise tolerances and a smooth surface finish.

It's also important to note that, Mandrel bending is typically used for smaller-diameter tubing, if the diameter of the tubing is too large, it may not be possible to insert a mandrel inside. Additionally, mandrel bending may not be suitable for certain types of steel tubing, such as those with very thin walls or those that are prone to cracking.

Mandrel bending requires a specialized machine called a mandrel bender, which is a tool that can bend the tubing with precise control over the angle of the bend and the radius. This type of machine also allows for multiple bends to be made in a single piece of tubing, and many of them have the capacity to program the machine with different angles and radius, which can help to automate the process of bending.

Wipe bending, also known as top-bending or bottoming, is a technique used to bend stainless steel tubing that allows for tighter radius bends and more precise control of the bend angle. The technique uses a V-shaped or U-shaped die that is wiped along the surface of the tubing during the bending process.

One of the main advantages of wipe bending is its ability to produce tight-radius bends without the need for a mandrel, which can be especially useful for larger-diameter tubing or for applications where mandrel access is difficult. Additionally, the V or U-shaped die also allows to have more control over the angle of the bend as well as the radius, so it's a good technique for precise and high-quality bending.

Wipe bending process can be carried out in two ways. One is bottoming or punch and die, this method uses a punch press to force the material against a V-shape die. Another one is air bending, where the material is forced to bend over a V-shape punch and then it is supported by the V-shape die that rest on the material.

However, wipe bending has some limitations. It can only produce bends of a certain minimum radius, which means that it may not be suitable for very tight-radius bends. Additionally, the process may cause surface deformation or scratches on the tubing. And also, the V-shape or U-shape die will have a wear limit and need to be replaced over time.

Roll bending, also known as roll forming or roll bending machine, is a technique that uses a set of three rollers to bend stainless steel tubing in a gradual manner. The rollers apply pressure to the tubing, causing it to bend around the central roller. Roll bending is a continuous process, which means that the tubing is fed through the rollers in a continuous stream and can produce a smooth and consistent bend.

One of the main advantages of roll bending is its ability to produce smooth, consistent bends without wrinkling or deforming the tubing. This is particularly useful for larger diameter and thicker walled tubing, which can be difficult to bend using other methods. Additionally, roll bending allows to bend tubing with a higher thickness than other methods and it doesn't require the use of lubricant, which can make the process cleaner.

Another advantage of roll bending is its ability to bend tubing with a large radius, which is not possible with other bending methods such as air bending. The radius of the bend can be adjusted by adjusting the distance between the rollers, and it is possible to achieve very large radii bends.

However, roll bending also has some limitations. It is not suitable for tight-radius bends, and it is also not suitable for very thin-walled tubing. Additionally, roll bending process is relatively slow compared to other techniques and it has a larger footprint due to the size of the rollers.

Draw bending, also known as rotary draw bending, is a technique used to bend stainless steel tubing that utilizes a mandrel and a set of dies to bend the tubing. The tubing is placed over a mandrel and then passed through a set of dies that are mounted on a rotating machine. As the tubing is passed through the dies, it is bent to the desired shape.

One of the main advantages of draw bending is its ability to produce tight-radius bends without wrinkling or deforming the tubing, which is made possible by the use of a mandrel. The mandrel supports the tubing as it is being bent, which prevents the tubing from collapsing or deforming. This technique can be used to produce complex shapes such as multi-plane bends, helical coils, and more.

Additionally, the Draw bending process uses less force to achieve the desired shape, which results in less material distortion and less thinning of the wall, which is particularly useful for thinner-walled tubing. Also, the use of dies allows high precision on the radius and angle of the bend.

However, draw bending has some limitations. It is typically slower and less efficient than other techniques such as air bending or roll bending. Additionally, the process may require specialized equipment and personnel, and it may not be suitable for very large-diameter tubing or for applications where high production rates are required.

Air bending is a technique used to bend stainless steel tubing that utilizes a press brake and a punch to form the bend in the tubing. The punch is pressed against the tubing, causing it to bend to the shape of the punch. This method is considered faster and more efficient than other bending methods, but it may not be as accurate or precise.

The press brake machine uses a punch that is pressed against the steel tubing, causing it to bend around the punch. The upper die is also part of the press brake, which is the surface against which the punch pushes the material, that shape the tubing. The precision of the bend is determined by the accuracy of the punch and the die, and the process can be adjusted to create the desired angle of bend.

One of the main advantages of air bending is its speed and efficiency. The process can be carried out quickly and with minimal setup time, which can save time and money for large-scale production runs. Additionally, press brakes can be found in different sizes, which allows for the bending of tubing with different diameters and thicknesses.

However, air bending has some limitations. It is not as accurate as other methods, such as mandrel bending or draw bending. The punch and die are both determined factors for the accuracy of the bend, and air bending may produce a wider radius of a bend than desired. Additionally, air bending can produce a slight rounding of the inside bend radius (referred to as “spring-back”) which can affect the precision of the final product.

There are a few challenges that can arise when bending stainless steel tubing:

Work hardening:

Stainless steel has a high strength-to-weight ratio and is resistant to deformation, which can make it difficult to bend. As the tubing is bent, the metal can become work hardened, meaning that it becomes more brittle and more prone to cracking. To minimize the risk of work hardening, it is important to use a bending machine with enough capacity and to apply the bending force evenly.

Springback:

As mentioned previously, stainless steel tends to spring back to its original shape after it has been bent. This can make it difficult to achieve precise bend angles and can require some trial and error to get the desired shape.

Corrosion resistance:

While stainless steel is resistant to corrosion, it is not immune to it. Bending the tubing can create small cracks or crevices on the surface of the metal, which can be breeding grounds for corrosion. To prevent corrosion, it is important to properly clean and finish the tubing after bending.

Cost:

Bending stainless steel tubing can be a time-consuming and labour-intensive process, which can increase the overall cost of the project.

There are several considerations to keep in mind when bending stainless steel tubing to ensure that the process is performed safely and effectively. These include:

Choose the right grade of stainless steel:

Different grades of stainless steel have different levels of strength and ductility, which can affect their bendability. It's important to choose a grade of stainless steel that is suitable for the intended application.

Use the appropriate bending method:

As mentioned previously, different bending methods are suitable for different diameters and thicknesses of tubing. Choosing the appropriate method to ensure that the tubing is bent accurately and without damaging it is important.

Use the appropriate bending equipment:

It's important to use the right type of bending equipment for the job to ensure that the tubing is held securely and bent evenly. Using the wrong equipment can result in deformities or even breakages.

Calculate the bend radius:

The bend radius is the distance between the center of the bend and the inside radius of the bend. It's important to calculate the bend radius accurately to ensure that the tubing has sufficient clearance and does not kink or deform.

Use appropriate safety equipment:

Bending stainless steel tubing can be a physically demanding process, and it's important to use appropriate safety equipment such as gloves and safety glasses to protect yourself.

By following these considerations, you can help ensure that the process of bending stainless steel tubing is performed safely and effectively.