Professionals often recommend mandrel bending as the safest method of making a bend in a tube/pipe without harming it. But what is mandrel bending, and how do you make mandrel bends in pipe bending.
This guide has all the information you need to know about how mandrel bending works.
What is Mandrel Bending?
It is a popular rotary draw bending technique – a process in which a solid rod is put into a tube or pipe during bending. The solid rod strengthens the tube/pipe and prevents collapse while making the mandrel bend.
When a pipe is bent, the outer radius of the bend stretches the material, thinning it. The material accumulates on the shorter side of the bend area. The result is typically tearing in the longer side and ripples in the shorter side.
Mandrel bending adds physical strength to the pipe to eliminate backpressure and pipe collapse.
The solid tool inserted inside the tube or pipe is called a mandrel. Choosing the ideal mandrel is important to achieve a good mandrel bend. A hard mandrel (such as a steel rod) is preferred for soft tubes. A soft mandrel is preferred for hard tubes.
Once the bending is completed, the mandrel is extracted from the tube.
Which Materials To Choose for Mandrels?
The choice of material for the mandrel depends on the tube. Some popular options are:
- A steel or chrome mandrel for copper, aluminum, bronze, or steel tubes.
- An aluminum or bronze mandrel for stainless steel, Inconel, or titanium tubing.
The Importance of Mandrel Bending
Mandrel bending is important for various reasons:
- Bending Thin Tubing: This can be challenging for beginners and professionals since the walls tend to break under high stress. A mandrel makes the job easy and prevents the tube from breaking.
- High Bend Angle: Mandrels are also indispensable when bending at a high angle or making multiple bends in a tube/pipe.
- Stopping Spring-back: The immense physical strength of the mandrel eliminates backpressure and prevents the tube/pipe from returning to its original shape after bending (spring-back).
Applications of Mandrel Bending
Mandrel bending is used for many parts in various applications.
- Automotive: Mandrel bending is a method used for bending the exhaust systems of vehicles.
- Gym: Special mandrels are designed for making gym equipment such as lifting machines, rods, and more.
- Furniture Frames: mandrel bending is used to manufacture the metal legs for chairs and frames for tables and other furniture items.
- Aerospace: Mandrels not only ease tube bending but also add to the strength of the bent tube.
- Roll Cages: Building roll cages for vehicles requires tube bending with a high bending angle. The mandrel bending technique makes the job easy.
How to Do Mandrel Bending?
Mandrel bending involves a series of steps that are similar for all types of mandrel benders.
Step 1: Readying the Tooling Set
Before bending, get all the tools you need ready. The mandrel is a part of the tooling set.
Select the mandrel’s size based on the tubing to be bent.
Other things you will need:
- Clamp die: holds the tube against the bend die as it moves.
- Bend die: moves around the tube/pipe, creating the bend.
- Wiper die: helps prevent wrinkles when bending tubing, one of the beneficial components of mandrel bending.
- Pressure die: holds one end of the tube in place as the bend die rotates the remainder of the tube/pipe. The pressure die is under constant counter pressure to the bend die.
Step 2: Setting Up the Tube
Once the tube and tooling are ready, it is time to begin the setup process. Place the mandrel and the tube/pipe in the appropriate position. Some bending machines automatically push the mandrel inside the tubing.
Placing the mandrel at the correct position inside the tube is vital. Usually, the mandrel must be at the tangent where the bend starts. In some cases (e.g., a ball mandrel bend), the mandrel pushes over the tangent point, and the balls go inside the bend area.
Ensure all clamps are tight so that the tube remains in a fixed position and doesn’t slip during the bending process.
Step 3: Executing the Bend
Today, most CNC tube bender machines allow the operator to create the bend at the push of a button. The die moves around the tube/pipe to create the desired bend angle.
Step 4: Extracting the Mandrel
The mandrel can be extracted during the last few degrees of tube bending or after the tube bend is complete.
Types of Mandrel Bending Machines
Mandrel benders come in many variations. The main difference is the type of mandrel used.
Plug Mandrel Machine
Plug mandrels are used for bending thick tubes with long radii. In this type of bending, a solid rod is slipped inside the tube/pipe before bending it. This method does not require a wiper die.
Form Mandrel Machine
A form mandrel machine uses a metal rod with one curved end for additional support. These mandrels are used for thick tubes with nominal pipe diameter.
Ball Mandrel Machine
This features a spherical-shaped ball at the end of the mandrel facing the curve. The balls go inside the curve area when bending beyond the tangent. Ball mandrel bending produces a precise bend.
Sand Mandrel Machine
Sand mandrel bending involves filling the hollow tube with sand to provide support. Since sand isn’t as strong as a solid mandrel, this type of bending requires heating the tube/pipe before bending.
Rogue Fab Tubing and Pipe Bender
Rogue Fab’s M600 series mandrel benders are premium products for producing the best mandrel bends. M600 benders have the broadest wall thickness range of any bender on the market. They are compatible with all materials, including steel, aluminum, and titanium. The M600 also incorporates a unique lubrication feature.
Alternatives to Mandrel Bending
Mandrel bending is the go-to option for people who want accuracy in critical pipe bending operations. However, people with budget constraints or other limitations might search for an alternative to mandrel benders.
There are a few alternatives to mandrel bending:
Crush Bending
- Crush bending is a simple bending process done without any internal support. A force is applied to crush the tube at the desired position and form the bend.
- The tube/pipe is often deformed at the bend location in this type of bending.
Press Bending
- Some manufacturers in the automotive sector suggest press bending instead of mandrel bending for exhaust systems that expel hot exhaust gases. However, it is not a good practice.
- The press bending process flattens the pipe at the bend location. This results in backpressure of the exhaust gas, i.e., the tube experiences pressure in the opposite direction.
- However, mandrel bending retains the circular shape of the exhaust pipe and eliminates backpressure in the system.
Conclusion
Mandrel pipe bending is the most popular pipe bending method used today. Professionals opt for this method whenever they need a clean bend with no visual or physical deformities at the bending point.
Modern mandrel benders, like Rogue Fabrication’s M600, produce high-quality bends without wrinkles. It looks like the pipe was forged in that shape during the manufacturing process.
Mandrel benders like the M600 make bends in metal pipes as easy as bending a straight plastic straw with your hand. As a bonus, these benders also support bending square and rectangular tubing.
Are you looking for the best mandrel bender on the market? Try Rogue Fab!