Tube bending machines, commonly called tube benders, come in a lot of variety. Predominantly, they work electromechanically. Thanks to the latest technological developments, these machines are capable of accelerating production and improving repeatability. At the same time they are reducing the number of errors in production at every scale.
The main parts of a tube bending machine are:
- Bend die
- Clamp die
- Pressure die
- Wiper die
The bend die, also known as the bend form or the radius die, is the most important part of a rotary-draw bending machine. The tube clamps to the bend die and the drawing process produces the necessary bend. The selection of die is very important, as the tube’s inside radius depends on it.
The clamp die presses the tube onto the bend die. Its main purpose is to prevent the pipe from slipping.
The pressure die makes sure the tube follows the bend die’s contour.
A wiper die places just after the bend die. The purpose is to avoid the formation of any humps on the inside radius.
During the forming process, the material turns plastic during bending. It may result in wrinkles with large deformations. Thus, adding a wiper die just after the bend die helps to smooth the surface.
In bending metal tubes, a mandrel is necessary for more difficult jobs. Bending a small radius, thin tubes or harder materials can result in an unsatisfactory outcome. In those cases, a mandrel can be handy. The mandrel’s objective is keeping the tube from collapsing.
Different Tube Bending Machines
There’s quite a few options to choose from, when you want to bend tubes. Pipe and tubing benders come in different forms. The choice of a bending process comes down to the required bending radii, material, etc.
Rotary Draw Bending Machine
This is the most common type of a tube bender. First, the machine operator secures the tube or pipe on the machine with a clamp die. Then the bend die starts turning around its axis. At the same time, the stationary pressure die makes sure the tube follows the bend die’s radius.
Adding a mandrel and a wiper die is a possibility to secure a better outcome. This is only necessary with more difficult jobs though, where deformations are not allowed. For example, a tube with a large diameter and a small wall thickness needs more support.
As a highly accurate and programmable machine, it allows the production of complex parts in batches.
Applications: handrails, frames, automotive roll cages, handles, etc.
Roll Bending Machine
These pipe bending machines are also known as 3-roll benders. Similarly to sheet metal roll benders, they are commonly used for achieving large radii bends. The two lower rollers have a fixed position. The upper roller’s height is adjustable. Gradually, with back-and-forth movement between the rollers, the tube bends until obtaining the optimal result.
Tube roll bending achieves an excellent result, causing little deformation in the cross section.
Applications: coils of pipe, long bends with a large radius.
Ram Bending Machine
Also known as a press bender, it’s probably the simplest pipe bender on the market. First, the stationary dies are placed onto the work bed. The distance between the dies regulates the length of the bend and the bending angle.
The bending radius depends on the radius of the ram. When everything is in place, the ram pushes against the pipe. As the outside wall of the tube is supported by the dies, the ram can effectively perform the metal forming.
Ram bending is only suitable if the deformation of the cross section is not an issue. Because there is no internal support, a pipe ends with an oval cross section.
Applications: simple bends where accuracy and a constant cross section are not that important.
Vector Tube Bending Machine
This forming machine is excellent for high quality results. The principle is similar to rotary draw bending. A pipe forms around a rotary draw, so it is very precise. But the automatic feeding system makes it also very fast. These machines are suitable for bending high strength materials.
Applications: aerospace and automotive industry.
Orbital Head Bending Machine
Usually used with automation and computer controls, they provide the possibility to rotate the heads and collets around the tubes and pipes. This increases efficiency and productivity. Automated feeding and offloading are available.
Applications: air conditioning, automotive and other complex parts.
Induction Bending Machine
With induction bending, a profile is drawn through a die. At the bending point, there is an induction coil. Thus, the metal heats up. Applying the pressure to a hot workpiece allows for energy-efficient bending.
It is an accurate method that does not require mandrels. At the same time, a wide range of pipe sizes fit the same machine and a large variety of bend angles are available.
Applications: large industrial structural parts, short radius bends, heating system parts, thick-walled parts, etc.
What is CNC bending?
Today, most bending only needs human assistance, not constant guidance. This is possible because of CNC bending machines.
CNC stands for Computer Numerically Controlled. It is a term frequently used in manufacturing to describe machines that work with a programming software to perform their operations. Common CNC machines include lathes, drills and other machining tools.
The operator uses the programming software to feed the data of the operation or operations required. Then the machine performs those operations automatically.
CNC controlled tube bending machines usually use a combination of presses and rollers to guide the tubes and pipes along the process.
In general, CNC bending is bending made more productive and efficient by using automation.