Choosing the Right Bending Machine

IMCAR hydraulic bending machine

To choose the most suitable bending machine for a given application, you must first determine whether it will be used for tubes, bars, or profiles.

Next, you need to take into account the dimensions of the part you will be bending, i.e. the diameter and thickness of the tube, or the height and width of the bar. With these elements, you can determine the right dimensions for the rollers, the distance between them, and the size of the bending machine you need.

You also need to know the minimum bending radius and the bending angle you want to achieve. As a general rule, the minimum bending radius of a tube is 2.5 times its outside diameter, and the minimum bending radius of a bar is 3 times its cross-section. To choose the parameters of your bending machine, you need to know the bending angles you want to achieve. For example, if you choose a bending machine with rollers, it will take several cycles to obtain bending angles greater than 90°.

Of course, you also need to take into account the characteristics of the material to be bent, such as its tensile strength and elongation.

Bending machines are usually designed for cold bending, but there are also bending machines that can be used to process bars, tubes, and profiles in a hot state, which are mainly used in iron and metalworking. Another hot bending technique is induction bending, which can be used to bend large stainless steel tubes, for example.

Unlike in hot bending, in cold bending, the mechanical properties of the metal are retained. Hot bending, on the other hand, offers greater flexibility in terms of deformation and makes it possible to obtain tighter bending radii.

ROTHENBERGER manual bending machine

Manual bending machines are suitable for one-off use or for the production of parts in small batches, where a high level of precision is not required. With a manual bending machine, bending accuracy and repeatability depend on the operator’s experience. However, investment is minimal compared to an industrial bending machine.

Manual bending machines can be mechanical or hydraulic:

• Mechanical bending machines are generally used for small-diameter tubes. They are equipped with a crank that drives the roller, which in turn moves the tube, bar, or profile.
• Hydraulic bending machines are used to bend larger diameter tubes. They are equipped with a hydraulic cylinder that exerts an even thrust on the bending roller.

TRACTO-TECHNIK automatic bending machine

To choose the right type of automatic bending machine you need to choose a model that meets the requirements in terms of operation speed, performance, and precision:

• Automatic hydraulic bending machines perform quality bending with high precision but are relatively slow, especially compared to electric bending machines.
• Electric bending machines are fast.
• CNC bending machines are programmable machines that offer a high level of repeatability and precision, but they require a major investment.

FACCIN three-roller bending machine

Bending machines are generally equipped with three rollers for bending. Depending on the model, either two or all of the rollers can be motorized. There are also four-roller bending machines that are available for specific jobs.

• Bending machines with two motorized rollers are the least expensive. They are mainly used for small production runs, where perfect finishes are not an important criterion, as the grooved rollers often leave marks on the parts.
• Bending machines with three motorized rollers are faster and provide better quality finishes, but they are also more expensive than models with two motorized rollers.
• Four-roller bending machines make it easier to bend both large and small-diameter tubes. These bending machines are the most efficient.

The rollers and the drive system will have an impact on the finish quality and durability of your machine. The rollers are hardened and ground to ensure long-lasting durability. The drive system is also designed to withstand heavy loads. If it is a gear system, the most resistant are gears with induction-hardened teeth. If it is a shaft drive transmission, the system can be equipped with a plastic part that will break if subjected to excessive loads, protecting the machine and facilitating maintenance.

AMOB pyramid-type bending machine

There are pyramid-shaped and asymmetrical bending machines:

• On a pyramid-type bending machine, only the top central roller moves. The distance between the two lower rollers cannot be changed. It is larger than on asymmetrical bending machines, which means that large-diameter tubes can be bent and a relatively large bending radius can be achieved.
• On an asymmetrical bending machine, the central roller is fixed and adjustments are made on the lower rollers, which move in a circular arc. This allows a wide range of work to be carried out with small deformations and minimal bending radii.

Depending on your working environment, bending machines can be vertical or horizontal:

• Vertical bending machines require very little space to work in, but the room’s ceiling height must be sufficient for the work to be carried out.
• Horizontal bending machines require a larger work area, and in some cases, guide rails are required to support the workpiece being bent.

Some bending machines have a mandrel that takes on the internal shape of the profile being bent, thus preventing the outer part of the profile from hollowing out.