Bending rectangular tubing is a more difficult process than round tube bending (all else being equal: surface area, radius, wall thickness, material type, etc.).
Before the bending rectangular tube
8 parameters of bending rectangular tube
There are several parameters to know for performing tube bending:
- Radius for the bend section – CLR
- Chord of the bend section – C
- Arc length – L
- Degree of bend – a
- Rise of bend section – R
- Tube size – D
- Wall thickness – t
- Tangents – A, B
Not all are necessary to be known but at least three are needed to produce a correct tube bend.
Even though procedures are the same for bending all tubes, square end rectangular tubes require special consideration.
After the information is collected and analyzed, the appropriate method of bending is chosen. All this information is a key for choosing the appropriate method of tube bending which may be rotary draw bending, the more parameters are known, the better the bending method can be chosen which will produce the best final results: accurate bends without distortion.
How to bending rectangular tube
Bending rectangular tubing is a more difficult process than round tube bending (all else being equal: surface area, radius, wall thickness, material type, etc.). As with almost all metal bending processes, the tighter the bend, the more difficult it becomes. Similarly, bending rectangular tubing with thinner walls is more difficult than bending thicker walls (provided the bending machine has the power to curve the thicker sections).
5 ways to bend rectangular tubes
Bending methods are the same for round, square, and rectangular material:
- Rotary draw bending
- Induction bending
- Roll bending
- Increment bending
- Compression bending
As with all bent parts, the customer’s tolerances and appearance requirements help determine the proper method.
Hard Way (X-X axis) or the Easy Way (Y-Y axis)
Rectangular Tube and Square Tube, sometimes referred to as HSS. Rectangular Tubing can be rolled either the Hard Way (X-X axis) or the Easy Way (Y-Y axis).
Other pitches of roll (off angle rolling) can be achieved with special tooling. In general, the thicker the wall, the less distortion achieved by the rolling process.
Radius also plays a crucial role with regard to distortion. The tighter the radius, the more distortion is to be expected.
bending rectangular tubing the hard way
Acceptable distortion limits should also be determined and agreed upon prior to commencement of any project. AESS standards are generally the most stringent.
The difference between the hard way and the easy way
Regarding the direction of the bend, although more pressure is required to bend a tube the hard way, the curved member is less likely to distort because it is more rigid than a section curved the easy way. Easy way bending often results in the inside diameter becoming somewhat concave.
Bending rectangular tube the hard way produces less distortion or concavity then bending the easy way especially when the difference between the sides of the tubing is greater. There is a greater chance for distortion in the larger tubes bent to a smaller radius than for the smaller tubes bent to a larger radius.
5 points for attention in bending design
Several methods exist to support the inside of the tube to achieve tighter radii.
- Location of the weld seam and the corner radii are required for proper mandrel fitting into the inside of the tube.
- For shop fabricated materials square or rectangular corner edges become work-hardened which may cause difficulty bending.
- Bending round, square, or rectangular tubes requires stretching of the outside diameter of the bend and compressing inside diameter.
- The heavier the wall thickness, the tighter the bend radius that can be achieved with less distortion.
- If tubes are to be architecturally exposed then more consideration is required to produce the clean bend.
:: Read More : HOW TO BENDING SQUARE TUBE
Tips For Bending Steel Tubes:
However, there is some troubleshooting to do when performing steel tube bending.
Bends often require achieving a tight radius. Since the outer wall of the bend becomes thinner, the result may be a distorted bend. To prevent this, using a mandrel to give support is recommended. That is also why press or ram bending is not recommended in these situations. The most adequate bending method would be mandrel bending, which is the same as rotary draw bending, but adding a mandrel to support the inside of the pipe.
The machine in the picture above can bend the rectangular tube after changing the mold. Of course, it supports the bending of the mandrel.
Sometimes the radius we need to achieve makes the steel to exceed its elastic limits. It can result in deformation in the form of a hump or wrinkles. To prevent the formation of humps and wrinkles, it is recommended to use rotary draw bending or three roll bending.
When bending stainless steel tubes and pipes, it is important to remember that some of the stainless steels require around 50% more power for bending than carbon steels. Therefore, that the machinery must be set accordingly.
Further reading: The difference between tube and pipe
Related Reading：Similarities Between Bending Round and Rectangular Tubing
THREE TYPES OF RECTANGULAR TUBE BENDING MACHINE
pbh rectangular tube bending machine
PBH series section bending machine can bends square hollow sections for structural projects including curved formwork, barrel vaults, roof trusses and bridge rails.
The roll bending of the rectangular tube is basically the same as the roll bending of the round tube, but the mold is different.
The picture below shows the rolling and bending molds for rectangular and round tubes:
BIT’s rectangular tube bending machine, also known as square tube bending machine, profile bending machine, section bending machine, has compact structure, generous appearance, low noise, low energy consumption, high efficiency, no noise, compact structure, It has the advantages of simple operation, easy maintenance, convenient installation and use.
|Model||Specification (mm)||Minimum Inside Diameter (mm)|
|PBH-120||65 × 6||1000|
|PBH-140||90 × 5||1500|
|PBH-200||100 × 6||2000|
|PBH-300||120 × 8||3000|
|PBH-360||150 × 8||5000|
|PBH-450||180 × 10||6000|
|PBH-500||200 × 10||8000|
|PBH-550||250 × 12||10000|
|PBH-600||300 × 12||15000|
|PBH-700||350 × 12||30000|
Working principle of the rectangular tube rolling machine
The rectangular tube rolling machine is mainly composed of the main machine, the hydraulic station and the electric control cabinet.
The high-pressure oil output by the electric oil pump is sent into the working oil cylinder or the motor through the high-pressure oil pipe, and the high-pressure oil pushes the plunger in the working oil cylinder or the motor to generate thrust and torque, and then bend the profile through the mold parts.
- Small size and light weight: Because not only adopts the new technology transmission structure, the input shaft and output shaft are on the same axis, so this machine has the characteristics of compact structure, small size and light weight.
- High mechanical efficiency, fewer failures, and long service life. The main transmission engaging parts of the rectangular tube bending machine are made of high-quality composite steel, and the work roll end bearing is supported by ZWZ bearings, which has a large load carrying capacity and reduces power loss caused by friction. Therefore, mechanical performance Good, good wear resistance, coupled with the use of rolling friction, so that it has fewer failures and long life.
- The operation is reliable and stable. The transmission process of the BIT series rectangular tube rolling machine (section bending machine) is multi-tooth meshing, so it runs smoothly and reliably. Low noise.
- Convenient disassembly and assembly, easy maintenance, adopts an integral structure, reasonable design, strong rigidity, simple disassembly and assembly, and easy maintenance.
- BIT series rectangular tube rolling machine (section bending machine) also has strong overload capacity, impact resistance, small moment of inertia, suitable for frequent starting and forward and reverse rotation characteristics. Improve the service life of the motor.
- It has the advantages of strong carrying capacity, long life, fast winding speed, reliable product quality and so on.
- Safe operation, high rolling efficiency, convenient adjustment, long service life, low energy consumption and good economy.
How to Choose the Right RECTANGULAR TUBE BENDING MACHINE?
- The type of square tube to be rolled: square tube or rectangular tube; such as 20 × 20 or 20 × 40, etc.
- How to bend a rectangular tube, such as a 40 × 60 rectangular tube, a flat-rolled 40 with a face elevation of 60 will save effort (easy way), and a flat-rolled 60 with a face elevation of 40 will make it more powerful (hard way), the choice of equipment should also use a larger model of equipment.
- Rolling method: three types are commonly used, one is round or a large arc. The second type is to bend as an angle, any angle within 180 degrees. The third category is the spiral coil.
- For coiling a single circle or a large arc, please choose a three-roller (section bending machine). For any angle within 180, please choose a NC rectangular tube bender. Most of the spiral coil pipes use CNC profile bending machine or multi-roller.
The above rectangular tube bending machines BIT are all produced, and we will recommend equipment according to your bending needs.
What is rectangular tube ?
RHS steel sections ( RHS beams ) aslo called rectangular tube are just one of three types of popular steel hollow sections.
RHS beams are popular in mechanical, structural and construction applications because they typically have a very flat structure that makes it more economical for welding, joining, and various other types of fabrication work.
In short, what is RHS? RHS beams are a type of rectangular steel tubing. They only need to be straight cut when joined to other flat services. This makes the RHS section very popular, as very little welding and joining preparation is needed. They are also used to glam up the look of a building, as they are very straight and smooth, as well as strong.
Rectangular tube bending is the same as rectangular tube bending for the profile bending machine. The difference is that the bending parameter size is determined according to the bending height.