Automatic Pipe Bending Machine

what is pipe bending
What is pipe bending?

Pipe bending (Tube bending) describes the process used to form metals and other types of materials into tubing or tubes. The processes by which metal tube bending takes place may involve a variety of methods using temperature, equipment, and materials.

The materials involved in metal tube bending often fall into two categories—either the materials are ferrous (primarily made from iron) or non-ferrous (metals coming from elements other than iron). Ferrous materials used in bending include steel, stainless steel, or steel alloys. In the case of steel alloys, a mix of steel with another metal is done for the purposes of avoiding corrosion of the materials as well as making the metal stronger.

Pipe bending and forming involves more than just welding metal into various shapes and uses. It uses a variety of techniques tailored to the needs of the manufacturer and requires accuracy in design and development. Some tube bending and forming might involve a tube mill or a roll forming machine, depending on the application intended for the tubing.

Types of Pipe Bending

There are a number of ways metal tube bending can take place. Generally, tube bending falls into two types – form-bound tube bending and freeform tube bending.

Form-bound tube bending describes a bending technique whereby the bending contour is dependent on the tool geometry and so shapes the piece of metal into the shape of a die (which is similar to a mold in that it is generally custom made for its intended application). Form-bound tube bending can be done manually in instances where a specialized piece needs one or several engineers to shape it the way it needs to be, or it can involve machinery to bend it into the intended shape.

Types of form-bound tube bending include rotary draw bending, compression bending, and mandrel bending.

Freeform tube bending, on the other hand, describes bending that does not intend to conform to the shape of a die. This is usually done through tube bending technology and presses that run the metal through the process of bending the pipe in a fluid motion without any breaks. This is helpful for materials like roll over cages where one continuous piece of a section is shaped.

An example of freeform tube bending includes roll bending where pipe or tube passes through three rollers set in a pyramid structure to shape the tube.

Both form-bound tube bending and freeform tube bending can employ Computer Numerical Control (CNC) machinery to precisely control the tube bending and forming process.

pipe bending machine

PBT-25 CNC automatic pipe bending machine (Rotary draw bending machine) are the most popular machines for use in bending tube, pipe and solids for applications like: handrails, frames, motor vehicle roll cages, handles, lines and much more. Rotary draw benders create aesthetically pleasing bends when the right tooling is matched to the application.

A rotary draw setup entails a pressure die that holds the straight section (sometimes called the tangent) of the tube; a clamp die that rotates the workpiece around a round bend die; a mandrel, sometimes with a series of articulating balls on the end to support the tube interior around the bend; and a wiper die that contacts the workpiece just before the tangent point of the inside radius, wiping against the material to prevent wrinkles that can form on the bend’s inside radius.

The pressure die (also called a pressure slide) supports the outside radius during bending. The pressure die can be stationary; it can follow the workpiece, sliding on rollers at the same rate the workpiece is being drawn into the bend; or it can be “boosted,” pushed with hydraulics or (more common today) electrical servomotors, further minimizing wall thinning. All these elements effectively control both the tube ID and OD throughout bending.

Further reading: 4 Key Points Cold Bending And Hot Bending In Pipe Bending

pipe bending machine

Principle

The pipe bending machine bends the pipe in the same way as the bending of the sheet.

In the case of pure bending, when the tube with the outer diameter D and the wall thickness t is bent under the action of the external moment M, the outer tube wall of the neutral layer is subjected to the tensile stress σ1, and the tube wall becomes thinner; The wall is subjected to tensile stress σ1 and the wall becomes thicker. Moreover, the shape of the cross section changes from a circle to an approximate ellipse due to the effect of the resultant forces F1 and F2. When the deformation is too large, the outer tube wall will crack and the inner tube wall will wrinkle.

Degree of deformation

The deformation degree of the pipe depends on the relative bending radius R/D and the relative thickness t/D value. The smaller the R/D and t/D values, the greater the deformation degree. In order to ensure the forming quality of the pipe fittings, the degree of deformation must be controlled within the allowable range. The bending forming limit of the pipe material not only depends on the mechanical properties of the material and the bending method, but also considers the use requirements of the pipe fittings.

Forming limit

The forming limit of pipe fittings should include the following:

  • The maximum elongation deformation in the tensile deformation zone outside the neutral layer does not exceed the plastic allowable value of the material to cause rupture;
  • In the compressive deformation zone inside the neutral layer, the thin-walled structure part subjected to tangential compressive stress will not wrinkle beyond instability;
  • If the pipe fitting has the requirement of ovality, control the distortion of its section;
  • If the pipe fitting has the strength requirement to withstand the internal pressure, the forming limit of its wall thickness reduction shall be controlled.
Specification PBT-25 -25 PBT-25 -38PBT-25-50 PBT-25 -63 PBT-25-75 PBT-25-89
Max.Bending.Pipe-Dia
× Thickness
(mm)
Φ 25×2Φ 38×2Φ 50×3Φ 63×4Φ 75×5Φ 89×6
Max.Bending.Rad (mm) R100R180R330R330R400R400
Min.Bending.Rad (mm) R15R15R20R20R30R40
Max.Bending.Angle 190°190°190°190°190°190°
Max.Feed.Length (mm) 200020002000200028003000
Feeding MethodDirect DeliveryDirect DeliveryDirect DeliveryDirect DeliveryDirect DeliveryDirect Delivery
Bending Speed180°/s90°/s80°/s80°/s40°/s40°/s
Turning Speed360°/s200°/s180°/s180°/s160°/s160°/s
Feeding Speed 1000mm/s1000mm/s800mm/s800mm/s800mm/s600mm/s
Bending Accuracy±0.15±0.3±0.3±0.3±0.3±0.3
Turning Accuracy ±0.1±0.1±0.1±0.1±0.1±0.1
Feeding Accuracy ±0.1±0.1±0.1±0.1±0.1±0.1
Data InputY.B.CY.B.CY.B.CY.B.CY.B.CY.B.C
Turning Tube Servo
Motor Power
(kw)  
0.40.40.750.7511.5
Feeding Tube Servo
Motor Power
(kw)  
1111.522
Maximum Allowable
Number of Elbows
323232323232
Number of
Storage Processes
200020002000200020002000
Hydraulic Motor Power (kw)4.05.57.57.51115
Max Pressure(MPa)121212121212
Size(mm)3500×1000×13003500×1000×13003800×1100×13004500×1100×13004900×1350×12305500*1500*1300
Weight(kg)120012002200280038004500
Remarks: The minimum bending radius shall not be less than 1.5D of the pipe diameter; the maximum bending radius and the maximum effective core length can be customized according to customer requirements.
Specification PBT-25 -100 PBT-25 -115PBT-25-130 PBT-25 -168 PBT-25-189 PBT-25-219
Max.Bending.Pipe-Dia
× Thickness
(mm)
Φ 100×8Φ 115×10Φ 130×8Φ 168×14Φ 189×14 Φ 219×16
Max.Bending.Rad (mm) R350R350R400R500R600 R700
Min.Bending.Rad (mm) R50 R50 R50 R50 R80 R80
Max.Bending.Angle 190°190°190°190°190° 190°
Max.Feed.Length (mm) 28502850300036004000 4500
Feeding MethodDirect DeliveryDirect DeliveryDirect DeliveryDirect DeliveryDirect Delivery Direct Delivery
Bending Speed 30°/s 30°/s 30°/s 25°/s 20°/s 20°/s
Turning Speed 160°/s 160°/s 160°/s 160°/s 160°/s 160°/s
Feeding Speed 800mm/s 800mm/s 800mm/s 600mm/s 600mm/s 600mm/s
Bending Accuracy±0.1±0.15±0.15±0.15±0.15 ±0.15
Turning Accuracy ±0.1±0.1±0.1±0.1±0.1 ±0.1
Feeding Accuracy ±0.1±0.1±0.1±0.1±0.1 ±0.1
Data InputY.B.CY.B.CY.B.CY.B.CY.B.C Y.B.C
Turning Tube Servo
Motor Power
(kw)  
2223.55 5
Feeding Tube Servo
Motor Power
(kw)  
3.53.5557.5 7.5
Maximum Allowable
Number of Elbows
3232323232 32
Number of
Storage Processes
20002000200020002000 2000
Hydraulic Motor Power (kw)1522222230 30
Max Pressure(MPa)12121214 14 14
Size(mm)5090×1350×123005090×1350×12306115×1860×12658100×1955×1600 8500×2000×1700 8500×2400×1900
Weight(kg)6000700080001200015000 18000
Remarks: The minimum bending radius shall not be less than 1.5D of the pipe diameter; the maximum bending radius and the maximum effective core length can be customized according to customer requirements.
  • Interactive PLC touch screen offers easy access to auto and manual operating modes.
  • System diagnostics and multiple language capability.
  • Standard clockwise bending direction.
  • Fully hydraulic clamping on clamp die and pressure die.
  • Drop-way hydraulic clamping.
  • Direct acting hydraulic pressure die with adjustable speed valve.
  • Maximum 2000 sets of program storage,Maximum 32 bends for each program.
  • With Independent programmable speeds Y, B, and C axes.
  • Programmable material spring back settings for each bend angle.
  • Automatic release of tube prior to final bend.
  • Bending Axis-Driven by Cylinder,Feeding Axis-Driven by Servo Motor,Rotating Axis-Driven by Servo Motor.
  • Obtain quality repeatable bends in steel, stainless, aluminum, titanium and brass.
  • Foot Pedal Cycle start.
  • With Air Cooling System or water cooling system.
  • One set of Tooling for Draw Bending.
  • Wiper die Bracket.
  • 1 Mandrel Rod.
  • Operation and Maintenance Manual.
  • Tool Box with Adjusted Tools.
  • Electric: As required (3 phase 220V or 380V or 415V…)
Tube Bending Terminology

Rotary Draw Bending: This method of form-bound tube bending includes usage of dies and other components to draw tubing into the machinery and create the desired bend. Rotary draw bending can also use mandrel bending, as explained below.

Mandrel Bending: A mandrel is a rod, usually cylindrical in shape, that can be placed inside of a metal tube and help shape it during the tube bending process, with the goal being to avoid defects in the bend such as rippling, flattening, or collapse of the tube. Mandrels are especially effective when the material being bent has thinner walls.

Compression Bending: A tube bending method where two dies are used – a die that stays stationary, and a counter die that bends the tubing around that die in order to achieve the desired shape.

Roll Bending: When the tube bending process requires large radius bends (bends in which the radius bend is eight times that of the material’s thickness), roll bending might be required. Rollers shaped into a pyramid configuration, or dies that can accommodate the large radius bends, usually facilitate this process.

What is Tube End Forming

Tube end forming describes the process by which some kind of connection to another media—such as a tube, hose, or block—can be used in tubing applications.

Tube end forming applications can be used in a variety of industries where tube bending and forming is needed, such as the automotive industry where a variety of media is used and creating a leak-proof environment is critical to functioning machinery.

Tube end forming involves machinery to establishing a secure connection and can include one of many categories, such as:

A process where the tube diameter is reduced using dies and tapered rings, depending on the application.

A process where the end of the tube is expanded to fit one tube end into another. This application might be necessary in heat pump assemblies, healthcare equipment, and other uses.

A process where beads are added to the end of the tube in order to strengthen a tube and/or to hold a hose on the other end.

A tube end forming process where a tight seal is formed at the end of the tube.

A process where, as the name suggests, the tube end is thickened.

Pipe Press Bending Process

Press Bending is a simplistic form of tube bending. Using a press brake, ironworker, hydraulic press or similar machine a simple “bend die” is pressed against the tube or pipe which is straddled across two fixed supports forcing it to conform to the shape. Image result for PRESS BENDING tubing

Advantage

  • Process is cheap, requiring only simple tooling that can be adapted to existing machinery.
  • Versatile can be adapted to provide versatility in bending tubing, pipe and barstock

Disadvantage

  • Tubing/Pipe crushes easily
  • Accuracy is poor
  • Repeatability is poor
  • Production is very slow.
pipe roll bending process

Roll Bending is another method of tube bending that utilizes a 3 or 4 roll machine called an Angle Roll or Section Roller to pull the tube or pipe through the rolls while pressing the tubing into an increasing bend. This method, much like Press Bending, utilizes a triangular pattern of support rollers and pressing roller, however unlike Press Bending this method can bend a variety of angles utilizing the same type of rollers as the tube or pipe moves through the bending sequence by the powered and turning rollers. This method can be an easy and precise way to bend a variety of radii without the need for specific tooling for the desired bend radius desired.

Advantage

A variety of tube radii can be performed on the same machine including variable angles.
Sections such as pipe, bars, and angle can also be formed with this method

Disadvantage

  • Slower process as each tube is manually processed with difficulty in obtaining exacting results.
  • Thin walled tubing can easily collapse if the bend radii is too small.
  • Accuracy is poor
  • Repeatability is Poor
Pipe Rotary Draw Bending Process

Rotary Draw Bending is by far the most popular form of tube bending as it is easiest to control, more precise,repeatable and a relatively affordable tube bending system. A Rotary Draw Bending system is made up of three different tools, the Clamping Die, the Pressure Die and the Radius Die that hold and form the tube throughout the bending process. The tube is clamped to the bend die and is ‘drawn’ around the die by the machine by either hydraulic or electric methods. As the bending die rotates the tubing is held in place firmly against the rotating bend die by the pressure die.

Advantages

  • Precise and Repeatable
  • Fast

Disadvantages

  • Machinery is dedicated to the bending process and thus is less flexible
  • Cost for initial machine
  • Requires Tooling for each different tube/pipe diameter used and for each radius formed
Mandrel Tube Bending Process

Mandrel Tube Bending is really not a separate process from the above, Rotary Draw Bending at all, but rather an addition to tubing bending mandrel. With the capability to form tighter and exacting radii the Rotary Tube Bender can begin to easily collapse the tubing during the forming process. By adding internal support, or mandrel, during the forming process the tube walls can be held firm from collapsing. With the addition of a mandrel, inserted within the tube and controlled by the machine during the bending process, the tube is kept from collapsing in on itself as it is stretched and formed around the bending die. The mandrel is only slightly smaller than the ID of the tubing being bent and affixed with several flexible supports on a flexible ball mandrel at its end. These ball mandrels flex with the tube being formed and allow the tube to bend while supporting the whole diameter of the tube while the tube is wiping over the mandrel during the entire bending process.

Advantages

  • Accuracy and Repeatability
  • Shape – Roundness of tube is kept throughout the forming process
  • Speed

Disadvantages

  • Cost
  • Setup time