Cold bending and hot bending, press bending, roll bending and stretch bending

C channel bending machine

Bending forming


A stamping process for bending metal sheets, pipes and profiles into workpieces with a certain curvature, shape and size.


Bending forming is widely used in the manufacture of high-pressure vessels, boiler drums, boiler tubes, steel plates and ribs of ship hulls, various utensils, instrument components, and cabinet inserts.

Bending deformation

When the material is bent, the stress state of each part in the deformation zone is different.

The part that does not deform in the middle of the cross section is called the neutral layer.

  • Metals other than the neutral layer are subjected to tensile stress, resulting in elongation and deformation.
  • The metal within the neutral layer is subjected to compressive stress, resulting in compression deformation.

Since the stress and strain directions of the metals on both sides of the neutral layer are opposite, when the load is removed, the directions of elastic deformation and recovery of the metals on both sides of the neutral layer are opposite, causing different degrees of rebound.

Although the bending deformation is limited to a local area of ​​the material, the rebound effect will affect the accuracy of the bending part. There are many influencing factors of spring-back, and these factors are difficult to control. The accuracy of bending parts caused by spring-back has always been the key to bending production.

Cold bending and hot bending

According to the physical process characteristics, the bending of the workpiece is divided into two types: cold bending and hot bending.

So what are the cold bending and hot bending, press bending, roll bending and stretch bending in the profile bending processing industry?

Definition of Cold bending

Bending at room temperature is called cold bending, which is often done by special bending machines.

Definition of Hot bending

When the cross-section of the workpiece is large and the radius is small, it needs to be bent under heating, which is called hot bending, which is often completed by intermediate frequency pipe bending equipment.

Cold bending

  • Most special-shaped materials are processed by cold bending.
  • According to the characteristics of the processing technology, the cold bending of the workpiece is divided into press bending, roll bending and stretch bending.

Stretch bending

Stretch bending is to pull the deformation point of the profile after changing the extension of the profile, and to draw the arc by the template. The process methods include template rolling, tension adjustment, extension calculation, rebound calculation, stretching speed, boom angle, single arm bending, double The arms are bent.

Press bending

Press bending is the most commonly used bending method.

Most of the equipment used are general mechanical presses or hydraulic presses, but also special bending presses.

Roll bending

Commonly used roll bending equipment is plate bending machine and profile bending machine.

The three-roller bending machine is based on the principle of three points to determine a circle, and continuously bends the slab.

The three-roller plate bending machine has two driving rollers (fixed) and a pressing roller (adjustable). The relative distance between the pressing roller and the driving roller can be changed by adjusting the upper and lower positions of the pressing roller.

When bending, the plate is placed between the driving roller and the pressing roller, and the driving roller rotates in the forward and reverse directions to make the plate reciprocate. By adjusting the pressing roller to gradually press it down, the plate can be bent into a cylindrical surface with a required curvature, a conical surface and a hyperboloid with a smaller curvature. One end of the pressing roller can be raised to facilitate the unloading of the workpiece.

There are also four-roller and multi-roller plate rolling machines. Four-roller plate rolling machines are used to roll thick plate cylinders. Multi-roller plate rolling machines with more than four rollers use multiple pairs of rollers to gradually bend the plates into complex shapes.

For bending parts that require high precision, large length and radius of curvature, and small transverse dimensions, they can be stretched and bent on a special stretch-bending machine. During stretching and bending, the entire thickness of the plate is subjected to tensile stress, so only elongation deformation occurs, and the deformation caused by spring-back after unloading is small, which is easy to ensure accuracy.

Profile bending machine

It is a kind of cold bending equipment for metal profiles and a commonly used bending machine for metal profiles.

Such as angle steel, channel steel, I-beam, metal square pipe, metal round pipe and various metal special-shaped profiles.

The shapes that can be processed are round, arc, ellipse, parabola and so on. Can be divided into vertical and horizontal, easy to operate, low cost, suitable for cold bending forming of small and medium-sized materials.

Cold bending application

Stretch bending

Aluminum doors and windows, automobile luggage racks, automobile high-speed rail structural parts, elevator handrails, yacht structural parts, bathroom stainless steel pipes, etc., are widely used in high-speed trains, automobiles, ships, large buildings, bridges, wind power generation, aviation and other high-end fields.

Roll bending

Used in the manufacture of circular flanges in automobiles, aerospace, rail transit elevators, conveyor guides, doors and windows, curtain walls, decoration engineering, ships, lighting, etc. and other industries.