Plate Rolling Machine: Definition, Types, Principle ＆ More

The plate rolling machine operates by applying external forces, such as hydraulic pressure and mechanical force, to the work rolls, thereby pressing or forming the sheet metal. Different shapes, including oval, arc, and cylindrical parts, can be created through the rotation and positional changes of the work rolls.

This machine is widely used in industries such as chemical, boiler, and shipbuilding, and is classified into two types based on the number of rolls: three-roll plate bending machines and four-roll plate bending machines.

What is Plate Rolling Machine?

The rolling machine, also known as a circle rolling machine, is a machine tool utilized for continuously bending metal sheets into cylindrical, arc-shaped, or other forms of workpieces.

The relative positional changes and rotational movements of the workpiece are used to continuously deform the plate and achieve a desired shape. The plate bending machine can be classified into two-roll, three-roll, and four-roll versions, with the three-roll machine further divided into upper roll universal, symmetrical, horizontal downward adjustable, and arc adjustable types

These machines can be further classified based on their transmission mode, such as hydraulic or mechanical. The two-roll plate bending machine is used for processing smaller plates, while the four-roll machine is used for larger plates, such as those made of marine steel.

The plate rolling machine is widely used in industries such as boiler and shipbuilding, as well as in the manufacturing of machinery in the petroleum, woodworking, and metal structure industries.

Working Principle of Plate Rolling Machine

There are many different specifications and models of plate bending machines. These machines can be classified based on their mechanical structure and the number of rolls, resulting in three-roll and four-roll versions. Additionally, plate bending machines can be classified based on their driving mode as either mechanical or hydraulic.

The structure of a three-roll plate bending machine is relatively simple, consisting of a pair of side rolls and an upper roll that can move up and down. The four-roll plate bending machine, however, has a more complex structure with a pair of side rolls, an upper roll, and a lower roll. Despite its higher cost, this type of machine offers superior performance and produces higher-quality rolled products.

The combined plate bending machine primarily consists of a dumping device, a transmission system, an upper roll, a lower roll, and a frame.

Its structure features pinions from multiple transmission systems meshing with the large gears at the end of the upper roll. The transmission system can be arranged in two groups, placed horizontally and symmetrically with the upper roll.

Alternatively, it can be arranged in three groups, with the upper roll symmetrically positioned around a 120-degree center circle. Lastly, the transmission system can consist of four groups, with the upper roll symmetrically positioned around a 90-degree center circle.

The operating principle of the rolling machine is consistent across all models. The upper roll and side roll’s relative position is adjusted to gradually bend and deform the sheet metal between the rolls. The main shaft’s positive and negative rotation causes the sheet metal to move back and forth between the rolls until plastic deformation occurs.

By continuously adjusting the roll’s relative position, the main shaft continuously reciprocates and the plastic deformation of the sheet metal increases until it is processed into a circular arc or circular pass product that meets the required specifications.

The working capacity of the plate bending machine refers to the minimum drum diameter that can be produced when the maximum plate thickness and width are rolled under specified yield limits in a cold state. This method is widely used domestically and internationally, as it offers high precision, simple operation, and low cost. However, it requires a high-quality plate with no defects or inconsistencies in its metallurgical structure.

For thicker plates or smaller bending radii that exceed the equipment’s working capacity, the hot rolling method can be used if the equipment permits. In cases where the plate cannot be cold rolled and the hot roll’s rigidity is insufficient, the warm rolling method is employed.

Processing method of bending forming of plate bending machine

In the manufacturing of steel structures, the bending forming process includes several methods such as rolling (rounding), bending (simmering), folding, and die pressing. This process can be completed through hot or cold processing.

Round bending is a bending deformation achieved through the elongation of the outer fibers and the shortening of the inner fibers of the steel plate under the influence of external force, while the middle fibers remain unchanged. If the cylinder radius is large, the steel plate can be rolled at room temperature, but if the radius is small and the plate is thick, heating is required.

There are three methods for rolling steel plates at room temperature: mechanical rolling, mold pressing, and manual manufacturing. Mechanical rounding is performed on the plate rolling machine, also known as the round rolling machine. The bending of the plates on this machine is achieved through the pressure generated when the upper roller moves downward. The working principle of rounding is shown in the figure below.

working principle of the rounding
A) Symmetrical three roll bending machine
B) Asymmetrical three roll bending machine
C) Four roll bending machine drawing

When using a three-roll bending (coiling) machine to bend the plate, both ends of the plate must be pre-bent. The pre-bending length is calculated as 0.5L + (30 to 50) mm, where L is the center distance of the lower roll.

The pre-bending process can be performed either through pressing with a press or by using a support plate in the rolling machine.

Pre bending
a) Press and pre bend with a press machine
b) Pre-bend with a support plate in the rounding machine

Different Types of plate rolling machine
As a specialized machine, the plate bending machine plays a significant role in basic industrial processing. If the formed steel needs to be cylindrical, the rolling machine is necessary for roll bending and is used in industries such as automobiles and military.

The rolling machine can produce steel columns that meet specific requirements and is a highly practical tool. In foreign countries, the roll bending machine is typically categorized based on the configuration of the work rolls.

In China, the classification is generally done based on the number and adjustment form of the work rolls and is typically divided into:

Three-roll Plate Bending Machine: This category includes symmetrical three-roll plate bending machines, asymmetric three-roll plate bending machines, horizontal adjustment three-roll plate bending machines, inclined adjustment three-roll plate bending machines, arc adjustment three-roll plate bending machines, and vertical adjustment three-roll plate bending machines.

Four-roll Plate Bending Machine: This category is divided into side roll tilt adjustment four-roll plate bending machines and side roll arc adjustment four-roll plate bending machines.

Special Purpose Plate Bending Machine: This category includes vertical plate bending machines, marine plate bending machines, double roll plate bending machines, cone plate bending machines, multi-roll plate bending machines, and multi-purpose plate bending machines, among others.

Different Types of plate rolling machine

Mechanical transmission has been used in plate bending machines for several decades now. Despite its simple structure and reliable performance, it is still widely used in small and medium-sized plate bending machines due to its low cost.

However, for low-speed and high-torque plate bending machines, the size of the transmission system and the high motor power required for operation have led to increasing use of hydraulic transmission.

In recent years, there have been plate bending machines with mixed mechanical and hydraulic transmission, where the movement of the work roll is controlled by a hydraulic motor, while the main drive remains mechanical. Additionally, there are also full hydraulic plate bending machines that use a hydraulic motor as the power source for the work roll’s rotation.