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4-roll bending machine

What is a 4 roll bending machine?

The four-roll bending machines have over the 3-roll bending machines is simplicity.

Four-roll bending Machines produce the fastest and most accurate bends. It has fixed-position top rolls and two offset, or lateral, rolls, one on each side, and has an additional roller underneath the top roll, which constantly pinches the plate during rolling, and can prebend both workpiece (plate or profile) ends without removal.

Type of 4 roll bending machine

4 roll profile bending machine
4 roll plate bending machine

BIT offers three types of 4-roll bending machines: PBH 4 roll profile bending machine, PBR 4 roll plate rolling machine, and the PBA 4 roll aluminum bending machine.

It should be pointed out that the working principle of the PBA 4 roll aluminum bending machine is different from the previous two.

Work principle of 4-roll bending machine

bending process of four-roll section bending machine

The metal workpiece is held securely in place between the top and bottom rolls, while the side rolls move vertically to create the bend. The bottom roll moves up to hold the metal profile or plate surface securely against the top roll while the side roll is raised to form an accurate prebend, minimizing the flat zone on the workpiece edge. 4 roll bending machine workpieces are loaded horizontally at the feed level for pre-bending, which allows the use of horizontal motorized roller tables to help feed the workpiece.

The side rolls are positioned to the right and left of the bottom roll and are on their own axes. The independent axis of each roll helps make a perfect bend. The so-called “back” side roll (at the far side of the feeding point) also functions as a back gauge to square the plate for proper alignment. This eliminates the need for someone to assist the operator.

The plate is kept square without slipping during both pre-bending and rolling because of the constant secure clamping of the top and bottom rolls.

The working principle of the 4-roll plate bending machine

Four-roll machines do not require the operator to remove, flip, and then try to square the plate a second time after pre-bending, as is the case with three-roll, initial-pinch machines. Because the material can be kept in the machine, a cylinder can be rolled to the required diameter immediately following pre-bending.

4 rolls vs. 3 rolls

  • Four roll bending machines are more precise, productive, versatile, faster, safer, and easier to operate than three roll machines. They are less dependent on operator competence.
  • The fastest and most accurate bends are made by four roll machines. The 4 roll machines have a slight advantage in cycle time because they permit pre-bending of the leading edge, rolling the cylinder body, and finishing off the trailing prebend, all while rolling in the same direction.
  • The bottom roll moves up to hold the workpiece securely against the top roll while the side roll is raised to form an accurate pre-bend, minimizing the flat zone on the workpiece edge. Pre-bending on a 3-roll bending machine requires that workpieces be tilted down as they are being fed. In contrast, workpieces are loaded horizontally at the feed level for pre-bending on a four-roll machine, which allows the use of horizontal motorized roller tables to help feed the workpiece.
  • The side rolls are positioned to the right and left of the bottom roll and are on their own axes. The independent axis of each roll helps make a perfect bend.
  • The workpiece is kept square without slipping during both pre-bending and rolling because of the constant secure clamping of the top and bottom rolls.
  • Cone rolling is easier on a four-roll machine. The side rolls can be tilted to establish the cone angle and the bottom roll can also be tilted to clamp and drive the workpiece.
  • 4-roll benders are better suited to have CNC controls since the material is held between two pinch rolls and the position can be controlled. Because of the constant clamping and driving of the material during all steps of rolling, bending difficult shapes like polycentric or elliptic workpieces can be easily done with 4 roll bending machines.


Must know section bending information: a practical guide to the section bending of various metal profiles