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3-Roll Bending Machine

3-roll initial-pinch, 3-roll double-pinch, 3-roll variable translating, 3-roll top roll horizontal movement, and 3-roll pyramid bending machine

What is 3-roll bending machine?

The three-roll bending machines are ideal for fabricators working with a wide range of material types. 
3-roll bending machines are offered in two distinct categories: single and double-pinch. General 3-roll bending machine types are three-roll initial-pinch, three-roll double-pinch, three-roll variable translating, top roll horizontal movement, and three-roll pyramid.

Working Principle

3-roll bending machine work by “pinching” the flat workpiece between two rolls and bending it as it comes in contact with a forming roll. This bends the workpiece into a cylindrical form, where it is welded together to produce a cylinder.

Five types of 3-roll bending machine

Plate or metal profile 3-roll bending machines are offered in two distinct categories: single and double-pinch, but they may vary in geometry or style. General machine styles are three-roll initial-pinch, three-roll double-pinch, three-roll variable translating, top roll horizontal movement, and three-roll pyramid.

The 3-roll bending machines are also built in a vertical format for special applications. Matching the most appropriate machine style to the application is important.

Three-roll initial-pinch or single initial-pinch bending machine

This machine is an asymmetric three-roller

Three-roll initial-pinch or single initial-pinch bending machines generally are for light-capacity applications and may be electromechanical or hydraulic. They work by pinching the flat sheet between two vertically opposed rolls while the third, offset roll—or bending roll—moves upward to contact and then bends the metal profile.

When rotation of the rollers is activated, the metal profile exits at a given radius. With the metal profile such as the plate cut to the developed length and the bending roll properly positioned, the part is rolled into a round (such as cylindrical) shape that can then be welded at the seam to produce a closed cylinder.

Double-pinch 3-roll bending machines

Double-pinch 3-roll bending machines are available in light to very heavy capacities. The terminology can be confusing as these units also may be referred to as double-pinch pyramid plate rolls or double-initial-pinch plate rolls. They have fixed-position top rolls and two offset, or lateral, rolls, one on each side.

Three-roll bending machines generally require pre-bending the leading end, running the sheet through the machine to prebend the trailing end, and then switching roll rotation direction to roll the cylinder body.

Smaller machines can be mechanical, but most are hydraulic and include drop-end yokes for easy extraction of the workpiece.

Variable-geometry 3-roll bending machine

Variable-geometry 3-roll plate bending machines are built to handle medium to extremely heavy plate rolling applications. Easy-to-remove end yokes can make material removal a quick process.

A metal fabricator doesn’t have too many machine tools that are dedicated to one job or one type of material. The nature of low-volume, high-mix work typically means a shop needs equipment that is versatile enough to tackle a range of jobs. When it comes to plate rolling, variable-geometry, a three-roll bending machine is that tool.

This type of plate roller differs from more traditional techniques in that it doesn’t have a fixed roller. The equipment is designed so that the top roll moves up and down and the two lower rolls move horizontally and independently of each other. The equipment’s flexibility makes it a suitable choice for medium to thick materials, say more than 1 in. thick.

The top roll moves up and down while the lower two rolls each move horizontally. This lower roll movement increases the offset distance from the top roll and in so doing delivers a distinct mechanical advantage in bending. A machine of this type works well over a wide range of material thicknesses.

With varying geometry, these rolls can be used like a single-pinch, double-pinch, or pyramid-style machine that requires minimal sheet movement during pre-bending.

Top roll horizontal movement 3-roll bending machine

The top roll horizontal movement 3-roll bending machines top roll crowning and adjustable Back-Up Rolls enable to achieve precise circularity and cylindricality to application with a wide range of material thicknesses.

Being formed in the procedure that top roll moves front/rear direction, the ends of the material plate are firmly bent as well as the one was done by the ordinal press. Top roll crowning and adjustment of back-up roll help correct deflection of both Top Roll and Back-Up Rolls to be more precise circularity and cylindricality of applications, which reduces the time of post-procedure.

Pyramid 3-roll bending machine

True pyramid machines are rarely used in cutting-edge facilities.

They have three rolls with both lower rolls fixed in position and the top or bending, roll moving up and down. The pyramidal bending machine‘s upper roller can move vertically up and down to pressurize the lower roller, so it cannot be pre-bent. In general, they leave a very long unbent flat and are not as user-friendly as other types of rolling machines.

How to choosing

Capacity

Machine capacity is equally if not more important than style. Bending machine manufacturers commonly rate their machines according to baseline material yield strengths of 36,000 to 38,000 pounds per square inch (PSI). However, you need to realize that steel mills are producing materials with ever-increasing yields.

When choosing a machine, you must refer to your bending machine certificates and verify the average yield strength of the metal profile (sheet metal, H-beam, angle iron, U-channel, pipe/tube, steel bar, etc) you are buying. It is not uncommon to find that the “mild“ steel you are rolling will have actual yields in the 48,000- to the 58,000-PSI range.

Remember, machine capacity must match your material, and most bending machine manufacturers can provide detailed capacity-versus-yield tables to assist you.

Pre-bending

Pre bending is performed on the 3-roll bending machine at the leading and trailing edges of the metal profile, and eventually the seam.

A metal profile cannot physically be bent right to the edge, and thus what remains is referred to as the unbent flat. The minimum flat you can expect is 1.5 times the material thickness and often 2.5 to 3.5 times the material thickness for the heavier metal profile.

It is the pre-bending operation, in attempting to minimize the unbent flat, which takes the most power. That’s why pre-bending ratings are lower than rolling capacities for any given machine.

PBH 3-Roll Bending Machines

angle roll machine

PBH 3-roll profile bending machine (also called section bending machine) has up to 9 sets of hydraulic components and supports extremely high profile section bending performance, it is a technologically advanced, reliable, and accurate machine, it can provide the best results for the bending of mild steel, stainless steel, aluminum, bronze, copper.

BIT three-roll profile bending machine which can accurately drive the 3D guide rollers of the profile bending machine. By adjusting two more powerful horizontal hydraulic 3D guide rollers, they can be adjusted in the six directions of up and down, left and right movement, and push/pull, respectively, and can support and accompany curved profiles to ensure optimal control of the rolling level Straightness, and correct the deformation of the profile rolling process.

It is very suitable for bending various profiles from small to large, thereby minimizing parts And scrap: flat bar, square & round bar, Tee steel, and angle steel in all bending methods, and through a set of BIT’s unique combined cross-section bending die, it can also bend I & H-beam and U-channels.

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PBA 3-Roll Aluminum Bending Machines

aluminum extrusion bending machine

PBA Series CNC Profile Bending Machine is an aluminum bending machine for aluminum profiles;
Up to`15 independent controllable servo axes; Automatic CNC systems; Three-dimensional bending. Accuracy is as high as ≤0.01mm.  which is the standard and optional equipment of the PBA-CNC series aluminum bending machine.
Can be bent in various shapes (3-D graphics, C-shaped, U-shaped, full circle, ellipse, multiple radii combination shapes, etc.)
Computer numerically controlled (CNC) section bending is a manufacturing process that is carried out by a CNC section bending machine (also known as a CNC aluminum bending machine), suitable for bending aluminum profiles for automobiles, doors, and windows.

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PR 3-Roll Plate Bending Machines

PRT Top Roll Horizontal Movement 3-roll Bending Machine

High rolling power combined with maximum pre-bending precision: PRT is the series of top roll horizontal movement 3-roll bending machines at the highest level of its category by performance and versatility.

PRT 3-roll bending machines designed, manufactured and marketed by BIT deliver performance equivalent to that obtained with the more expensive 4-roll plate bending rolls and are therefore ideal for medium-heavy duty machining.

PRT series models feature a very fast and secure pre-bending stage because the plate is never tilted but always parallel to the ground.

Thanks to the special configuration of PRT electronic plate bending machines, the machine’s top roll moves vertically and horizontally, by minimizing the length of the straight part, they offer better quality pre-bending.

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PRV Variable Geometry 3-roll Bending Machine

PRV Variable Geometry 3-Roll Plate Rollers with the variable geometry design, the bottom rolls move on a horizontal axis and independently from each other with variable steps, while the top roll motorized, moves on a vertical axis. It has the function of pre-bending the end of the plate, which can feed the metal plate at one time, and can complete the pre-bending of the plate end and the rolling of the workpiece without turning around. The three work rolls are the main driving rolls. The lifting and lowering of the upper roll and the horizontal movement of the two lower rolls are hydraulically driven. The lifting displacement is controlled by a computer, automatically leveled, and displayed on the screen. The synchronization accuracy is ±0.2mm.

Advantages

  • Great versatility (increasing the distance between the bottom rolls and maintaining the same thrust from the top roll, we are able to bend big thickness, decreasing such distance we are able to bend smaller thicknesses.
  • The plate is kept horizontal during the pre-bending process (increasing safety for the operator).
  • The total dimensions of the machine are decreased compared to a 4-roll machine, due to the side roll cylinders being mounted horizontally. Therefore, no need for a pit up to 1.5 times plate size.

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PRD double pinch 3-roll bending machine
PRA initial pinch 3-roll bending machine
PRS pyramid 3-roll bending machine

PRD Double Pinch 3-Roll Bending Machine

The upper roller of the PRD double pinch 3-roll bending machine is fixed and rotated, and the two lower rollers are respectively lifted and lowered around the fixed center arc. The two lower rollers can be easily adjusted through the CNC control system to form a symmetrical three-roller plate rolling machine type, which means that it has the function of a symmetrical 3-roll plate rolling machine at the same time.

Pre-bending at both ends

The two lower rollers of the PRD Double Pinch three-roller plate bending machine can be lifted and lowered independently in an arc.
During operation, one lower roller is lifted and the upper roller is clamped to the sheet material, and the other roller is placed at the bottom for support. That is, an asymmetric sheet rolling process method is formed, so as to pre-bend one end of the sheet material; One side of the roller is lowered and the other side of the lower roller is raised, so that the metal plate on the other side can be pre-bent.

Conical workpiece

It is necessary to install a rolling cone device roll device at the end of the upper roll body on the discharge side of the equipment.
The device consists of a sleeve, a fixed ring, and a friction key. The principle of the roller is to decelerate by friction, to achieve the same speed at the large and small ends of the fan-shaped plate, and to complete the roll forming of the tapered roller-shaped workpiece.

Sheet center alignment

Ordinary three-roller plate bending machine center alignment mainly depends on the operator’s experience, low work efficiency, and easy-to-produce waste. On one side of the PRD Double Pinch three-roller plate rolling machine, there is a hydraulically-operated overturning centering mechanism. Accurately realize that the axis of the sheet is parallel to the axis of the work roll to avoid skewing of the sheet.

Wide roll bending range

The two lower rollers of the ordinary three-roll plate rolling machine are the main driving work rollers, and the upper roller is the driven roller, which is easy to slip when rolling thin plates and small-diameter workpieces. Generally, the thickness of the plate can be less than the maximum plate thickness specified by the parameters 1/3, the minimum rolling diameter is 2.5 times the diameter of the upper roll.
The upper roll and the two lower rolls of the PRD Double Pinch three-roll plate bending machine are the main drive work rolls. That is the three-roller full drive. Allows to roll metal sheets with a minimum thickness of 1/5 of the maximum coil thickness specified by the parameters, and the minimum roll diameter can reach 1.25 times the diameter of the upper roll. It can also be equipped with inner brackets and outer brackets to meet the needs of large thin plate drums. Rolling of diameter workpieces.

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PRA Initial Pinch 3-Roll Bending Machine

PRA initial pinch 3-roll bending machines ensure you get excellent results with a single operator thanks to its ease of use feature, it with a familiar asymmetrical construction, providing a simple and inexpensive approach for thin sheet metal bends.

The PRA 3-roll bending machine is the best solution for bending plates with thicknesses between 1 mm and 9 mm and widths from 1000 mm to 3000 mm.

The reliability of the PRA series is guaranteed by its solid electro-welded structure, oversized and assembled on steel rods. In addition, asymmetric geometry in the roll movement featured by the 3-roll bending rolls of the series assures optimal traction and prevents slipping of thin plates during pre-bending: the side roll moves on a linear guide that bends the material close to the pinching point, thus assuring a high-quality result comparable to that obtained with more expensive models of 4-rolls plate bending rolls.

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PRs Pyramid 3-Roll Bending Machine

Pyramid roll bending is a cold-bending method where a member is bent progressively by repeatedly passing it through a set of three adjustable rolls in a pyramid arrangement. Force is applied by opposing rolls. The distance between rolls is manipulated before each pass, bending the member into successively smaller radii. This process is repeated until the proper curvature is formed.

PRS pyramid 3-roll bending machines are designed to cater to the basic requirements of bending & forming metal plates, PRS 3-roll plate roller belongs to 3-roll symmetrical mechanical structure. The top roller moves up and down at the central part of the two bottom rolls. Screw nut and worm gear both driver roller of transmission. Two bottom rollers act as main driving rollers. Through the meshing, they are able to rotate between the output gear of the gearbox and the bottom roller, so as to supply the torque to the bent plate. PRS plate rolling machine does well in compact structure, easy operation, and convenient maintenance.

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