In plate folding, bending is static. It’s a little easier to measure the load that it takes to get the metal to a certain point. Plate rolling is a constant process where the material and bending rolls are moving simultaneously. It’s a little more complicated.
Plate Metal Rolling and metal folding have emerged as essential manufacturing techniques based on a broad range of materials and thicknesses. Roll bending and folding techniques accomplish material shape transformation by inducing changes in the required combination of surface topology and geometrical aspects of the material.
For plate rolling, enormous alloy-reinforced cylinders are employed to bend thick steel plating. Placed alongside a plate folding machine, there are obvious differences between the two deformation techniques. In the latter machine type, corners and edges, not curves, are added to the plating.
Plate rolling is a method of curving sheets of metal into round or conical shapes. During this process, the metal workpiece is placed in a plate rolling machine and curved multiple times. Normally, metal sheets are curved around three to four times so they can acquire the needed properties of the manufacturer. The roller diameter, however, can limit the diameter of the rolling process. Once the plate rolling process is done, the metal sheets are expected to have reduced thickness.
Plate rolls can also prebend plate to minimize straight tails but usually not as well as press brakes. At times plate is nosed in a press brake and then rolled in a plate roll to get the best results.
Plate rollers can usually roll 360-degree cylinders better than press brakes can. The ends of the curved cylinders can end up being obstructed by the press brake die or by the machine itself. Plate rolls can roll a cylinder through 360 degrees. This process is sometimes used to “round up” an out-of-round cylinder.
The plate rolling process can only be done by utilising plate rolling machines. These machines maximise work rollers to carry out continuous point metal sheet bending, generating a wide array of cylindrical parts, conical parts, and other parts with varying arc shapes and appearances. As sheet metals pass through the lower and upper rollers of these machines, they are expected to boast an altered shape and undergo a curvature.
The radius of the curvature then depends on the mutual position of the rollers. Rollers should be moved away if a product should boast a wide radius. Rollers, on the other hand, must move closer if a product must have a smaller radius.
Basic Material Considerations
When rolled into a ferrule or arched shape, the sheet or plate will spring back a certain amount, and that amount depends on myriad factors. In fact, as highlighted by studies and tests carried out in various parts of the world, the precise amount of workpiece spring back can only be determined experimentally.
Regardless, some basic factors usually apply:
- Thinner sheet—more springback
- Larger radius—more springback
- Smaller radius-to-thickness ratio—less springback
- Bending sheet in fewer steps (when rolls move to produce a different radius)—less springback
- High yield strength—more springback
- High elastic modulus—less springback
Work-hardening factors into the equation as well, especially when rolling material like stainless steel.
The material’s chemical composition influences yield strength and hardness.
This time, the project requires flat surfaces and angular features. The rollers are gone, replaced by straight-edged clamps and two-dimensional shaping dies. Instead of a robust gearing assembly, high-tonnage force is applied via a ramming mechanism, a piston that presses a blank steel sheet into an assortment of shapes. Using another colorful metaphor, the process resembles an origami creation, although the medium utilized here is hardened steel, not paper.
Metal Folding Principles
In folding, the metal sheet is typically positioned and tightly held using a clamping beam tool. During the folding cycle, the beam swings up or down around a pivot point, and the workpiece is folded into the required shape.
- The blank is placed on the CNC-controlled integrated sheet support back gauge system.
- Blank is clamped between an upper beam tool and a lower clamping beam.
- The folding beam then sweeps up or down in accordance with the programmed direction of the first flange.
- It takes only one set of universal tools to complete the job.
The dimensional accuracy achieved by folding is controlled by the metal folding machine – the bending edge is utilized as a reference while the folding angle is controlled by the flange angle of the folding machine. This ensures high precision.
Sensitive material surfaces
Folding operations do not induce surface scratches as the material rests on the metal folding machine table and the process is performed at a shorter cycle time and without the need for turnovers. This results in high surface quality.
Metal folding machines often employ all-electric drive build designs which require lower maintenance and not susceptible to environmental factors. This results in high folding accuracy.
Shared Sheet Metal Deformation Features
Whether the metal sheets are folded or bent, those contrasting deformation techniques are still controlled by finely tuned technological solutions. For the plate folding equipment, 7-axis CNC controllers manipulate the metal and shape it until it satisfies the desired product profile. Granted, the geometry assigned to a curved steel panel by a plate rolling machine probably won’t be as complex as a folded part, but that rolling machine has enough power, plus up to 4 cylinders, to bend thick panels. Conversely, steel folding equipment typically processes thinner sheet workpieces. After all, it’s not difficult to impart a radial feature on a thick panel, but it takes a great deal of kinetic energy to apply an angular bend to a dense steel piece.
All about the angles, plate folders create corners and edges and flat surfaces. Using a hydraulic ram and a relatively thin sheet of steel, geometrically complex items are not a problem, not when a computer-controlled 7-axis manipulation assembly is on the job. For plate rollers, similar complexities are dealt with by computer software. This time, however, it’s the radius of a turn that presents the biggest challenge. Material “spring” and heat-treated steel plasticity are also issues here, for curved surfaces can recoil slightly.