The best way to determine the best plate or sheet rolling machine (see Figure 1) for the job is to find out what various machines can do. By obtaining this information, you can properly size and select a machine to fit your particular bending application.
If you are looking for more details, kindly visit roller bending machine.
Of course, for more in-depth information and application engineering expertise, you can contact plate or sheet metal rolling equipment experts directly.
Plate or sheet bending rolls 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, four-roll double pinch, three-roll variable translating, three-roll pyramid, and two-roll systems. Plate rolls are also built in a vertical format for special applications. Matching the most appropriate machine style to the application is important.
Machine capacity is equally if not more important than style. Plate roll 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 mill certificates and verify the average yield strength of the plate 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 58,000-PSI range. Remember, machine capacity must match your material, and most plate roll manufacturers can provide detailed capacity-versus-yield tables to assist you.
You often will see capacities for both prebending and rolling for any plate rolling machine. Prebending is performed on the plate roll at the leading and trailing edges of the sheet (see Figure 2)—and eventually the seam (see Figure 3).
A sheet cannot physically be bent right to the edge, and thus what remains is referred to as the unbent flat (see Figure 4). 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 heavier plate.
It is the prebending operation, in attempting to minimize the unbent flat, which takes the most power. That’s why prebending ratings are lower than rolling capacities for any given machine.
You must be mindful when reviewing machine capacities that the maximum rolling capacity is usually expressed with the basic requirement of multiple rolling passes and very long unbent flats. You also must note the material thickness and width and equipment characteristics such as cylinder diameter, machine type, yield, and diameter of rolls. Operator proficiency also should be taken into consideration.
NCs and CNCs are becoming more common in the workplace. Most NC and CNC machines are four-roll types.
Automated controls are recommended for high-volume cylinder or shell production and to roll complex shapes that are not easily reproduced using standard manual controls. Multiple bends, variable-radius bends, and ovals are common examples of these complex shapes.
Three-roll initial-pinch (see Figure 5) or single initial-pinch plate rolls 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 bend the sheet. When rotation of the rollers is activated, the sheet exits at a given radius. With the sheet cut to the developed length and the bending roll properly positioned, the part is rolled into a cylindrical shape that can then be welded at the seam to produce a closed cylinder.
When a cylinder is completely rolled, it is extracted from the top roll. Machines generally are equipped with some type of top roll release mechanism that allows for the cylinder’s extraction. This extraction is accomplished with the help of a forward-tilting or forward-releasing top roll or a removable end yoke.
In most applications, these machines require removal and reinsertion of the sheet to prebend both ends. They are cost-effective, but may be more labor-intensive in a production setting than their modern counterparts.
Many large, mechanical initial-pinch machines were built during the 1950s and may occasionally be found on the used market. All have cast frames, as modern alloys and welding techniques had yet to be invented.
Double-pinch plate rolls are available in light to very heavy capacities and can have three (see Figure 6) or four rolls (see Figure 7). 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. Both three- and four-roll styles have fixed-position top rolls and two offset, or lateral, rolls, one on each side.
The four-roll styles have an additional roller underneath the top roll, which constantly pinches the plate during rolling. Double-pinch rolls can prebend both plate ends without removal, as is required with single-pinch rolls.
Three-roll machines generally require prebending 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. Four-roll plate rolls have a slight advantage in cycle time because they permit prebending of the leading edge, rolling the cylinder body, and finishing off the trailing prebend, all while rolling in the same direction.
Smaller machines can be mechanical, but most are hydraulic and include drop end yokes (see Figure 8) for easy extraction of the workpiece.
Four-roll plate rolls generally are the only equipment with NCs or CNCs because the fourth roll provides constant pinching action, minimizing the chance for slippage. Automatic controls use an encoder to track movement of the plate through the machine. If the plate slips, the bending roll movements will be out of synch with the rolling movement.
Variable-geometry three-roll plate rolls are not new, but are gaining in popularity around the world (see Figure 9). They are built to handle medium to extremely heavy plate rolling applications.
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 prebending. In the past these machines commonly were found in shipyards, but are now being placed in general job shop and manufacturing applications.
True pyramid machines are rarely used in cutting-edge facilities. They usually can be found on the used market.
They have three rolls (see Figure 10), with both lower rolls fixed in position and the top, or bending, roll moving up and down. In general, they leave a very long unbent flat and are not as user-friendly as other types of rolling machines.
Two-roll machines (see Figure 11) are designed for thin-gauge material rolled to reasonably small diameters. They use a large-diameter, urethane-coated pinch roller that moves up with extreme pressure against a small-diameter steel top roll. A mandrel or drum, very close in OD to the desired ID of the finished part, is fitted over the top roll.
Two-roll sheet rolls are extremely fast and will roll round parts even if the blank has cutouts or holes. Because they require a mandrel for each part diameter and material thickness, they are not as versatile as some other machines, but for dedicated high-speed production, they are often the absolute best choice.
In terms of optional equipment for rolling machines, the most important items to consider are hardened roll surfaces and cone rolling devices.
Today’s harder materials and laser/plasma cutting techniques require hard outer roll surfaces on rolling equipment. Look for a hardness rating from 50 to 55 Rockwell C scale. Hardness in this range will have a reasonable penetration depth and provide long-lasting protection against roll surface wear. Hardness exceeding 60 will have a shallow penetration and result in cracking or crazing of the roll surface.
Cone rolling devices, which permit you to roll a conical shape, are standard on some machines. Lateral material supports and overhead supports are also optional, but less frequently requested. Overhead supports prevent light materials from collapsing when rolled to large diameters. A side support can also assist in preventing light materials from recurving toward the floor if the radius is very large.
Some machines have extended roll shafts that protrude through the machine frame. Section or pipe dies can be fitted on these stub shafts, but it is not practical to roll angle iron on a plate roll. Angle tends to twist when rolled, and plate rolls do not have outboard, adjustable, lateral material guides to prevent this twist. You should consider using a section rolling machine or angle roll for that type of bending. In general, section dies on plate rolls are good for bending flat bar the hard way, rods, or small pipe.
Additionally, most new roll bending machines are equipped with modern safety devices such as emergency-stop buttons; safety trip wires; 24-VAC, low-voltage control circuitry; and detached operator control consoles. However, it remains the responsibility of the owner to ensure the installation and proper use of operation safety guards or devices.
Ever wondered how the metal around you is getting its shape? Be it an automobile part, a ship, or a large metal container. It's not magic, but a machine breathing life into metal and turning it into breathtaking art.
Plate rolling is an incredibly essential part of any metal industry. The task of these rolling machines is simple: shaping metal plates into cones, cylinders, and curved shapes.
The definition looks simple, but the plate bending/rolling machines deliver sophisticated, cutting-edge, unique products. Different types of plate rolling/bending machines are available in the market. This blog will have a detailed view of a 3-roll plate rolling/ bending machine's working principle and rolling process.
What is a Plate Bending/Rolling Machine?
A Plate Rolling machine, also known as a roller machine, is a metal rolling equipment. Its main purpose is to shape metals into conical, cylindrical, or curved shapes. Industries worldwide require different machines according to their needs.
Plate rolling is a complex process but crucial for expanding the bending options available to your customers. Moreover, it depends on the precision levels and skill set of operators.
What Are the Types of Roll Plate Bending Machines?
There are three types of plate rolling/bending machines that individual industries need:
2-roll Plate Bending/Rolling machine
3-roll Plate Bending/Rolling machine
4-roll Plate Bending/Rolling machine
As mentioned above, each machine has its individual use, but here we will have a look at the 3-roll Plate Bending/Rolling machine.
What is the Working Principle of a 3-Roll Plate Rolling/Bending Machine?
Before understanding the working, let's have a brief look at a 3-Roll Plate Rolling/Bending Machine.
Industries of all sizes, from shipping to metal fabrication, need 3-roll plate bending/rolling machines. The process/task of the machine remains the same: bending metal sheets into the desired shape.
A 3-roll bending machine has three rolls: two side rolls that move back and forth, while the upper roll stays fixed but rotates. You can interchange this upper roll to fit shells of varying sizes.
Images 1, 2, and 3 show how a 3-roll plate bending machine uses rollers A, B, and C to shape metal plates. This is a pre-pinching/pre-bending process in plate bending.
The company is the world’s best parts of cylindrical grinding machine supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.
The manufacturer can control the amount and speed of the rollers to achieve the desired shape. As you can see, the plate smoothly and uniformly bends/rolls using the three rollers. The engineer can also bend or roll the desired location to achieve the required shape during the pre-bending process.
Let’s have a look at the mechanism in detailed steps.
Step 1: Placing the Plate
The first step for rolling a plate is placing the plate between the upper (I) and lower rollers (II and III). This process bends the plate into an arc or closed circle. As the metal sheet passes through the three cutting points created by the rollers, the plate will mold into the desired shape.
(Have a look at Diagram 1 of the working principle of a 3-roll rotating/ bending machine.)
Step 2: Plastic Bending Deformation
After the insertion of the metal plate, the top roller applies downward pressure on the plate. As a result, the plate undergoes a plastic bending deformation process due to compression.
Plastic bending deformation of metals occurs when an object's shape and size change due to applied force. Deformation happens when the shape of a material or object changes due to pressure. Plastic deformation occurs when the applied force is enough to cause a permanent deformation.
Step 3: Rotation & Friction
Due to the friction between the rollers and the plates, the lower rollers begin rotating, causing the plate to move back and forth along its longitudinal direction.
The plate moves back and forth as the lower roller alternatively does a forward and reverse rotation. At the same time, the upper roller continuously exerts vertical pressure or downward pressure on the plate.
The stress will exceed the yield limit during this process. Now the plastic deformation will occur. You can see the plate going through a plastic bending deformation. This entire process lets the plate take the required shape.
Key Factors of a 3-Roll Plate Bending/ Rolling Machine
To bend the plate to a radius no longer than the upper roller, you can modify the relative position of the upper and lower rollers.
A motor and a reducer power the lower roller (II and III), making them rotate in a similar momentum and the same or opposite direction.
To vary the curvature of the desired plates, you can adjust the position of the upper rollers.
You can change the position of the upper rollers to vary the curvature of the desired plates. Moreover, you can readjust the upper roller if you do not receive the desired curvature after a single rolling process. Then, you can redo the process until you achieve the desired shape.
There is one disadvantage of this machine. When you look at the above diagram, you can notice that the three rolls of the 3-roll bending/rotating machine form an isosceles triangle.
During the process, this triangle-forming shape forces the two ends of the machine to leave a straight part. The straight part of the machine is half the distance between the centers of the two lower rollers. This is the part where the rollers cannot roll.
Despite this one disadvantage, there are several benefits and features of a 3-roll plate bending machine. The main benefits of this plate rolling machine are structure, ease of operation, and low cost.
Wrapping Up!
3-roll plate bending machines have played an important role in history and continue to do so. You can rely on our plate-bending machines across various industries, including shipping, oil tanks, metal structures, tubes, and pipes. Be it 2-roll bending, 3-roll bending, or 4-roll bending machines.
We hope this blog helped you understand the working principle of our 3-roll bending machine. Feel free to contact us for all your plate-bending machinery needs. Our team at Himalaya Machinery would love to help you.
For more grinding is commonly used oninformation, please contact us. We will provide professional answers.