Walk into most commercial or precision sheet metal processing workshops, install CNC metal clamps on the floor, and you may also find a series of CNC bending machines. Of course, bending machines have a longer history in American metal manufacturing than bending machines, but this is usually not the reason why manufacturers put both types of forming machines on the floor. They have both, because in many ways, metal folding machines and bending machines are not competing technologies. In fact, they are complementary.
There are opportunities for both, but to take advantage of them, you need to understand how folders work and their inherent advantages and limitations. Although there are still some limitations, folders can do even more than they did ten years ago. They also add much-needed forming capabilities to manufacturing operations, thanks to fiber lasers, which have greater no-load capabilities than ever before.
CNC bending occurs in a variety of machines, from machines that require the full participation of the operator to fully automatic light-off operations. It all depends on the task at hand.
Many stores are seriously considering the problem of metal folding, which not only improves efficiency, but also improves work efficiency. Can you imagine that the operator does not have to support the weight of the part when moving during bending? Does certain large or heavy parts require multiple operators to manipulate by bending? Eliminating these concerns is one of the most basic inherent advantages of folding.
When you buy a bending machine, you need to consider the length of the bed, the tool, and the tonnage of the machine and tool selected. When you invest in a folder, the tonnage will not enter the dialogue, just the material quantity table. The machine is designed to handle a specific material thickness, with carbon steel as a typical benchmark. For softer aluminum, the thickness capacity of the material should be a few specifications thicker (lower specifications), while for stainless steel, it should be thinner specifications (higher specifications).
For example, when you fold 14-ga. If the rated value is 14 ga. If carbon steel is used on the machine, the machine should be able to fold the material along the entire length of the bed. However, the bending length is a factor. As long as the tool is suitable for heavier materials, the folder can bend some thicker materials than the rated capacity and have a shorter length. Most machine manufacturers provide performance graphs reflecting the capabilities of the tools.
In a typical metal folding setup, the sheet metal is placed on the metering table behind the working envelope. This includes the upper beam with the upper beam tool, the lower beam with the lower beam tool, and finally the folding beam with the folding beam tool.
During the air bending process of the press brake, the punch descends into the mold space, the material is dragged on the mold shoulder, and the inner radius is formed as a percentage of the mold width.
The metal clip can also be “bent” (in a sense, the material has no bottom or no molding), so for most folding applications, the mold has little wear. But the way the machine bends is completely different. In most cases, the folding machine uses servo technology to drive and position all axes. In this way, the most accurate product can be obtained.
With the integrated sheet support and anti-regulation system, the parts can be placed flat on the workbench, and only the flange can be bent. During the molding cycle, the operator does not need to balance or support the part in any way. The segmented upper beam tools are grouped to accommodate the bending length and the necessary clearance of the previously formed flange (see Figure 1). The upper beam tool is lowered and the workpiece is clamped between the upper beam tool and the lower beam tool. Then, the folding beam tool is moved into position, contacts the material, and then rotates to form the first flange.
Figure 2 Two-way folding system can bend the positive and negative flanges without turning the parts.
Entry-level only editable folders require the operator to flip the part to achieve negative bending. In the semi-automatic folding machine, the folding beam can be bent in both forward and backward directions without turning over the material, thus greatly reducing the running time. Specifically, these two-way folders can rotate the beam upwards for positive bending, then reposition themselves to a new pivot point, and then swing down for negative bending (see Figure 2). Hybrid metering and suction cup metering can reduce operator intervention and parts positioning problems (see Figure 3).
The distance between the two contact points on the workpiece-the edge of the lower beam tool and the tip of the folded beam tool-determines the internal bending radius. Although the relationship between the internal bending radius and the material thickness may be a one-to-one relationship, the typical setting depends on the clamping force of the machine tool and the retention force of the workpiece, so that the relationship between the internal bending radius and the material thickness is The relationship between 1.25 and 1. Material type and thickness. On some folding systems, the beam can move slightly outward. Just like having a larger mold opening on a bending machine, this allows a larger internal radius on certain material thicknesses. At certain thicknesses, more than 1.25 times the thickness radius bending can be achieved. If the workpiece requires a larger radius, the folder will usually bend or bump gradually. The lower beam is programmable and can automatically adapt to different material thicknesses until the machine’s rated capacity is reached.
In fact, most folding machines automatically adjust to changes in material thickness. After the program is developed and verified by the offline software, the machine can run. And because the programming is done offline, the machine can produce other parts while generating new programs.
The degree of automation of CNC folding machines is different. In semi-automatic machines, the operator’s participation is limited to the loading, positioning, rotation and unloading of parts.
In a fully automated folding system, once the material is loaded, the machine checks the part to provide its identity. For example, some systems use infrared light focused on a specific area of the sheet metal blank. After the part is identified, the machine will automatically be replaced with the required tool, and the manipulator will position and rotate the part during the bending cycle.
The automatic folding system can be integrated with material loading towers, reciprocating loading systems and robotic loading/unloading. In essence, material handling is driven by application requirements.
Offline programming software also helps to further automate and simplify folding. Today, some software can import STEP files generated by CAD and many other formats. It will automatically generate a 3D model for viewing, create a recommended bending sequence for viewing, and simulate the resulting product. From there, the job is converted into the machine language. All of these can be done offline, effectively eliminating the need for on-machine programming.
The crowning system can also improve the overall accuracy. According to the level of folding technology you consider, manual, automatic and engineering design crowning systems can be used.
In a typical bending machine, the surface of the lower beam protrudes just below the position where the mold is placed. In the wedge convexity system, the wedges slide against each other to provide a convexity that offsets deflection during bending.
On a folding machine, convexity can be created at or below the folding beam tool, in the folding beam tool or in the beam itself. In the manual crown system, the operator uses a special folding beam tool that allows them to dial in a specific crown. This is common for construction stores that may require a concave-convex shaped sink or similar products.
Commercial and precision sheet metal workshops often use CNC folding machines with intelligent convexity in the folding integrated beam. The mechanism itself is similar to the wedge system seen on the bending machine, but the overall crown system of the folding machine is significantly different overall. The folding beam swings up 10 degrees, inspects the material, joins the convexity where needed, and then starts the folding cycle.
In metal folding, the folding beam tool moves upward in an arc during the forming process, and thus maintains constant contact with the outer surface of the workpiece. This makes the process very suitable for surface sensitive materials.
This process is also very suitable for high product mix, even kit-based production, because it again uses the toolset common to most applications. In fact, for most molded parts, a set of tools is usually sufficient. The tools are precision ground and are fixed in place, so there is no need for alignment except for positioning along the length of the machine bed to fit the size of the part. No punch needs to be centered on the bottom V mold.
In a typical shift, standard folding beam tools are used for multiple material thicknesses, although multiple upper beam tool segments can be placed in sections over the length of the beam to provide the necessary clearance for the working mixture at hand. Segmented upper beam tools may need to be rearranged to accommodate different bending lengths and required clearances.
Some operations will gradually place these tools over the entire length of the machine to accommodate all or most of the work in a shift, and are equipped with tools designed to bend some common shapes, such as upper tools with rotating feet, Can provide clearance for adjacent return flanges. Many manual tool positioning systems (such as those in semi-automatic machines) provide pneumatic clamping. Some advanced folding systems have automatic tool change functions, which can further reduce setup time.
The folding machine does not have a flange height limit for open elbows, but at an angle of 90 degrees or higher, the flange height limit depends on at least some machines and depends on the closing height of the upper beam tool.
That said, many folders do have a significant tool height for deep box bending. In addition, the upper crossbeam of some folding machines is inclined to provide clearance for very high flanges (see Figure 4). The only practical limitation is material handling and integrity (large, fragile parts, etc.).
Certain parts that were actually considered impossible to form on a file file a few years ago are now being formed on a folding machine. This is largely due to special tools. For example, folding beams may require narrower tools to access tight zigzags and channels (see Figure 5). The application may also use a special folding beam tool, which can approach the workpiece at an angle to allow folding of certain internal flange geometries.
The beam tool is usually left in place, but special beam tools can provide clearance for certain geometric shapes, such as when the bend line is interrupted by a solder tab. The tool stays low to maintain the clearance required for other bends, and then rises so that the remaining tabs can be bent. Other special tools can leave a gap in the negative flange on some machines. “Some machines” is the operating phrase here. Nowadays, folding machines can be designed and customized for certain parts series.
Some commercial and precision manufacturers may choose to fold the workpiece and then complete the molding on a bending machine. The operator may bend some internal flanges that cannot be folded. Yes, this sounds counterintuitive; adding auxiliary operations violates traditional efficiency rules. But cycle time math often adds up. This is especially true for large, awkward workpieces, especially slow, laborious or even dangerous workpieces that are completely manipulated on the bending machine.
Figure 4 The upper beam direction of the folder provides a gap for very high bends. Note also how this setting provides clearance for the narrow downward flanges on both sides of the workpiece.
Some machines can adapt to challenging measurement requirements. In addition to the special stop on the table, the folding beam itself can also be used as a front stop.
When the part blank is cut at an angle to form a tapered edge, the folding beam of some systems has limited travel (about 6 inches) and can be used as a front gauge. Similarly, only certain machines can perform this function, and the folding beam can only be moved enough to measure the workpiece. But under the right circumstances, toeing with folding beams can bring many folding opportunities.
Folders have two main limitations, the second is simpler than the first. The first limitation is the geometry of the part. The folding beam needs to be able to enter the bend without colliding with other areas of the workpiece, so the internal flange is located in the middle of the large workpiece. Especially in the automatic folding machine, the workpiece does need to have a certain size. It is difficult or impossible to form tiny brackets or fragments with complicated sharp bends on traditional folders.
The robot not only needs to grab the workpiece somewhere, but also needs enough surface area to grab the upper and lower beam tools. If it cannot be firmly clamped, it cannot be folded reliably. In addition to special circumstances, the part also needs to be able to be placed flat on the back gauge for molding.
However, “special circumstances” is an important issue, because special tools often combine some creative thinking to make folds that were previously impossible to unfold possible. For example, the folder may not be able to fold a small bracket, but can these brackets be stuck together in a label, folded into a whole, and then broken after folding? Once again, if the folding beam has special forming tools, even some internal flanges may not be a problem.
The second main folder limit is much simpler, it has to do with tonnage. Consider the typical hemming operation on a folder. Fold the beam into a sharp bend and position it under the beam tool. The upper beam tool is lowered to form the lower pendulum (open, close or drip) without special tools.
However, the hem of this folder cannot be sewn. why? Because the bottom hem is driven by high tonnage, and forming by tonnage is where the bending machine really excels. Indeed, some folding machine models use hydraulic pressure to increase the servo-driven clamping force between the upper and lower beams, thereby extending the folding capacity to certain panels. But beyond that, the machine simply cannot exert enough force. In most cases, the folding machine is not a flatbed bending machine.
If the operation requires a tonnage-based forming strategy (such as a hem, a bottom with a sharp radius on the sheet or an air-formed plate), the bending machine is the ideal choice. Consider air-curved armor plates. To reduce the forming tonnage of the application, you only need to choose a wider V-shape. This may also solve the forming and cracking problems. As long as the formed tonnage does not exceed the tonnage of the machine or tool, and the bending radius produced by the wider mold meets the working requirements, it is fine. Similarly, if the part design requires a sharp bottom radius on the sheet metal, the bending machine can do the job.
Imagine a forming department with metal folders and bending machines. A large number of parts may be run through a series of folders. The manufacturer may even send some seemingly difficult parts through the folder, including jobs that require flange connection in the internal window (using special tools). It can also fold small parts that share bending lines and pull them all together to improve folding efficiency. First, some parts are formed on the folding machine, and then they are sent to the brake for a rapid bending, which is much faster than forming the entire part on the bending machine.
But some parts are not suitable for this folder at all. Small and complex parts (parts that use custom or unusual backgauge sequences and bending sequences so that the folding machine does not leave any flat surfaces) enter the bending machine. Another large bending machine requires a certain tonnage to bend the board, and may perform some delicate hemming and radii in the board.
This hypothetical arrangement may be a very flexible and particularly productive molding department. With high-efficiency lasers conveying the blanking capabilities of the industry through the roof, the time is ripe for new methods to form productivity.
Many manufacturers who have both a folding machine and a bending machine may hand over small, complex parts to the bending machine. But there is another fully automated option. Specifically, there are some systems on the market for turning off and bending small parts. These machines do not use folding beams or clamping materials like typical folding systems. Similarly, they can’t, because these parts are too small and the tools for folders are difficult to master. Instead, a small special parts manipulator fixes the middle of the small blank on top and bottom. It then transports the blank to the work envelope and places it between a set of upper and lower clamping tools. Behind these tools are two bending tools, one bending tool moves up to perform positive bending, and the other is bent down to perform negative bending. To bend the other side, open the clamping tool, the robot rotates the part, and then restart the process.
Some systems for extinguishing bending of small parts use small manipulators and narrow clamping tools to grasp and manipulate the parts during the bending cycle.
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Post time: Sep-10-2020