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High-yield bending becomes flexible.

Figure 1 In CNC bending (commonly called panel bending), the metal is clamped in place, and the upper and lower bending blades form positive and negative flanges.
A typical sheet metal shop may use a combination of bending systems. Of course, bending machines are the most common, but some stores also invest in other forming systems, such as panel bending and folding. All these systems can help the operation to form various parts without the need for special tools.
Sheet metal forming in mass production has also been developed. Such factories no longer need to rely on product-specific tools. Now, they adopt a modular production line that can meet various forming needs, combining panel bending with multiple variants of automatic forming, from corner forming to stamping braking and roll bending. Almost all of these modules use very few product-specific tools to perform their operations.
Today, the automatic bending line of sheet metal parts uses “bend” in a general sense. This is because they provide various types of bending in addition to what is commonly called panel bending (also called CNC bending).
CNC bending (see Figures 1 and 2) is still one of the most common processes on automated production lines, mainly because it is so flexible. The paper can be moved into place by a manipulator (with a “feet” feature to fix and slide the paper) or a dedicated conveyor. If the paper has been punched previously, the conveyor belt will usually work well, which makes it difficult for the robot to move them.
Before bending, two fingers are exposed from below to center the part. After that, the paper is placed under the clamping tool, the clamping tool is lowered and the workpiece is clamped in place. The blade curved from below moves upward to form a positive curve, and the blade curved from above downward to form a negative curve.
You can think of the bending mechanism as a large “C” shape with the upper and lower blades at both ends in it. The maximum length of the flange is determined by the throat behind the curved blade or the back of the “C” shape.
This process increases the bending speed. A typical flange can be formed in half a second, whether it is a positive flange or a negative flange. The movement of the curved blade is infinitely variable, allowing many forms from simple to incredible. This also allows the CNC program to change the external bending radius by changing the exact position of the bending blade. The closer the blade is to the clamping tool, the tighter the outer radius of the part, which is reduced to about twice the material thickness.
This variable control also provides flexibility when it comes to bending sequences. In some applications, if the final bend on one side is negative (folding down), the bending blade can be removed and the transfer mechanism lifts the workpiece and transports it downstream.
Traditional panel bending does have shortcomings, especially in the important work of beauty. The curved blade tends to move in a way that the tip of the blade does not stay in one position during the bending cycle. Instead, it tends to drag slightly, roughly similar to the way the sheet is dragged along the radius of the die shoulder during the bending cycle on the bending machine (although in panel bending, the drag occurs between the bending blade and the part. Only one point of contact between) the outer surface).
Enter a rotating bend, similar to folding on a standalone machine (see Figure 3). During this process, the curved beam rotates so that the tool always maintains contact with a single location on the outer surface of the workpiece. If the application requires, most modern automatic rotating bending systems can be designed so that the rotating bending beam can bend up and down. That is, they can be rotated upward to form the positive flange, reposition themselves to rotate about a new axis, and then bend the negative flange (and vice versa).
Figure 2 replaces the traditional manipulator, this panel bending unit uses a special conveyor to manipulate the workpiece.
Certain rotary bending operations (called double rotary bending) use two beams to create special forms, such as a Z-shape involving alternating positive and negative bending. The single beam system can rotate and bend these forms, but to access all the bending lines, the sheet needs to be turned over. The dual beam rotary bending system can access all the bending lines in the Z-shaped bending without turning the sheet.
Rotational bending does have its limitations. If the automation application requires very complex geometries, CNC bending (infinitely variable motion with curved blades) is a better choice.
When the last elbow is negative, a rotating elbow challenge also occurs. Although the bending blade in CNC bending can move backwards and backwards, the rotating bending beam cannot move in this way. The final negative bend will require someone to physically slide it out. Although feasible in systems that require manual intervention, this is usually impractical in fully automated bending production lines.
The automated production line is not limited to panel bending and folding-the so-called “horizontal bending” option, in which the sheet remains flat when the flange is bent up or down. Other molding processes expand the possibilities. They include specialized operations that combine bending machines and bending rolls. This method was invented to manufacture products such as roller shutter boxes (see Figures 4 and 5).
Imagine a blank sent to the brake station of a bending machine. The fingers slide the blank horizontally above the brush table and between the upper punch and the lower die. Like in other automatic bending processes, the blank is in the centered state, and the controller knows where the bending line is, so there is no need for a spare gauge behind the mold.
In order to bend by the operation of the bending machine, the punch is lowered into the mold to bend, and then the finger pushes the sheet to the next bending line, just like the operator in front of the bending machine. Just like a traditional bending machine can, this operation can also bend the radius (also called incremental bending).
Of course, just like a bending machine, bending on an automatic production line will leave traces of the bending line. For large radius bends, the use of collisions alone may increase cycle time.
This is where the curl function comes into play. When the upper die and the lower die are in a specific position, the tool effectively becomes a three-roll roll bending machine. The tip of the upper punch is the upper “roller”, and the shoulders of the lower V-die are two lower rollers. The fingers of the machine push the sheet through to form a radius. After bending and rolling, the upper punch moves upward and away, leaving space for the fingers to push the molded part forward and out of the working space.
Roll bending on an automated system can quickly create large and curved curves. But for some applications, there is a faster way. This is called variable radius bending, which is a patented process originally developed for aluminum parts in the lighting industry (see Figure 6).
To get an overview of the process, consider what happens when you drag the ribbon between the scissors blade and your thumb. curly. The same basic idea applies to variable radius bending, only tools can be touched lightly and carefully, and the formation of the radius is controlled in a very controllable way.
Figure 3 When rotating bending or folding, the rotating way of the bending beam makes the tool always keep contact with a single position on the outer surface of the sheet.
Imagine a thin workpiece clamped in place, with the material to be formed completely supported underneath. The bending tool descends, presses on the material, and then moves forward to the fixture holding the workpiece. The movement of the tool causes tension and causes the metal to “curl” behind it to form a specific radius. The force of the tool on the metal determines the magnitude of the induced tension and the resulting radius. When moved in this way, the variable radius bending system can create large radius bends very quickly. And because a tool can produce any radius (again, the pressure applied by the tool, not the shape, determines the shape), so the process does not require product-specific bending tools.
The corner forming of sheet metal poses unique challenges. Invented an automated process for the exterior wall (cladding panel) market. This process eliminates the need for welding and produces good curved edges, which are important for products where appearance is critical (such as exterior walls) (see Figure 7).
You first need to cut a blank shape to keep the required amount of material on each corner. A special bending module combines sharp and soft radii into adjacent flanges to create a “pre-curved” flaring for subsequent corner forming. Finally, the corner forming tool (integrated into the same workstation or another workstation) will create the corner.
Once an automated production line is established, it will not become a fixed monument. It’s like building with LEGO®. You can add, rearrange and redesign workstations. Assume that a part in the assembly previously needed to be welded twice at the corner. In order to improve manufacturability and reduce costs, engineers eliminated welding and redesigned crimp joints. In this case, an automatic riveting station can be added to the bending line. And because the production line is modular, it does not need to be completely dismantled. It’s like adding another Lego brick to a larger whole.
All of these make automation inherently reduce risk. Imagine a production line designed to produce twelve different parts in sequence. If the production line uses product-specific tools and the product line is changed, then considering the complexity of the production line, the tool cost may be very high.
But with flexible tools, new products may only require the company to rearrange Lego toys. Add some blocks here and rearrange some other blocks here to resume normal operation. Of course, this is not that simple, but reconfiguring the lines is not a difficult task.
In general, Lego is a suitable metaphor for automatic bending lines, whether they are processing batches or kits. They only use any product-specific tools to achieve the general molding productivity level of the production line.
The entire factory is designed around mass production, and it is not easy to convert them to kit-based production. Rearranging the entire plant may require extended downtime, which is an expensive proposal for a plant that produces thousands or even millions of parts each year.
That is to say, for some high-volume sheet metal bending operations, especially raw factories that use new slate for work, kit-based mass molding has been carried out. For the right application, the rewards can be huge. In fact, a European manufacturer shortened the delivery time from 12 weeks to one day.
This does not mean that the conversion from batch to kit in an existing plant is meaningless. After all, shortening the lead time from a few weeks to just a few hours will provide a huge return on investment. However, the initial cost may be too great for many operations. In other words, for undeveloped locations or brand new production lines, kit-based production may make economic sense.
Figure 4 In this combined bending machine and bending roll module, a piece of paper can be placed between the punch and die and bend it. In roll bending mode, position the punch and die to push the material in to form a radius.
When designing a high-volume production line in kit-based production, carefully consider the feeding method. The bending line can be designed to receive material directly from the coil. The material will be untied, flattened, cut into a certain length, sent through the punching module, and then sent through various molding modules specially designed for a single product or product series.
All of this sounds very efficient, and for batch processing. However, it is often impractical to convert batch processing bend lines from coil feed to kit-based production. Kits that form different parts in sequence are likely to require different material grades and thicknesses, which requires replacement of the coil. This can result in up to 10 minutes of downtime-this is not a long time for high-mix/small batch production, but it is a miracle for high-speed bending lines.
Traditional depalletizers have similar ideas. In traditional depalletizers, the suction mechanism picks up a single blank and sends it to the stamping and forming production line. They usually have only a single blank size or space for a few different blank geometric shapes.
For most kit-based bending lines, racking systems are best suited. The shelf tower can store dozens of blanks of different sizes, which can be transported to the production line on demand, one by one in unique parts.
Automated kit-based production also requires a reliable process, especially during the molding process. As people who work in sheet metal bending know, sheet metal properties will vary. Thickness can vary from batch to batch, as can the tensile strength and hardness, all of which change the forming characteristics.
This is not the main problem in batch processing of automatic bending lines. Products and their associated production lines are usually designed to handle material changes, so the entire batch of products should not exceed the specification range. But again, sometimes the material changes to an extent that the production line cannot compensate. In these cases, if you cut and shape 100 pieces and find that some of them are out of specification, you only need to run 5 more pieces, and then within a few minutes, you have 100 pieces for the next operation.
In a kit-based automatic bending production line, every part must be correct. For maximum productivity, these kit-based production lines operate in a highly choreographed manner. If a production line is designed to run seven different parts in sequence, automation will run in that order from the beginning to the end of the production line. If part 7 is not good, part 7 cannot be rerun because the automation is not programmed to handle that single part. Instead, you need to suspend the production line and start with part 1.
To avoid this, the automatic bending line uses laser-based real-time angle measurement, which can quickly check each bending angle, so that the machine can correct the deviation.
This quality check is essential to ensure that the production line maintains a kit-based process. With the improvement of the process, the kit-based production line can save a lot of time and shorten the delivery time from months and weeks to hours or days.
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Post time: Jul-31-2020
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