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Sheet metal bending is an extremely critical process in the field of metal forming, with a long history of development and significant evolution and development with the continuous progress of science and technology. It is mainly with the help of external forces, sheet metal processing into a variety of shapes people expect, the development so far, it covers a variety of operating methods, and will be used in different types of machinery and equipment.
Sheet metal bending, in simple terms, is the process of applying an external force to the metal, causing it to deform and then bend it at a certain angle, ultimately forming a specific shape such as a “V” or “U” shape. This process has a long history, as early as in ancient times has appeared prototype, to the modern manufacturing industry, has become an indispensable key link.
It has become an essential part of modern manufacturing, and it plays a significant role in a wide range of industries. In the automotive manufacturing industry, sheet metal bending is widely used in the chassis, body panels and engine components of the manufacturing process. In the aerospace field, whether it is to build the fuselage frame of the aircraft, or to build the fuselage of the other components, are highly dependent on this process, after all, in this type of application scenarios, the precision and strength have stringent requirements.
When bending sheet metal using a PRESS brake, the first step is to accurately align and properly secure the sheet metal to be bent on the PRESS brake’s tool. Once this is done, the press of the PRESS brake moves downward, applying the appropriate force to the sheet metal to form a specific angle, which in turn creates a new shape. It is important to understand that the external force exerted by a PRESS brake is considerable, and for steel with a thickness of 3 mm and above, the external force exerted can be well over 100 tons.
Taking a CNC PRESS brake as an example, the entire bending process consists of the following key steps:
Before starting the PRESS brake, you need to calculate the design parameters in advance, such as the size of the external force required for the bending operation, the specific location of the bending line (that is, the location of the point of action of the external force), if there are a number of bending operations, but also to determine the sequence of the various bending. In addition, the mold used to achieve the bending effect also needs to be selected in advance.
The parameters calculated earlier are entered into the control system of the CNC PRESS brake, so that the PRESS brake knows exactly how much force to apply to the sheet metal and in what order the bending operations are to be carried out. At the same time, the appropriate tools and molds are correctly installed on the PRESS brake in order to prepare it for the upcoming bending operation.
Position the sheet metal accurately between the tools and dies to ensure precise alignment. When the PRESS brake is started, it will be able to bend the sheet metal according to the established bending line.
Start the PRESS brake so that it applies the corresponding force to the sheet metal according to the external force parameters set in step two. Once the sheet metal has been bent, the processed part can be removed and ready for the next stage of the production process.
Free bending is one of the most widely used methods of sheet metal bending. It works by applying external forces to the surface of the workpiece with the help of a tool to bend it into a “V”, “U” or other specific shape. During the entire bending process, the workpiece does not come into contact with the side walls of the mold.
Advantages:
– No initial investment in tooling, such as molds, is required.
– High compatibility with almost any thickness of metal material.
– It is a low-pressure bending method and rarely causes damage to the surface of the workpiece.
Disadvantages:
– Due to the limitations of the bending accuracy, not quite suitable for bending angles less than 45 ° shape.
– The production cost of a single product is relatively high.
– The accuracy of the bending is often difficult to ensure if older equipment is used and is not equipped with laser measurement technology.
– After bending, the workpiece is prone to rebound phenomenon, that is, it will partially return to its original shape, which in turn affects the accuracy of the bending angle.
Undercut bending is similar to freehand bending and is also a PRESS brake bending method based on stamping the surface of the workpiece. In this way, sheet metal can be bent precisely into the desired shape. However, it differs from free bending in that the workpiece comes into contact with the sidewalls of the mold while it is being bent during the press-bending process.
Advantages:
– It is possible to bend shapes at various angles because the bending accuracy can be flexibly adjusted.
– The overall bending accuracy is high.
– The production cost of a single product is lower.
– There is no rebound phenomenon after bending the workpiece.
Disadvantages:
– The tooling often requires a high initial investment cost.
– Some specific shapes of bending may require customized molds.
– The tooling tends to leave marks on the surface of the part.
– More pressure needs to be applied to the metal than in free bending.
Imprint bending is an interesting process that, as its name suggests, is commonly used in the manufacture of products such as coins, and in fact is often used whenever a manufacturer needs to press mold sheet metal. It works by applying up to 30 times more pressure to the sheet metal than free bending, forcing it into a bottom mold that permanently deforms the workpiece to create the desired shape and, if desired, the pattern etched into the surface of the bottom mold.
Advantages:
– No rebound phenomenon at all, which ensures the stability of the bending effect.
– The overall bending accuracy is quite high and can meet various bending accuracy requirements.
– Able to produce parts with stamping pattern design.
Disadvantages:
– Belongs to the higher cost of the process, the first in the mold and other tools need to invest a lot of money.
– The manufacturing cost of a single product is at a medium-high level.
– Most shapes require customized, specialized tooling.
– Molds leave marks on the surface of the workpiece and it is a high pressure bending method.
Fold bending is the process of bending a workpiece at a precise angle, just as we usually do with paper airplanes. The principle of operation is to use a clamping beam tool to position and fix the sheet metal, and then the tool drives the workpiece around a pivot point to realize the bending operation of the material.
Advantages:
– The operation is relatively simple and easy to master.
– Manufacturing costs per piece are low to medium.
– Low initial investment in equipment.
– Overall bending accuracy is high.
Disadvantages:
– The mold will leave marks on the surface of the workpiece.
– After bending the workpiece will appear a certain degree of rebound phenomenon.
– There are strict limitations on the bending angle that can be realized.
Edge bending, also known as edge bending, it is actually a deformation process of the edge manufacturing technology, essentially the same way of plastic deformation of sheet materials. The principle of operation is to place the workpiece between the pad and the mold fixed, and then push the rubbing edge flange (or punch) downward sliding, with the resulting external force to make the workpiece bent into a specific angle shape.
Advantages:
– Compared to some other bending methods, the damage caused to the surface of the workpiece is minimal or even negligible.
– The external force applied can be evenly distributed on the surface of the workpiece to ensure a more uniform and stable bending effect.
– The overall bending accuracy is high, and the workpiece can be bent several times during one operation.
Disadvantages:
– After bending the workpiece will appear a certain degree of rebound phenomenon.
– Belongs to the higher cost of the process, the need for high investment costs in the early stage.
– The manufacturing cost of a single product is in the middle of the high level.
– For the processing of some curved shapes, often need to customize special molds.
Rotary bending is mainly used for the bending of metal tubes, not to mention that the object of its processing is tubes, but in fact it is similar in principle to the bending of flat metal sheets. This is a relatively complex process, can produce a wide range of centerline radius of all kinds of pipe fittings. The working principle is to insert a mandrel inside the pipe so that its outer diameter is adapted to the mandrel, and use the mandrel to provide internal support to prevent the pipe from collapsing during the bending process, while at the same time, the rotary mold will be pushed to move the pipe forward while the rotary operation is carried out, so as to achieve the bending of the pipe.
Advantages:
– During one operation, the workpiece can be bent several times at different angles.
– After bending, the workpiece has a slight rebound phenomenon.
– Can support the production of a variety of complex and sophisticated pipe and tube molding design.
– Theoretically, it is possible to process most materials of different thicknesses.
Disadvantages:
– A high cost process, requiring a moderately high degree of up-front investment costs.
– Manufacturing costs per piece are moderately high.
– Certain shapes require customized tooling.
– This is a high-pressure bending method, which, if not operated properly, can easily lead to damage to the surface of the workpiece, or even the collapse of the tube.
– The overall process complexity is high.
Joggle Bending, also known as segmental bending, it is through the longitudinal beams and forming molds for metal sheet by segment bending molding process. This technique is uniquely advantageous when longer workpieces need to be bent in a cyclically repeating pattern. The principle of operation is to place the sheet metal workpiece into the corresponding equipment or PRESS brake, the use of forming dies to bend the metal 20 ° to 30 °, and then release the workpiece, turn it over, and bend the operation again, and so on and so forth, until the desired height of the section or the shape of the bend until.
Advantages:
– It is a highly versatile process, capable of producing a wide range of complex and delicate shapes according to predefined patterns.
– The springback of the bended workpiece is relatively slight.
– Manufacturing costs per piece are low to medium.
Disadvantages:
– It is a costly process that requires a moderately high level of upfront investment.
– The cost of manufacturing a single piece is medium to high.
– Some shapes require customized tooling.
– It is a high-pressure bending method where the applied force is not evenly distributed.
– Some degree of damage to the surface of the workpiece is inevitable.
– The overall process is more complex.
Electro-Hydraulic Servo PRESS BRAKE
Not all materials are suitable for sheet metal bending operations, such as those elastic-plastic materials can not be bent on the PRESS brake, if forced to try, not only the bending effect is difficult to guarantee, and may even damage the bending equipment. Therefore, extra care must be taken when determining the materials to be used for sheet metal bending in the manufacturing process. The following are a few of the more recommended materials for use in the sheet metal forming and bending process:
Carbon steel is one of the most flexible and strongest materials used in sheet metal processing operations. In addition, carbon steel is recyclable, which helps to reduce carbon emissions and is environmentally friendly.
Aluminum is a material used in a wide variety of lightweight applications. However, when bending aluminum, special care should be taken to avoid collapsing or cracking at the corners of the material.
Stainless steel is often the first material that comes to mind when one expects good robustness and high metal strength in the final product. Of course, bending and shaping stainless steel usually requires the use of high-powered sheet metal bending equipment.
Titanium is a corrosion-resistant, high-strength features of the material, and sheet metal bending technology is well adapted, especially for the manufacture of such products as medical equipment, sports equipment, if your product belongs to this category, then titanium should be one of the preferred materials.
Copper is a highly corrosion-resistant and relatively low-cost material, making it a cost-effective alternative to other metals. Copper can be used to bend sheet metal with high precision and is widely used by the metal bending industry in many different applications.
Of these materials mentioned above, carbon steel is the most commonly used. Of course, there are actually many other metal materials that can be used in the bending process, but it is important to do adequate research before finalizing which material to use.
PRESS brake in the metal bending process plays a crucial role, it is the key equipment to realize the bending operation, and there are a variety of different types, such as mechanical PRESS brake, pneumatic PRESS brake, hydraulic PRESS brake, as well as CNC PRESS brake, etc., each of which has its own characteristics and application scenarios.
Mechanical PRESS brakes have certain limitations in design, making it less suitable for free bending operations. However, it also has its own significant advantage, that is, in the bending operation to ensure high speed and accuracy, of course, compared to some other types of PRESS brakes, such as CNC PRESS brake, it may be slightly inferior in terms of operational safety and convenience.
Pneumatic PRESS brake mainly relies on the air power provided by the compressor to realize the bending operation of the metal plate. When the pressure exerted on the metal plate is relatively small, often choose the pneumatic PRESS brake, and it is particularly good in bending some small metal parts.
Hydraulic PRESS brake is usually a blend of the latest technological achievements, in the metal plate for accurate bending has outstanding advantages, so favored by the majority of users, is the metal plate bending operation is more commonly used in a type of equipment.
CNC PRESS brake can achieve very accurate bending effect, its processing capacity is very strong, whether it is only a few millimeters wide small sheet metal workpiece, or those with a length of several meters of large-scale workpiece (in the large CNC PRESS brake), it is able to successfully complete the bending processing task.
In the metal plate bending process, there are often some defects that affect the quality and performance of the final product, the following are several common defects and the corresponding avoidance methods:
The rebound phenomenon refers to the metal plate after the completion of the bending operation, will be slightly back to the original shape, which leads to the bending angle deviation, can not meet the expected precision requirements. The key to solving this problem is to accurately and reasonably calculate and adjust the bending allowance, in this process, you need to take into account the characteristics of the material itself, the bending radius and the use of molds and other relevant specifications.
Sheet metal in the bending, if the stress is too large, the use of the mold is not suitable or the material itself has defects, etc., there is a high risk of cracking phenomenon. Once cracking occurs, it will destroy the structural integrity of the bent part, and in serious cases, it may even lead to the scrapping of the whole workpiece. In order to avoid this situation, we should regularly check and maintain the mold of the PRESS brake to ensure that it is in good working condition.
Wrinkles appear as undesired folds or creases on the metal surface after bending. This is usually caused by insufficient support of the workpiece during the bending process, or incorrect configuration of the selected mold. To avoid wrinkles, it is necessary to ensure that the workpiece is adequately supported during the operation. And to select the correct mold and the corresponding setup parameters according to the actual situation.
Over-bending and under-bending are two defects that can cause the bending angle of the final processed part to not meet the design requirements. These problems may be due to the previous calculation of the relevant parameters are not accurate, mold adjustment is not in place, or the material itself has inconsistent quality and so on.
To avoid such problems, on the one hand, such as bending pressure tonnage, bending radius and die opening size and other bending parameters for fine adjustment and optimization. On the other hand, with the help of modern PRESS brakes equipped with simulation software, before the official production, through the software simulation of the bending process, in advance of the discovery of possible problems, and then optimize the adjustment of bending order and other aspects.
Metal sheet bending is a complex and extremely important process in modern manufacturing. In-depth understanding of different bending technologies, mastering the characteristics of various suitable materials, clarifying the important role of PRESS brakes, and knowing how to effectively avoid various defects in the bending process are crucial for producing high-quality metal sheet bending parts that meet the diverse needs of various industries. Only by fully considering and properly handling the above-mentioned issues can manufacturers continuously optimize their metal sheet bending operation processes and achieve more ideal production results.
