Mechanical Processing Technology Chapter 3 Bending

Mechanical Processing Technology Chapter 3 Bending

Looking at the scope of metal processing, the bending process seems simple and ordinary, but in fact there are many technical details hidden in it, which will directly affect the quality and cost of the final product.

Basic principles of bending process

The process of bending materials such as metal sheets into specific angles and shapes is called bending. The key is to use external force to plastically deform the material. For example, using equipment such as a press and using a mold to apply force to the sheet. When the internal stress of the material exceeds the yield limit, permanent deformation will occur.

This deformation process does not occur uniformly over the entire workpiece. It mainly focuses on the expected arc of bending area. The outer fibers of the material are pulled and the inner fibers are compressed. There is a "neutral layer" between them with a basically unchanged length. Understanding this basic principle is the key to controlling all future technical points.

Common bending methods and equipment

According to production needs and workpiece characteristics, there are a variety of bending methods to choose from. The most common one is to use a special bending mold on a crank press or hydraulic press. This method is suitable for mass production and the manufacture of parts with relatively fixed shapes.

It is a more specialized equipment used for pipes, profiles or large-sized plates. Like pipe bending machines, which are used for pipe processing. Rolling bending machines are often used to make large radius arc parts. The stretch bending machine can effectively reduce the cross-sectional deformation when bending the profile. Which method to choose requires comprehensive consideration of materials, batch size and accuracy requirements.

Detailed process of bending deformation

Bending deformation is a process that develops step by step. In the initial stage, it is free bending. The plate is in contact with the mold part, and the bending radius is relatively large. As the punch continues to exert downward pressure, the contact area increases, the bending radius gradually becomes smaller, and the straight edge part begins to close to the surface of the mold.

At the end, the punch and die are completely closed, and the workpiece is calibrated so that its rounded corners and straight edges completely fit the shape of the mold. The entire process requires precise control of stroke and pressure. Mistakes at any stage may cause the product to fail to meet the standards.

Material flow and thickness changes in the bend zone

Within the curved area, the material is not simply bent, but a complex flow occurs inside it. The material in the outer layer becomes thinner under tension, while the material in the inner layer becomes thicker under pressure. Generally speaking, the thickness of the plate in the bending area will tend to become thinner during Chapter 3 bending of the mechanical processing process. This is a compensation factor that must be considered during mold design and process planning.

The material, its side shape, will also change. For narrower strips, after bending, their cross-section will become a trapezoid with a narrow outside and a wide inside. Such distortion will have an impact on the assembly and performance of parts. This impact makes it necessary to use technological means to control it when processing precision parts.

The occurrence and prevention of bending defects

During bending production, the two most common problems encountered are: cracking and springback. Cracking is caused by the tensile strain of the outer material exceeding its limit. It is more common in machining bending problems when the bending radius is too small or the material has poor ductility. Selecting appropriate materials, increasing the bending radius, or performing annealing treatment are common preventive measures.

Shape deviation is the springback caused by the recovery of elastic deformation after unloading. It is affected by many factors such as material properties, bending angle, and mold clearance. In the actual production process, machining bending problems often require the use of empirical data or trial molds to pre-compensate for the mold angle to offset the springback effect and obtain accurate part angles.

Development trends of modern bending technology

Along with the process of manufacturing upgrading, bending technology is moving towards intelligence and higher precision. CNC bending machines are widely used. With the help of programming, parts with complex and diverse corners can be processed quickly, greatly improving efficiency and consistency. Robotic automatic loading and unloading systems are also gradually becoming popular.

When faced with new materials such as high-strength steel and aluminum alloys, new bending processes, such as hot bending, incremental forming and other technologies, are constantly progressing and developing in order to cope with the challenges caused by difficult forming and large springback. Simulation software can predict springback and cracking risk machining bending problems in advance, and can also optimize process parameters, thereby reducing the cost of trial and error, which shows that the field is changing from being driven by experience to being driven by data.

After knowing everything about the bending manufacturing process from principles to defect control, what is the most challenging bending processing example that you have encountered in real work or study? What specific problems were overcome? Welcome to share your experience in the comment area. If you find this article helpful, please like it to support it.