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Views: 101 Author: Site Editor Publish Time: 2025-06-25 Origin: Site
As a seasoned professional in the metalworking industry, I have worked extensively with various tools and equipment, including bending machines. One crucial aspect of achieving precise bends is selecting the right equipment, particularly the common bending molds for bending machines. In this article, I will share insights into the different types of bending molds, their applications, and how each mold can enhance the efficiency and accuracy of your bending processes. By understanding these common molds, you can make informed decisions that lead to better results in your fabrication projects. Let’s dive into the world of bending molds!
Commonly used bending molds, as shown below. In order to extend the life of the mold, the parts are designed with rounded corners as much as possible.
Too small a flange height, that is, the use of a bending die is also disadvantageous for forming, and generally the flange height L ≥ 3t (including the wall thickness).
Step processing method.
Some low-profile sheet metal Z-shaped steps are bent, and the processing manufacturers often use simple molds to process on punching machines or hydraulic presses. The batches can be processed on the bending machine by the differential mold, as shown in the following figure. However, the height H should not be too high, generally should be (0 ~ 1.0) t, if the height is (1.0 ~ 4.0) t, the mold form of the loading and unloading structure should be considered according to the actual situation.
The height of the molding step can be adjusted by adding a spacer. Therefore, the height H is arbitrarily adjusted. However, there is also a disadvantage that the length L is not easily ensured, and the verticality of the vertical side is not easily ensured. If the height H is large, consider bending on the bender.
1、4–Upper mold; 2、5–Workpiece; 3、6–Lower die;
The bending machine is divided into two types: ordinary bending machine and CNC bending machine. Due to the high precision requirements and the irregular shape of the bend, the sheet metal bending of the communication equipment is generally bent by a numerical control bending machine. The basic principle is to use the bending knife (upper mold) and the V-shaped groove of the bending machine. Die), bending and forming sheet metal parts.
Advantages: convenient clamping, accurate positioning, and fast processing speed;
Disadvantages: The pressure is small, and only simple forming can be processed, and the efficiency is low.
The basic principle of forming
The basic principle of forming is shown in the figure below:
1–Upper mold； 2–Post positioning； 3–Width length； 4–Lower die； 5–Lower die；
Bending knife (upper die)
The form of the bending knives is as shown in the figure below. The processing is mainly based on the shape of the workpiece. The shape of the bending knives of the general processing manufacturers is large, especially for the manufacturers with a high degree of specialization, in order to process various complicated bending. , custom-made bending knives with many shapes and specifications.
The lower mold is generally modeled with V = 6t (t is the material thickness).
There are many factors affecting the bending process, including the arc radius of the upper die, the material, the thickness of the material, the strength of the lower die, and the die size of the lower die. In order to meet the needs of the products, the manufacturer has already serialized the bending die in the case of ensuring the safety of the bending machine. We need to have a general understanding of the existing bending die during the structural design process. See the upper part on the left and the lower part on the right.
The basic principle of the bending process sequence:
(1) bending from the inside to the outside;
(2) bending from small to large;
(3) first, bend the special shape and then bend the general shape;
(4) After the previous process is formed, it does not affect or interfere with the subsequent process.
The current form of bending is generally as shown below:
1、4–Upper mold; 2、5–Workpiece; 3、6–Lower die;
When the sheet metal is bent, a bending radius is required at the bend, and the bending radius should not be too large or too small and should be appropriately selected. If the bending radius is too small, the bending will be cracked, and the bending radius is too large so that the bending is easy to rebound.
For ordinary low carbon steel plates, rust-proof aluminum plates, brass plates, copper plates, etc., the fillet 0.2 is no problem, but for some high carbon steel, hard aluminum, super hard aluminum, this bend fillet This can cause the bend to break or the bullnose to crack.
Rebound angle Δα=b-a
Where b is the actual angle of the workpiece after the rebound;
A—the angle of the mold.
Rebound angle
Factors affecting rebound and measures to reduce rebound.
（1）Mechanical properties of the material The rebound angle is proportional to the yield point of the material and inversely proportional to the elastic modulus E. For sheet metal parts with high precision requirements, in order to reduce the rebound, the material should be as low-carbon steel as possible, not high carbon steel and stainless steel.
（2）The larger the relative bending radius r/t, the smaller the degree of deformation, and the larger the rebound angle Δα. This is a more important concept. The rounded corners of sheet metal bends should be chosen as small as possible, which is good for accuracy. In particular, it should be avoided to design large arcs as much as possible. As shown in the figure below, such large arcs have great difficulty in production and quality control:
Expand the calculation principle:
1. During the bending process, the outer layer is subjected to tensile stress, and the inner layer is subjected to compressive stress. A transition layer between tension and pressure is neither neutral nor pressure. The neutral layer is in the process of bending. The length is the same as before bending, so the neutral layer is the benchmark for calculating the length of the curved part.
2. The position of the neutral layer is related to the degree of deformation. When the bending radius is large and the bending angle is small, the degree of deformation is small, and the neutral layer is located near the center of the thickness of the sheet. When the bending radius becomes smaller, the bending angle increases. When large, the degree of deformation increases, and the neutral layer gradually moves toward the inner side of the bending center. The distance from the neutral layer to the inside of the sheet is indicated by λ.
On the other hand, with the advent and popularity of computer technology, in order to make better use of the powerful analysis and computing power of computers, people are increasingly using computer-aided design, but when computer programs simulate the bending of sheet metal Or a calculation method is needed when expanding to accurately simulate the process.
