Sheet metal design] sheet metal design guide
Source: | Author:佚名 | Published time: 2021-06-29 | 71 Views | Share:

Sheet metal design] sheet metal design guide

The bending of sheet metal design guide is a stamping process, which uses pressure to force the material to produce plastic deformation, thus forming angle and curvature shape. Common bends include V-bend, z-bend and reverse pressure. The bending height of sheet metal is at least twice the thickness of sheet metal plus bending sheet metal, that is, H ≥ 2T + R. as shown in the figure below, the bending height of sheet metal is too low, and the bending of sheet metal is easy to deform and twist, and it is not easy to obtain the ideal part shape and ideal dimensional accuracy. When the bending is beveled, because the bending height is too small, it is very likely to cause bending and deformation, as shown in the figure below. In the design, because the bending height of the left side is too small, it is easy to deform in the bending process, resulting in low bending quality. In the improved design, the left bending height can be increased or a small part of the bending height can be removed, so that the sheet metal will not be deformed and the bending quality is high. 2. The bending radius should ensure the bending strength. The bending radius of sheet metal parts should be larger than that of small bending sheet metal of materials and small value of various commonly used sheet metal materials. The bending radius is shown in the table below. The following figure shows the original and improved sheet metal bend radius design. Of course, the bending radius of sheet metal parts will not be as large as possible. The larger the bending radius is, the greater the springback is. The bending height is more difficult to control, so it is necessary to determine the sheet metal radius reasonably. In addition, sheet metal mold manufacturers tend to set the bending radius to zero, so sheet metal is not easy to repeat after bending. The bending height and bending angle are easy to control, but the bending with zero bending radius can easily lead to the bending of sheet metal parts and even the external fracture of this part. At the same time, the bending strength of metal plate is relatively low, especially for hard metal plate materials. As time goes on, the right angle on the die will gradually become smooth, and the bending size will become difficult to control. In order to reduce the bending force and ensure the bending size, the sheet metal die manufacturer adopts another method to increase the pressure before the bending process. Welding wire process, as shown in the figure below, this design can also cause defects such as relatively low bending strength of sheet metal and easy fracture

The pressing process is to force the local extrusion of the material and extrude the groove on the metal plate to facilitate the bending and ensure the bending accuracy. 3. The bending direction of the metal plate should be perpendicular to the metal fiber as far as possible. When the bending of the metal plate is parallel to the direction of the fiber of the metal material, the metal plate is prone to crack, low bending strength and easy to fracture, as shown in Figure 1. As shown in Figure 4 below. Avoid bending root failure due to material bending failure. When the metal plate is bent, it is usually because other features are too close to the root of the metal plate, which leads to the failure to extrude the material and serious bending or bending deformation. Generally speaking, it needs to be at least above the root of the sheet metal. Make sure that there are no other features within the distance of twice the thickness of the sheet metal plus the bending radius to prevent extrusion of the sheet metal during bending. As shown in the figure below, in the original design, the position of the reflection plane is too close to the root of the sheet metal bending, resulting in the sheet metal bending can not be pressed and bending failure. Another example is that the metal plate shoots too close to the root of the bend to bend. At this time, the extraction tooth can be moved to the position of the main sheet metal root, as shown below. Improve a design in the design. If the pull-out and bending position cannot be moved due to the design requirements, the corresponding machining notch can be added at the root of bending to ensure the smooth progress of bending, such as the improved design.

5. Ensure the bending clearance to avoid bending interference. Due to the existence of bending tolerance of sheet metal parts, it is necessary to ensure the bending clearance in the direction of bending movement of sheet metal parts, so as to avoid the interference during bending and lead to bending failure. The following figure shows a simplified view of a sheet metal part with complex bends. The bending order is to bend the upper side first and then the right side. In the original design, there was no gap between the two curved edges. After the upper side is bent, when the right side is bent, due to the bending tolerance of the sheet metal part, the right side may interfere with the upper side during the bending process. In the improved design, the gap between the right side and the upper side is at least 0.2mm, which can effectively avoid bending interference. 6. Ensure the bending strength when bending metal plate, it is necessary to ensure the bending strength. Long and narrow bending strength is lower, while short and wide bending strength is higher, so sheet metal bending should be attached to the longer side as much as possible. As shown in the figure below, bending with the same function. In the original design, the bending strength was lower because the bending was attached to the shorter side. In the design, the bending part is attached to the longer side, so the bending strength is high. 7. Reduce the bending process of sheet metal parts to avoid complex bending. The more the bending process of sheet metal parts, the higher the die cost and bending accuracy. Therefore, sheet metal design should minimize the bending process. As shown in the figure below, in the original design, sheet metal required two bending processes. In the improved design, sheet metal only needs one bending process. The bending on both sides can be done at the same time. The more complex the bending process of sheet metal parts is, the more material waste may be caused. Therefore, when the sheet metal has complex bending, it is considered to divide the complex bending into two parts. Although this violates the principle of reducing the number of parts, it is more likely to bring about the reduction of product cost and the improvement of product quality. Of course, this design needs to be verified by strict calculation. The bent sheet metal part is divided into two parts, and the two parts are assembled by studs, self rivets or spot welding

8. For many engineers, it is difficult to make a hole in multiple elbows to experience such a painful experience. Why is the screw or stud hole on the sheet metal bending part always misaligned, so that the screw and stud cannot be fixed? This is because the bending tolerance of sheet metal parts is large, especially when the sheet metal has multiple bends. It can be seen from the above table that the more times the sheet metal parts bend, the greater the bending tolerance. Moreover, it is difficult to ensure the dimensional accuracy of the sheet metal parts by multiple bends. This is why it is difficult to correct the screw holes, rivet holes and self rivet holes in the sheet metal bending. Therefore, when designing products, engineers need to consider the characteristics of multiple bending tolerances and avoid requiring too strict tolerances for multiple bending features. At the same time, the sheet metal design is optimized to avoid the misalignment of the assembly holes, the difficulty in ensuring the assembly size, and even assembly interference and other adverse phenomena. The bending hole is difficult to solve because of the large bending tolerance. 1. Design a long round hole or a large hole on the elbow to allow greater bending tolerance and ensure the assembly of parts. 2. Add two internal positioning holes, and increase the internal positioning of the mold to reduce the tolerance of the parts. Bend the sheet metal during the process to ensure that the holes at the two bends are aligned. 3. First bend the dimensional accuracy of the two holes, and then punch them. Yes, but it will increase the complexity of the stamping die and the cost of the die head. Generally not recommended