Bending is a stamping process that uses the pressure of a sheet metal cutting machine to force plastic deformation of the material to form a shape with a certain angle and curvature. Commonly used bends include V-shaped bending, Z-shaped bending, and back-pressure bending.
The height of the bend
The bending height of the sheet metal is at least 2 times the thickness of the sheet metal plus the bending radius, that is, H” 2t+R. The bending height of sheet metal is too low, and it is easy to deform and distort when bending, and it is not easy to obtain the ideal shape and size.
When bending is a beveled edge, it is most likely to cause bending distortion deformation due to the bending height too small in the original design, because the leftmost bending height is too small, and the bending quality is low, in the improved design, the left bending height can be increased or the part with a small bending height can be removed, so that no distortion deformation occurs during sheet metal bending, high bending quality.
To ensure bending strength, the bending radius should be greater than the minimum bending radius of the material. The bending radius of sheet metal cutting machine is not the larger the better, the larger the radius, the greater the bending rebound, the less easy to control the bending angle and bending height, so the sheet metal bending radius needs to be reasonable. Sheet metal mold manufacturers tend to have a bending radius of 0, so that the radius is not easy to rebound after bending, and the size of the bending height and bending angle is easier to control. However, a bend with a zero bending radius can easily cause the outside of the sheet metal bend to crack or even break. At the same time, the bending strength of sheet metal is relatively low, especially for harder sheet metal materials, and the right angle on the mold will gradually become smooth after a period of production, and the bending size will become difficult to control.
In order to reduce the bending force and guarantee the bending size, another method used by sheet metal mold manufacturers is to add the crimping process in advance before the bending process. Of course, such a design will cause defects such as relatively low bending strength and easy breakage of sheet metal.
The crimping process is a stamping process that forcibly partially extrudes the material and extrudes a groove on the sheet metal to facilitate bending and ensure bending accuracy.
Sheet metal cutting machine should be as perpendicular to the direction of the metal fiber as much as possible when bending. When the sheet metal is bent parallel to the direction of the metal fiber, it is easy to crack at the sheet metal bending, which is low in strength and easy to break.
Avoiding bending failure due to the inability to press the material at the root of the bend
When bending sheet metal, it is often impossible to bend because other features are too close to the sheet metal bending root, so the material cannot be pressed or the bend is severely deformed. Generally speaking, at least 2 times the sheet metal thickness above the bending root plus the distance of the bending radius, there is no other feature that blocks the pressing material during sheet metal bending.
If the bending and flattening position is too close to the sheet metal bending root, the bending fails; if the sheet metal tooth extraction is too close to the bending root and the bending cannot be carried out, then the tooth extraction can be moved away from the sheet metal root; if the tooth extraction and bending position cannot be moved because of the design requirements, then a process incision can be added to the bending root corresponding to the tooth extraction. So as to ensure smooth bending Carried out.
Guarantee the bending gap and avoid bending interference
Due to the existence of sheet metal bending tolerances, it is necessary to ensure a certain bending gap in the direction of movement of the sheet metal cutting machine to avoid bending failure caused by interference during bending.
In the original design, there is no gap between the two bends, when the upper side is bent, and then the right side is bent, due to the existence of sheet metal bending tolerance, it is likely that the right side will interfere with the upper side during the bending process, and in the improved design, the gap between the right side and the upper edge is at least 0.2mm. Interference can be effectively avoided.
Guaranteed bending strength
Sheet metal cutting machine needs to ensure the bending strength, the long and narrow bending strength is low, the short and wide bending strength is high, so the sheet metal bending is attached to the long edge as much as possible, the same function of a bend, the original design because the bend is attached to the relatively short edge and the bending strength is low, the improved design bending is attached to the longer side and the bending strength is high.
Reduction of bending processes
The more processes of the sheet metal cutting machine, the higher the mold cost and the lower the bending accuracy, so the sheet metal design should minimize the bending process. As shown in the figure, the original design requires two bending processes for sheet metal, and in the improved design, the sheet metal only needs one bending process to complete two bends at the same time.
Avoiding complicated bends
The more complex the sheet metal bending process, the higher the mold cost, the lower the bending accuracy, and the complex bending may cause waste of part materials. Therefore, when the sheet metal has a complex bend, consider splitting the complex bending into two parts, and assembling by means of pull nails, self-riveting or spot welding.
Holes on multiple bends are difficult to align
Sheet metal bending tolerances are large, especially for multiple bends, where the accumulation of tolerances makes it difficult to align holes to holes.
The more times sheet metal bends, the greater the bending tolerance. Multiple bends of sheet metal are difficult to ensure dimensional accuracy. This is the reason why the screw holes, rivet holes and self-riveting holes on sheet metal bends are difficult to align.
The hole on one bend of the sheet metal cutting machine is designed as a large hole or an elongated hole, so as to allow a large tolerance for bending, add two internal positioning holes, increase the internal positioning of the mold, reduce the tolerance of the sheet metal when bending, so as to ensure the alignment of the holes on the two bends, bending first and then punching, the dimensional accuracy of the two holes can be guaranteed, but this will increase the stamping mold's Complexity, increase mold costs, and is generally not recommended.