At present, the automobile industry is facing worldwide market competition, but the competition is very fierce. This is inseparable from the strict requirements for various indicators of the car, but also because people have high requirements for the quality and performance of the car. Sheet metal stamping is an important manufacturing technology of automobile panels, and the stamping quality will directly affect the quality and performance of automobiles. However, due to the inevitable defects and errors in production, we must have a certain understanding of this in the process of production and processing.

So, what are the reasons that affect the defects in the stamping process?

1、

material parameter

However, the forming quality of sheet metal mainly depends on the forming limit diagram as the standard. Therefore, the related parameters of the material itself will have a certain influence on the panel, such as hardening index and thickness anisotropy index, and we can study the influence of these parameters on the trend of forming limit curve. When the hardening index increases, the limit curve formed by fracture and the uniformity of material tension will be improved. The same is true of bulging deformation. The greater the thickness anisotropy coefficient, the greater the intersection value between deformation path and fracture limit curve.

2、

Die surface parameters

One of the key factors for the success of deep drawing is whether the radius of die fillet is appropriate, and the simulated radius of typical cylindrical parts will have a certain influence on the forming. In addition, under the control of atmospheric BHF, if the die is designed with uniform fillet, the fillet radius should not be less than 4mm in order to increase the drawing success rate of giant sheet metal, otherwise tensile cracking will occur.

In processing and production, we can also change the conventional uniform fillet design and numerical casting of fillet of transition die to improve the forming quality, which is also helpful to the forming after drawing. However, due to the heavy workload, this method has not been widely used in complex panel resin simulation. In production and processing, lubricating oil is often used in processing, which is helpful to unify the radius of die fillet and improve the unevenness of material flow speed.

3、

Technological process parameters

The process parameters mainly include friction, forming resistance of drawbead, blank holder force, forming speed, lubrication condition and deformation path. Among them, the reasonable arrangement of drawbead and the solution of drawbead forming resistance are the main contents of panel forming process design, and related parameters are important components of optimizing model design variables. The general principles of drawbead arrangement mainly include:

( 1)

In order to increase the resistance in the feeding process and improve the deformation degree of materials, drawbead is usually laid around the contour line of blank holder.

(2)

In order to increase the radial tensile stress in the force transfer zone, reduce the tangential stress and prevent the sheet from wrinkling, local short drawbead should be set at the position where wrinkling is easy.

(3)

In order to adjust the feed speed and feed resistance, drawing ribs are usually not set on curves, especially on curves with large drawing depth. When the drawing depth is quite different, low-resistance drawbead is not set in the deep part, and drawbead with relatively high resistance is set in the shallow part.

Attention should be paid to the factors causing defects in the stamping process to ensure the quality and quality of the parts and the normal work after they are put into use. Therefore, the compensation of stamping should be carried out before machining to avoid stamping defects.