Sheet metal stamping defects generally fall into five categories: cracking, wrinkling, springback, surface defects, and shape and dimensional defects. Let’s take a closer look:
- Cracking
This is akin to overstretching a thin film, where the weakest point will rupture first. The reason for this phenomenon is that the local tensile stress borne by the material exceeds its strength limit. Once this occurs, it will undermine the structural integrity of the part, thereby affecting the safety and service life of the product. - Wrinkling
Contrary to cracking, wrinkling arises from the loss of stability of the sheet material under compressive stress. When the flow of material is obstructed or excessive, it will be squeezed and arched against each other, forming wrinkles. This defect not only affects aesthetics, but in severe cases, it can also prevent parts from being assembled smoothly, or even cause them to get stuck in the mold, leading to production interruptions. - Rebound
This defect is an inherent physical characteristic of the material and is difficult to eliminate completely. Its cause is the natural release of elastic stress accumulated inside the part, which leads to rebound deformation in its shape and dimensions. Rebound is crucial for ensuring the geometric accuracy and assembly fit of the part. - Surface defects
When the surface finish of the mold is insufficient, lubrication is improper, or there are impurities, it is extremely easy to cause scratches, indentations, or patterns resembling “orange peel” on the surface of the parts. These defects not only affect the appearance but also have the potential to become stress concentration points, thereby affecting the fatigue strength and long-term durability of the parts. - Shape and size issues
When parts are twisted, dented, or have critical dimensions out of tolerance, we know that such defects have occurred. This is usually caused by improper mold design, blank positioning, or process parameter settings. Such deviations are common problems in stamping processes and can directly lead to non-conforming products that fail to meet design and functional requirements.
From the above, it can be seen that the causes of the five major types of sheet metal stamping defects are complex, involving multiple aspects such as product design, experimental verification, and mass production. Materials, molds, processes, and other topics are also inescapable. Considering their important position in modern industry, accurately addressing these defects has become an imperative task.
However, a precise solution hinges on a crucial prerequisite – precisely identifying the problem. Only by promptly detecting defects (such as springback deviation and surface scratches) after the parts are formed can we inversely optimize process parameters (such as blank holder force and mold surface). Therefore, the importance of conducting rigorous quality inspection during the production process, as a bridge connecting defect detection and resolution, is self-evident.
