Orange peel prevention in deep drawing process by using multi draw radius technique

The deep drawing process is typically applied for forming sheet metal into a desired shape of cup, can, or bowl for a variety of applications in the automotive, aerospace, and packaging sectors. One excellent example of a deep-drawn part is a beverage can. The major defects in the deep drawing process are the tearing and fracture that cause the unusable deep-drawn parts. However, there are still many defects that, even if they do not damage the deep-drawn parts to the point of being unusable, will reduce the quality of those deep-drawn parts, such as galling and orange peel defects. These shortcomings have a serious impact on cosmetic packaging that requires aesthetics. In the deep drawing process, a major cause of the orange peel defect is the different mechanical properties in different directions of sheet metal, which is called anisotropy.  This can lead to unequal strain distribution around the cup while the sheet metal is drawn into the die cavity, contributing to the orange peel texture. Therefore, to prevent the orange peel defects by encountering this uneven strain distribution, the multi draw radius technique was proposed, and its feasibility was investigated based on the finite element method (FEM) and experimental works. The cylindrical deep drawing model of 60 mm in outer diameter and 5 mm in cup radius was investigated. The sheet metal material used was a low-carbon steel sheet grade SPCC (JIS) with 1 mm in thickness, and the initial blank size of 100 mm in diameter was fixed. Based on the strain distribution, the uneven strain distribution was clearly shown in the case of the conventional deep drawing process, which agreed well with the deep drawing theory. In particular, the strains were approximately 0.30, 0.20, and 0.30 in the direction of along the plane, at 45° and 90° to the rolling direction, respectively, as shown in Figure 1(a). In contrast, in the case of the multi draw radius, the strain distribution showed the relatively even strain around the cup. In particular, the strains were approximately 0.20, 0.15, and 0.20 in the direction of along the plane, at 45 and 90 to the rolling direction, respectively, as shown in Figure 1(b). Based on these results, the multi draw radius could be applied for orange peel prevention in the deep drawing process.