Increase in formability of redrawn cylindrical cup by using zoning lubricant technique

Recently, deep drawing and redrawing processes are mostly used in various manufacturing fields, especially the aerospace, electronics, automobile, and beverage can industries. Therefore, an increase in the formability of the redrawing process is critical. In this research, the proposed zoning lubricant technique die was used in a deep drawing die for producing deep-drawn cups and then redrawn once more to create the redrawn cup to improve the formability of redrawn cups. The new technique was investigated based on the finite element method (FEM). The sheet metal material was the low-carbon steel sheet grade SPCC (JIS) with 1 mm in thickness, and the initial blank size of 100 mm in diameter was fixed. The cylindrical deep drawing model of 60 mm in outer diameter and 5 mm in cup radius was investigated. The redrawing model of 41 mm in outer diameter and 5 mm in cup radius was investigated. The zoning lubricant was designed to encounter the different mechanical properties in different directions of sheet metal, which is called the anisotropy or the R-value. In particular, a small friction coefficient of 0.03 was positioned along the plane and at 90° to the rolling direction, whereas a larger friction coefficient of 0.3 was positioned at 45° to the rolling direction. It was found that a more uniform strain distribution and cup wall thickness around the cup were achieved in the case of the zoning lubricant deep-drawing process compared with those in the conventional deep-drawing process. Next, using the zoning lubricant deep-drawn cups to fabricate redrawn cups, the limiting drawing ratio (LDR) could not be increased. However, in terms of cup wall thickness, a more uniform cup wall thickness around the cup could be achieved. Furthermore, the cup wall thickness could be increased by approximately 7% when comparing with the cup wall thickness of the redrawn cup achieved by using the conventional deep drawing process.