The effect of constrained groove pressing process on micro deep drawing parameters of thin pure copper sheets

Sheets with sub-millimeter thicknesses are increasingly used in micro-forming processes. Micro deep drawing is a sheet metal forming process commonly applied in industries such as electrical component manufacturing. Copper is widely used in the electronics industry, and in many cases, thin sheets with thicknesses below 1 mm are required. However, reducing the thickness of copper sheets introduces challenges, such as increased result variability and decreased strength. In this study, an effort was made to enhance the mechanical properties of copper sheets by applying Constrained Groove Pressing (CGP) as a cold working method. The results show that CGP increases ultimate strength by up to 25% and yield strength by up to 114%. Additionally, it reduces maximum strain by up to 77% and increases hardness by up to 100%. A comparative analysis was then conducted to examine the effects of these changes on several Micro Deep Drawing parameters, including maximum punch stroke, maximum punch force, punch force at 2.5 mm stroke, wrinkling, and thickness uniformity across the cup’s cross section. The results indicate that applying CGP results in less than a 10% decrease in maximum punch stroke, a 7% increase in maximum punch force, and up to a 27% increase in punch force at 2.5 mm after two CGP passes. Moreover, CGP reduced the wrinkling of the blank. One particularly significant finding is that CGP meaningfully reduced data scatter and improved cross-sectional thickness uniformity, enhancing the predictability of material behavior.