Evaluation of forming methods for a cup-part used in an ultra-miniatured radio-frequency connector

The signal-receiving contacts of ultra-miniature radio-frequency connectors are made of copper alloy sheets and stamped with progressive dies. However, the drawn cup corner often becomes extremely thin after progressive stamping, resulting in contact defects, insufficient mechanical strength, and reduced signal transmission quality. The present study investigates the effect of three forming methods, drawing with a blank holder, drawing without a blank holder, and drawing with a synchronous blank holder, on the corner-thinning phenomenon of the drawn cup by enlarging the scale of 10 for the workpiece. The feasibility of the first three forming stages was investigated. Finite element analysis was used, and the die-tryout further verified the findings. The results show that both drawing methods, with or without a blank holder, would cause necking or breakage at the corner at the third forming stage. The corner-thinning phenomenon becomes mild when drawing with a synchronous blank holder. The corner-thinning phenomenon is due to the low height of the drawn cup, resulting in too much plate material remaining on the flange, which makes the subsequent drawing ratio too large. Therefore, the conventional drawing methods are unsuitable, but drawing with a synchronous blank holder can be effective in this case study.