Application of Punch Surface with Micro-Ridges to Micro Forming and Multi-Stage Forming

• Main Authors: YANG,CHENG-YU, 楊正鈺
• Other Authors: LIN,BOR-TSUEN
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/8pyp9a

博士 === 國立高雄第一科技大學 === 工學院工程科技博士班 === 106 === The development trend of the new generation 3C/IT, optoelectronics and biomedical products is miniaturization. Because of product miniaturization, micro forming technology has been rapidly developed because of its mass production, high efficiency, high precision, low cost and no pollution. Reducing the thickness of metal sheets causes a marked decrease in microscale/mesoscale deep drawing rates. This study examined the influences of a drawing punch with a microridged surface on the deep drawing of stainless steel. First, this study proposes a novel drawing punch design with microridges on the surface neighboring the punch nose for deep drawing processes used in the manufacture of stainless steel cylindrical cups. Subsequently, the microridged drawing punch design geometric variables were tested based on the Taguchi method. Moreover, DEFORM 2D simulation software and an ANOVA analysis were employed to determine the combination of design variables that produced the minimal thinning rate. Finally, a drawing die was designed, produced, and employed to confirm the analysis results. The test and simulation results were highly consistent, where the significance at which the geometric variables influenced the thinning rate was, in order of significance, the ridge nose radius, ridge-topunch nose distance, ridge height, and ridge distance. The microridged design increased the forming force of deep drawing by only 7 %; however, it increased the forming depth by more than 60 % when compared to a nonridged drawing punch. Next, Draw ratio experiment was carried out using a micro-drawing die to investigate the effect of different heat treatment conditions, different grain sizes, and with/without of micro-ridged punches on formability. It is found through the draw ratio method that the micro-ridges on the surface of the punch can increase the draw ratio by 10.65% for different grain size materials, and the micro-ridged punch can effectively reduce the variability of 3.32%. Finaly, application of microridge punches in multistage deep drawing processes. A microridge punch improves drawing performance, thereby reducing the number of stages required in deep forming processes. As an example, the original eight-stage deep forming process for a copper cylindrical cup with a high aspect ratio was analyzed by finite element simulation. Microridge punch designs were introduced in Stages 4 and 7 to replace the original punches. In addition, Stages 3 and 6 were eliminated. Finally, these changes were verified through experiments. The results showed that the microridge punches reduced the number of deep drawing stages yielding similar thickness difference percentages. Further, the numerical and experimental results demonstrated good consistency in the thickness distribution.