| Summary: | 碩士 === 國立高雄應用科技大學 === 模具工程系碩士班 === 102 === Flat-type motor cases, flat-type battery shells, and quartz oscillator cases are general flat-type case products. Large aspect ratio is their common feature, and elliptical cup redrawing is a necessary forming operation in their production. Due to their complex contour, more drawing stages are needed, and so is the time for designing, processing, assembly. Thus, reducing drawing stage may improve the quality of these products while lowering the cost. The present study, therefore, attempts to explain the forming features of elliptical cups redrawing through [deep drawing with offset of cneter] so as to reduce drawing stages and the risk of fracture.
Elliptical redrawing displays different characteristics in thickness distribution and flange geometry along the major and minor axes. This study proposes a [deep drawing with offset of cneter] hypothesis to explain the difference of thickness distribution and flange geometry along the major and minor axes in elliptical redrawing. Employing finite element software DYNAFORM to simulate the forming scheme, the researcher predicts the influences of elliptical eccentricity, redrawing ratio, and [offset of center] and testify the hypothesis through the die test of [deep drawing with offset of cneter].
The results of simulation reveal that thinning at the corner of approaching eccentricity is much more serious than that at departing eccentricity. In elliptical redrawing from elliptical cups, major axis departs departing eccentricity while minor axis approaches departing eccentricity, so thinning at minor axis is more serious; in elliptical redrawing from circular cups, nonetheless, major axis approaches departing eccentricity while minor axis departs departing eccentricity, so thinning at major axis is more serious. Elliptical eccentricity, redrawing ratios, and [offset of center] also influence the thickness distribution at the corner of major axis in elliptical redrawing. The decrease of elliptical eccentricity causes more apparent thinning, but the increase of redrawing ratio causes more apparent thinning. Redrawing ratio influences the thickness distribution more greatly than elliptical eccentricity. If the [offset of center] of elliptical redrawing from circular cups increases, thinning becomes more apparent; in elliptical redrawing from elliptical cups, the value of drawing path remains the same and [offset of center] will not vary, so it is beyond discussion.The thickness distribution of deep drawing with offset of cneter is highly related to the location of die radius during redrawing. When die radius is at center of radius left, the thinning at major axis is reduced; when die radius is at center of radius right, the flange block obstruct the flow of materials and results in thinning. Based on the findings, a Die is utilized to examine these patterns, and the outcome is consistent with the simulation.
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