- 學位論文
板金沖壓模具之逆向工程設計與分析
A Study of Reverse Engineering and CAE Technology for Stamping Die Design
摘要
國內汽車售後服務沖壓件之模具開發，早期係仰賴石膏模仿製而成，模具精度較差，且初次試模成功率低。為提升模具精度與試模成功率，導入逆向掃描設備與CAE分析已為國內業者的趨勢。由於逆向掃描設備精度已提升至微米等級，因此掃描之點資料能完全反應掃描件之造型，但若將掃描完成的點資料鋪設成A或B級的CAD曲面檔案，在進行CAE分析則需耗費相當多的時間與金錢成本。因此，本研究先探討藉由掃描完成的模面點資料直接進行CAE分析，或是以成品掃描完成的點資料，搭配CAD餘肉造型設計進行CAE分析，以縮短開發時程與提高試模成功率。 本研究以引擎蓋外板為例，探討模面掃描點資料的大小與還原模面CAD資料對模擬結果的影響與差異，同時另外本研究將比較相同餘肉造型下，全為CAD模型與成品點資料搭配CAD餘肉造型之模擬結果的差異性。最後以實際沖壓樣品與模擬結果比較，藉此驗證此兩種模擬模式的正確性。 由於餘肉造型的設計為影響沖壓成形品質的主要因素，故本研究對引擎蓋與葉子板的特徵造型與餘肉造型做歸納，並針對餘肉造型對於其成形性的影響做探討。 此外，為節省模具開發成本，模具結構輕量化已為目前的趨勢，本研究利用有限元素法分析實體模具的動態受力情況，以了解模具在沖壓成形的受力行為，而邊界條件的設定對於模擬結果會有所影響，故本研究對動態實體模具的邊界條件設定進行探討，並建立動態實體模具之模擬邊界條件設定方式。
並列摘要
In the production of after-market car body panels in the automobile industry, gypseous models are applied to develop the stamping dies, resulting in problems in die tryouts and poor product quality. The advanced scanning equipment and CAE technology are then adopted to help the stamping die design. Due to the high precision of the scanning equipment, the scanning data matches to the product shape to a very small tolerance. The scanned data is usually converted into a CAD format to construct the CAE meshes. In the present study, the CAE simulations using the STL format of the scanned gypseous die were studied. The CAE technology with the scanned part shape for the die cavity and CAD format for the die addendum was also developed. The developed CAE technology can save much time and cost in the reverse stamping die design process. The design of the die addendum for engine hood and fenders was investigated in the present study as well. The existing addendum designs for the engine hood and fenders were surveyed and studied first. The effects of the addendum shapes on the formability of parts were then examined by the finite element analysis. The forming of either part without die addendum was simulated and the flow pattern of the material under the blank-holders into the die cavity was analyzed. The effects of different features of the addendums were identified and proper addendum designs were suggested. The suggested die addendum designs can be used as guidelines for the stamping die designs for engine hood and fenders. In order to reduce the cost of die manufacturing, the reduction of die weight is desired by the die engineers. To achieve this goal, the stress distribution of the die structure during the stamping process is required to be calculated first. The current approach needs two operations of the finite element simulations. The first operation is to simulate the stamping process, followed by the die stress calculation in the second simulation using the force distributed in the stamped part as load boundary condition. In the present study, the dynamic/explicit finite element code was employed to simulate the stamping process and calculate the stress in the die structure in one simulation. The die stress distribution at any stage of the stamping process is then obtainable from the finite element simulation and only one simulation is required. The developed approach can then be applied to optimize the die structure with the use of an optimization code.