Application of Triangular Mesh Morphing and Surface Reconstruction for Springback Compensation of Automobile Sheet Metal Die Face

由於環保與能源議題之崛起，車體輕量化遂成為各大車廠的重大課題。從普通碳鋼轉向先進高強度鋼及鋁、鎂合金等輕金屬可有效減輕車身重量，同時車體強度仍能達到碰撞法規之要求，然後者於沖壓製程時易產生嚴重之回彈情形，若仍依照傳統模具不斷試模修模補償之方式，不僅增加模具在開發過程中的時間成本，且模面品質極易在調整過程中降低。而隨著電腦硬體之開發，運算效率大幅提升，能夠有效縮短電腦輔助分析軟體的執行時間，故輔以CAE軟體模擬分析及數位模面調整重建之技術，加速解決沖壓回彈後模面之修正，成為當前車廠及模具廠致力研究的重點。 為了加速回彈分析後模面之建立，縮短模面設計時程，本研究透過三角網格調整分群與曲面嵌合，提出一套適用於汽車沖壓鈑金模面之補償重建法則。整體流程以初始設計完成之模面CAD模型檔案及其網格資料，和CAE軟體回彈補償後的網格資料作為輸入端，使用原始網格與回彈補償網格之頂點資料對應關係，輸入參數以調整網格造型，達到使用者設計補償的需求；接著將整筆網格資料分群，最終逐一針對單一網格塊重建曲面，完成整個模面回彈補償的流程。Owing to the rising attention of environment and energy issues, weight reduction of automobile has become the top challenge for the automotive manufacturers. It can effectively reduce weight by replacing conventional steels with advanced high strength steels (AHSS) or light metal such as aluminum and magnesium alloys. Using these materials can reach the requirements of collision regulations; however, it has encountered a serious springback problem in sheet metal forming process. During the conventional die compensation process, it is not only increasing the time costs of die development process but also falling off in quality of die face. The improvement of computer hardware and operational efficiency can significantly reduce the execution time of computer aided engineering (CAE) software. With the simulation analysis of computer aided engineering and digital die face morphing and reconstruction, rapidly resolving the springback adjustment problem has become the major research priority for auto-making and mold industry. In order to accelerate the construction of springback die face and reduce the time of die face design, this paper addresses a method of die face springback compensation adapted to automobile sheet metal based on surface reconstruction and triangular mesh morphing and segmentation. The proposed compensation scheme takes the original die face CAD and STL mesh files and the STL mesh file through die compensation as three input data and is composed of three major processes: adjustment of mesh model with parameters, segmentation of whole mesh data and surface reconstruction of each mesh patch. By proceeding the processes above, the reconstruction of die face springback compensation is fulfilled