| The NC incremental sheet metal forming process is a flexible forming process, which is originated from the stratification of rapid prototyping manufacturing. The sheet metal is formed step by step with a forming tool according to a certain trace prescribed by the feed system of the NC forming machine until the required shape is obtained. The incremental forming can reduce the development cycle of the product and the cost without die or with simple die. So, it is very suitable for small-lot, varied sheet metal products in the aerospace product. By analyzing the feature of the incremental forming, it has some disadvantages: excessive thinning of thickness, low geometric accuracy and forming efficiency. Forming angle is restricted and the forming angle must be within the limit angle, or the sheet metal will rupture.To solve above problem, the hybrid forming: incremental forming combined with stretch forming was presented. By transforming the NC tutor into stretch tool, the sheet metal was pre-formed by the stretch tool and local grooves were yield by the incremental forming at last. Firstly, the advantages, features and the part suitable range of the hybrid forming were analyzed. Secondly, for one-way curvature parts, pre-forming(stretch forming) and hybrid forming under once clamp was realized by developing the dedicated equipment. Comparing the different parts formed by the hybrid forming and incremental forming by experiments, the results are presented that hybrid forming can increase the geometric accuracy, reduce the material thinning and reduce the forming time. At last, for the complex two-way curvature parts, a new forming process was presented. The boundary which need be forming by the incremental forming was marked by the use of CAD/CAM/CAE. The digital manufacture was realized in this process. The advantage of the hybrid forming compared with the incremental forming was analyzed and the best process of the hybrid forming was decided by experiment. |
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