A new sheet metal forming system based on incremental punching.

• Other Authors: Luo, Yuanxin.
• Format: Others
• Language: English; Chinese
• Published: 2010
• Subjects: Punching machinery; Sheet-metal work
• Online Access: http://library.cuhk.edu.hk/record=b6074883; http://repository.lib.cuhk.edu.hk/en/item/cuhk-344516

In order to ensure the desirable performance of the machine, dynamic analysis of the machine is necessary. The analysis is conducted by the mean of computer simulation in consideration of applying a large impulsive force. This study validates the machine stability and accuracy. === In order to verify the new mechanics model, numerical and experimental studies are conducted using the new incremental punching system. The final shape and thickness distributions of parts are compared to verify the mechanics model. It is found that the model prediction fits the experiment result well. Forming parameters are also investigated. === In this research, a new incremental forming system based on incremental punching is designed and built. The system consists of a 3-axes CNC platform, a high speed hydraulic cylinder with a hemispherical forming tool, and a PC-based CNC control system. The hydraulic system provides the forming force to deform the sheet metal with constant stokes, while the CNC system positions the part. When forming a part, the forming tool punches the sheet metal along the given contour of the part punch by punch; when one layer of the part is completed, the forming tool moves down to the next layer; and the process is finished till all layers are completed. The CNC control system works with standard NC code, and hence, is easy to use. === ISMF uses a small generic tool to apply a sequence of operations along the given path to deform the sheet incrementally. These small deformations accumulate to form the final shape of the part. As a result, different parts can be made by the same setup. Despite of some 30 years of research and development, however, ISMF technology is still premature for industrial applications due to the following reasons: The accuracy of the part is limited; the surface roughness is poor; and the productivity is low. This motivates the presented research. === One of the keys to successful application of sheet metal forming is to be able to predict the deformation and the strain/stress of the part incurred during the forming process. Because of the complexity of the ISMF process, it is not possible to derive an analytical method. The alternative is to use Finite Element Analysis (FEA). However, based on our experience, it takes about one week to solve a simple case. A mechanics model is therefore developed. It consists of two steps. The first step is to computer the final shape: the initial geometric surface is obtained using the punch positions; then using the minimum energy principle, the virtual forces drive the nodes of geometric surface to their lowest energy positions, which gives the final shape of the forming part. The second step is to predict the strain and stress distributions. This is done using the inverse Finite Element Modeling (FEM). An in-house computer software is developed using MATLABRTM. === Stamping is one of the most commonly used manufacturing processes. Everyday, millions of parts are formed by this process. The conventional stamping is to form a part in one or several operations with a press machine and a set/sets of dies. It is very efficient but is not cost effective for small batch production parts and prototypes as the dies are expensive and time consuming to make. Recently, with the increasing demands for low-volume and customer-made products, a die-less forming method, Incremental Sheet Metal Forming (ISMF), has become one of the leading R&D topics in the industry. === To evaluate the capability of the presented ISMF process, the formability is studied by the means of theory and experiment. A modified M-K model is proposed for predicting the forming limit of the formed part which is undergoing a very complicated strain path. The maximum forming angle is also investigated by experiments. === Luo, Yuanxin. === Adviser: Ruxu Du. === Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . === Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. === Includes bibliographical references (leaves 121-133). === Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. === Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. === Abstract also in Chinese.