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Abstract: Wire electrical discharge machining (wire-EDM) has a significant position among production technologies mainly due to its capacity of machining hard materials and intricate shapes. One of the major problems with this process is the error in cutting corners. Processing forces acting on the wire and low rigidity of the wire are responsible for wire deformation, which has a direct influence on the accuracy of the corner cutting. In this research, investigation is focused on the convex corner radii errors and alternative solutions are proposed for the case of successive cuts (one roughing and two finishings). Experiments are carried out for roughing operation by considering frequency of discharges and feed speed. The residual materials on straight and curved paths are the output parameters. Results indicate that optimization of these parameters have a better influence for control of residual material thickness on straight paths than on curved corners. One important conclusion is that roughing is the most influential stage of cutting by WEDM. Then, concave corner radii produced during successive cuts, the effect of corner angle and corner radii are investigated. Errors at radii of different corner angles are identified and related to arc length and residual material thickness in the curved corner. Finally, an effective approach is presented for improving the accuracy of the small-radius concave corner radii of finishing stage. The main conclusion is that to achieve accurate corner radii, one must increase the traversed corner arc length by wire in the small-radius concave corner radii.

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Single point incremental forming is a sheet metal forming process that has more flexibility than another methods. This process don't require to die and could formed various shape white use the simple tool and CNC machine. In this paper the influence of process parameters on the forces and dimensional accuracy and thickness distribution in single point incremental forming is investigated. These parameters include the feed rate, tool rotation, vertical step, movement strategy of tool and lubrication. Beginning with the design and construction of the fixture and clamping it on the dynamometer and create of tool (tungsten carbide), the preparation process was done on a CNC milling machine. Then, the experimental tests were carried out on Aluminum alloy sheets (Al-1200) with creation of pyramid frustum; after the measuring of force in different directions, the influence of parameters on the forming force was investigated. Also parts were measured with CMM devices and compared. The results showed that with increasing the feed rate, the vertical force decreases and with increasing tool rotation speed, horizontal force decreases. The use of lubricant, is effective on the improvement of process.

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Metallic bipolar plate is one of the main parts of fuel cell. Several methods were used by researchers to manufacturing bipolar plate such as stamping, hydroforming and electromagnet forming. The effect of process parameters on dimensional accuracy of metallic bipolar plates in rubber pad forming process has been investigated in this study. ABAQUS/Standard finite element software is used to simulate the process. The accuracy of the results of simulation process is evaluated by using experimental results. To perform experimental procedures, rigid die with parallel flow field is used to form SS316 bipolar plate with 0.1 mm thick. For this purpose the effect of punch load, rubber hardness, rubber thickness and clearance between die and container on the dimensional accuracy of the formed parts is investigated. In this regard, rubber layer with hardness of 55, 70, 85 and 90 Shore A and thickness of 1.5mm up to 5.5mm were used. The result show difference between lateral and central channel depth, the amount of disparity will decrease by increasing in punch load, as a result the dimensional accuracy will increase. According to the result, increase in hardness and thickness of the rubber layer lead to improve the dimensional accuracy. Also considering clearance between die and container decrease the difference between lateral and central channel depth and eventually cause increasing in dimensional accuracy of formed part.

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Single point incremental forming is a new and flexible method for 3D parts production of sheet metal. In this way, a hemispherical tool forms incrementally the sheet being clamped in perimeter. Because of the nature of localized deformation in this process, the formability is higher and forming forces are lower as compared to traditional sheet metal forming process. However, in this method dimensional accuracy is somewhat low due to spring back and bending occurred in boundaries. Recently, the incremental forming process using frictional heat has been developed. In this research, the experimental effect of generated heat by friction stir of the tool on dimensional accuracy in components of AA3105 sheet has been studied at high rotational speeds. By this method, due to friction movements of tool, the temperature of formation area rises while fixing the general temperature of sheet by spraying cooling liquid. Then, the sheet has low strength in contact region with tool while it has high strength in other areas. As a result, the force imposed on the sheet as well as the undesirable plastic deformation will decrease. Also, by decreasing the yielding stress, elastic strain and spring back decreases as well. An increase in formability because of softening of forming area is another contribution of this strategy. This idea has been studied by production of some parts of truncated-pyramid geometry and changing rotational speed from 1000 to 7000 RPM. The results show that at speed higher than 3000 RPM, formability and dimensional accuracy of the parts increase.

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