Preliminary investigation on homogenization of the thickness distribution in hole-flanging by SPIF

A drawback of the hole-flanging process by single-stage SPIF is the non-uniform thickness obtained along the flange. Multi-stage strategies have been used to improve it, however they increase notably the manufacturing time. This work presents a preliminary study of the tool paths for a hole-flanging process by SPIF in two stages. An intermediate geometry of the piece is proposed from the analysis of the thickness distribution observed in previous single-stage process. A simple optimization procedure is used to automate the intermediate part design, the NC code generation for the tool path and the validation of the optimal forming strategy by means of FEA

A Process/Machine coupling approach: Application to Robotized Incremental Sheet Forming

International audienceIn this paper, a Process/Machine coupling approach applied to Robotized Incremental Sheet Forming (RISF) is presented. This approach consists in coupling a Finite Element Analysis (FEA) of the process with an elastic modelling of the robot structure to improve the geometrical accuracy of the formed part. The FEA, assuming a rigid machine, is used to evaluate the forces at the interface between the tool and the sheet during the forming stage. These forces are used as input data for the elastic model, to predict and correct the tool path deviations. In order to make the tool path correction more effective, the weight of three numerical and material parameters of the FEA on the predicted forces is investigated. Finally, the proposed method is validated by the comparison of the numerical and experimental tool paths and geometries obtained with or without correction of the tool path

incremental sheet forming for prototyping automotive modules

Abstract Actually, in many industrial applications, like automotive industry, mass decreases and fuel economy constitute very important features. Light alloys are extensively used in automotive applications and simultaneously, the constant industrial progress forces low-cost innovative machining routes to be used after the manufacturing process oriented to transform the product into a right shape with high accuracy of the geometry and good surface quality. In this paper, a general overview of the actual state-of- the-art about the Incremental Sheet Forming (ISF) is presented including some experimentally results of the current research in this field performed by the authors. The target of the research is oriented on the validation of the possibility to use a common milling machine, as ISF apparatus, and to find the most suitable process parameters to be assumed for the production of automotive sheet made by Ti alloys

Off-line compensation of the tool path deviations on robotic machining : Application to incremental sheet forming

International audienceIn this paper, a coupling methodology is involved and improved to correct the tool path deviations induced by the compliance of industrial robots during an incremental sheet forming task. For that purpose, a robust and systematic method is first proposed to derive the elastic model of their structure and an efficient FE simulation of the process is then used to predict accurately the forming forces. Their values are then defined as the inputs of the proposed elastic model to calculate the robot TCP pose errors induced by the elastic deformations. This avoid thus a first step of measurement of the forces required to form a test part with a stiff machine. An intensive experimental investigation is performed by forming a classical frustum cone and a non-symetrical twisted pyramid. It validates the robustness of both the FE analysis and the proposed elastic modeling allowing the final geometry of the formed parts to converge towards their nominal specifications in a context of prototyping applications

Optimization of hole-flanging by single point incremental forming in two stages

Special Issue of the Manufacturing Engineering Society (MES)Single point incremental forming (SPIF) has been demonstrated to accomplish current trends and requirements in industry. Recent studies have applied this technology to hole-flanging by performing different forming strategies using one or multiple stages. In this work, an optimization procedure is proposed to balance fabrication time and thickness distribution along the produced flange in a two-stage variant. A detailed analytical, numerical and experimental investigation is carried out to provide, evaluate and corroborate the optimal strategy. The methodology begins by analysing the single-stage process to understand the deformation and failure mechanisms. Accordingly, a parametric two-stage SPIF strategy is proposed and evaluated by an explicit Finite Element Analysis to find the optimal parameters. The study is focused on AA7075-O sheets with different pre-cut hole diameters and considering a variety of forming tool radii. The study exposes the relevant role of the tool radius in finding the optimal hole-flanging process by the proposed two-stage SPI

Numerical study on the thickness homogenization in hole-flanging by single-point incremental forming

Incremental sheet forming is a novel technology that has significant benefits compared to conventional forming. However, it is a time-consuming process that is usually carried out in several forming stages to homogenize deformation and avoid material failure. In hole-flanging operations by SPIF, a single-stage strategy might provide functional flanges in considerably less time, however a non-uniform thickness is obtained along the flange. This work proposes a two-stage process as the best strategy to increase production rate, and an optimization methodology to produce a homogeneous thickness distribution of the flange. The procedure is used to automate the design process of parts and tool trajectories by CAD/CAM, and validate the optimal forming strategy by FEAGobierno español DPI2015-64047-

Design and validation of a fixture for positive incremental sheet forming

Incremental sheet forming is an emerging manufacturing technique in which sheet metal is formed into desired shape through the application of localized force using a hemispherical tool. Potential advantages of the process are its relatively low cost and small lead times, and these have to be balanced against the disadvantages of low dimensional accuracy and a limited understanding of the process’ internal mechanics. Incremental sheet forming system can be classified as positive, or negative, depending on whether the sheet material is progressively deformed onto a protrusion or a cavity. In negative systems, the work piece is held on a static fixture; whereas, in positive incremental sheet forming, the fixture must be incrementally lowered onto a protruding die. Although the vertical movement of positive incremental sheet forming fixtures is easily illustrated schematically, its implementation is challenging; if the descent is actuated, the motion has to be carefully coordinated with those of the forming tool; if free sliding on vertical columns, the rig must move without jamming or rocking. This article reports the development and testing of a positive incremental sheet forming fixture design that uses nylon sleeve bushes. Symmetric and asymmetric components were formed using the designed fixture, modular wooden dies and a rotating tool with multiple diameters and the results are discussed