Single Point Incremental Forming Process Research Articles

The formability of annealed and pre-aged AA-2024 sheets in single-point incremental forming

The formability of AA-2024 sheets, an aerospace grade material, in the annealed and pre-aged conditions has been investigated in the single-point incremental forming (SPIF) process. The major operating parameters, namely step size, tool radius, and forming speed, of SPIF process were varied over wide ranges, and their effect on the formability was quantified through a response surface method called as central composite rotational design. It was found that the interaction of step size and tool radius is very significant on the formability. Moreover, a variation in the forming speed does not affect the formability of annealed AA-2024 sheet. However, the formability of pre-aged AA-2024 sheet decreases with the increase in the forming speed. Furthermore, the annealed sheet shows higher formability than the pre-aged sheet.

On a Simplified Model for the Tool and the Sheet Contact Conditions for the SPIF Process Simulation

The numerical simulation of the Single Point Incremental Forming process (SPIF) is time consuming due to the necessity to take into account various non-linearity such as the material behaviour, large strain deformation and the evolution of the tool-flange contact. Classical contact algorithms give good agreement with experimental results, but are time consuming. In this paper, we investigate the development of a procedure to simplify the management of the contact interface between the tool and the sheet. Nodes with imposed displacements are determined by a geometrical approximation of the deformed sheet. In order to have a better approximation of the local stresses in the flange, a pressure is applied on the tool side of the elements in the contact zone. The pressure value is obtained by an analytical model. A classical contact algorithm and the present simplified approach are compared in terms of an incremental forming benchmark. It has been shown that, for the benchmark problem studied here, a CPU time reduction of approximately 65% can be achieved while at the same time have good simulation results.

A CALCULATION OF POWER FOR FORMING METAL SHEET BY SPIF PROCESS

This paper attempts to represent a case of calculating of the energy power that is consumed by CNC milling machine when manufacturing via forming membrane metal sheet by SPIF (Single Point Incremental Forming), the recent manufacturing process of metal sheet forming by drafting a no cutting-edge spheric tip tool on a clamped metal sheet. The calculation is based on the disclocation, the crystal plasticity and the slip of lattices inside the structure of the deformed metal. In the while time there is a series of empirical species of 24 groups batch of workpieces that were also machined by CNC milling machine Bridge Port VMC500, CAD/CAM Lab., FME of HCMUT for checking this calculation on consumed power.

Empirical modelling of the influence of operating parameters on the spifability of a titanium sheet using response surface methodology

Single-point incremental forming (SPIF) has the potential to replace conventional sheet forming processes for customized and small batch size sheet metal products. In this research work, the operating parameters (i.e. step size, tool size, and forming speed) which can affect the formability during SPIF process were altered over wide ranges and their effect on the formability of a titanium sheet was investigated. A six-dimensional hyper-surface showing the influence of investigated parameters on the formability was developed by using a response surface methodology. The capability of the SPIF process to enhance the cold formability of titanium sheet was also examined. This was carried out by comparing the sheet formability in SPIF and stamping processes.

Dimensional Accuracy of Single Point Incremental Forming

Dimensional Accuracy of Single Point Incremental Forming (SPIF) is studied with the use of a Box-Behnken design analysis. The dimensional accuracy of this process is determined by comparing parts manufactured using SPIF with the part drawings used to create the manufacturing toolpaths. Five factors are varied in the manufacturing of the SPIF process, and they are: material type, material thickness, formed shape, tool size, and incremental step size. The Box-Behnken design analysis allows for determination of how these factors affect the dimensional accuracy.

Identification of material parameters to predict Single Point Incremental Forming forces

The purpose of this article is to develop an inverse method for adjusting the material parameters for single point incremental forming (SPIF). The main idea consists in FEM simulations of simple tests involving the SPIF specificities (the “line test”) performed on the machine used for the process itself. This approach decreases the equipment cost. It has the advantage that the material parameters are fitted for heterogeneous stress and strain fields close to the ones occurring during the actual process. A first set of material parameters, adjusted for the aluminum alloy AA3103 with classical tests (tensile and cyclic shear tests), is compared with parameters adjusted by the line test. It is shown that the chosen tests and the strain state level have an important impact on the adjusted material data and on the accuracy of the tool force prediction reached during the SPIF process.

Three-dimensional finite element method simulation of sheet metal single-point incremental forming and the deformation pattern analysis

Further research of the sheet metal single-point incremental forming (SPIF), which is a flexible sheet metal numerical forming method without dedicated dies, has used finite element method (FEM) simulation to analyse the forming principle and the effect of process parameters on the forming. In SPIF, the located region of the blank in contact with the forming tool is formed incrementally along the trajectory. There is no symmetric load and geometry condition, so the FEM model could not be simplified to a symmetrical model and the efficiency of simulation is bad. In this paper, brick elements are used to establish the whole three-dimensional FEM model and a simplified three-dimensional FEM model of a truncated cone and truncated pyramid. Comparison of the simulation results from the two models indicates that both models fit the simulation of SPIF but the simplified model is more efficient. Therefore, based on the simplified FEM model of a truncated pyramid, the SPIF process with different parameters was simulated to study the incremental forming principle. It was found that the deformed blank could be divided into three regions with different deformation patterns and the main character of the deformation could be conceded as a combination of bending and stretching.

DEFORMATION ANALYSIS OF SHEET METAL SINGLE-POINT INCREMENTAL FORMING BY FINITE ELEMENT METHOD SIMULATION

Single-point incremental forming (SPIF) is an innovational sheet metal forming method without dedicated dies,which belongs to rapid prototyping technology. In generalizing the SPIF of sheet metal,the deformation analysis on forming process becomes an important and useful method for the planning of shell products,the choice of material,the design of the forming process and the planning of the forming tool. Using solid brick elements,the finite element method(FEM) model of truncated pyramid was established. Based on the theory of anisotropy and assumed strain formulation,the SPIF processes with different parameters were simulated. The resulted comparison between the simulations and the experiments shows that the FEM model is feasible and effective. Then,according to the simulated forming process,the deformation pattern of SPIF can be summarized as the combination of plane-stretching deformation and bending deformation. And the study about the process parameters’ impact on deformation shows that the process parameter of interlayer spacing is a dominant factor on the deformation. Decreasing interlayer spacing,the strain of one step decreases and the formability of blank will be improved. With bigger interlayer spacing,the plastic deformation zone increases and the forming force will be bigger.

Single‐point incremental forming and formability—failure diagrams

In recent work, the present authors constructed a closed‐form analytical model that is capable of dealing with the fundamentals of single‐point incremental forming (SPIF) and explaining the experimental and numerical results published in the literature over the past couple of years. The model is based on membrane analysis with in‐plane contact frictional forces but is limited to plane strain, rotationally symmetric conditions. The aim of the present paper is twofold: first, to extend the previous closed‐form analytical model into a theoretical framework that can easily be applied to the different modes of deformation that are commonly found in general single‐point incremental forming processes and, second, to investigate the formability limits of SPIF in terms of ductile damage mechanics and the question of whether necking does, or does not, precede fracture. Experimentation by the present authors, together with data retrieved from the literature, confirms that the proposed theoretical framework is capable of successfully addressing the influence of the major parameters of the SPIF process. It is demonstrated that neck formation is suppressed in SPIF, so that traditional forming limit diagrams are inapplicable to describe failure. Instead fracture forming limit diagrams should be employed.

Feature Based Approach for Increasing the Accuracy of the SPIF Process

One of the main issues of the single point incremental forming (SPIF) process is still the achievable accuracy. A number of methods have been suggested to increase this accuracy, but many of these contain a significant drawback. Reprocessing the workpiece can increase the accuracy but also significantly increases the manufacturing time and leads to a worse surface finish of the part. Other methods iteratively correct the toolpath based upon the deviations measured on the previously manufactured parts. This method is not very well suited for one of a kind products, since instead of one part, multiple parts need to be manufactured before the desired accuracy can be reached. Our method proposes to use feature detection to split the workpiece in a configuration of planes, edges, freeform surfaces and other features. For each of these features an optimised toolpath strategy can be determined and the toolpath in that zone can be adjusted for this strategy. The proposed method generates a single pass toolpath that leads to more accurate parts compared to the standard CAM toolpaths. This paper describes the feature based optimised toolpath generation method (FSPIF) and contains the results of experiments performed to validate this method.

Incremental Forming Process for the Accomplishment of Automotive Details

In the last decades the scenario of the industrial production is remarkably changed, since new market requirements have to be faced by the industries. The market, actually, more and more, asks for vary models and niches product. The necessity to intercept dynamically and to satisfy the demands for the market, driver of the innovation process, involves the necessity to reduce the Timeto- market introducing to new methodologies of engineering, like the 3D-prototyping, for the qualitative and structural analysis of the final component. For these reasons, at the beginning of the nineties, a new philosophy of sheet metal forming process begins to assert on the industrial scene, whose basic logic is to obtain the shape wished through the progressive action of a tool of simple shape. In this job the application of the simplest process of incremental process on an industrial detail - famous in international field like SPIF (Single Point Incremental Forming) - will be described. The process is intrinsically flexible, and therefore is adapted to the rapid prototyping. The cases are still least, notice in the scientific literature, in which the details of industrial interest have been developed by Incremental Forming process; for this reason, the subject of this job is focused on the evaluation of the possibility to obtain real components of the automotive industry through the SPIF process. The job has been carried out in the R&D laboratory of "Fontana Pietro S.p.A.”, leader in the field of die manufacturing and stamping of component of the automotive industry. In particular, two parts of automotive auto body of aluminium sheets have been considered. It has been lead an analysis of technological and process feasibility, optimizing tool path considering experiences to obtain a product/process for the production of auto body prototypes.

Formability evaluation of a pure titanium sheet in the cold incremental forming process

Owing to its ability to deform a sheet metal locally, the single point incremental forming (SPIF) process produces larger deformations as compared to the conventional forming processes. In the present study, we investigated the effect of some process parameters – pitch, tool diameter, feed rate and friction at the interface between the tool and blank – on the formability of a commercially-pure titanium sheet. Trends between the process parameters and formability are presented in this paper.

OS9-1-1 Full field optical measurement of large deformation fields in Single Point Incremental Forming (SPIF) Processes

The Single Point Incremental Forming (SPIF) process is an interesting innovative production technique for industries involved in metal forming and metal stamping. SPIF is based on the relative movement of a simple small punch with respect to the blank. The advantages of SPIF are a high flexibility and the fact that there is no need for a die to obtain the final shape of components. Forming strategies in SPIF are strongly dependant on the formability of the used metals. Therefore, the optimization of forming parameters requires an understanding of the strain history during the SPIF process. The present paper reports the strain evolution observed by a Digital Image Correlation (DIC) technique in a partial cone with flanges of 50° during SPIF. The results show a bending/reverse bending mechanism when the tool approaches, passes and moves away from a given material point on the tool path. Also the large strains typical for a SPIF process are measured. The paper discusses how to solve some encountered technical problems and presents procedures to obtain reliable strain results during the DIC-SPIF experiment.