Incremental Sheet Metal Forming Process Research Articles

Performance Analysis of Multi-Point Incremental Forming Tool using Martensitic AISI 420 Sheet Metals

Incremental Sheet metal Forming (ISF) Process is a suitable process which helps to produce various parts used in automotive sector by rapid prototyping. This method of producing a prototype helps industry in reducing the production cost. In ISF process, a final product is evolved through local deformation of the sheet metal made by the tool. Usually better formability is obtained when the tool makes a better contact with the sheet metal throughout the process. Improved formability elevates dimensional accuracy of the product, thus increases the market value of the product. A new tool with multiple ball ends capable of making multiple mating points over sheet metal was used in this research to enhance the efficiency of formability and surface finish. Ability of the new Multi-Point Incremental Forming Tool (MPIF) was investigated and compared to the existing Single Point Forming Tool (SPIF) based on the formability and surface finish. Forming Limit Diagram (FLD), Strain Distribution (SD) and Scanning Electron Microscope (SEM) were used to examine the formability of the sheet metal. The SEM & 3D-Surface roughness profilometer were used to observe the sheet metals surface finish. In addition to these experimental techniques a simulation results were also used to predict the stress and strain rate during forming process. The experimentation and simulation outcome shows that the MPIF provides superior formability and surface finish.

Design and implementation of magnetic field effect sensor for ISF process

In this paper, an efficient approach for sheet metal thickness measurement is proposed. It is based on the concept of magnetic field effect resonance commonly called as Hall effect. The combination of magnet and metal tools generates the DC voltage signal. The magnitude of the generated signal is inversely proportional to the distance between magnet and tool and hence the thickness of the sheet metal. The proposed idea is designed and implemented successfully using suitable hardware. Initially, the designed circuit is tested manually using the Hall-effect sensor and the sheet metal of different thicknesses. Further, the various experimentations are carried out on the complete CNC machine-based incremental sheet metal forming setup to examine the effectuality of the proposed design. Moreover, the evaluation of the manufactured ISF part has been carried out using the image processing technique. It is observed that the proposed approach can be used efficiently in the application such as the incremental sheet metal forming (ISF) process in real-time for thickness measurement.

A new void coalescence mechanism during incremental sheet forming: Ductile fracture modeling and experimental validation

• Investigated a new void coalescence mechanism and its effect on ductile fracture of ISF. • Improved formability of ISF is attributed to closely-packed void cluster. • Proposed extended GTN model for ISF by considering oriented void cluster. • Validated proposed model with various process conditions and deformation states. The forming limit of sheet metal can be significantly improved by incremental sheet metal forming(ISF) process, however lacks of relevant fundamental researches. Besides, accurate prediction of formability based on deeper understanding of deformation mechanism is beneficial for the evaluation of ductile failure behavior in ISF process. In the present work, a new void coalescence approach, that voids coalesce closely along meridianal direction rather than conventional thickness direction, is proposed and its influence on formability is investigated. The improved formability is attributed to the formation of closely-packed void clusters along meridianal direction, and these void clusters can stably exist inside the sheet metal even after void coalescence. By introducing two independent parameters into classic GTN model, an extended GTN damage model is developed to describe this new void coalescence mechanism in ISF process, and is validated through a series of experiments. Through investigations in this work, the fundamental understanding of improved formability in ISF is revealed, and the extended GTN model shows its comprehensive capability in predicting ductile fracture behavior with a satisfactory accuracy.

Comparison of incremental sheet metal forming process using newly designed multipoint tool with the existing single point tool by optimization and characterization methods on austenite stainless steel 202

Incremental Sheet metal Forming (ISF) is a reliable process of converting a blank to work piece with better outputs compared to conventional forming process. The flexibility of ISF in producing the rapid prototype based on the customer needs is increased which is also desirable in the industry. But Single Point Incremental Forming (SPIF) process takes more time to form a product and hence the longer time is a barrier in implementing this process in industries. In this research work, the ISF process was made on sheet metal SS 202 using a newly designed multi-point tool and the obtained outputs were compared with the same material of sheet metal formed by traditionally available single point tool. This Multi Point Incremental Forming (MPIF) process takes lesser process time to give better formability, improved wall angle and good surface roughness. The input process parameters selected for the process are type of tool, speed, feed, Vertical Step Depth (VSD), and lubrication. They are arranged by using the taguchi Design of Experiments (DOE) approach. The responses considered are wall angle, formability, surface roughness, spring back and forming time. The multiple outputs obtained were optimized by Grey Relational Analysis (GRA) to predict the superior parameter. Confirmation test was also made to validate the output result. Fractography analysis was carried out to predict the fracture mechanism obtained during the forming process. The surface topography was also made on the surface of the formed area of the sheet metal. This research work concludes that newly designed MPIF outperforms SPIF.

Real-time applications and novel manufacturing strategies of incremental forming: An industrial perspective

Incremental Sheet-Metal Forming (ISMF) is a flexible and evolving metal forming technology for rapid free-form prototyping and small-batch metal components manufacturing. The end product has evolved by means of localized deformation in addition bi-axial stretching during that deforming tool squeezed on blank with predefined process variables. Owing to a unique process advantages and low manufacturing cost, its market requirement continuous enlargement and the process gradually transforms from prototyping to real-time manufacturing perspective. Over the preceding decades, ISMF technology has been adequately established in research and development, although it is less explored in the real-time industrial environment. The main intention of this exploration is to bring-forth insight into potential applications such as aviation, automotive, bio-medical, research and concept development through implementation of ISMF. Further, component evaluation performed to establish a convenient and feasible solution from deep-drawing and hydro-forming. For customized part forming, conventional forming process seems to be insufficient. Due to industrial transformation, dependent on cost-effectiveness, even prototyping and low-volume manufactured components relying on superior quality. Although, understanding the effect and influence of process variable, which needs the data analysis with implementing the optimization models and Artificial neural-network (ANN) model. These types of analysis majorly focus on monitoring and predict target values at each cycle and also reconfigure to optimistic or organize the iterative method for describing the appropriate process guidelines. Further, recent advances in ISMF process variants are explored, while looking at the benefits of ISMF for real-time part production. ISMF continues to mature into technology for production applications, while exploring the potential field to transform the way sheet components are fabricated in the new-era of digital manufacturing. This study will, in turn, enhance the capabilities of ISMF technology, which has grown significantly over the preceding decades, allowing technology adopters to innovate new design principle and achieve greater production flexibility.

Thermal modeling and experimental investigation on the influences of the process parameters on warm incremental sheet metal forming of titanium grade 2 using electric heating technique

Incremental sheet metal forming (ISMF) is one of the most innovative flexible processes for small volume production of complex sheet metal components. Formability of titanium grade 2 sheets is limited at room temperature and can be improved by forming at elevated temperature. Therefore, warm ISMF process has been explored to enhance the material formability. In this paper, thermal model has been proposed to predict the effect of temperature on the formability of sheet metal in warm ISMF process. Sine law has been used to determine the final thickness of the formed sheets. Experimental investigations on titanium grade 2 sheet at warm temperature has been carried out to study the effects of incremental depth, wall angle, and temperature on formability, geometrical accuracy, and thickness reduction during warm ISMF process using Taguchi L9 orthogonal array. Based on the experimental results, it was found that titanium grade 2 sheets formed with incremental depth of 0.1 mm and temperature of 300 °C showed higher formability with geometrical deviation of 1.52% and thickness reduction of 37.90%. Predictions of thermal model are validated by experimental work, and it has been found that experimental results are in good agreement with the thermal model. Analysis of variance (ANOVA) was used to identify the percentage contribution of each process parameters. To analyze the fracture behavior of the formed component, fractography study has been carried out using scanning electron microscopy (SEM).

Optimization of AA5052 in incremental sheet forming using grey relational analysis

In this paper, the main goal is to achieve enhanced formability and reduced surface roughness in Incremental Sheet Metal Forming (ISF) process in three directions – rolling, transverse and angular. This methodology combines Taguchi's orthogonal L9 array (34) for design of experiments, grey relational analysis and ANOVA. The experimental results verify that the suggested technique efficiently enhances the performance of ISF process. Lubrication has been identified as the highest contributing factor for all the three directions and feed rate as the least. Vertical step down and speed are the second and third contributing parameters.

Controlling Product Stiffness by an Incremental Sheet Metal Forming Process

Each process and each machine is subject to fluctuations, which lead to deviations in the quality of the components to be manufactured. In order to counter these uncertainties, a flexible incremental sheet forming (ISF) process for the production of truncated cone components is presented. These flexible methods are in contradiction with conventional forming processes, which are mostly designed for steady processes with large batch size. However, with the multi-technology machine 3D Servo Press, such a highly flexible process can be implemented on a forming machine for the first time. Through a determination of influence parameters and derivation of a model by means of simulative and experimental investigations, a closed-loop control for axial stiffness of the part can be realized. The control of the stiffness is not trivial in that, it depends on the geometric features as well as on the material properties, i.e., Young's modulus. The fluctuations are inherently present and can be adjusted by a stiffness correction model as shown in the presented work.

FEM Investigation of Ductile Fracture Prediction in Two-Point Incremental Sheet Metal Forming process

Abstract Two-point incremental sheet forming (TPIF) is an advanced forming technology for production of complex customized functional components in small batches for aircraft, biomedical and automobile applications. This paper is concerned with FEM damage modelling using VUMAT in Abaqus/Explicit for fracture prediction in TPIF. The enhanced Lemaitre damage model accounting for the effect of micro-crack closure is adopted to predict ductile fracture in TPIF with a varying wall angle hemispherical shape. The material constants in the damage model are calibrated by minimizing force error using a Newton approach in a tensile test. The TPIF simulation results with the enhanced Lemaitre damage model are validated by the thickness distribution, fracture location and forming force evolution trends. It is concluded that the enhanced CDM-based Lemaitre model can be used for ductile fracture of AA 7075 aluminium alloy in TPIF with a hemispherical shape.

Simplified numerical approach for incremental sheet metal forming process

The current work presents a finite element approach for numerical simulation of the incremental sheet metal forming (ISF) process, called here “ISF-SAM” (for ISF-Simplified Analysis Modelling). The main goal of the study is to develop a simplified FE model sufficiently accurate to simulate the ISF process and quite efficient in terms of CPU time. Some assumptions have been adopted regarding the constitutive strains/stresses equations and the tool/sheet contact conditions. A simplified contact procedure was proposed to predict nodes in contact with the tool and to estimate their imposed displacements. A Discrete Kirchhoff Triangle shell element called DKT12, taking into account membrane and bending effects, has been used to mesh the sheet. An elasto-plastic constitutive model with isotropic hardening behaviour and a static scheme have been adopted to solve the nonlinear equilibrium equations. Satisfactory results have been obtained on two applications and a good correlation has been shown compared to experimental and numerical results, and at the same time a reduction of CPU time more than 60% has been observed. The bending phenomenon studied through the second application and the obtained results show the reliability of the DKT12 element.

Experimental Investigations on Forming Time in Negative Incremental Sheet Metal Forming Process

The prominent features of incremental sheet metal forming (ISMF) process make it suitable to cover the requirements of today's industries and various preferences of costumers. In this article, the forming time aspect in negative ISMF process was studied. This aspect was investigated by disclosing the effects of four different process parameters: forming tool diameter, vertical tool pitch, feed rate, and support type. By using Taguchi analysis with the help of design of experiment (DOE) and analysis of variance (ANOVA), the effects of four process parameters and different influential combinations have been studied to optimize parameter levels to realize minimum forming time. The analysis results have shown that the most important parameter that has the greatest effect on the forming time is the vertical pitch followed by the feed rate and then tool diameter. The confirmation experiments have shown that the interaction between the significant parameters plays a prominent role in the negative ISMF process. It is demonstrated that Taguchi parameter design, response table, response graph, and ANOVA are a systematic procedure where the optimum level for each design parameter and their interactions can be effectively and efficiently identified to produce the minimum of forming time.

점진적 성형 기술을 이용한 자동차 차체 모형 제품의 제작

Recently incremental sheet metal forming (ISF) has used widely in making prototypes and small-volume products in automotive industry etc. We apply the ISF to make a 1/4 sized automobile body-in-white. First, ISF tests for rectangular shaped cup have been performed to clarify the formability denoting the relationship between the component wall angle and maximum cup height of safe forming. Next, a CAD model for the automobile was designed and segmented into several components in order to accommodate the working space of the CNC machine we adopted and the formability of the sheet metal. Then, a CAM software was employed to generate the tool path for manufacturing wooden dies and all the small parts. Finally, the different parts were joined into a single component by laser welding after the ISF process. By using the ISF we successfully produced the 1/4 sized automobile body-in-white.