High-Speed Incremental Forming Process: A Trade-Off Between Formability and Time Efficiency

Single point incremental forming (SPIF) process has proven benefits in terms of formability, flexibility, and low cost as compared to conventional sheet forming, although it has some issues such as dimensional accuracy and low quality of surface finish for some materials. The SPIF is considered as a potential method of producing customised medical parts such as craniofacial implants using a titanium sheet. This investigation aims to analyse the overall surface roughness of grade 1 pure titanium along the wall of the hyperbolic truncated cone formed by the SPIF process with different forming parameters (i.e. forming tool diameter, step size, and feed rate). Focus variation microscopy was used to measure the surface roughness experimentally along the wall of the truncated cone. Abaqus/Explicit was used to predict the equivalent stress and equivalent plastic strain along the wall of the truncated cone part from the top to the fractured region to evaluate the relationship between the stress, strain, and roughness distribution. It was found that the surface roughness changes with the deformed part height and rough surface could be produced in the region of high equivalent stress and low equivalent plastic strain. Such a surface roughness and equivalent stress and plastic strain correlation has a clear implication to the design and the surface quality of sheet parts made by SPIF.

Investigation of mode-I fracture behavior by essential work of fracture during the single-point incremental forming process

Single point incremental forming of Ti-6Al-4V titanium alloy for biomedical applications: Process optimization and in vitro biocompatibility assessment.

Single point incremental forming (SPIF) has potential to be employed commercially and can replace conventional sheet stamping process if its defects, such as poor geometrical accuracy, can be overcome. In the present article, three forming defects, namely, squeezed out wall formation, corner fold corner, and bulge height, are introduced. It is demonstrated that the formation of these defects has adverse effect on the formability in SPIF. In order to eliminate, if possible, the formation of these defects, the potential effect of operating (i.e., tool radius and step size), geometrical (i.e., wall angle), and material (i.e., sheet thickness and material property) parameters and their interaction on the defect formation and growth has been quantitatively investigated by employing response surface design method. With the help of proposed empirical models, the investigated defects can be overcome through parametric optimization.

In this work, the forming behavior of the High Strength Low Alloy (HSLA) 420 steel sheet during the Single Point Incremental Forming (SPIF) process was investigated. The formability is enhanced by increasing the spindle rotational speed, reducing the tool feed and reducing the incremental step-down. A numerical simulation was also performed and the results were compatible with experimental results. The studies are further extended to microstructural analyses. A large dislocation density was obtained due to a high swiveling effect. Therefore, the possibilities of high-angle grain boundaries were increased, which caused an increase in the percentage of ultra-fine grain formation. Hence, the strong texture was obtained by increasing the swiveling effect and the texture components were favored to enhance the formability.

The failure strain level in a single point incremental forming (SPIF) process is found to be much higher than that in the traditional stamping process. Based on the assumption that forming limits in SPIF are dominated by fracture failure, the Oyane ductile fracture criterion is introduced in this paper to predict the fracture initiation site, and hence the forming limit, given the stress and strain values obtained from finite element simulations. The predicted results compare well with those obtained from the SPIF experiments. Furthermore, this fracture criterion is used to study the size effects in SPIF. Analytical equations are derived to comprehensively consider the effects of design and process parameters on sheet formability including sheet thickness, tool diameter, and incremental depth. Previously published experimental data is used to verify the feasibility of the proposed size effect equation.

Metal forming process is one of the most important manufacturing processes that translate the sheet and bulk metal to the final product with simple punch and. Single point incremental forming (SPIF) process is considered as a modern flexible manufacturing techniques that is use a simple tool and non-specific fixture die to complete the forming, this method is used in prototype manufacturing system due to the time consuming during the forming. The advantage of this process is low cost and simple equipment. However, some limitation was founded including poor geometric accuracy, non- uniform thickness distribution, dimple and high forming time. Multi-point forming (MPF) is another modern forming method that is used in industrial applications due to its advantage such as uniform thickness distribution with low forming time consuming. This method used matrix of simple tools to deform the sheet metal to the desired shape. Wrinkle and dimple due to small contact area between tool and blank under high forming force are considered the main limitation of using MPF process. To take the advantages of this processes with reduced the limitations a hybrid forming (HF) process of both MPF and SPIF are used. The experimental work was applied to produce a hemi-spherical product of brass blank using the SPIF, MPF, and HF processes. Satisfactory results are obtained using a hybrid forming process with free of defects products and reduction in production as compared to the SPIF. A high improve in microstructure including refinements in grain size with twins effects. The sample produced with SPIF process showed a high microhardness as compared to the sample produced using MPF process, however, the hybrid MPF and SPIF forming process showed slightly improving in microhardness as comparing to the as received materials, reflecting the microstructure development of the processed samples.

Evaluation of forming forces in ultrasonic incremental sheet metal forming

The present paper aims to study the behavior of tailor welded blanks subjected to a single point incremental forming (SPIF) process from an experimental point of view. This process was chosen to deform truncated cone shapes of AA1050 aluminum alloy with different thicknesses. A uniaxial tensile test was performed to determine the mechanical characteristics of the alloy. Initial experimental tests implicated the use of variable wall angle parts which were processed on unwelded sheet blanks for determination of the behavior of the material and the forming forces. Afterwards, the wolfram inert gas (WIG) welding technique was used for joining two sheet blanks with different thicknesses either through one pass on one side, or by one pass on both sides. The conclusion of this paper indicates that one-sided welded blanks cannot be deformed successfully without fracture. In case of two-sided welded blanks, the results showed that the desired depth of 25 mm can be reached successfully. In case of the SPIF process, if welded blanks must be deformed, then the suitable method is to weld the blanks on both sides.

ABSTRACTA novel configuration of bilayer composite sheets containing different polymers is described and used for the first time in the single point incremental forming (SPIF) process. These bilayer sheets made of polypropylene (PP) and Santoprene are fabricated by hot welding, and shaped with cone‐like geometry by SPIF. The bilayer configuration is such that only one of the containing polymers is in contact with the forming tool. During the SPIF processing, the bilayer sheets show a noticeable difference in the mechanical response, depending mainly on the polymer that is not in contact with the forming tool, which is related to a lower polymer softening. The performance of the bilayer sheets is compared against the neat polymers and a blend of these with a mass ratio of 1:1. The observed effect is introduced as a dual effect of properties that brings together in a single composite sheet, properties for a better performance in SPIF and wider functionality of the fabricated parts, evidenced by a lower material softening and higher mechanical strength, in comparison with the two individual polymers, and even better than the blend of both. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47093.

Single-point incremental forming (SPIF) is relatively a novel sheet forming process to produce small lots with low cost. In this article, guidelines for tool size selection for SPIF of an aerospace grade alloy (AA-2024) are presented. The role of tool size, with respect to sheet thickness employed, on the formability in SPIF (i.e., spifability) is clarified. The response surface method is employed in order to study the significance of sheet thickness (t o) and tool radius (r) on the spifability. The results of analysis of variance (ANOVA) show that the sheet thickness and tool radius are not significant individually, however, a strong interaction between these parameters exists. Moreover, for a particular sheet thickness, there exists only one r/t o value at which the spifability can be maximized under a given set of conditions. Furthermore, for a given sheet thickness, if a tool with radius lesser than a particular value is used (i.e., r/t o < 2) the material squeezes out from the tool/sheet interface. And, such a condition adversely affects the material spifability. FEA using LS-DYNA has also been carried out.

Single Point Incremental Forming (SPIF) is a modern and flexible alternative to traditional forming techniques. It thanks its flexibility to the fact that it does not require a dedicated tool set to operate. Numerical simulation of the SPIF process requires an accurate FE model. In the past several attempts have been undertaken to use inverse methods for sheet metal SPIF material model identification based on shearing, tensile and indenting tests. The basic idea of this paper is that the results of inverse methods can be improved by using the SPIF process itself as experimental data source. A SPIF experiment dedicated for material identification on a simple geometry using large step sizes is presented and compared with the FE simulation of the forming process based on an initial guess for the material behavior.

Investigation of material deformation mechanism in double side incremental sheet forming

Forming a metallic sheet along with the consideration of computer simulation and experiment had benefited the milling industry for a long time. The ideal forming, without an error, is a concerning topic. So, the computer simulation had the advantage then direct forming. To observe the results before doing the real experiments simulation comes handy. Which helped to set the parameters for the milling process for the single point incremental forming (SPIF) process. For milling, a CAD design was converted into a 3D model. For this, a conical shape of 3D modeling was made in fusion 360. After onwards, it was simulated for finding the maximum depth for the cracking point. Next for the experimental part, the maximum forming depth was considered, and used lubricant grease for reducing friction. While forming with the grease, the impact of parameters was also changed. Throughout the process, an optimization approach was set to reduce the cracking areas for the G-code. Along with the lubricant use, smooth milling finished surface was observed. To reducing the depth forming errors, an optimization approach was introduced in this research.

Investigations on failure-to-fracture mechanism and prediction of forming limit for aluminum alloy incremental forming process