Brass 70/30 and Incremental Sheet Forming Process

Incremental Sheet Forming (ISF) process emerges as an alternative to classic shaping processes. Two variants of the IS process are used: negative forming or SPIF (Single Point Incremental Forming), in which it is not necessary using a die and positive forming or TPIF (Two Point Incremental Forming) ISF is usually performed on specifically designed machines controlled by CNC or in retrofitted CNC milling machines However, in the most of cases, the possibility of combining milling and ISF is not considered This paper is focused on a study about the implementation of ISF process in a CNC machining center through the specifi design of the clamping tools. So, it is not necessary to retrofit the machining center and it is possible to think abou combining both processes in multitask operations.

Process feasibility and material formability are two of the most concerning factors which are studied in Incremental Sheet Forming (ISF) process. They are two important matters under study of the scientific community with the final goal of improving the process performances and to make it reliable to allow its use for rapid prototyping and for small batch production. In recent years, the application of neural network techniques to forming processes has been a research topic for optimizing and predicting process parameters and ISF process has not been an exception. Unfortunately, there are some drawbacks in using Backpropagation (BP) neural networks, such as easily falling into local minimum point. Because of that, recently Genetic Algorithms (GA) are applied to BP networks in order to optimize them. This paper describes the application of BP networks and GA applied to BP networks for the prediction of the forming force in ISF process. These models have been developed using experimental data from several tests. The two point incremental forming (TPIF) tests were performed on a horizontal CNC milling machine and DC04 deep drawing sheets steel 0.8 mm thick were worked. The reliability of the proposed approach has been evaluated by testing the trained networks with unseen experimental data and the comparison between the two BP and GA-BP models are presented. All the details are accurately discussed in the paper.

Incremental forming is a recent forming process that allows a sheet to be locally deformed with a hemispherical tool in order to gradually shape it. Despite good lubrication between the sheet and the tip of the smooth hemisphere tool, ductility often occurs, limiting the formability of titanium alloys due to the geometrical inaccuracy of the parts and the inability to form parts with a large depth and wall angle. Several technical solutions are proposed in the literature to increase the working temperature, allowing improvement in the titanium alloys’ formability and reducing the sheet thinning, plastic instability, and failure localization. An experimental procedure and numerical simulation were performed in this study to improve the warm single-point incremental sheet forming of a deep truncated cone in Ti-6Al-4V titanium alloy based on the use of heating cartridges. The effect of the depth part (two experiments with a truncated cone having a depth of 40 and 60 mm) at hot temperature (440 °C) on the thickness distribution and sheet shape accuracy are performed. Results show that the formability is significantly improved with the heating to produce a deep part. Small errors are observed between experimental and theoretical profiles. Moreover, errors between experimental and numerical displacements are less than 6%, which shows that the Finite Element (FE) model gives accurate predictions for titanium alloy deep truncated cones.

Investigation of material deformation mechanism in double side incremental sheet forming

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

Making use of “optimal experimental design,” the paper attempts to investigate individual and interactive effects of predictor parameters, namely tool size, pitch size, feed rate, spindle rotational speed, and blank thickness, on sheet formability in single point incremental forming (SPIF) process. For the sake of precision, a novel sensor system was developed and employed to detect crack as it initiates on SPIF test specimens. A novel benchmark for formability in SPIF was established by addressing normal strain along sheet thickness, maximum attainable forming angle, and the rate of variation in forming angle. The process was finally optimized in terms of maximum achievable formability and minimum processing time. Accordingly, high-speed forming (with forming speed of at least 5000 mm/min) was realized to be perfectly viable, whereas the sheet formability remains quite satisfactory (over 90% of the maximum value). The key role of high spindle speed (up to 3000 rpm) was also highlighted in this regard.

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

Amidst increasing governmental regulations and global initiatives to decarbonize manufacturing, there is a growing emphasis on environmentally sustainable, energy-efficient, and cost-effective production methods. Sheet-forming processes have made it possible to manufacture a variety of products we use and depend on in today’s globalized world, in the automotive, aerospace, medical, and food industries. Stamping or deep drawing are the preferred sheet-forming methods for mass-producing thin sheet parts due to its high production rate. However, the process involves high costs associated with the fabrication of specific dies for each part. Incremental sheet forming (ISF) has emerged as a promising technique and has gained widespread recognition as an alternative to traditional sheet forming. Researchers have studied ISF for the past decades, addressing and exploring alternatives to optimize the technique. Single-point incremental forming (SPIF) is one of the most popular ISF approaches because it can be accomplished using a CNC machine, a sheet clamp, and a small forming tool to make a wide variety of products of different shapes and materials. However, the technology’s cost-saving potential needs to be better understood, and predictive models must be improved to assess the process flows required to make parts using ISF. The cost prediction model presented in this work is intended to break down the cost dependencies of the ISF process to estimate a predetermined cost for each part before it is manufactured, considering material preparation, forming, and post-processing operations. A step forward in sheet forming research will be to provide a process-based cost model that can be flexible and adaptable to different types of machinery and tooling utilized. Cost calculations of a part made with ISF require knowledge of the systema as whole, such as forming process parameters, equipment characteristics, and forming geometry capabilities. The model relies on gathering process-based costs, including facilities, labor, equipment, materials, tools, consumables, and utilities, for all factors necessary to produce parts using ISF. The process-based cost model in this work involves an analytical bottom-up cost calculation methodology that is flexible and adaptable to various machine types. The ISF process is flexible, which means that the cycle time for different parts can vary by a considerable amount depending on the process parameters chosen (e.g., step down and feed rate) and the fixture and tools used. The aim of the present work is to lay the foundation for predicting the cost-effectiveness of products produced via the ISF process by considering the key processes involved. By gaining deeper insights into all costs involved in ISF and other innovative, environmentally friendly production methods, more sustainable manufacturing practices can be facilitated. These findings will contribute to global efforts to reduce carbon emissions, support responsible consumption and production, and benefit people, economy, and environment.

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.

Incremental sheet forming process has been proved to be quiet suitable and economical for job and batch type production, which exempts expensive and complex tooling for sheet forming. Investigation of forming forces becomes important for selecting the appropriate hardware and optimal process parameters in order to assure perfection and precision of process. Moreover, lack of available knowledge regarding the process parameters makes the process limited for industrial applications. This research paper aims at finding out effects of different input factors on forming forces in single-point incremental forming (SPIF) process. For operation sustainability and hardware safety, it becomes critical to optimize forming forces for a given set of factors to form a particular shape. In this study, optimization of input factors has been performed to produce conical frustums with helical tool path using Taguchi analysis as design of experiment (DOE) and analysis of variance (ANOVA). The optimal experimental conditions for forming forces have been calculated as sheet thickness (0.8 mm), step size (0.2 mm), tool diameter (7.52 mm), tool shape (hemispherical), spindle speed (1000 rpm), feed rate (1000 mm/min) and wall angle (50o). Effects of tool shape and viscosity of lubricants have also been investigated. An intensive understanding of the mechanism of forming forces has been presented, which shows that force trend after peak values depends upon instant input factors that can be categorized as a safe, severe and crucial set of parameters.

Hole-flanging by incremental sheet forming is developing as an innovative metal forming technology for flexible small batch-production of cylindrical or conical flanges in blanks with pre-cut holes. The process is seen as an alternative to hole-flanging by conventional press-working due to significant cost savings through the replacement of complex press-tools by simple dieless forming apparatuses and to widespread belief that the limiting forming ratio of hole-flanging by incremental sheet forming is always higher than that of hole-flanging by conventional press-working. This article focuses on the aforementioned assumption and investigates the influence of material failure by necking and fracture on the limiting forming ratio. The experimental work is performed in a CNC machining center and a hydraulic press equipped with apparatuses for multi-stage single point incremental forming and conventional press-tooling, and the strain loading paths resulting from each forming process are determined by circle grid analysis. Results in Aluminium AA1050-H111 and Titanium (grade 2) blanks demonstrate that contrary to what has often been said in the literature there are process operating conditions leading to higher limiting forming ratio of hole-flanging by conventional press-working than by incremental sheet forming due to closeness of the forming limit curve and fracture forming limit line in the principal strain space.

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.

Many aluminum alloy sheet metal parts with complex geometry in airplane are often formed by drop hammer forming with intermediate annealing and then heat treated into T temper. The manufacturing cost is very high because of a number of forming and heat treatment steps. Incremental sheet forming can form complex parts because of larger forming limit than conventional stamping. So the research that the part is formed directly from T temper aluminum alloy sheet using incremental sheet forming is very attractive. 2024-T3 is the aluminum alloy used mostly in aerospace manufacturing. Single-point incremental forming experiments with 2024-T3 are carried to form cone shape parts. In this work, the formability of 2024-T3 aluminum alloy sheets in single-point incremental forming was preliminarily studied. Effect of tool diameter and wall angle on the formability were investigated. It is found that the surface roughness can be reduced and the forming depth of the cone shape part can be increased by increasing the tool diameter.

Optimization of pyramid shaped single point incremental forming of AA5052 alloy sheet

The present article describes a comprehensive literature review on multi-stage single point incremental forming (MSPIF). Multi-stage single point incremental forming is an advance metal forming process used to form sheet metal parts with steep wall angles. In MSPIF, overall deformation is distributed in intermediate stages. MSPIF provides better thickness distribution, geometrical accuracy and formability than single point incremental forming (SPIF) process. In the present literature review, research papers published during 2000–2021 are critically reviewed. Literature review is categorized in three major sections—geometrical accuracy, numerical simulation and surface roughness. Influence of various process parameters, forming conditions on responses, is studied and presented. Based on the literature review, future scope is also discussed.