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The single-point incremental forming process is useful for manufacturing prototypes and customised sheet metal parts. The application of single-point incremental forming to perform hole-flanging operations has been explored by many researchers. The flange can be formed by a single-stage or a multi-stage strategy of single-point incremental forming. A comparative study of both strategies is essential to understand their applicability. In this work, the formability of AA5052-H32 sheet metal has been analysed by finding the Limit Forming Ratio and thickness of the flanges formed with the single-stage and multi-stage strategies. The single-stage strategy reduced the operation time by 105%, whereas the multi-stage strategy increased the formability by 11%. Further, an experimental study has been carried out to understand the effect of process parameters on the flange quality in single-stage single-point incremental hole-flanging. The results show that the step depth is the most effective process parameter and there is a high interaction between the spindle speed and the feed rate. [ABSTRACT FROM AUTHOR]

Incremental sheet metal forming is known for its high flexibility, making it suitable for fabricating low-batch, highly customized complex parts. In this article, a localized multipass toolpath referred to as localized reforming, with reverse forming in a region of interest, is employed within the double-sided incremental forming (DSIF) process to manipulate the mechanical properties of a truncated pyramid formed from austenitic stainless steel sheet, SS304, through deformation-induced martensite transformation. DSIF forms a clamped sheet through localized deformations by two opposing tools. The toolpath effect in localized reforming is examined in terms of martensite transformation, geometrical accuracy, and thickness distribution. The results are compared with a conventional toolpath, i.e., forming in a single pass. The results show that varying toolpaths lead to different martensite transformation levels, while final geometry and thickness remain similar. The study demonstrates that localized reforming significantly increases martensite transformation in the specified region, i.e., the center of the pyramid wall, to ~70%, with a martensite fraction remaining around 25% elsewhere. In comparison, using a single pass forming toolpath leads to a decreasing martensite fraction from the base of the pyramid toward the apex, due to the heat generated, with values <10% along the entire wall. Through finite element simulation, it is shown that the increase in martensite transformation of the region of interest is with the plastic deformation accumulation during the reverse pass. These findings highlight the potential to tailor mechanical properties in specific areas using a reforming toolpath in DSIF. [ABSTRACT FROM AUTHOR]

This study reveals the mechanisms by which efficiency parameters affect surface quality, mechanical properties, and configuration offset in incremental sheet forming (ISF), focusing on surface morphology and microstructural evolution. By constructing an efficiency-quality graph, a method is developed to determine efficiency parameters that balance quality and efficiency synergistically. The results show that increasing the step depth (Z) and decreasing the feed rate (v) intensify plowing and adhesion effects at the interface, degrading surface quality and enriching the presence of {001} Cube and {112} Copper textures, while the cross-sectional crystal orientation remains unaffected. Additionally, increasing Z enlarges grain size and reduces high-angle grain boundaries (HAGBs), amplifying micro-stress and defects, which deteriorates mechanical properties and increases configuration offset. Conversely, increasing v has minimal impact on mechanical properties but significantly increases configuration offset due to the rise in HAGBs, micro-stress, and defects. The efficiency-quality graph elucidates the complex synergistic relationship between forming efficiency and comprehensive quality of the formed parts, and the optimal efficiency parameters are identified by considering the priority order of different quality dimensions. Specifically, when prioritizing surface quality and hardness, the optimal parameters are Z = 0.1 mm and v = 5000 mm/min; when prioritizing configuration offset, the optimal parameters are Z = 0.1 mm and v = 1000 mm/min. Therefore, this study provides a comprehensive method for evaluating efficiency parameters in ISF, emphasizing the importance of balancing efficiency with quality.

Metallic components with surface microfeatures are increasingly used in aerospace, automotive and other applications due to their drag-reducing properties. In this situation, we proposed a novel shape-surface integrated incremental sheet forming (S2-ISF) process to achieve the simultaneous fabrication of both surface microfeatures and desired geometric shape. It was found that an increase in the forming angle was most effective in improving the formation of microgroove array, followed by the step size, the spindle speed and the feed rate. Moreover, when the forming angle is constant, the step size and microgroove pitch increase linearly. Compared to the as-received sheet, the yield strength is increased by more than 20% after the S2-ISF process. Moreover, we observed that the increase of forming angle in the S2-ISF process has promoted grain deformation and grain fragmentation, which is favorable for the formed part to obtain more uniform and finer grains. The grain size distribution along the thickness direction shows the characteristics of ‘coarse in the middle and fine at both ends’. Finally, we found that the formed parts with different microgroove pitch from the S2-ISF process have the significant enhancement on the hydrophobicity and anti-friction property. When microgroove pitch is 155.5 μm, the surface contact angle of formed part improved from 70.65° to 101.39°, and the wear volume of formed part decreases from 4.89 × 10−3 mm3 to 3.65 × 10−3 mm3. This work provides a solution for the efficient and economical fabrication of three-dimensional thin-walled parts with microgroove array to enhance surface functionality.

Incremental sheet forming has been largely investigated in the last two decades because of its versatility and cost-effectiveness, which make it viable for manufacturing highly customized parts as well as small- and medium-sized batches. This process allows for reaching greater formability compared to conventional sheet-forming processes. In contrast, it is affected by defects like twisting, which strongly influence the geometric accuracy of the formed parts. These aspects are dramatically accentuated when forming soft materials like thermoplastics. With these premises, the following research aims to investigate the effects of the toolpath strategy on the occurrence of failures and defects in the incremental sheet forming under very severe process conditions. Cone frusta with a fixed wall angle were obtained by thin polycarbonate sheets, imposing four unidirectional helical trajectory-based toolpaths, one traditional, and three stair strategies. The analysis of the forming forces, the evaluation of the worked surfaces, and the monitoring of the defectiveness highlight the advantages of a stair toolpath strategy in terms of reduced twisting and loading and high surface quality, regardless of the lubrication conditions. [ABSTRACT FROM AUTHOR]

While incremental sheet metal forming offers the potential for producing sheet metal parts in small lot sizes, the relatively low forming accuracy prevents widespread industrial use. For improving the forming accuracy, research institutes are using machine learning techniques to predict the geometric accuracy and modify the toolpath based on the prediction. A critical challenge is it to ensure the generalizability of the prediction model as only a small amount of process data is available to train the model due to the lack of industrial collaborations. This publication presents a highly transferable feature engineering approach where surface representations of the part's geometry around each toolpath point are transferred into a standardized coordinate system. Several artificial neural networks were trained and used for predicting the forming accuracy and modifying the toolpath. During the validation experiments, the forming errors of parts which were independent of the training process were reduced by up to 68.5 %. The framework for computing the surface representations alongside with several pre-trained artificial neural networks is publicity available for download. [ABSTRACT FROM AUTHOR]

Incremental sheet forming is a process for the production of sheet metal parts in small batch sizes. Due to the relatively low geometrical accuracy and the lack of precise and fast finite element analysis simulations of the process, industrial use cases are rare. Recently, a vast amount of scientific approaches simulated the process by utilizing machine learning techniques. Their success is limited by the quantity and quality of the used process data. Research institutes are struggling to gather enough data without industrial cooperations. For maximizing the distribution of process data in an experimental series and therefore their applicability for machine learning, the authors present a novel cluster analysis approach to systematically extend an existing database. The whole established process database consisting of 70 forming experiments and their toolpaths and digitizations is published to be used as a foundation for similar research. [ABSTRACT FROM AUTHOR]

In the context of versatile and environmentally friendly joining techniques, joining by forming has proven to be a very useful tool. From this category, hemming is widely used for sheet metal parts like car body panels. Still, hemming of concave and convex geometries represents a challenge for conventional hemming as well as for the more flexible roller hemming. Especially for smaller radii and greater flange lengths, these methods can reach their limits. In the present work, incremental sheet forming (ISF), a flexible forming process without dedicated tools and high formability, is utilized to implement the hemming process. Due to its local and incremental deformation characteristics, a favorable material flow in the flange area is expected, which might prevent cracking and wrinkling. Therefore, the material flow in ISF-hemming will be investigated. Closed circular specimens with radii of 50 mm and 200 mm and varying flange lengths are analyzed. Conclusions about the material flow are drawn by measuring the change in sheet thickness and elongation of the flange. The results show that, for stretch hemming, considerable thinning and elongation of the flange takes place and no cracking is detected. For shrink hemming, significant thickening of the flange and elongation in radial direction is observed, which suppresses wrinkling. [ABSTRACT FROM AUTHOR]

The incremental sheet metal forming process, characterized by the step-by-step deformation of sheet metal using a simple die, is classified as a type of plastic deformation technology. This method allows for the formation of complex-shaped parts even without the use of a specialized die. Its notable characteristic lies in its low forming load and high flexibility. To accurately forecast finite element simulation outcomes for the incremental sheet forming of 2024-O aluminum alloy sheets, constructing a precise constitutive model is essential. Typically, the uniform strain range in traditional unidirectional tensile tests does not surpass 0.3, primarily due to the necking phenomenon. This limitation hampers the accurate prediction of the actual large plastic deformation process. To address this issue, a theoretical model describing the stress-strain relationship in metal plastic deformation processes is developed using crystal plasticity theory. The constitutive model for the forming of 2024-O aluminum alloy is then constructed by adjusting the hardening coefficient and hardening index. Utilizing the improved constitutive model, the incremental sheet forming process is simulated using ABAQUS software. Upon comparison with experimental results, it is observed that the Thickness Average Absolute Relative Errors (TAARE) of the adjusted constitutive model at forming angles of 60°, 55°, and 50° are 0.414%, 0.467%, and 0.256%, and The Thickness Root Mean Square Errors (TRMSE) are determined as 0.0121, 0.0116, and 0.0094, respectively. These results indicate that the constitutive model and parameters established in this study can adequately capture the mechanical behavior of 2024-O aluminum alloy during the incremental sheet forming process. [ABSTRACT FROM AUTHOR]

Incremental sheet forming (ISF) uses a simple CNC milling machine to produce 3D geometries at very low cost and time using the CAD geometry of the parts. Due to the localised plastic deformation of the process, it can be used to make it easier to shape materials that are hard to shape, such as magnesium and titanium. Magnesium AZ31B alloy sheets of 1.5 mm thickness were formed at room temperature using the conventional Erichsen cupping and ISF process to quantify the maximum room temperature formability of the alloy. Using the conventional Erichsen cupping test, a maximum forming depth of 2.88 mm was obtained. ISF was performed using the helical toolpath strategy up to fracture for three different feed rates (F) (50, 1000, and 2500 mm/min), spindle speeds (S) (50, 500, and 3000 rpm), and pitch sizes (P) (0.1, 0.5, and 2.5 mm). A maximum forming depth of 8.86 mm was obtained for the process parameter condition—F50S3000P0.5 during the ISF process. It was observed that the formability of the alloy was reduced with increasing feed rate and pitch size, whereas it was enhanced while increasing the spindle speed. The starting material possessed a strong basal texture, which does not favour the activation of (10–12) tension twins during the uniaxial stretching of the conventional process. In contrary, the enormous frictional heat generated at high spindle speed (3000 RPM) and the plane strain and biaxial stretching nature of the ISF process resulted in the activation of newer twins during the ISF process, thereby improving the formability of the alloy sheets up to 8.86 mm. This shows that the ISF process is capable of forming hard-to-shape materials, like magnesium, at room temperature without compromising their excellent ambient temperature mechanical properties. It is also imperative that the ISF process can be used as a substitute to the conventional forming process and form Mg AZ31 sheets at room temperature at very low cost and lead time, thereby widening its usage in the automotive sectors. The higher formability of AZ31B sheets at room temperature imparted by the ISF process will be useful to down-gauge the input sheet metal thickness, thereby improving the fuel efficiency and reducing carbon emission in the automotive sector. [ABSTRACT FROM AUTHOR]

The effect of process parameters on geometric dimensions is complex during belt-heated incremental sheet forming, leading to control difficulties in the geometric dimension of parts. In this study, the geometric errors were analyzed under the action of different process parameters, and the corresponding influence law was obtained through macro- and microexperiments. On this basis, the micromorphology of the deformation region section was analyzed in detail, and the effect of process parameters on micromorphology characteristics was obtained during belt-heated incremental sheet forming. Meanwhile, the dislocation density of the deformation region section was analyzed through XRD, and the change law of the dislocation density was revealed under the action of different process parameters. Therefore, the macro and micro effect mechanism of process parameters on geometric dimensions was verified, and then the control method of the geometric dimension was obtained in belt-heated incremental sheet forming. [ABSTRACT FROM AUTHOR]

This research presents a new hybrid stretch forming and double-layer two-point incremental sheet forming (hybrid stretch forming and DL-TPIF). The novelty of the proposed hybrid process is first to employ double-layer blank sheets in the conventional two-point incremental sheet forming (TPIF) process, which allows the material in the flange region to flow into the deformation region for achieving more uniform thickness distribution and less thinning. The use of an upper dummy sheet prevents the forming tool from direct contact the target blank sheet to improve the surface quality. Secondly, the combination of the stretch forming and the DL-TPIF processes enables seamless integration of the two forming processes to take advantages of both processes. The proposed new hybrid process was evaluated by two case studies through experimental testing and finite element (FE) simulation. Three pre-stretching conditions were examined to evaluate the effect of the prior stretching operation. The results showed that the maximum thickness reduction of the dome shape produced by the new stretch forming and DL-TPIF process was less than one third of that obtained from the conventional TPIF process. The geometrical accuracy and surface quality were also improved by using this new hybrid forming process.

This study employs the finite element (FE) method to analyze the Incremental Sheet Forming (ISF) process of Ti-6Al-4V titanium alloy. The numerical modeling of pressure-assisted warm forming of Ti-6Al-4V sheets with combined oil-heating and friction stir rotation-assisted heating of the workpiece is presented in this article. The thermo-mechanical FE-based numerical model took into account the characteristics of the mechanical properties of the sheet along with the temperature. The experimental conditions were replicated in FEM simulations conducted in Abaqus/Explicit, which incorporated boundary conditions and evaluated various mesh sizes for enhanced accuracy and efficiency. The simulation outcomes were compared with actual experimental results to validate the FE-based model's predictive capacity. The maximum temperature of the tool measured using infrared camera was approximately 326 °C. Different mesh sizes were considered. The results of FEM modeling were experimentally validated based on axial forming force and thickness distribution measured using the ARGUS optical measuring system for non-contact acquisition of deformations. The greatest agreement between FEM results and the experimental result of the axial component of forming force was obtained for finite elements with a size of 1 mm. The maximum values of the axial component of forming force determined experimentally and numerically differ by approximately 8%. The variations of the forming force components and thickness distribution predicted by FEM are in good agreement with experimental measurements. The numerical model overestimated the wall thickness with an error of approximately 5%. By focusing on the heating techniques applied to Ti-6Al-4V titanium alloy sheet, this comparative analysis underlines the adaptability and precision of numerical analysis applied in modeling advanced manufacturing processes. [ABSTRACT FROM AUTHOR]

Incremental sheet forming (ISF) is a controlled and die-less forming process that can produce customized products from the sheets layer by layer using the same setup, i.e., forming tools and machine. This novel and emerging forming technique can potentially be useful as a green aspect of manufacturing by reducing the required power and by saving the resources for producing the components of lightweight materials because material is deformed locally during ISF. The surface quality of the formed parts from sheet material affects the aesthetics aspects, stress concentration, fatigue life and their applicability. This review article aims to provide a state-of-the-art review for various aspects and parameters of ISF process that affect the surface roughness significantly by conducting literature survey quantitatively. Furthermore, the techniques of ISF and roles of various parameters responsible for affecting the surface quality of parts have also been explored for providing the critics for existing literature and setting the further guidelines for the researchers. Various instruments used for measuring the surface roughness of parts formed by ISF has also been discussed. Comparative analysis of exiting literature available in the context of various process parameters, ISF hardware, and surface roughness makes this study comprehensive and exhaustive for the researchers to find the gaps and challenges in this field. The relationship of wall angle with other process parameters can be explored in the future to obtain the desired surface quality of a particular material. Significant parameters responsible for the surface quality have also been discussed critically. Further, the new tool paths can be developed for high surface quality and low forming time. A study on the selection of feed rate for various applications and relation with other parameter is also recommended for the future work. The lubricants with additives can further be tested for high surface quality of ISF. Further, significant study on surface roughness is not conducted on hybrid sheet forming and other advanced variants of ISF (like hot forming, friction stir assisted incremental forming, waterjet forming). It is required to develop the comparisons between the different techniques of ISF. Results also showed that majority of researchers used SPIF technique followed by DSIF and hybrid ISF.

In this work, a single point incremental forming method was applied using both a roller-ball tool and a standard forming tool with oil application. Aluminium AA1050 sheet with 0.8-mm thickness was used as the experiment material. The experiments were applied according to Taguchi L18 experimental design. Surface roughness measurements and thickness distributions were evaluated in terms of tool type, amount of the stepdown and the wall angles. ANOVA and regression analysis were also performed to show the influence of the process parameters on the surface roughness measurements. According to results, roller-ball tool with a wall angle of 40° and stepdown amount of 0.25-mm yielded the lowest surface roughness as 1.389-µm for Ra and 7.433-µm for Rz. Compared to the standard forming tool, the roller-ball tool performed better both surface roughness and thickness distribution results. However, the most effective parameter was found to be the wall angles in relation to the surface roughness. FEM analysis was made for thickness distributions with the same process conditions for each tool type. The actual measurements for thickness distribution were similar to the results obtained from FEM analysis. [ABSTRACT FROM AUTHOR]

In incremental sheet forming (ISF), the geometrical accuracy is still a challenge that is only solved for specific applications. The underlying mechanisms of geometrical defects in ISF are very complex and still not fully understood. Nevertheless, the process understanding is constantly evolving. Recent work has shown, for example, how bending moments resulting from residual stresses affect geometric accuracy. It has become clear that resulting bending moments with an axis parallel to the main tool path direction are dominant. Based on that, the current paper investigates the hypothesis that linear and parallel tool paths lead to an unfavourable accumulation of residual bending moments along a common axis, and whether this accumulation effect can be reduced by wave-shaped tool paths. Thus, the described research investigates the influence of novel path strategies on the residual bending moments and the resulting geometrical deviations. The path strategies are based on wave-shaped path lines, whereas the curvature is within the sheet plane. The investigations focussed on a rectangular sheet that is clamped at its shortest edges and a part geometry-sensitive to springback. Experimental and numerical investigations show a significantly positive influence of some investigated path strategies on the geometric deviation, compared to a conventional path strategy. [ABSTRACT FROM AUTHOR]

This article investigated the formability of aluminum/copper bimetal sheets during single-point incremental forming. First, the two-layer sheets were produced by the explosive welding process; then, the rolling process was performed with 50% strain on two-layer samples. Considering the importance of examining the mechanical and metallurgical properties on the formability of the two-layer samples, the mechanical properties were first examined, including the uniaxial tensile and micro-hardness tests. Then, metallurgical tests were performed, including scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDX) to investigate the fracture surface and penetration depth and an X-ray diffraction (XRD) test to check the secondary phase particles in the penetration zone of Al and Cu in five different annealing temperature conditions. Considering that the forming limit diagram (FLD) is dependent on the strain path, to study the effect of the strain path, the two-layer samples were formed by three geometries: pyramid, cone, and straight groove. Simulations of FLD by Abaqus software 6.14-4 with four different methods were studied: FLDCRT, effective strain rate (ESR), second derivation of thinning (SDT), and maximum strain rate (MSR). The results showed that the FLDCRT criterion provided a more accurate estimate of the necking time. In the following, the values of the thickness distribution were carried out by experimental and numerical methods, and the results between the methods were in good agreement. [ABSTRACT FROM AUTHOR]

As the influence of Incremental Sheet Forming (ISF) grows in manufacturing sectors, so does the demand for precise and updated knowledge construction in this domain. In this research, we evaluate the capability of Large Language Models (LLMs) to capture domain-specific knowledge, using ISF as a case study. Recognizing common LLMs' limitations such as potential inaccuracies and outdated information reliance, we propose a comprehensive approach involving automated and adaptive knowledge extraction, enrichment, and integration into an ISF-specific dataset. We then fine-tune the LLMs for ISF-related text classification and prompt response tasks. Our results reveal a significant enhancement in LLMs' performance within the ISF domain, with a domain knowledge acquisition rate exceeding that of GPT-3.5 by 10.4%, achieved by the fine-tuned Alpaca-33B model. Additionally, we introduce a novel conversational prototype designed to refine the accuracy and relevance of LLMs in the ISF domain. Our findings will guide future efforts in downstream tasks such as ISF-domain knowledge graph construction and quality prediction. [ABSTRACT FROM AUTHOR]

The edge warpage of a Ti-6Al-4V ripple disc is a major forming defect during electric hot incremental forming, which can lead to a significant dimensional error. In this paper, a novel manufacturing method, namely the combination of electric hot incremental forming and electrically assisted sizing, has been proposed to improve the forming defect. The effect of process parameters on forming fracture was analysed in detail, and then an optimal combination of process parameters was obtained to ensure the successful forming of a Ti-6Al-4V ripple disc. On this basis, a sizing device and a sizing current were separately designed and analysed to eliminate the warpage defect of Ti-6Al-4V ripple discs. According to the experimental result, Ti-6Al-4V ripple discs can be satisfactorily fabricated through the method proposed. [ABSTRACT FROM AUTHOR]

In incremental sheet forming, geometrical deviations occur due to deflections of the forming stylus. To compensate the deviations, a non-contact in-process tool deflection measurement is required that is capable of measuring the tool tip position with a measurement uncertainty of 15 μm in a volume of 2.0 m × 1.0 m × 0.2 m. For this purpose, an optical multi-sensor system is designed. Each sensor evaluates lateral shift and magnification of the shadow cast from the LED attached close to the tool tip, to enable measuring the lateral and axial tool tip position component, respectively. The experimental validation shows that the sensing principle is sufficiently robust regarding ambient light. As a result, despite a remaining systematic error after calibration that dominates the uncertainty, the measurement requirements are fulfilled by a single sensor regarding the lateral position component. For the axial position component, a triangulation with two sensors is necessary.

The integrated fabrication of accurate forming shapes and micro–macro properties of metal components have promoted carbon neutrality in industrial manufacturing. We found that the multi-stage incremental sheet forming (MISF) process can achieve shape–performance integrated fabrication of thin-walled parts. However, the performance-influencing mechanism of the MISF approach remains unknown, and the methods for mechanical property prediction have received little attention. Therefore, MISF strategies were investigated for a square copper part through experiments, microstructural analysis, and theoretical predictions. The parts formed with different strategies had the same shape, but their strength–ductility synergy increased with the number of stages. In addition, the MISF-produced copper demonstrated an outstanding strength–ductility trade-off, where the yield stress with the optimized strategy was improved to 231.7 MPa, an increase of over 2.6 times compared with that of the raw material, with a uniform elongation of 20.5 %. A microstructural analysis was performed to investigate the material reinforcement mechanism attributable to dislocation accumulation, which decreased with an increasing number of stages. Based on the deformation procedures and microstructure evolution, an efficient theoretical model of the MISF mechanical properties was proposed for the first time using a dislocation-based constitutive function, where the effectiveness was improved by considering the back stress. This work demonstrates the practicality of the shape–performance integrated fabrication of thin-walled parts and sheds light on the application of the MISF technique.

This investigation aims to propose a novel framework for designing and manufacturing cranial prostheses through incremental sheet metal forming (ISF). First, the three-dimensional models of the defective crania and the prosthesis were constructed from the CT data. Then, to verify the formability of the prosthesis model, a method for testing the mesh sheet's incremental forming limit (IFL) was proposed with a variable angle cone model. The angle between the normal vector of the fracture point and the Z-axis calculated the IFL. The tests showed that the method could realize the testing of the IFL of the mesh sheet with the reduction of processing time and cost. In addition, finite element modeling and experimental trials were used to evaluate the ISF process of the prosthesis, including thickness distribution and geometric accuracy. The results showed that the incremental forming can form prosthesis samples with high precision, while the thickness distribution is relatively uniform without excessive thinning. Finally, the obtained prosthesis sample was practically assembled with the cranial defect model to verify the fitting effect and feasibility of the prosthesis formed by the ISF process. [ABSTRACT FROM AUTHOR]

Incremental sheet metal forming is one of the promising sheet forming processes, in which local nature of the applied forming forces and independency of the process on the die, induces higher formability in the sheet and increases flexibility of the process in producing intricate geometries. In current study, from damage mechanics window, one of the prominent features of the process, i.e. forming limits of AA5052 sheets has been investigated. For this purpose, firstly, Bao-Wierzbicki damage model is coded and implemented into Abaqus finite element program via VUMAT subroutine. The constants of the damage model, hardening model and Hill48 yield model have been obtained utilizing the uniaxial tensile experiments in three directions of 0º, 45º and 90º with respect to rolling direction. To examine the formability, truncated cone and pyramid geometries with variable increasing wall angles have been considered and the experimental tests and simulation of the process were conducted. Using the stress and strain distribution, fracture phenomena and onset of fracture were described. The results show that the sheet metal fractures before it reaches the designed final height, so that for the geometries of truncated pyramid and truncated cone, the fracture height is obtained 19.9 mm and 16.9 mm, respectively. Considering the sheet anisotropy properties in the process simulation, the fracture height of specimens was predicted with an average accuracy of 9%, and the results reveal that with excluding the anisotropy properties of the sheets, the prediction accuracy decreases. Also, an acceptable agreement was obtained in predicting the fracture location. [ABSTRACT FROM AUTHOR]

A three-finite element model to simulate the single point incremental forming (SPIF) of AA3003-H12 parts is developed. Tool motion in the simulation environment and the CNC milling machine is controlled using new protocols developed especially for SPIF process of pyramidal parts. Numerical measured part thickness and geometry are found to best agree with the experimental ones. Due to the lack of tools, enabling a proper selection of numerical factors to overcome computation convergence problems and product conformity error, trial and error method is applied alternately and proves to be effective. Thickness distribution, equivalent stress distribution, finite element size and friction coefficient effect on the final thickness distribution, geometric profile and computation time are studied. In order to understand the failure and fracture mechanisms in the produced part, the stress state, thickness and equivalent stress history at the thinned finite element are equally studied. Results show a critical thinning occurs at the part corners more dramatic than in the walls. Equivalent stress presents great values first at the part corners and second at the fillets. Failure areas do not coincide with fracture ones due to different deformation mechanics. The increase of the finite element size increases the thickness and the geometry error, but reduces significantly the computation time. The friction coefficient does not significantly affect the thickness and geometry, leading to a significant computation time reduction. [ABSTRACT FROM AUTHOR]

Incremental sheet forming (ISF) is a promising die-less metal forming process where a rotating tool applies incremental pressure on the sheet to be deformed. However, a lack of available knowledge about the effect of process parameters on the produced part hinders the process from being widely used in the industry. One aspect to be considered is the effect of process parameters on the mechanical properties of the final product. For instance, hardness is a mechanical property that indicates the resistance of a material to elastoplastic deformation. This work investigates the effects of tool rotational speed, vertical step down, and feed rate on the hardness of high carbon steel (AISI 1075) sheet. A full-factorial experimental design for the three process parameters establishes a set of 27 experiments for a cone-forming process. Micro-hardness of the material is found to increase considerably from 185 to 252 HV due to strain hardening during the ISF process. Tool rotational speed and feed rate parameters have an insignificant effect on the hardness (p values of 0.829 and 0.538, respectively). Vertical step down of the tool is identified as the most influential parameter on hardness, with a p value of 0.001. [ABSTRACT FROM AUTHOR]

As incrementally formed sheets show large geometric deviations resulting from the deflection of the forming tool, an in-process measurement of the tool tip position is required. In order to cover a measuring volume of 2.0 m × 1.0 m × 0.2 m and to achieve measuring uncertainties of less than 50 µm, a multi-sensor system based on triangulation is realized. Each shadow imaging sensor in the multi-sensor system evaluates the direction vector to an LED attached to the tool, and the three-dimensional position of the LED is then determined from the combination of two sensors. Experimental results show that the angle of view from the sensor to the LED limits both the measurement range and the measurement uncertainty. The measurement uncertainty is dominated by systematic deviations, but these can be compensated, so that the measurement uncertainty required for measuring the tool tip position in the ISF is achieved. [ABSTRACT FROM AUTHOR]

The temperature of a forming region has a gradient distribution characteristic in the belt heating incremental sheet forming process, in which the relation between the heating power and the temperature distribution is ambiguous in the pre-heating stage. The setup of the heating power is therefore challenging, and the whole forming efficiency might decrease due to the above issue. Therefore, this paper proposes a belt heating method for electric conduction heating and presents a temperature calculation model for the forming region of the plate in the preheating state based on the heat conduction model. The calculated accuracy of the model is analysed through physical experiments, and the thermal transfer efficiency of heating tubes is analysed in detail. Based on the result, the thermal transfer efficiency value for heating tubes is determined to improve the accuracy of the suggested model. In addition, the effect of the model slope on the calculated result is further analysed, and the setting method of the slope value for the model is proposed according to different accuracy requirements. [ABSTRACT FROM AUTHOR]

Within the rapidly growing market for fiber-reinforced plastics (FRPs), conventional production processes involving molds are not cost-efficient for prototype and small series production. Therefore, new flexible forming techniques are increasingly being researched, many of which have been inspired by incremental sheet metal forming (ISF). Due to the different deformation mechanisms of woven reinforcement fibers and metal sheets, ISF is not directly applicable to FRP. Instead, shear and bending of the fibers need to be realized. Therefore, a new dieless forming process for the production of FRP supported by metal wire mesh as an auxiliary material is proposed. Two standard tools, such as hemispherical punches, are used to locally bend a reversible layup of metal wire mesh and woven reinforcement fiber fabric enclosed in a vacuum bag. Therefore, the mesh aids in introducing shear into the material due to its ability to transmit compressive in-plane forces, and it ensures that the otherwise flexible fabric maintains the intended deformation until the part is cured or solidified. Basic experiments are conducted using thermoset prepreg, woven commingled yarn fabric, and thermoplastic organo sheets, proving the feasibility of the approach. [ABSTRACT FROM AUTHOR]

This study employs the finite element (FE) method to analyze the Incremental Sheet Forming (ISF) process of Ti-6Al-4V titanium alloy. The numerical modeling of pressure-assisted warm forming of Ti-6Al-4V sheets with combined oil-heating and friction stir rotation-assisted heating of the workpiece is presented in this article. The thermo-mechanical FE-based numerical model took into account the characteristics of the mechanical properties of the sheet along with the temperature. The experimental conditions were replicated in FEM simulations conducted in Abaqus/Explicit, which incorporated boundary conditions and evaluated various mesh sizes for enhanced accuracy and efficiency. The simulation outcomes were compared with actual experimental results to validate the FE-based model’s predictive capacity. The maximum temperature of the tool measured using infrared camera was approximately 326 °C. Different mesh sizes were considered. The results of FEM modeling were experimentally validated based on axial forming force and thickness distribution measured using the ARGUS optical measuring system for non-contact acquisition of deformations. The greatest agreement between FEM results and the experimental result of the axial component of forming force was obtained for finite elements with a size of 1 mm. The maximum values of the axial component of forming force determined experimentally and numerically differ by approximately 8%. The variations of the forming force components and thickness distribution predicted by FEM are in good agreement with experimental measurements. The numerical model overestimated the wall thickness with an error of approximately 5%. By focusing on the heating techniques applied to Ti-6Al-4V titanium alloy sheet, this comparative analysis underlines the adaptability and precision of numerical analysis applied in modeling advanced manufacturing processes.

In the single point incremental hole flanging (SPIHF) process, a sheet material with pre-cut holes is deformed using the SPIF technique to generate a flange, making it an effective approach for low volume manufacturing and quick prototyping. In the case of the SPIHF technique, the post-forming hardness property, the forming limit diagram (FLD), and spring-back phenomena are not completely evaluated. To this end, this paper employs experimental investigation and numerical validation to analyse the impact of SPIHF process parameters like tool diameter, feed rate, spindle speed, and initial hole diameter on these aspects for the truncated incrementally formed components made from AA1060 aluminium alloy and DC01 carbon steel. The plasticity behaviour of both sheet metals was simulated using the Workbench LS-DYNA model and ANSYS software version 18. Additionally, Cowper Symonds power-law hardening was added to the model to account for material properties. The average post-hardness of AA1060 and DC01 was evaluated using an SPIHF prediction model based on the performance of an artificial neural network (ANN). This ANN model was developed using a feed-forward back-propagation network trained using the Levenberg-Marquardt approach. The ANNs 4-n-1 were created by varying the transfer functions and the number of hidden neurons. Greater spindle speed and bigger pre-cut holes were shown to significantly increase the post-formed hardness of the truncated components, whereas the converse was seen when using a higher feed rate and a larger tool diameter. In addition, the FLD and spring-back improved dramatically with larger hole diameters. Employing correlation coefficient (R) and mean square error (MSE) as validation measures, it was shown that the established ANN models accurately predicted the SPIHF process response. Both the DC01 and AA1060 neural network models with a 4-8-1 network architecture performed very well, with MSE and R values of 0.0000105 and 1 for DC01 and 0.02613 and 0.99982 for AA1061.

The geometrical accuracy of incrementally formed products is the key focus in the incremental sheet forming (ISF) process. Pillow defect hinders the material's formability, which limits geometrical accuracy. Therefore, considering the pillow defect as the major objective, the present study is aimed to evaluate the benefits of adding vacuum to the conventional ISF process for limiting the pillow effect. This work also studies the impact of forming parameters like tool diameter and vertical step increments on pillowing. Using the digital image correlation (DIC) technique, the material characteristics of AA5052 Al alloy were determined from a room-temperature tensile test. The vacuum-assisted ISF (VISF) experiments were then conducted, and the shape error was computed using the 3D scan data to check the part's geometrical accuracy. The test results revealed that the forming tool diameter is the most important parameter, followed by the vertical step increment, affecting pillowing; with a small forming tool diameter, vacuum presence greatly reduced material pillowing. Besides, the vacuum uniformly deforms materials and controls shear deformation by balancing local element strain accumulation; however, when the tool diameter increased, the produced parts had no shear deformation. The numerical results showed that pillow formation largely relied on stress values from the forming tool motion and transverse directions and that the pillow height was lowered when the stress values were decreased in magnitude; however, there was no change in direction with a vacuum. In conclusion, the meaningful outcomes from the VISF process confirm the benefits of using vacuum to control pillowing. [ABSTRACT FROM AUTHOR]

This study aims to determine optimal forming parameters for Incremental Sheet Forming process Commercially Pure titanium Grade 2 sheets in terms of formability improvement, force reduction, and efficiency of forming. Based on the central composite design, data were collected during 20 runs and then variation analysis was performed. The experiments were performed on a 3 axis CNC milling machine equipped with a Kistler dynamometer plate. Subsequently, regression models have been developed to describe process responses by input factors. As crucial parameters, the relative velocity and step size of the tool that affect the forming force and the height of the fracture have been determined. Finally, the application of optimization algorithm has emerged optimal input factors in terms of selected multi-criteria goal. The results of this study suggest that there is a process window that allows the formation of 45° wall angle drawpieces of commercially pure titanium Grade 2.

This paper presents the results of experimental research on the fabrication of thin-walled panels with longitudinal stiffening ribs by the single point incremental sheet forming technique. The bead-stiffened panels were made of Alclad 2024-T3 aluminium alloy sheets commonly used in aircraft structures. The influence of forming parameters and tool strategy on surface quality and the possibility of obtaining stiffening ribs with the required profile and depth was tested through experimental research. Two tool path strategies, spiral with continuous sinking and multi-step z-level contouring, were considered. The results of the experiments were used to verify the finite element-based numerical simulations of the incremental forming process. It was found that the main parameter which influences the formability of test sheets is the tool path strategy; the tool path strategy with multi-step z-level contouring allowed the rib to be formed to a depth of 3.53 mm without risk of cracking. However a greater depth of rib equal of 5.56 mm was achieved with the continuous tool path. The tool path strategy was also the main parameter influencing the surface finish of the drawpiece during the single point incremental forming process.

A methodology is presented to implement robotic actuators into diaphragm forming of composite laminates. This Hybrid Vacuum-Robotic (HyVR) process is specifically targeted to prevent 'bridging' type defects. Examples are presented of successfully forming laminates with deep concave features that would otherwise be impossible by diaphragm forming. The robotically controlled end effectors apply localised pressure to concave regions during the diaphragm forming process. This force application is analogous to the incremental sheet forming process. A generalised methodology is presented which can be applied to develop a bespoke HyVR process for a specific mould. It can then inform what type of end effector should be used and how to apply it within the HyVR process. A key development included in this methodology is the use of the robot to 'pin' the laminate to the mould, preventing any unwanted movement. This process could enable automated production of more complex components using diaphragm forming, taking advantage of its lower tooling and equipment costs. [ABSTRACT FROM AUTHOR]

Die-less single point incremental forming (SPIF) is a highly versatile process that can form sheet metal blanks into desired geometries. A significant drawback of this process is the poor geometric accuracy largely attributed to material spring-back. This paper presents the use of Convolutional Neural Networks-Forming Prediction (CNN-FP) to predict this error, allowing users to better understand the expected distribution of geometric error prior to actual forming. The reported work differs from other published approaches in that a CNN was used as an automatic and flexible method for quantifying local geometries. The CNN-FP model was trained using a set of SPIF geometries with varying wall angles and corner radii. The performance of the trained model was validated using two SPIF geometries: one consisting of untrained wall angles and the other combining various features to create a complex geometry. The CNN-FP model achieved an RMSE (Root mean squared error) of 0.381 mm at 50 mm depth for the untrained wall angle. For the untrained complex geometry, the CNN-FP performance was found to be 0.391 mm at 30 mm depth. However, a significant deterioration was observed at 50 mm depth of the complex geometry, where the model's prediction had an RMSE of 0.903 mm. While the model was shown to be efficacious in most of the validation tests, limitations in the breadth of training samples was attributed to the model's degraded performance in some instances. [ABSTRACT FROM AUTHOR]