Single Point Incremental Forming Research Articles

Innovative High Degree of Freedom Single-Multipoint Incremental Forming System for Manufacturing Curved Thin-Walled Components

This study proposed a new design and control framework for a novel high degree of freedom single-multipoint incremental forming (HDoF-SMIF) system to manufacture curved thin-walled components. First, a novel HDoF-SMIF system was designed based on the principles of HDoF-SMIF technology (including the description of the mechanical structure and network topology). Following that, to realize the process control of the HDoF-SMIF process, this study introduced a novel control strategy for the tool deflection angle specific to robotic incremental forming. It also developed a synergistic motion control approach for the lifting platform and an accelerated computation method to determine the forming parameters for a multipoint reconfigurable die. Then, a novel HDoF-SMIF principle prototype and control program were built for the designed HDoF-SMIF system structure and control method. Finally, the feasibility of the HDoF-SMIF system was verified with the forming test on the domed component, and the geometrical accuracy and wall thickness distribution of the samples were measured using a 3D optical scanner system to evaluate the forming quality of the established HDoF-SMIF system. The results showed that compared to the conventional single-point incremental forming (SPIF) process, the developed HDoF-SMIF system can provide a more uniform thickness distribution of the formed part with a lower overall thickness thinning rate. Furthermore, by increasing the tool deflection angle with a 1mm elastomeric interpolator, the overall part's forming accuracy and surface quality can be effectively improved.

Innovative tool designs to improve formability in case of single point incremental forming

Single point incremental forming (SPIF) is one of the dieless sheet metal forming processes that offer flexibility in the customized fabrication of required parts. Improvement in formability in the case of SPIF has been one of the burning issues in the metal-forming fraternity in the past decades. In the present study, different tool tip geometries, namely hemispherical, elliptical, en-grooved, and triangular tool tips, were employed in the SPIF of 0.8 mm thick CRCA (cold rolled close annealed) steel, and the influence on the forming height was assessed in reference to the commonly used hemispherical tool tip. It was observed that tool geometry has a significant influence on forming height obtained with SPIF, and a maximum of 27% increase in forming height was observed with the en-grooved tool tip with a considerable reduction in the forming force required.

Optimizing the SPIF parameters for enhancing microhardness and surface quality in Inconel 625 superalloy components

Inconel 625, a high-strength superalloy with excellent corrosion resistance, discovers wide applications in critical sectors such as aerospace, nuclear, marine, and petrochemical. Single-Point Incremental Forming (SPIF) has appeared as an adequate fabricating process for shaping superalloy components. This work used a systematic approach, implementing Response Surface Methodology (RSM) to explore the influence of SPIF process variables, including tool nose diameter, step size, tool spindle speed, and wall angle, on microhardness (MH) and surface roughness (SR). The experimental results have been analyzed to determine the influencing process variables and their optimal settings, which simultaneously enhance MH and reduce SR of Inconel 625 superalloy truncated cones using analysis of variance and the desirability function analysis approach. The most significant parameters that influence MH and SR were TND and SS, respectively. The development of quadratic models for MH and SR has been completed successfully. The maximum MH of 486.8 HV and minimum SR of 0.432 µm have been obtained at the optimal parametric setting of TND = 15 mm, SS = 0.4 mm, TSS = 900 rpm, and WA = 57.5° with the desirability values for MH, SR and combined are 0.832, 0.933, 0.881 respectively. The F-value of the MH model = 109.18 and SR Model = 78.24 implies that both models are significant and both models have excellent prediction strength. The percentage error between predicted and actual values of MH and SR in confirmation run results is less than 5 %.

Fabrication of a prototype of bumper beam by single point incremental forming of laser welded tailored blank and characterization of its quasi-static crushing performance

Fabrication of a prototype of bumper beam by single point incremental forming of laser welded tailored blank and characterization of its quasi-static crushing performance

Feasibility Study of Single-Point Incremental Forming for Discontinuous-Fiber CFRP Using Oil-Bath Heating

Although, three-dimensional printing has several advantages, however there are currently many limitations. In particular, printed products using composite materials such as fiber-reinforced plastic have yet to achieve the same mechanical properties as those obtained from conventional manufacturing methods. In addition, fabricating thin plates or thin shell shapes with sufficient strength is challenging. Incremental forming enables high-mix, low-volume production of thin sheets. This method applies incremental deformation to thin sheets, the desired shape is obtained by accumulating the deformation, and no dies are required. Carbon-fiber-reinforced plastic (CFRP) materials have high specific strength. Discontinuous-fiber CFRP is capable of large plastic deformation under appropriate conditions due to the discontinuity of the reinforcement, and its mechanical properties are nearly isotropic due to the random fiber arrangement. The authors focused on this property and studied the application of single-point incremental forming to discontinuous carbon-fiber-reinforced polyamides. In this study, the workpiece was formed by heating it locally to a deformable temperature by the frictional heat between the rotating tool and the workpiece. The forming experiment was also conducted in an oil bath to keep the entire material at a suitable forming temperature. The results showed that the spindle speed affected forming results even in an oil bath and that heating using an oil bath suppressed deviations from the sine law for thickness and wall angle due to elastic deformation.

Springback prediction using point series and deep learning

One of the main challenges that prevent wide adoption of Single Point Incremental Forming (SPIF) is the geometric accuracy of the process resulting primarily from the effect of springback. There are various expedients that can be adopted to address this, but one of the most common is tool path correction. The challenge is then how best to predict springback so as to implement tool path correction. It is established that springback, to a large extent, is related to the geometry of the part to be manufactured. The proposed mechanism uses a novel point series representation to capture local geometries that then form a global bank of geometries for general use. Each point series can then be associated with a predicted springback value generated using deep or machine learning. Experiments are reported using a Long Short Term Memory (LSTM) model coupled with a Multilayer Perception Network (MLP), and a Support Vector Machine (SVM) regression model. A best R2, “Coefficient of Determination”, of 0.9181 was obtained indicating that the proposed approach provided a realistic solution to the current limitations of SPIF.

Experimental Investigation of Load-Bearing Capacity in EN AW-2024-T3 Aluminum Alloy Sheets Strengthened by SPIF-Fabricated Stiffening Rib.

The aluminum strength-to-weight ratio has become a highly significant factor in industrial applications. Placing stiffening ribs along the surface can significantly improve the panel's resistance to bending and compression in aluminum alloys. This study used single-point incremental forming (SPIF) to fabricate stiffening ribs for 1 mm and 3 mm thick aluminum alloy EN AW-2024-T3 sheets. A universal compression machine was used to investigate sheet deformation. The resulting deformation was examined using non-contact digital image correlation (DIC) based on several high-resolution cameras. The results showed that deformation progressively escalated from the edges toward the center, and the highest buckling values were confined within the non-strengthened area. Specimens with a larger thickness (3 mm) showed better effectiveness against buckling and bending for each applied load: 8 kN or 10 kN. Additionally, the displacement from the sheet surface decreased by 60% for sheets 3 mm thick and by half for sheets 1 mm thick, which indicated that thicker sheets could resist deformation better.

In vivo validation of highly customized cranial Ti-6AL-4V ELI prostheses fabricated through incremental forming and superplastic forming: an ovine model study

Cranial reconstructions are essential for restoring both function and aesthetics in patients with craniofacial deformities or traumatic injuries. Titanium prostheses have gained popularity due to their biocompatibility, strength, and corrosion resistance. The use of Superplastic Forming (SPF) and Single Point Incremental Forming (SPIF) techniques to create titanium prostheses, specifically designed for cranial reconstructions was investigated in an ovine model through microtomographic and histomorphometric analyses. The results obtained from the explanted specimens revealed significant variations in bone volume, trabecular thickness, spacing, and number across different regions of interest (VOIs or ROIs). Those regions next to the center of the cranial defect exhibited the most immature bone, characterized by higher porosity, decreased trabecular thickness, and wider trabecular spacing. Dynamic histomorphometry demonstrated differences in the mineralizing surface to bone surface ratio (MS/BS) and mineral apposition rate (MAR) depending on the timing of fluorochrome administration. A layer of connective tissue separated the prosthesis and the bone tissue. Overall, the study provided validation for the use of cranial prostheses made using SPF and SPIF techniques, offering insights into the processes of bone formation and remodeling in the implanted ovine model.

Numerical analysis of stress & strain and thickness variation in single point incremental forming of tailor welded steel blanks

Numerical analysis of stress & strain and thickness variation in single point incremental forming of tailor welded steel blanks

Experimental analysis of forming forces in incremental forming and its prediction by AI-based methods

Single point incremental forming (SPIF) is an emerging approach to manufacture the user-specific parts of greater strength economically without involving dedicated tools and dies. In this study, peak deforming loads have been measured and estimated in order to determine the size and capacity of forming machinery for manufacturing components, using the SPIF process, for designed process conditions on AA7075-O sheets. Estimation of maximum deforming loads has been accomplished with the help of hybrid artificial neural network (HANN) approach by taking experimental load values as the input dataset. The load values, estimated by HANN approach, have been compared with the load values estimated by two state-of-art regression approaches, that is, Support Vector Machine (SVM) and Gaussian Process Regression (GPR). Results show that the regression methods (SVM and GPR) are outperformed by the HANN model with an accuracy of 99.80%. HANN model estimated force values very close to experimental results. The forming forces were found to be greater when the flat-end tools were used as a forming agent in place of hemispherical-end tool. The proposed study would help the researchers and scientists to assess the capacity the machines used in SPIF process to prepare a particular sheet-part and to prevent the failure of hardware during the SPIF process.

Maximum Thinning Rate Prediction of Friction Heat Single-Point Incremental Forming for AZ31B Magnesium Alloy Based on BP Neural Network

The purpose of this project is to build an accurate prediction model for the maximum thinning rate of the truncated cone made of magnesium alloy AZ31B by single-point incremental forming. A truncated cone’s thickness distribution is analyzed using ABAQUS. Orthogonal experiments and supplementary data were performed as training samples within the maximum refinement rate obtained from the finite element (FE) results. Back-propagation (BP) neural network is established by taking into account tool diameter, initial sheet thickness, and forming angle as input responses, and maximum thinning rate as output responses, and nine hidden layers are involved. The results showed that the incidence of process parameters on the maximum thinning rate of the truncated cone is in the order of forming angle, initial thickness of sheet, and diameter of tool from large to small; The correlation coefficient of BP neural network model training [Formula: see text]. The test results and FE results contrast, and the average error rate of the maximum thinning rate is only 0.97%. The results indicate that the model is reliable and accurate for the prediction of incremental forming, and it is a useful reference value.

Characteristics of 2D Ultrasonic Vibration Incremental Forming of a 1060 Aluminum Alloy Sheet.

Currently, 1060 aluminum alloy is widely applied in the electronics industry, construction, the aerospace field, traffic engineering, decorations, and the consumer goods market for its good chemical, physical, and mechanical properties. In general, excellent processing property is necessary and important for the manufacturing of complicated panels. In this paper, a special 2D ultrasonic vibration incremental forming method is designed to improve its plasticity and mechanical properties. Three kind of processing methods, including traditional single-point incremental forming, longitudinal ultrasonic vibration incremental forming, and 2D ultrasonic vibration incremental forming, are used for the flexible manufacturing of cones and cylindrical cups of 1060 aluminum alloy sheet. Then, micro-hardness tests, residual stress tests, and scanning electron microscopy tests are carried out to probe the changes in micro-structure and mechanical properties and to analyze the effects of different types of ultrasonic vibration on the plasticity and fracture characteristic of 1060 aluminum alloy. It is proven that 2D ultrasonic vibration facilitates the improvement of plasticity and surface qualities of 1060 aluminum alloy better than the other two processing methods. Therefore, the novel 2D ultrasonic vibration incremental forming process possesses substantial application value for the flexible and rapid manufacturing of complicated thin-walled component of aluminum alloy.

Explicating tensile response of AA6061-T6 sheet post single point incremental forming: Two camera-DIC strain measurement and texture analysis

Incremental sheet forming (ISF) produces 3D components imposing localized deformation by spherical-ended tool moving on a predefined path without requiring component-specific die/punch. The formability achieved in ISF is much higher than the conventional sheet forming processes; however, the deformation imposed during ISF alters the mechanical properties of the component. The present work investigates the tensile behavior and strain localization during the uniaxial tensile test of the AA6061-T6 component after single point incremental forming (SPIF). The influence of incremental depth (Δz) and tool diameter (dt) on the tensile response and strain localization is illustrated by a digital image correlation setup with two cameras. The tensile strength of SPIF components increases with Δz and mildly decreases with dt. The changes in scallop heights/undulations formed due to tool movement at higher Δz and dt influence the localized strain accumulation. Regions of localized strain are more when Δz is high, but strain accumulation is more even with an increase in dt. Texture analysis showed increased dislocation density due to the strain hardening after SPIF. The presence of brass {011}<211>, copper {112}<111>, and S {123}<634> texture indicates the plane-strain deformation in the wall region of the component formed by SPIF.

Comparison of Vibration Assisted Single Point and Two-Point Incremental Forming of Sheet Metal

Vibration-assisted single-point incremental forming (VASPIF) and two-point incremental forming(TPIF) are two innovative techniques employed in sheet metal forming processes, each offering distinct advantages and limitations. VASPIF utilizes high-frequency oscillations applied to the forming tool to reduce friction and improve material flow, resulting in enhanced formability and surface finish. Conversely, TPIF employs two independently controlled forming tools to deform the sheet metal incrementally, allowing for greater geometric complexity and improved accuracy compared to VASPIF. However, TPIF typically requires more complex tooling and setup, potentially increasing manufacturing costs and setup time. Both techniques have shown promise in improving the formability of sheet metal components while offering unique capabilities suited to specific manufacturing requirements. Vibration-assisted single-point incremental forming (VASPIF) and two-point incremental forming (TPIF) are two advanced methods used in sheet metal forming, each with its unique characteristics, advantages, and limitations. In this comprehensive comparison, we will delve into the fundamental principles, process parameters, applications, advantages, and challenges associated with both techniques. Starting with VASPIF, this innovative approach involves applying high-frequency oscillations to the forming tool during the incremental forming process. These vibrations serve to reduce friction between the tool and the work piece, facilitating material flow and enhancing formability. By effectively decreasing the frictional forces, VASPIF enables the deformation of difficult-to-form materials and improves the surface finish of the formed parts.

Predictive and experimental analysis of forces in die-less forming using artificial intelligence techniques

The use of a novel technology for producing the components of lightweight materials and to reduce the requirements of power utilized during manufacturing processes can be a great aspect to decrease pollution and save resources. Single point incremental forming (SPIF) is the viable and novel approach for manufacturing the parts of high strength and lightweight materials without involving dedicated tools and dies economically. This die-less forming technique outperforms the conventional forming techniques by saving the energy and materials. In this work, the estimation and investigation of forming forces have been accomplished to ensure the secure uses for the SPIF machines for performing this process for the designed conditions on AA2024 sheets which is a lightweight aluminum alloy being widely used in aerospace and automotive sectors. To predict the peak deforming load, machine learning (ML) techniques are employed in the current work along with the artificial neural network (ANN) by taking experimental results as the input dataset. The proposed ML model revealed better accuracy (99%) than previous work performed using similar approaches. The proposed ANN model produced lower mean absolute percentage error 4.35 as compared to other models. Authors also calculated the computing time taken during estimation of forming force. Combination of the Flatend-R1 tool and the 1.6 mm blank thickness increased the deforming loads drastically and can become the limiting factor for forming machine which should be avoided whereas the combination of hemispherical tool and lower blank thickness (0.5 mm) reduced the deforming loads that are needed to manufacture the conical frustum. It was also noticed that as the tool shape was changed from hemispherical-end to Flatend-R1, the axial peak forces were increased by 13.16%, 16.59%, 20.43%, and 22.78% for the levels 1, 2, 3, and 4 of the blank thickness, respectively.

Experimental and Numerical Investigation of Forming Limit Diagrams during Single Point Incremental Forming for Al/Cu Bimetallic Sheets

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.

Development of a Compact Incremental Forming Machine

Since the beginning of the 21st century, incremental sheet-metal-forming processes, such as single-point incremental forming (SPIF), have been the subject of extensive research. The SPIF process is highlighted as an efficient and cost-effective solution for producing complex parts with different materials and scales, surpassing conventional methods and being ideal for small series and customized products. Various machines can be used to implement SPIF, such as adapted milling machines, serial robots, and dedicated machines, each with its own advantages. However, although it requires a higher initial investment, a dedicated machine offers superior performance. The objective of this project was the creation of a compact and portable dedicated machine, which included the design of suitable kinematics, a mechanical project, and numerical control. The structural design led to the optimization of the dimensions of the robot arms. Direct and indirect kinematics were analyzed. Finally, the careful selection and adaptation of components were carried out, bearing in mind the support system of the forming punch, including the selection and sizing of motors, reducers, and linear actuators. A functional early prototype was successfully built and tested.

SPIF of micro-FSWed dissimilar AlMgSi alloy: formability analysis

ABSTRACT Tailor-welded blanks (TWB) facilitate strategic material placement, ensuring desired materials are positioned appropriately, while single-point incremental forming (SPIF) enables versatile shape manufacturing with minimal tooling. Despite both methods offering customization benefits, their combined potential remains largely unexplored. This study utilized friction stir welding to create one-millimeter-thick similar and tailor-welded blanks from AA6061 and AA6003. The weld quality was ensured through metallurgical analysis and mechanical testing. SPIF of welded blanks exhibited formability comparable to parent materials, free from weld-line movement or fractures in the weld zone during forming. However, TWBs demonstrated formability between their constituting parent materials. Fractures occurred in almost all blanks due to bi-axial stretching in the corner of the D-shape. Investigation into the effect of tool size and geometry revealed that too small tool diameters induced localized deformation, contributing to failure. While flat-bottomed tools exhibited higher material thinning than hemispherical tools.

A Hybrid Optimization Approach of Single Point Incremental Sheet Forming of AISI 316L Stainless Steel Using Grey Relation Analysis Coupled with Principal Component Analysiss

A Hybrid Optimization Approach of Single Point Incremental Sheet Forming of AISI 316L Stainless Steel Using Grey Relation Analysis Coupled with Principal Component Analysiss

Study of single point incremental forming limits of Al 1050/Mg-AZ31B two-layer sheets fabricated by roll bonding technique: Finite element simulation and experiment

In this work, for the first time, the two-layer Aluminum (Al 1050) and magnesium (AZ31B) sheet were used in the single point incremental forming (SPIF) process. Due to the high strength-to-weight ratio of the Al 1050/Mg-AZ31B sample, today it is used in significant industries such as automotive and aerospace. The finite element simulation process was carried out using the Abaqus Software considering five approaches to determine forming limits. These approaches were forming limit diagram criterion (FLDcrt), effective strain rate (ESR), second derivation of thinning (SDT), Major strain rate (MSR) and Thickness strain rate (TSR) methods. The results showed that the failure prediction in the FLDcrt method was more accurate than other methods. The thickness distribution process was carried out both by simulation and experiment to validate the simulation results. The results show a good agreement between simulation and experimental results. Finally, the results obtained from the SPIF process were compared with the FLD results of the conventional hemispherical punch test, and it was observed that the FLD was higher in the SPIF process. Moreover, the layer arrangement, which affects formability, was investigated. The results showed that the FLD with Mg-AZ31B/Al 1050 arrangement fails in higher strains compared to Al 1050/Mg-AZ31B. After validating the simulation results, the parameter effect of the step-down and tool diameter on the two-layer formability was investigated by the design of experiment. Considering the greater importance of the step-down and tool diameter effect on the created stresses and forming time compared to other parameters, their effect will be investigated. The results showed an optimal condition for the tool diameter, but an opposite relationship with formability was obtained for the step-down.