Hemispherical Tool Research Articles

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.

Asymmetry in microstructure and mechanical properties of FSWed joints using a hemispherical tool tilted towards the retreating side

This study explores a novel technique using a hemispherical tool tilted towards the retreating side for friction stir welding AA6061-T6. Mechanical properties assessment proved the competitiveness of the new method over friction stir welding using a conventional tool with backwards tilting. The ultimate tensile strength, yield strength and elongation at break reach efficiencies of 60, 40 and 85% compared to BM. The new tool shape and the tilt towards the retreating side accentuate asymmetry in the stirred zone. Grain morphology and dislocations vary within the stirred zone when comparing the center and the sides due to different degrees of dynamic recovery and dynamic recrystallization. Dislocation density is increased at the center due to the complex stirring along an extended circular trajectory. The artificial aging at 180 °C for 18 h positively affects the joint strength while reducing the elongation at the break due to an inhomogeneous response of the softening zone to the aging. The highest hardness recovery within the stirred zone occurs at the center due to the higher concentration of strengthening precipitates which nucleate around dislocations. The weakest point of the weld identified in the stirred zone at the advancing side after artificial aging modifies the fracture behavior of the sample from a ductile to a rather ductile–brittle rupture.

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.

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.

Extremely thin intermetallic layer in dissimilar AA6061-T6 and mild steel friction stir lap welding using a hemispherical tool

The dissimilar friction stir lap welding of AA6061-T6 and mild steel using the hemispherical tool tilted towards the retreating side is investigated. Critical defects such as hook features and internal voids are avoided by limiting the plunge depth in the lower plate to a tenth of a millimeter. The low heat generation guaranteed by the hemispherical tool produces a nanoscale intermetallic compound layer alternatively composed of an Al-rich and a ternary Al–Fe–Mg phases. The complex and extremely thin interlayers strengthen the Al–Fe mechanical bonding, guaranteeing high mechanical properties and rupture within the Al-stirred zone. Thermomechanical phenomena governing friction stir lap welding with the hemispherical tool drastically limit the growth of intermetallics, leading to the high mechanical strength of the lap joint.

Modeling and Experimental Investigation of the Impact of the Hemispherical Tool on Heat Generation and Tensile Properties of Dissimilar Friction Stir Welded AA5083 and AA7075 Al Alloys.

This study investigated the effect of a hemispherical friction stir welding (FSW) tool on the heat generation and mechanical properties of dissimilar butt welded AA5083 and AA7075 alloys. FSW was performed on the dissimilar aluminum alloys AA5083-H111 and AA7075-T6 using welding speeds of 25, 50, and 75 mm/min. The tool rotation rate was kept constant at 500 rpm. An analytical model was developed to calculate heat generation and temperature distribution during the FSW process utilizing a hemispherical tool. The experimental results were compared to the calculated data. The latter confirms the accuracy of the analytical model, demonstrating a high degree of agreement. Sound FSW dissimilar joints were achieved at welding speeds of 50 and 25 mm/min. Meanwhile, joints created at a welding speed of 75 mm/min exhibited a tunnel-like defect, which can be attributed to the minimal heat generated at this particular welding speed. At a lower welding speed of 25 mm/min, a higher tensile strength of the dissimilar FSWed joints AA5083 and AA7075 was achieved with a joint efficiency of over 97%.

Robust Surface Recognition With the Maximum Mean Discrepancy: Degrading Haptic-Auditory Signals Through Bandwidth and Noise.

Sliding a tool across a surface generates rich sensations that can be analyzed to recognize what is being touched. However, the optimal configuration for capturing these signals is yet unclear. To bridge this gap, we consider haptic-auditory data as a human explores surfaces with different steel tools, including accelerations of the tool and finger, force and torque applied to the surface, and contact sounds. Our classification pipeline uses the maximum mean discrepancy (MMD) to quantify differences in data distributions in a high-dimensional space for inference. With recordings from three hemispherical tool diameters and ten diverse surfaces, we conducted two degradation studies by decreasing sensing bandwidth and increasing added noise. We evaluate the haptic-auditory recognition performance achieved with the MMD to compare newly gathered data to each surface in our known library. The results indicate that acceleration signals alone have great potential for high-accuracy surface recognition and are robust against noise contamination. The optimal accelerometer bandwidth exceeds 1000 Hz, suggesting that useful vibrotactile information extends beyond human perception range. Finally, smaller tool tips generate contact vibrations with better noise robustness. The provided sensing guidelines may enable superhuman performance in portable surface recognition, which could benefit quality control, material documentation, and robotics.

Feasibility of friction stir welding using a hemispherical tool tilted towards the retreating side

The use of a hemispherical tool tilted towards the retreating side for friction stir welding 6061-T6 aluminum alloy is investigated. Joints with smooth surfaces and without internal voids are obtained. Under the same welding and rotational speeds, adapting the tilt angle makes it possible to weld various thicknesses up to 3.5 mm. Plunge depth and tilt angle are demonstrated to be key geometrical parameters driving material flow when using the hemispherical tool. Microstructural features in the weld are equiaxed and refined grains below 5 µm in the stirred zone and narrow thermo-mechanical affected zones. The through-thickness thermomechanical gradient developing beneath the hemispherical tool leads to different extents of dynamic recrystallization and recovery in the stirred zone. The tool orientation towards the retreating side and the division of the tool-workpiece interaction in continuous and intermittent contact leads to an asymmetrical thermal field around the stirred zone. Hence, the new derivative friction stir welding solution allows the welding of multiple aluminum alloy blank thicknesses using the same tool.

Experimental investigations on Inconel 625 using single point incremental forming

Single point incremental forming (SPIF), which can form sheets without any prior setup is an ideal option for prototype and batch production. Geometrical accuracy is a major challenge in the formation of Inconel 625 super alloys. Parameters such as spindle speed, feed rate, step size and wall angle were considered to assess the influence of the forming factors on the geometric accuracy of the Inconel 625 super alloys. The investigation was performed on 100 × 100 mm flat sheets with a thickness of 1 mm. Sheet metal with the desired shape was designed and developed using computer aided design (CAD) software. A circular shape was manufactured via incremental forming using a hemispherical tool with a 5.8 mm radius. A tool path was generated using Fusion 360 software to perform SPIF on Inconel 625 super alloys by varying the parameters. When experimental and simulation data were examined, significant agreements were found.Thickness thinning of sheets were most affected by wall angle. Multi-stage solutions will improve the formation limits.

Fabrication and Analysis of Denture Plate Using Single Point Incremental Sheet Forming

Incremental sheet forming (ISF) is a metal forming technology in which small incremental deformations determine the final shape. The sheet is deformed by a hemispherical tool that follows the required shape contour to deform the sheet into the desired geometry. In this study, single point incremental sheet forming (SPIF) has been implemented in dentistry to manufacture a denture plate using two types of stainless steel, 304 and 316L, with an initial thickness of 0.5mm and 0.8mm, respectively. Stainless steel was selected due to its biocompatibility and reasonable cost. A three-dimensional (3D) analysis procedure was conducted to evaluate the manufactured part's geometrical accuracy and thickness distribution. The obtained results confirm the capability of SPIF to produce thin-walled biomedical components with satisfactory dimensional accuracy, as geometrical deviations between the developed and the actual models are predominantly in the range of ±0.25mm.

Mechanical behaviour for aeronautical structures with embedded electric cables under low energy impact

The work focuses on the mechanical strength of composite structures with embedded electrical functionalities submitted to low energy impact. This material is defined for aeronautical applications as multilayers of glass fibre composite with flat electrical cable layers embedded. The main question is about the damage involved by the low energy impact, and its influence on the electrical cables layer performances. The impact leads to failure with no external signs of damage and insulation degradation. The dynamic experimental campaigns are carried out on drop tower tests with hemispherical tool. localized damage mechanisms at conductor interfaces are observed and a finite element model is performed. A link between impact energies and loss of electrical performance of multifunctional samples is established.

Processing Strategies for Dieless Forming of Fiber-Reinforced Plastic Composites

The demand for lightweight materials, such as fiber-reinforced plastics (FRP), is constantly growing. However, current FRP production mostly relies on expensive molds representing the final part geometry, which is not economical for prototyping or highly individualized products, such as in the medical or sporting goods sector. Therefore, inspired by incremental sheet metal forming, we conduct a systematic functional analysis on new processing methods for shaping woven FRP without the use of molds. Considering different material combinations, such as dry fabric with thermoset resin, thermoset prepreg, thermoplastic commingled yarn weave and organo sheets, we propose potential technical implementations of novel dieless forming techniques, making use of simple robot-guided standard tools, such as hemispherical tool tips or rollers. Feasibility of selected approaches is investigated in basic practical experiments with handheld tools. Results show that the main challenge of dieless local forming, the conservation of already formed shapes while allowing drapability of remaining areas, is best fulfilled by local impregnation, consolidation and solidification of commingled yarn fabric, as well as concurrent forming of prepreg and metal wire mesh support material. Further research is proposed to improve part quality.

Investigation of Surface Roughness in Novel Magnetorheological Finishing of the Internal Hemispherical-Shaped Acetabular Cup Workpieces

Abstract In today’s world, the hemispherical-shaped component’s fine finishing with high wear resistance and dimensional accuracy is required in different applications such as shells, molds, and implants. The magnetorheological finishing (MRF) method using a novel hemispherical tip-based tool is used to finish the hemispherical cups. The study aims to develop a novel theoretical mathematical model to predict the surface roughness reduction of the hemispherical cups using the present MRF process. Because the magnetic field regulates forces in the MRF process, the effect of the magnetic flux density (MFD) in the fine finishing of the hemispherical acetabular cup workpiece has been examined theoretically and experimentally. The mathematical model for reducing surface roughness is next tested experimentally on a hemispherical acetabular cup workpiece surface. The results of the predicted roughness match well with the experimental values with the error ranging from 1.17% to 6.15%. Further, surface morphology, microhardness, and dimensional accuracy tests are done on the workpiece using scanning electron microscopy, a microhardness tester, and coordinate measuring equipment to evaluate the efficacy of the present process. The present mathematical model for the MRF process predicts fine finishing along with the overall enhancement in the surface quality of the hemispherical acetabular cup surface.

볼 타입 공구를 사용한 판재 점진 성형 공정의 성형 특성 분석

The incremental sheet forming (ISF) process is a method of forming a metal sheet with a machine tool, such as a CNC or robot arm. In this study, the surface characteristics of the ISF process using the ball type tool and the conventional hemispherical tool were analyzed. Comparative experiments were conducted with the same size of the hemispherical tool and ball type tool. In experiments, the tool feed rate and spindle were fixed, and the step down was set up with seven levels. The surface profiles and roughness such as R<SUB>a</SUB> and R<SUB>z</SUB> after the ISF process with different values of the step down were compared. Additionally, the surface morphologies were analyzed through the scanning electron microscope. A ball type tool which can move and roll, can reduce the effect of friction effectively. As a result, the ISF process with a ball type tool can greatly reduce the damage of the surface of the product.

Automatic generation of 3d spiral tool path for incremental sheet metal forming of mechanical parts with complex geometry

Incremental sheet metal forming is a flexible manufacturing technology that allows to form of various components on the same milling machine, without expensive tools. A hemispherical tool moves along a CNC-controlled tool path and deforms the sheet into the desired shape. The tool path has a significant role in the geometric accuracy of the final part. There has been very little research on the problem of the forming of sophisticated parts with asymmetric wall angles. This paper presents a new approach to generating optimized tool paths for single-point incremental sheet forming (SPIF). At first, a strategy is proposed for the automatic generation of a 3D tool path during forming in a single-step operation. Then, a systematic technique of creating intermediate shapes is investigated by defining tool paths interpolated from the final part shape. The proposed methodology is applied to form a hip cup prosthesis. This part has a complex asymmetric geometry with important angles, a multi-step approach is used. The proposed methodology to define the different tool paths was implemented in Matlab. A numerical simulation of the incremental forming process is performed to predict the final geometry of the aluminum sheet. A comparison of desired and predicted geometries shows the reliability of the proposed method.

Multipass double-sided incremental forming method for improving geometric accuracy and forming quality

Double-sided incremental forming (DSIF) has been extensively researched due to its high flexibility, good formability, and low cost when performed in small batches, and it enables the production of personalized sheet parts. However, the influences of process parameters on the geometric accuracy, thickness distribution, and forming quality are not well understood. In this paper, a multipass DSIF method is proposed. Based on the law of sines, the distance between the closest surface of the hemispherical forming tool and the supporting hemispherical tool is given, and a series of experiments are conducted. The influences of process parameters such as the toolpath strategy, incremental depth, and squeeze factor on the quality metrics in multipass DSIF, such as the geometric error, thickness distribution, and forming quality are investigated and compared to those formed by DSIF, accumulative double-sided incremental forming, and mixed double-sided incremental forming. The results show that multipass DSIF can effectively improve the geometric accuracy, thickness distribution, and surface quality. The thinning of the material increases slightly with the squeeze factor of the first D-pass decreases, and the different incremental depths have little effect on the thickness distribution. The multipass DSIF method provides some significant engineering advancements for improving geometric accuracy and forming quality.

Accuracy and Sheet Thinning Improvement of Deep Titanium Alloy Part with Warm Incremental Sheet-Forming Process

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.

Tube Expansion by Single Point Incremental Forming: An Experimental and Numerical Investigation

In this paper, we revisit the formability of tube expansion by single point incremental forming to account for the material strain hardening and the non-proportional loading paths that were not taken into consideration in a previously published analytical model of the process built upon a rigid perfectly plastic material. The objective is to provide a new insight on the reason why the critical strains at failure of tube expansion by single point incremental forming are far superior to those of conventional tube expansion by rigid tapered conical punches. For this purpose, we replaced the stress triaxiality ratio that is responsible for the accumulation of damage and cracking by tension in monotonic, proportional loading paths, by integral forms of the stress triaxiality ratio that are more adequate for the non-proportional paths resulting from the loading and unloading cycles of incremental tube expansion. Experimental and numerical simulation results plotted in the effective strain vs. stress triaxiality space confirm the validity of the new damage accumulation approach for handling the non-proportional loading paths that oscillate cyclically from shearing to biaxial stretching, as the single point hemispherical tool approaches, contacts and moves away from a specific location of the incrementally expanded tube surface.

Analysis of deformation behavior in various incremental tube forming processes

ABSTRACT Incremental Tube Forming (ITF) is a comparatively new forming process in which the ends of a tube are expanded into the desired shape using a hemispherical tool. ITF process finds its applications in various sectors like automotive, aerospace, and heavy industries for interconnection of the piping system, structural elements, etc. It is crucial to analyze the tube’s deformation behavior for its successful forming and good accuracy of the formed part. The current work investigates the tube’s deformation behavior during the grooving and tube end forming in single and multistage strategies. Both the experimental and simulations are performed to analyze the strain distribution, thickness variation, and formability of the AA6063 tube. The experimental and simulated strain distribution reveals that the bottom end of the tube where forming started is in the plane strain state and the free end of the tube is uni-axial tension. The thickness variation and reduction percentages for experimental and simulations are in agreement with each other. An error of less than 2% was found for thickness variation at all the considered wall angles. Finally, the microstructural analysis performed using electron back scattered diffraction (EBSD) technique has revealed the changes in grain size, local misorientations and grain aspect ratio formed at various wall angles.

Effect of inclination and rotation of the sheet on sheet thinning and formability in robot assisted incremental sheet metal forming

Single point incremental forming (SPIF) has higher formability than other sheet metal forming processes. In SPIF, the existing computer numeric control (CNC) incremental forming which adopts 3-axis CNC milling machine to form the part incrementally by using a hemispherical tool has the limitation of forming steeper wall angle parts. An additional 2-degree of freedom (DOF) manipulator has been proposed to integrate with the existing 3-axis CNC milling machine to improve the formability of the sheet. In this method, to control the material flow and deformation state, the posture of the sheet has been changed by tilting the sheet along the needed direction and rotating at specific speed with respect to the vertical forming tool. Formability of the sheet has been investigated in terms of sheet thinning and strain distribution after deformation. Numerical simulation has been implemented initially and has been validated by conducting the experiments. The result of the research shows that formability can be improved by adding the 2-DOF manipulator to the existing system.