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The friction-spinning process is an innovative incremental forming technique that enables high degree forming operations in the field of tube and sheet metal forming. The integration of friction-sub-processes from friction welding in a metal spinning process permits selfinduced heat generation of the part. Compared with conventional spinning processes, this in-process heat treatment allows the extension of existing forming limits and the production of more complex geometries from tubes and sheets. Additionally, the material/part properties like hardness, stress, grain structure/orientation, surface conditions etc. can be adjusted in a defined way during the forming process. This can be achieved using appropriate process parameter settings in combination with the degree of deformation. The choice of feed rate, relative motion and friction coefficient gives rise to a defined temperature profile and allows the use of specific process control strategies to produce parts with different material properties in different areas. Thus, the production of a new class of individually adjustable components is enabled. For example, these parts could be designed for load-optimized applications like complex hollow parts in aluminium or steel. This paper presents the results of the grain structure investigations and clarifies the influence of different process parameters in aluminium tube processing, especially during flange forming operations. A flange will thus be formed from an aluminium tube and, by using an additional tool system, its wall thickness can be adjusted in a defined manner. The paper addresses the influence of the significant process parameters (feed rate, rotation speed, temperature, wall thickness reduction and forming time) on grain structure refinement during flange forming. In addition, the impact of the material properties (hardness, stress/strain behaviour) is considered. [ABSTRACT FROM AUTHOR]

Recently, various methods for the metal spinning of noncircular shapes have been proposed to overcome the limitation of its application range. In this study, a metal spinning method for noncircular shapes with oblique bottoms is proposed. This method is a combination of synchronous spinning and multipass spinning, in which the roller is synchronized with the mandrel rotation to track a noncircular cross section while the workpiece is gradually deformed without much thinning through some paths of the roller. The roller trajectory is calculated by linear interpolation in the radial direction and axial direction between the inclined blank shape and the inclined cross section of the product. A circular cup and square cup with an oblique bottom and vertical side walls are successfully spun using this method. As the wall thickness locally increases at the side edges of the square cup, the thickness distribution is equalized by using an intermediate circular shape. This method interpolates the roller trajectory between the blank shape and intermediate shape and between the intermediate shape and the product. The difference in the wall thickness is reduced since the square shape is formed via a cylindrical shape. In addition, the effect of the process parameters on the forming results is experimentally investigated. [ABSTRACT FROM AUTHOR]

This study is an investigation into the effect of the different parameters of the pass set on the formability in synchronous multipass spinning. Synchronous multipass spinning is a metal spinning method that can produce a noncircular cylindrical shape with a noncircular bottom and vertical walls from a metal sheet. The radial position of the roller tool is synchronized with the spindle rotation while the work piece is formed from a flat disk into the shape of the mandrel step by step along varying trajectories. The tool trajectory is calculated by linear interpolation between the mandrel shape and the blank disk shape along a pass set. Here, a pass is the tool trajectory in the normalized two-dimensional space defined by the radial and axial directions of the mandrel. The aim of this study is to examine the effect of different parameters of the pass set on the formability of two sample shapes, a circular cup and a rectangular box. The formability was experimentally examined using a rotational pass set and a translational pass set as simple tool trajectories. The rotational pass set consists of curved passes with the same start point and a constantly increasing angle inclination. The translational pass set consists of passes with the same inclination and a start point that is moved by a constant amount. The angle of growth of the rotational pass set, the incremental movement of the translational pass set, and the nominal product height are varied for comparison in the experiments. [ABSTRACT FROM AUTHOR]

Abstract: The main objective of this paper is to study the influence of longitudinal ultrasonic vibrations on the tube spinning process. A robust experimental tube spinning system was designed and manufactured, in which the preform and mandrel can be excited by ultrasonic vibrations. Tube spinning experiments under ultrasonic vibrations were carried out on annealed AA-6061 preforms. A modal analysis was used to study the vibrational behavior of the system. The forming forces acting on the non-vibrating roller were measured in radial, axial, and tangential directions. Experimental results showed that low power longitudinal ultrasonic vibrations can improve the inner surface quality of annealed 6061 aluminum samples. In addition, high power ultrasonic vibrations can affect forming forces and material escape. Analysis of forming forces variations under ultrasonic vibration revealed that these changes are mostly because of contact effects of ultrasonic vibrations. [Copyright &y& Elsevier]

Abstract: A flexible method of forming circumferentially variant wall thickness distributions on the same shape is attempted using two oblique sheet spinning processes. The fundamental strategy entails the inclination of the flange plane of the workpiece during forming. In one type of synchronous dieless spinning, edge-hemmed aluminum blanks are formed for truncated cone shells, by synchronizing the motion of the spherical head roller in the axial and radial directions with the angle of the general purpose mandrel fixed on a bidirectionally rotating spindle. On the other hand, in the other type of force-controlled shear spinning, flat aluminum discs are formed by feeding perpendicularly to the flange plane of the workpiece and maintaining the thrust force along the plane via the roller tool, exerted onto the rotating truncated-cone-shaped die. The estimated wall-thickness distribution based on a simple shear deformation model nearly conformed to the measured thickness distributions of the products formed at several inclination angles of up to 15 degrees in the forming and both spinning methods. The low-cost value-added forming method seems to be practicable not only for metal spinning but also for other incremental sheet forming processes. [Copyright &y& Elsevier]

Abstract: Sheet metal spinning has seen significant developments in recent years. However, in the present industrial practice, the process design still highly relies on undocumented expertise; trial-and-error approach is commonly used to design the roller path and passes. In this paper, four different roller path profiles, i.e. combined concave and convex, convex, linear, and concave, have been designed and used to carry out spinning experiments and to conduct finite element (FE) analysis. The effects of these roller paths on tool forces, part wall thickness and stress variations in conventional metal spinning have been analysed numerically. The results show that the concave path produces highest tool forces among these four roller path profiles. Using the concave roller path tends to cause higher reductions of wall thickness of the spun part and using the convex roller path helps to maintain the original wall thickness unchanged. A greater curvature of the concave path would result in more thinning in wall thickness of the spun part. [Copyright &y& Elsevier]

Abstract: Asymmetric conventional metal spinning was performed in this study to break through the limitation of ordinary axisymmetric spinning. A synchronous spinning machine was developed for this purpose; in this case, the mandrel motion, mandrel feed, and roller feed were synchronized by pulse control. Trial spinning experiments were carried out on a 1-mm-thick aluminum sheet to obtain an asymmetric truncated-elliptical-cone-shaped product. The roller path was traced using a control software by taking into account the errors caused by the step pulse control. Asymmetric sheet metal forming was successfully carried out by using the developed synchronous spinning method. The characteristics of asymmetric spinning were discussed by comparing the shape of the product, strain distributions, and force components with those obtained in the case of axisymmetric spinning. [Copyright &y& Elsevier]

Abstract: Flow forming, as a kind of metal spinning processes, is mainly used to produce thin-walled high-precision tubular components. In this study a coupled set of experiments and numerical simulations using the commercial finite element code ABAQUS/Explicit was used to study the evolution of redundant strains in a single-roller flow forming process in one pass. The modified embedded pins were used to evaluate the shear strains. It is shown that high shear strains occur not only at the longitudinal but also at the cross section. Sketched longitudinal lines also show that ɛ θz of the cylindrical coordinate system cannot be neglected. Beside of the shear strains, reversal straining is recognized as another type of redundant work. It is shown that this type of redundant strain results from the incremental nature of flow forming process in which the deformation is highly localized. Good agreements between the force measurements of frictionless model simulations with the experiment imply that the frictional work can be neglected in comparison to the redundant work. [Copyright &y& Elsevier]

Abstract: This review presents a thorough survey of academic work on the analysis and application of the mechanics of spinning. It surveys most literature published in English and the most important publications in German and Japanese languages. The review aims to provide insight into the mechanics of the process and act as a guide for researchers working on both metal spinning and other modern flexible forming processes. The review of existing work has revealed several gaps in current knowledge of spinning mechanics: the evolution of the stress state and the strain history of the workpiece in both conventional and shear spinning is not well understood, mainly due to the very long solution times that would occur in modelling the process throughout its duration with a sufficiently fine mesh to capture detailed behaviour through the workpiece thickness; the evolution of microstructure, residual stress and hence springback, has not been examined—either numerically or by experiment; the failure mechanisms of spinning – fracture and wrinkling – are only partially understood, through analogy with other processes, and as yet models of the process have not made use of contemporary damage mechanics; the design of toolpaths required to make particular parts without failure remains an art, and cannot currently be performed automatically with confidence. Studies on novel process configurations in spinning have shown that great potential for innovation in spinning exists. The process has the potential to be more flexible, to produce a wider range of shapes, and to form more challenging materials. [Copyright &y& Elsevier]

Abstract: The correlations of microstructure and texture with deformation history in backward tube spinning were studied. Deformation history was calculated with initial and some intermediate configurations as reference configuration from FEM analysis. Microstructure and texture were investigated in the experimental workpiece of Ti–6Al–2Zr–1Mo–1V. The results show an obvious through-thickness inhomogeneity in deformation, microstructure and texture. Large material rotation occurs and plenty of grains are kinked and distorted in the outer layer, especially when thick-wall billet is spun. Deformation difference diminishes with wall thickness decreasing. The inhomogeneity of as-spun microstructure is reduced obviously in multi-pass and large deformation (for example, 85% total reduction) tube spinning. {0002} texture develops generally without orthotropic symmetry. Textures in the outer and inner layers evolve differently because of inhomogeneous deformation histories. [Copyright &y& Elsevier]

Abstract: Continuous mullite ceramic fibers were fabricated by a sol–gel dry spinning process and sintered at 1100°C to examine the influence of the solid content and process parameters on solidification and structure evolution. The spinning sol was prepared from an aqueous solution of aluminum nitrate (AN), aluminum isopropoxide (AIP) and tetraethylorthosilicate (TEOS). By adjusting the temperature, the gelling degree could stabilize at a certain value and the sol–gel transition can be transferred to the spinning line. The samples were investigated by thermal gravity analysis/differential scanning calorimetry (TG/DSC), scanning electron microscopy (SEM), X-ray diffraction (XRD) and nuclear magnetic resonance (NMR). The results show that only sintering of the precursor fibers from sols with solid content above 50% at 1100°C yields crack-free mullite ceramic fibers. The ceramic fibers were good handling and had smooth surfaces. The XRD and NMR analysis indicated that sintering of the precursor fibers at 1100°C yields complete crystal, which is a tetragonal metric-like mullite. [Copyright &y& Elsevier]

Abstract: A hot shear spinning process of cast aluminium alloy parts was developed to eliminate casting defects and to obtain a desired distribution of wall thickness. The forming load of the shear spinning is comparatively low even for large deformation requisite for eliminating the casting defects. Dendrites and shrinkage cavities in the cast aluminium alloys were successfully eliminated without occurrence of a fracture by the hot shear spinning. Surface cracks around the corner of the mandrel caused by large shear deformation were reduced by decreasing the feed rate of the roller and by increasing the tip radius of the roller. It was found that hot shear spinning is effective in improving the mechanical properties of cast aluminium alloys parts. [Copyright &y& Elsevier]

Abstract: As a successively and locally plastic deformation process, backward ball spinning is applied in order to manufacture thin-walled tubular part with longitudinal inner ribs. Based on the experiments and rigid-plastic finite element method (FEM), the influence of the ball size on deformability of thin-walled tubular part with longitudinal inner ribs during the backward ball spinning is investigated in the present study. The size of ball plays a significant role in backward ball spinning of thin-walled tubular part with longitudinal inner ribs. The size of the ball not only is a critical factor in determining the magnitude of the spinning force, but also has a great influence on the surface finish of the spun part, the steady flow of the metal material as well as the formability of the inner ribs. The results have shown that increasing the size of the balls contributes to the formability of the inner ribs as well as the steady flow of the metal material on the surface of the spun part, but too large ball size leads to poor dimensional accuracy and inferior surface quality of the spun part. [Copyright &y& Elsevier]

Abstract: The distribution of equivalent plastic strain through the thickness of several AISI 1020 steel plates formed under different conditions over a smooth cylindrical mandrel using a single-roller forward flow forming operation was studied by measuring the local micro-indentation hardness of the deformed material. The equivalent plastic strain was higher at the inner and outer surfaces and lowest at the center of the workpiece. Empirical expressions are presented which describe the contribution of the roller and mandrel to the total local equivalent plastic strain within the flow formed part. The dependence of these expressions upon the thickness reduction during flow forming is discussed. [Copyright &y& Elsevier]

Spinning technology is widely applied in the production of the axisymmetric industrial parts. The application of spinning technology in tube forming is increasing recently corresponding to the increased usage of the tubular parts. In this study, an experiment of paraxial spinning on one end of circular aluminum tube is performed with the parameters of diametral reduction and spinning pitch. The experimental results show that the thickness strain, the spinning force, the twisting angle and the surface roughness increase as the tube diameter reduces and the spinning pitch increases. The axial strain increases as the tube diameter reduces and the spinning pitch decreases. The diametral accuracy becomes better as tube diameter reduces and the spinning pitch decreases. The forming characteristics of paraxial spinning on one tube end are made clarified in this study. [Copyright &y& Elsevier]

Spinning is a very effective and flexible manufacturing technology for short production runs in a variety of sizes and shapes. Spinning is widely applied in the tube forming corresponding to the increased usage of the tubular parts. Authors have built a prototype computer numerically controlled spinning machine which uses the numerical control technology to spin a tube instead of dies in order to improve the tube processing. The indented feed of a roller tool is one of the important spinning conditions. The effects on the spinning force, spinning accuracy and thickness strain are experimentally examined in this study as a function of indented feed of the roller tool on parallel spinning of a circular aluminum tube. The spun tube properties are also made clarified. Results show that with the increment of indented feed of roller tool, the wall-thickness strain and the axial strain becomes steady, the spinning force increases, the diameter accuracy becomes worse, and the surface hardness as well as surface roughness increase. [Copyright &y& Elsevier]

This paper reports the results of modelling of the spinning of thin sheet aluminium with the MSC MARC finite element (FE) package and its domain decomposition facility using Patent MPI software. The use of networked computers, both single and dual processor machines, is compared. The network used consists of over twenty computers and a 3COM switch with a nominal capacity of 100 Mbit/s. The effect of reduced network capacity is noted. The effect of increasing the number of computers involved is investigated in terms of resulting solution times. The results show the potential for large reductions in solution times. The impact of the background support of a network solution on the conventional computer user is examined.Partitioning of the model into ‘super-elements’ or separate domains is reviewed. Various partitions of the meshed geometry are compared, giving some indication of where pitfalls may lie in this critical aspect of multi-domain FE models.The results of the modelling are compared with experimental measurements of a conventional spinning operation using a CNC lathe. A flat disk is formed by a spinning operation into a dished shape. The material used is commercially pure aluminium. [Copyright &y& Elsevier]

Spinning sheet metal parts successfully requires the design of a complex toolpath to avoid workpiece failure. Notwithstanding decades of research, industrial CNC spinning of new parts today still relies on trial and error, which results in considerable time waste and does not guarantee optimisation of the toolpath. Yet, hand spinning artisans in non-industrial settings can successfully spin new parts first time thanks to the skill accumulated in years of practice. So this paper asks: is there a way to capture and parameterise human skill to drive research into automation? What rules do hand spinners follow? A haptic spinning system is implemented to capture and parameterise the skill of six spinning artisans. Their speech and actions are recorded in a set of over 70 experimental trials and a database of toolpaths is created including information on the trajectory of the roller, applied forces and shape of the workpiece, alongside their speech. The database is analysed, and seven principles for toolpath design are formulated: 1. Take small bites, 2. Stay on the mandrel, 3. Use forward and backward passes, 4. Push in the right place, 5. Go at the right speed, 6. Keep the flange at the right angle, 7. Use a draft. Quantitative toolpath parameters are developed to parameterise the first six principles: the average plastic strain in each toolpass, the fraction of workpiece shape on the mandrel, the fraction of backward passes, the position of the force peak, the feed ratio and the concavity of the toolpass. In trials on thinner and larger blanks than previously investigated in the literature, these parameters appear to be a good predictor of success. This suggests that displacement control alone is not sufficient to automate toolpath design, and that new parameters relating to force and shape control must be employed. [ABSTRACT FROM AUTHOR]

Flange wrinkling is one of the most common defects affecting the forming quality of workpieces in conventional spinning. To this end, the flange wrinkling mechanism is analyzed and a new robust theoretical prediction model for the flange wrinkling is developed in this work. It is found that the initiation of flange wrinkling is closely related to the excessive circumferential compressive stress in the zone affected by the roller action rather than the whole flange. Then, a theoretical model for the critical circumferential stress producing flange wrinkling is developed based on the generalized variational principle of limit analysis. By comparing the instant maximum circumferential stress in the zone affected by the roller action with the calculated critical stress, the flange wrinkling can be predicted. Compared with the prediction model based on energy method, the main improvements of the new model can be summarized as follows. First of all, the incremental displacement amplitude of deflection mode in the effective compressive region, which dramatically affects the critical stress but overlooked in the model based on energy method, is considered in the new model. Secondly, the sheet blank is regarded as a rigid plastic material in the new model, so the calculation of elastoplastic matrix which is very sensitive to the mechanical states does not need to be considered, thereby avoiding the adverse effect of the extraction deviation of mechanical states on prediction accuracy. Thus, compared with the prediction model based on energy method, the new model has higher prediction accuracy and better robustness under the extraction deviation of mechanical states. In addition to realizing the prediction of flange wrinkling, the new model can also be used to analyze the influence of sheet blank geometric parameters and material parameters on the initiation of flange wrinkling under various forming conditions. In view of this, the new model is applied to reveal the influence of material parameters (material strengthening coefficient K , hardening index n and elastic modulus E) on the initiation of flange wrinkling by combining response surface methodology and central composite design (CCD). The results show that K has the greatest influence on the initiation of flange wrinkling, followed by E and n. Considering the interaction between the parameters, the interaction between K and E also has a greater effect on the initiation of flange wrinkling. The smaller E and larger K are helpful to reduce the risk of flange wrinkling. Changing the value of n has no significant effect on delaying the occurrence of flange wrinkling. The results can deepen the understanding on the prediction and rules of flange wrinkling in conventional spinning. [ABSTRACT FROM AUTHOR]

In spinning process of large thin-walled aluminum alloy parts, the wrinkling phenomenon easily tends to appear on the blank flange. By applying a constraint condition to the flange, such as a backup roller, the flange stiffness can be increased, and the wrinkling tendency is delayed. In order to understand the deformation mechanics under the flange-constrained conditions, the effects of two kind of flange-constrained methods on the spinnability of an aluminum alloy hemispherical part are studied in this paper, and the effects of the flange-constrained conditions and process parameters on the wrinkling initiation at the flange are analyzed. At the same time, multi-pass flange-constrained spinning processes are completed. The spinnability test results show that the forming defect of the single-side flange-constrained(SSFC) spinning is wrinkling, and that of the double-side flange-constrained (DSFC) spinning is cracking; the two flange-constrained methods can both increase the spinnability of the hemispherical spun part. And the analysis of process parameter shows that with the increase of the feed rate and the operating angle, and with the decrease of the roller nose radius, the flange wrinkling initiation in the SSFC spinning occurs in advance. Besides, in the multi-pass forming of the hemispherical part, compared with the conventional spinning, the two flange-constrained spinning processes can not only make forming passes fewer, but also improve the wall thickness uniformity. [ABSTRACT FROM AUTHOR]

Metal spinning is an incremental forming technique commonly employed in the production of hollow axisymmetric components. In recent years, asymmetric spinning processes have been developed to expand the range of component geometries achievable by the technique. However, most of these processes have employed a solid mandrel to set the target shape and provide internal support to the workpiece, thus requiring new tooling to be manufactured for every new part. Moreover, no studies have been performed on the link between the geometry of the target part and the achievable forming height. In this paper, the range of curvature in the target part's planform is used to quantify its degree of asymmetry, and the influence of this parameter on the formability of spun parts is investigated in a series of experimental trials. The hypothesis that the range of planform curvature predicts the likelihood of workpiece failure is tested. Methods to design the multi-pass toolpaths and the blanks required to spin both axisymmetric and asymmetric components without a mandrel are developed. The results show that increasing the degree of asymmetry of the target part only weakly influences the achievable forming height. This finding points to the potential of the technique to produce multiple geometries flexibly and to reduce the costs of prototyping and testing new sheet metal parts considerably. [ABSTRACT FROM AUTHOR]