Manufacturing Of Sheet Metal Parts Research Articles

Sequence planning of sheet metal parts manufactured using progressive dies

Progressive dies are widely used for the mass manufacture of sheet metal parts requiring several stamping operations. Sequencing these stamping operations is vital as it influences the design of the die, especially the number of stations required to make the part. This paper presents a method for automatically generating the sequence plan for parts manufactured using progressive dies. This method establishes a scheme that maps sheet metal features into their corresponding stamping operations, including shearing, bending and forming. The mapped operations are initially placed in one of two categories and then the operations in one category are clubbed together using heuristic rules. The essential characteristics of each group are analysed to establish fuzzy relationships between any selected group and the remaining groups. The final membership value vector obtained from the fuzzy set theory is used to sequence these groups. A program developed in C++ based on this method has been tested on representative industrial sheet metal parts. The methodology is validated by comparing the generated sequences, for two case studies, with those used in industry.

Setting Residual Stresses in Tensile Stress-Superposed Incremental Sheet Forming

Incremental sheet metal sheet forming (ISF) is a flexible forming process to manufacture sheet metal parts. ISF processes allow a control of residual stresses depending on the process parameters and the acting forming mechanisms. These forming-induced residual stresses highly influence the product properties. This paper presents numerical and experimental results demonstrating the influence of biaxial tensile stress-superposed incremental forming (TSSIF) on the residual stress of truncated cones. An adjustable clamping frame is used to apply defined tensile stresses over the sheet plane in biaxial direction during forming. Residual stresses are evaluated by means of x-ray diffraction on both sides of the cone wall. Tensile stress-superposition shifts the residual stress amplitudes to the tensile residual stress region, depending on the amount of initial tensile stress. TSSIF can be used to improve the product properties of compressive stress-imposed components.

Investigation of Cutting and Ironing Performance of DC04 EN10130 Experimentally and Numerically

Precision cutting is a method used for the manufacture of sheet metal parts with narrow dimensional tolerances and where the cutting surface quality is desired to be much superior compared to conventional cutting methods. Sheet material properties and the design of the cutting die, ironing clearance and machining parameters are important factors in precision cutting of metals. In this study, the precision cutting and ironing process for the crank felt made of DC04 EN10130 cold rolled steel quality sheet metal with high impact resistance and strength, which is used in the production of automotive spare parts, was investigated by the finite element method. In the study, the simulation results with a cutting gap of 1, 3, 6 percent and a spinning ratio of 0.5, 7.5%, among the mold geometries designed for the target geometry, and the experimental results were in good agreement with each other.

A Generalized Stress State and Temperature Dependent Damage Indicator Framework for Ductile Failure Prediction in Heat-Assisted Forming Operations.

Heat-assisted forming processes are becoming increasingly important in the manufacturing of sheet metal parts for body-in-white applications. However, the non-isothermal nature of these processes leads to challenges in evaluating the forming limits, since established methods such as Forming Limit Curves (FLCs) only allow the assessment of critical forming strains for steady temperatures. For this reason, a temperature-dependent extension of the well-established GISSMO (Generalized Incremental Stress State Dependent Damage Model) fracture indicator framework is developed by the authors to predict forming failures under non-isothermal conditions. In this paper, a general approach to combine several isothermal FLCs within the temperature-extended GISSMO model into a temperature-dependent forming limit surface is investigated. The general capabilities of the model are tested in a coupled thermo-mechanical FEA using the example of warm forming of an AA5182-O sheet metal cross-die cup. The obtained results are then compared with state of the art of evaluation methods. By taking the strain and temperature path into account, GISSMO predicts greater drawing depths by up to than established methods. In this way the forming and so the lightweight potential of sheet metal parts can by fully exploited. Moreover, the risk and locus of failure can be evaluated directly on the part geometry by a contour plot. An additional advantage of the GISSMO model is the applicability for low triaxialities as well as the possibility to predict the materials behavior beyond necking up to ductile fracture.

Modeling of the springback in folding using the experimental design method

Bending is one of the most frequently used processes in the sheet metal products industry. The major users are mainly the automotive, aeronautics and electrical engineering industries. It is necessarily a cold forming operation of a flat material, with or without lubricant, obtained notably by exceeding its elastic limit. After retraction of the tools and relaxation of the stresses, a springback consequently occurs and a permanent deformation persists causing certain geometric modifications of the product. As a matter of fact, this phenomenon, will absolutely affect the angle and curvature of the bend, for such reason it must be taken into consideration in order to manufacture sheet metal parts bent within acceptable tolerance limits. However, the value of this springback is influenced by a multiplicity of process parameters, such as the thickness of the sheet, the hold time of the bending operation, the material properties and last but not least the depth of strike of the tool. In this paper, we have developed a model for predicting springback in the air V-bending process using the design of experiments method. Four three-level factors were considered in order to model springback in using the response surface method (RSM). The experimental tests were carefully carried out on a HACO press brake and on aluminum, ordinary steel and stainless steel specimens with different thicknesses. The in-depth study of the response surfaces to the different tests with the method of analysis of variance (ANOVA), allowed us to determine a robust empirical model linking the springback to the variables of the study. In addition, several relevant numerical simulations using the finite element method (FEM) with software (Abaqus) were performed to predict the evolution of springback when varying the parameters in the field of design of experiments. In fact, the comparison of the values predicted by the two approaches shows a satisfactory agreement.

Analysis of Proximity Consequences of Coil Windings in Electromagnetic Forming

Multiturn coils are required for manufacturing sheet metal parts with varying depths and special geometrical features using electromagnetic forming (EMF). Due to close coil turns, the physical phenomena of the proximity effect and Lorentz forces between the parallel coil windings are observed. This work attempts to investigate the mechanical consequences of these phenomena using numerical and experimental methods. A numerical model was developed in LS-DYNA. It was validated using experimental post-mortem strain and laser-based velocity measurements after and during the experiments, respectively. It was observed that the proximity effect in the parallel conductors led to current density localization at the closest or furthest ends of the conductor cross-section and high local curvature of the formed sheet. Further analysis of the forces between two coil windings explained the departure from the “inverse-distance” rule observed in the literature. Finally, some measures to prevent or reduce undesired coil deformation are provided.

A high-fidelity simulation of double-sided incremental forming: Improving the accuracy by incorporating the effects of machine compliance.

Double-Sided Incremental Forming (DSIF) is a technology for the rapid, flexible manufacturing of sheet metal parts. DSIF is highly nonlinear, requiring the use of complex finite element (FE) models to optimize and control the process in order to meet geometric accuracy and sheet thinning design criteria. Current FE models do not properly take into account the effects of machine compliance, which reduces their accuracy and hinders their use for optimization and control. The aim of this work is to create a greatly improved FE model of DSIF by taking a novel approach of modeling the aggregate effects of machine and tool compliance. The accuracy of the new model was extensively validated using the local geometry, thickness distribution, principal strains, and forming forces from a funnel experiment. The validated model was used to accurately predict the spatial distribution and time-histories of the equivalent plastic strain, von Mises equivalent stress, stress triaxiality, and Lode angle parameter across and along the sheet metal. The stress state was found to rapidly change through the sheet thickness, from highly compressive between the tools and the sheet, to a mixture of generalized shear and plane strain elsewhere. Moreover, the compressive regions between the two DSIF tools created a constrained deformation zone, which likely aids in prolonging the onset of excessive thinning. This improved FE model can now be used to quantitatively characterize the nonlinear local deformation mechanisms inherent to the DSIF process, thereby providing a solid foundation for future advances in process control.

Effects of process variables optimization on the quality of parts processed in high speed single point incremental sheet metal forming by ranking algorithm

Single point Incremental shaping (SPIF) is a metal forming process which rose to unambiguous quality toward the commencement of the 1990 s. ISF is an exceptionally limited twisting procedure in which a device, modified to take after in a specific direction, moves over a sheet metal and structures the coveted shape and a prosperous process to manufacture sheet metal parts that is well adapted for prototypes or small batch production. On contrast with the traditional sheet forming technologies this is relatively a slow process and is only profitable for the above mentioned production types but it can be used in different applications in automotive and aircraft industries, in architecture engineering and in medical aids manufacturing. SPIF is a die less method of forming which offers high formability. In this study the SPIF, process parameters such as the spindle Speed 1000/1500/2000 (Rpm), Feed 100/300/500 (mm/min), Tool Diameter 8/10/12 (mm) and step down 0.2/0.4/0.6 (mm) at the specimen interface greatly influence in the Cone shaped Mechanical quality such as Maximum Thinning rate (%), Surface roughness (µm), spring back (%) & formability of Forming for Aluminium alloy AA 8011. The aim of the present work is to study these parameters to build up a cone quality, formed by VMC and to carry out a detailed study of these parameters, experiments were conducted by using the L9 orthogonal array. The output parameters such as affecting mechanical and forming quality were analyzed by TOPSIS and ranking was analyzed.

Influence of a drawbead passage in deep drawing processes on surface values and the tribological system

In recent times, lightweight design and functional integration in metal forming and especially in deep drawing operations lead to complex geometries. These geometries can cause variable defects in production. Especially with modern materials like AHSS or UHSS, deep drawing becomes more challenging. One common way to meet these challenges and manufacture sheet metal parts without defects is the application of drawbeads in the forming tool. Drawbeads are used for an exact control and forecast of the material flow during the deep drawing process. It was already shown, that different material parameters like the tensile strength and the fracture strain are changed significantly after running through a drawbead. In addition, there are various indications that the tribological system in a drawbead passage is also changed significantly and that this has further influence on the ongoing drawing process.This assumption is examined with an experimental setup derived from industrial deep drawing processes. Therefore, different sheet metal materials are drawn through a drawbead geometry under the same conditions like the blank holder force, the drawing velocity or lubrication. After the drawbead passage, 3D surface parameters are measured and compared to the values in its initial state. Following, conventional strip-drawing tests with preloaded strips are carried out. The variation of the friction coefficient after a drawbead passage is analysed and compared to the initial state. The results are correlated with the surface values. For these investigations, three different materials are used: a conventional deep drawing steel because of its wide application as well as an advanced high strength steel AHSS and an aluminium alloy of the 6xxx series as representatives for modern lightweight materials.

Experimental and Numerical Investigation of Single Point Incremental Forming of Aluminium Alloy Foils

Single Point Incremental Forming (SPIF) is a flexible process to manufacture sheet metal parts that is well adapted and profitable for prototypes or small batch production. Compared to traditional sheet forming technologies this relatively slow process can be used in different applications in automotive and aircraft industries, in architecture engineering and in medical aids manufacturing. In this paper indirectly obtained axial forming force on SPIF of variable wall angle geometry were studied under different process parameters. The estimation of the forces on AlMn1Mg1 sheets with 0.22 mm initial thickness is performed by continuous monitoring of servo motor currents. The deformation states of the formed parts were analysed using the ARGUS optical strain measurement system of GOM, while the roughness measurements were carried out by a System of Mitutoyo. Some initial Finite Element Analysis simulations and a crack monitoring method together with an interaction plot of forming speed, incremental depth, tool diameter and lubrication were also reported.

Optimisation of process parameters for energy-efficient electro-hydraulic forming of Al-Mg alloy sheets

ABSTRACT Electrohydraulic Forming (EHF) is a high strain rate-forming process which has potential applications in manufacturing of sheet metal parts. In EHF, the energy from a charged capacitor bank is delivered to the workpiece through a fluid medium. In the present work, an experimental setup has been developed for bi-axial stretching of sheets (free bulging) with a 5.25 kJ capacitor bank. It has been established that the important process variables are stand-off distance (SOD), wire diameter, electrode gap (EGAP), and the medium through which the energy is transferred. For the given die set-up and bank, three levels of SOD, EGAP, and wire diameter have been used to study the effect of these parameters on formability of AA5052 alloy sheets. The compressibility of the medium affects the propagation of shock wave and hence water and oil have been used in this work. Variation in wire diameter and electrode gap influences the pulse characteristics and hence formability. Formability was determined by conducting limiting dome height tests using full factorial design of the experiments. Maximum dome height has been obtained with the smallest EGAP and intermediate values of SOD and wire diameter.

Study on forming sequences of the auxiliary roll height in flexible asymmetric rolling process

Flexible asymmetric rolling process has been conceived to manufacture sheet metal parts with high efficiency. In the asymmetric rolling process, the metal plate is fed into the roll gap at a tilted angle. The nip angles of the top and bottom rolls are not equal, and inconsistent thickness thinning occurs on the two surfaces of the metal plate. It is easy to bend the metal plate during the asymmetric rolling process. Then, desired metal parts with three-dimensional deformation are generated though non-uniformly rolling in the thickness direction. Compared with the 3D rolling technology, shape precision of the metal part with desired configuration is significantly improved. In this paper, the forming sequences of the auxiliary roll height are investigated for forming surface parts. A series of auxiliary roll heights are selected for the metal plate in condition of same roll gap distribution. Numerical simulations and experiments for typically surface parts have been performed. Deformation degree and shape accuracy of the surfaces parts formed in different auxiliary roll heights have been respectively compared and analyzed. Through analyzing deformation degree and shape accuracy of the surfaces parts, it is beneficial for parameters optimization of the flexible asymmetric rolling process.

Research on manufacturing of pyramidal frustum parts using single point incremental forming process

The incremental sheet metal forming is a flexible “die-less” process used to manufacture sheet metal parts in cold pressing domain. Especially talking about single point incremental forming, it is a process which does not require a special die to allow the sheet metal forming. To implement this process, a fixing device and a simple rounded tool are needed. The paper presents some research on the influence of a support plate upon the parts dimensional precision. Because, the main advantage of single point incremental forming process is the flexibility, in experiments, a fixing device that it was initial designed for incremental deformation of frustum cone parts, is used to deform pyramidal frustum parts. Different configurations of pyramidal frustum parts are simulated using a finite element method and a special software tool named TMPG, to check if the sheet material, deep drawing steel DC05, can be deformed without fracture. The manufactured parts are measured using a 3D scanner, and a comparison with the 3D CAD models of the original parts is made.

Ovality and Bow Defect of Pre-punched Sheets in Roll Forming of Trapezoidal Sections

Roll forming process is used for manufacturing sheet metal parts by successive bending and creating the final shape with gradual deformation. In this article, deformation of a pre-punched sheet due to the roll forming process was studied. Two main defects in the roll forming process are ovality of holes and bow defect. The ovality of the hole is influenced by the process parameters including sheet strength, thickness, initial hole diameter and distance of hole center to lateral edge. Due to the roll forming process, the sheet undesirably bent along longitudinal direction to a slight curved part which called bow defect. Also, the magnitude of product’s curvature along longitudinal direction (bow defect) was measured. The experimental tests were conducted on ASTM 230, 275 and 340 galvanized steels. The results showed that increase in the yield strength elongates the hole along rolling direction and shortened the hole perpendicular to rolling dimension. Therefore, the ovality of hole increases by increasing the yield strength. Also, similar trends were observed by increasing the thickness and the distance between hole center and lateral edge. The results showed that the bow defect decreases by increasing the material yield strength, while with increase in the sheet thickness, initial hole diameter and hole distance from lateral edge the bow defect was increased.

Electrohydraulic sheet metal forming with flexible tools

In cold metal forming usually a die and a punch are required to form sheet metal in the desired shape. These two parts of the tool need to be produced of hardened materials in high precision. In this paper it is shown, that by using electrohydraulic forming the punch is replaced by a hydraulic punch and the die can be made easily out of softer materials that seem absolutely not suited at first sight. This allows for rapid and cheap manufacturing of sheet metal parts.

Deburring and rounding of sheet metals and functionally relevant edges of parts using laser radiation

The manufacturing of sheet metal parts or component edges often leads to burrs. Due to different requirements regarding the appearance, haptics, tribology et cetera the edges have to be deburred or rounded in a subsequent process. Especially for complex geometries, automated post-processing has been difficult up to now. Laser remelting is one possible solution. It is fully automated and suitable for most 3D geometries. During laser remelting the laser beam is focused on the surface, thus a thin surface layer up to 100 μm is melted. The surface tension in the liquid state is smoothing out the surface and the edge resolidifies rounded. The radius of the rounding is adjustable by the chosen process parameters, especially laser power PL and feed speed vfeed. Furthermore the resulting roughness and the gloss level are controllable via the process parameters. Typical processing speeds are 100 mm edge length per second. First studies with industry partners showed promising results. Laser remelting of push belts for the torque transmission in CVTs lead to an increase of fatigue strength by up to 200% which enables a higher torque.

Investigation into bulging-pressing compound forming for sheet metal parts with very small radii

A newly proposed method for the manufacturing of sheet metal parts with very small radii is the bulging-pressing compound-forming process (Wang et al. Chin J Eng 39:1077–1086, 2017). The principle of this method is introduced, and the key process parameters such as the hydraulic pressure loading path, punch velocity, and initial punch position are optimized by establishing a new optimization strategy. The optimum setting was obtained in order to achieve minimum possible radius with the highest process robustness. Meanwhile, the influences of the punch velocity and friction on the stress state and deformation situation of the rounded corner region are analyzed by FE simulation. Finally, the proposed method is applied for the actual manufacturing of an aluminum alloy sheet metal part. The result showed that the part has high forming quality, and the feasibility of the method was proven.

Numerical and experimental investigations of laser shock forming aluminum alloy sheet with mold

Laser shock forming (LSF) technology employs shock waves to form sheet metal into three-dimensional complex parts, and has application potential in manufacturing sheet metal parts. In this paper, the forming of 2024 aluminum alloy sheet with LSF was investigated through numerical and experimental methods. The numerical model was established with the commercial code ABAQUS/Explicit. The formed conical cup was obtained from the simulation, and validated by the experiment. With the verified numerical model, the deformation behaviors, including deformation velocity, sheet thickness variation and strain distribution, were studied. In addition, the influence of different shock wave pressures on the forming precision was also investigated. The experimental and numerical results show that the metal sheet loaded by shock wave can take the shape of the mold, and the non-uniform thickness is distributed in the formed cup. The investigations also display that there exists reverse deformation at the central region of deforming sheet owing to severe collision during LSF. In order to obtain formed part with better quality, an appropriate pressure of applied shock waves is required.

Guideline for Forming Stiffened Panels by Using the Electromagnetic Forces

Electromagnetic forming (EMF), as a high-speed forming technology by applying the electromagnetic forces to manufacture sheet or tube metal parts, has many potential advantages, such as contact-free and resistance to buckling and springback. In this study, EMF is applied to form several panels with stiffened ribs. The distributions and variations of the electromagnetic force, the velocity and the forming height during the EMF process of the bi-directional panel with gird ribs are obtained by numerical simulations, and are analyzed via the comparison to those with the flat panel (non-stiffened) and two uni-directional panels (only with X-direction or Y-direction ribs). It is found that the electromagnetic body force loads simultaneously in the ribs and the webs, and the deformation of the panels is mainly driven by the force in the ribs. The distribution of force in the grid-rib panel can be found as the superposition of the two uni-directional stiffened panels. The velocity distribution for the grid-rib panel is primarily affected by the X-directional ribs, then the Y-directional ribs, and the variation of the velocity are influenced by the force distribution primarily and secondly the inertial effect. Mutual influence of deformation exists between the region undergoing deformation and the deformed or underformed free ends. It is useful to improve forming uniformity via a second discharge at the same position. Comparison between EMF and the brake forming with a stiffened panel shows that the former has more advantages in reducing the defects of springback and buckling.

Research on Computer Integrated Manufacturing of Sheet Metal Parts for Lithium Battery

Lithium battery has been widely used as the main driving force of the new energy vehicle in recent years. Sheet metal parts are formed by means of pressure forming techniques with the characteristics of light weight, small size and high structural strength. The sheet metal forming has higher productivity and material utilization than the mechanical cutting, therefore sheet metal parts are widely used in many fields, such as modern automotive industry, aviation, aerospace, machine tools, instruments and household appliances. In this paper, taking a complex lithium battery box as an example, the integrated manufacturing of sheet metal parts is studied, and the digital integrated design and manufacturing process system is proposed. The technology is studied such as sheet metal design, unfolding, sheet nesting and laser cutting, CNC turret punch stamping programming, CNC bending etc. The feasibility of the method is verified through the examples of products and the integrated manufacturing of sheet metal box is completed.