Sheet Metal Products Research Articles

Reduction of adhesive wear with use of tool coating reducing thermoelectric currents

Blanking is one of the main processes in producing sheet metal components. The impact of adhesive wear of the blanking tools on the cost efficiency is high, especially when processing aluminum. As an influencing factor on adhesive wear in blanking, thermoelectric currents have been considered to a very small extent. Recent investigations have shown that thermoelectric currents occur in every blanking tool due to the rise of temperature in the shear zone in interaction with a difference of the material-specific Seebeck coefficients of tool and sheet metal. A reduction in the amount of wear was observed in case of a smaller difference of Seebeck coefficients and therefore lower levels of flowing thermoelectric currents. This paper follows the approach of adjusting the Seebeck coefficient of the tool material CF-H40S+ to the one of the sheet material by means of coating with CrAlN, in order to reduce the flowing thermoelectric currents and consequently adhesive wear. For this purpose, the effect of coating on the Seebeck coefficients, the thermoelectric currents during blanking as well as resulting wear quantities were investigated. Basic correlations could be revealed.

Multipoint Forming Using Hole-Type Rubber Punch

Reconfigurable multipoint forming is a flexible sheet forming technique aimed at customised sheet metal products. However, one drawback of multipoint forming is the cost and time needed to set up and align the upper and lower pin matrices. This study introduces an optimisation study of a novel hole-type rubber punch replacing the top pin matrix of multipoint incremental forming, aiming to reduce pins setting up and alignment complexity and time. Finite element modelling and design of experiments were used to investigate the effect of hole-type rubber punch configuration such as hole size, hole type, and the compression ratio on the wrinkling, thickness variation, and shape deviation. This research shows that the most significant process parameter in all responses was the hole size. The compression ratio of the material was found to be insignificant in wrinkling and shape deviation. The hole-type rubber punch parameters were found to be a hole size of 9 mm, circular hole type, and a compression ratio of 75%. This experimentally resulted in an improved parts wrinkling of 80%, when compared to using solid rubber punch, with the added benefits of reduction of the cost and time needed to set up and align the pin matrices.

Implementation of calculation methods in a specialized computer system of the stress-deformation and temperature state of steel bar coils

The theory of formation and transformation of the stress-deformation and temperature state of rolls of hot-rolled and cold-rolled steel bars during their winding-unwinding in the processes of rolling, heat treatment, training, transportation, storage, and performance of other production operations at metallurgical plants has been developed. Mathematical models, algorithms and a computer system implementing them are proposed. A description of the possibilities of using this system when solving various tasks is given. In the computer system, an approach to assessing the influence of the parameters of the process of cold rolling and winding the stock into rolls, the temperature and speed regimes of their heating and cooling during annealing in hood furnaces is considered. For the first time, the methodology for identifying patterns of influence of inter-turn gaps in rolls on their stress-strain state was disclosed. The procedure for detecting the effects of cold rolling speed, temperature, tension of the rods rolled and wound into rolls, and their surface roughness on the stress-strain state of the rolls is shown. In detail, the implementation of new ideologies and approaches to solving the problem of determining the stress-strain state (STS) of rolls is shown in the computer system. Models and algorithms for calculating VAT, which are the basis of the computer system, are developed on the basis of classic solutions in the field of materials science, theories of elasticity, metal pressure treatment, heat engineering, gas dynamics, numerical methods and other fields of knowledge. The computer system revealed the mechanisms of forming the temperature and stress-strain state of rolls of steel bars in the processes of rolling, heating, isothermal aging and cooling during annealing in hood furnaces; the influence of the temperature and speed regimes of rolling and annealing on the occurrence of critical inter-turn pressures in the rolls, which lead to surface defects of the "bend line" (breaks) and defects in the shape of the rolls, is taken into account. The possibilities of influencing the VAT of rolls during rolling by adjusting the tension of the staffs, and during annealing by adjusting the duration of isothermal exposure and the rate of subsequent cooling of the rolls, are revealed. References to literary sources are provided, which detail the results of research on scientific and technical problems implemented in the computer system. In the computer system, methods of winding cold-rolled bars into rolls are used, which exclude the loss of their stability and the formation of "bends", subsidence, "bird" defects during the production of thin sheet steel in industrial conditions. Recommendations are given regarding the choice of a rational technology for the roll production of hot-rolled and cold-rolled sheet metal. The developed solutions are implemented in the "CoilTemper3D" computer system and are used in production.

Multistage Tool Path Optimisation of Single-Point Incremental Forming Process.

Single-point incremental forming (SPIF) is a flexible technology that can form a wide range of sheet metal products without the need for using punch and die sets. As a relatively cheap and die-less process, this technology is preferable for small and medium customised production. However, the SPIF technology has drawbacks, such as the geometrical inaccuracy and the thickness uniformity of the shaped part. This research aims to optimise the formed part geometric accuracy and reduce the processing time of a two-stage forming strategy of SPIF. Finite element analysis (FEA) was initially used and validated using experimental literature data. Furthermore, the design of experiments (DoE) statistical approach was used to optimise the proposed two-stage SPIF technique. The mass scaling technique was applied during the finite element analysis to minimise the computational time. The results showed that the step size during forming stage two significantly affected the geometrical accuracy of the part, whereas the forming depth during stage one was insignificant to the part quality. It was also revealed that the geometrical improvement had taken place along the base and the wall regions. However, the areas near the clamp system showed minor improvements. The optimised two-stage strategy successfully decreased both the geometrical inaccuracy and processing time. After optimisation, the average values of the geometrical deviation and forming time were reduced by 25% and 55.56%, respectively.

Sheet metal technology and production – a look at ambitions and trends

In the 21st century, sheet metal production is developing on the basis of improving existing technologies and introducing innovations in the production of thick and thin sheet of the III and IV metallurgical processing. And this is accompanied by an increase in requirements for quality indicators and an increase in production costs. This prompted the research and development of developments in the production process, as well as in the automated control system and automated control system systems, aimed at improving the quality of metal products, increasing the productivity of equipment and reducing energy consumption. Large funds were allocated to solve problems related to reducing the harm caused to the environment. The introduction of modern process automation systems and the growing possibilities of using digital technologies for the production and technological processes of metallurgical production significantly help to solve the problems posed to the distributors. Modern trends in the development of technology and production, construction of mills for the production of sheet metal are considered.

Li2CO3 Surface Pre-Treatment for Improved Corrosion Control of Mg Alloy Sheet Metal

The objective of this work was to determine the extent to which a Li2CO3 surface-pretreatment can control corrosion of ZEK100 Mg alloy sheet metal product for automotive applications. The Li2CO3 surface treatment was applied through a dip coating processing using an alkaline Li salt aqueous solution. The structure and composition of the coating was determined using XRD and electron microscopy and associated techniques. The extent of corrosion control was determined using conventional electrochemical measurements including open-circuit potential, potentiodynamic, and electrochemical impedance spectroscopy measurements conducting in 0.1 M NaCl (aq). The performance of the surface pre-treatment was benchmarked against a commercial hexafluro-titanate/zirconate-based conversion coating. Cyclic corrosion testing was also conducted to gauge corrosion control under more realistic conditions, following a commercial OEM testing protocol. The results show that the Li2CO3 surface pre-treatment offers improve corrosion control relative to the commercial baseline coating. The manner in which the dissolution chemistry controls corrosion of the substrate will be discussed in this presentation.

Remanufacturing end-of-life passenger car waste sheet steel into mesh sheet: A sustainability assessment.

This study analysed the business sustainability of remanufacturing waste steel sheet from the shells of end-of-life vehicles into mesh steel sheet for manufacturing sheet-metal products. Hybrid statistical, fuzzy, and overall sustainability-index curve-fitting models were used to analyse the technical, economic, environmental, management, and social feasibility of remanufacturing, where the sales price, eco-cost savings, and CO2 emission reductions were used as typical statistical indicators. The remanufacturing process was optimised to allocate hardware for a plant recovering 480 m2/shift of waste sheet steel and producing 2851-5520 m2/shift of mesh sheet steel. Six scenarios were used to model the sustainability parameters to normalise the sustainability index values. The sustainability index of each parameter was calculated by multiplying its weight of importance by its weight of satisfaction. The highest sustainability index of 0.95 was calculated for the economic feasibility index, while the lowest sustainability index of 0.4 was calculated for the management feasibility. Remanufacturing of waste sheet steel into mesh sheet steel can be applied with an estimated overall sustainability index of 0.88.

METHODS OF TEACHING FIFTH- AND SIXTH-GRADE STUDENTS TO DESIGN AND MANUFACTURE SHEET METAL PRODUCTS

The article considers the current issues of forming students’ skills in applying the acquired knowledge in practice as an essential factor in the implementation of the project-technological system of labor education in modern general secondary education institutions. It is established that the issues of taking into account the age characteristics of fifth- and sixth-grade students in labor training in the design and manufacture of products from structural materials remains poorly understood. It is proved that the success in the design and manufacture of sheet metal products is determined by students’ design and technological activities, which are properly organized and phased. The peculiarities of the choice of the design object at the first (organizational and preparatory) stage are substantiated. The peculiarities of students’ sketching of potentially possible variants of the designed product at the design stage of product design are revealed. The content of the third (technological) stage of product manufacturing is determined. It provides for the implementation of planned operations and self-control and evaluates the quality of the work performed. The process of teaching students labor techniques and operations is considered, namely the formation of the mode of action, analytical and synthetic stages of mastering the components of techniques and operations. The method of teaching students to correctly learn the procedure for performing labor operations for processing thin sheet metal is described. It is the following: marking blanks, cutting metal with scissors, sawing the edges of parts, bending and drilling holes, assembly and finishing of the product. The peculiarities of assessing the quality of products made by students on the accuracy of processing of construction materials are characterized. The content of the final stage of design and technological activities for the control, comparison, and evaluation of the structures made of sheet metal products made by students is revealed.

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.

Elaboration of weatherproof steel 06гн3мд for structures of bridges exploited in coastal zone

At present decreasing of costs and increasing of efficiency are the most priority directions in any industry. Developing in this way, JSC “Ural steel” together with FGUP “CNIIchermet after I.P. Barding” had mastered production of sheet metal product with increased resistivity against atmosphere corrosion made of steel 14ХГНДЦ for construction of bridges. Because of specific chemical composition of the steel, in the process of metal structures running in the open air, a solid strong oxide film is formed on the metal of the structures which prevents further corrosion without painting. For bridge builders elimination of costly operation of painting of span structures will enable to decrease considerably the costs of bridges construction and running. Having many advantages, steel 14ХГНДЦ has some restrictions in applications for steel structures without painting, as follows: - in sea zone according to domestic norms no close than 500 m from coastline; - in case of disorderly conditions of protective film formation and/or application of salt solutions for surface cleaning (as a rule the restrictions refer to traffic area of bridge span). In view of that for JSC “Ural Steel”, as the leading producer of bridge steel in Russia, an actual task erose: to elaborate and create a weatherproof steel, which could not only operate the whole period of a bridge running without additional protection at bridges con­struction through sea areas or close to coastline, but also withstand severe climate conditions of our country, including areas of High North with temperature lower -50°С. To solve the task together with OJSC “Institute Giprostroymost” and JSC BNIIZhT, a research work was accomplished to elaborate a system of alloying new steel 06ГН3МД with nickel content ~3.0 %, as well as production modes ensuring required corrosion resistance for operation in sea zone. Results of laboratory studies of the new weatherproof steel 06ГН3МД for application in bridge structures for coastal conditions and sea areas presented. Results of mechanical, technological, corrosion as well as fatigue tests of rolling products of the elaborated steel presented. It was established by laboratory studies that the new steel is weatherproofed and ensures lower corrosion losses, higher impact toughness at negative temperatures and plasticity comparing with steels used at present. It was shown that the strength class, technology and modes of factory welding of steel 06ГН3МД meet the requirements to steel span structures of bridges. Base on the results of the studies, the chemical composition of the steel 06ГН3МД was specified, as well as modes of heat treatment, ensuring the required characteristics with significant acceding. It was established that samples of the new steel 06ГН3МД showed considerably higher corrosion resistance - in average by 20% comparing with steel 14ХГНДЦ. At that corrosion resistance tests of welded joints of the new steel showed even higher resistance of the seam comparing with the basic metal, which speaks about quality selection of welding modes and welding materials.

A new cracking resistance index based on fracture mechanics for high strength sheet metal ranking

Driven by current safety and weight reduction policies in the automotive sector, the development of new high strength sheet metal products has experienced unprecedented growth in the last years. With the emergence of these high strength materials, new challenges related to their limited ductility and higher cracking susceptibility have also raised. Accordingly, the development of new fracture criteria accounting for the material’s cracking resistance has become unavoidable. In this work, a new cracking resistance index (CRI) based on fracture mechanics is proposed to classify the crack propagation resistance (i.e. the fracture toughness) of high strength metal sheets. The index is based on the fracture energy obtained from tensile tests with sharp-notched specimens. The procedure is very fast and simple, comparable to a conventional tensile test, and it may be used as routine testing for quality control and material selection. The CRI is investigated for several advanced high strength steel (AHSS) sheets of 0.8-1.6 mm thickness with tensile strengths between 800 and 1800 MPa. The results show that the proposed index is suitable to rank high strength steel sheets according to their crack propagation resistance and it can be correlated to the material’s crashworthiness and edge cracking resistance.

Parametric Shape Optimization of Stretch Webs in a Progressive Die Process using a Neural Network Surrogate Model

Progressive die stamping provides a solution for producing sheet metal parts in large quantities. These parts are connected to carriers by stretch webs. As the part undergoes bending and forming operations, the stretch webs are exposed to translational and rotational deformation. A suitable design of these entities is crucial to avoid failure caused by splits or excessive thinning. A common way to evaluate such designs is to use finite element (FEM) simulation. Since it is not efficient to run FEM based optimization studies for the design optimization and to enable further automation of the stretch web design, this paper is proposing the use of machine learning (ML) technologies. A surrogate model based on an artificial neural network is used as a predictor in the presented study. This neural network is used to optimize the geometric parameters of the stretch web to obtain a quality result. The model is trained using FEM results and the study shows that it was possible to obtain an accurate model with a prediction error of 5%. The trained surrogate model can be used for the optimization study. This approach is computationally inexpensive and can provide very good results.

Research on a Control Strategy of the Symmetrical Four-Roller Bending Process Based on Experiment and Numerical Simulation

The intelligent production of sheet metal is a comprehensive technology involving control science, computer science, and sheet metal production. Intelligent rolling is an important development in the production process of sheet metal. In this paper, a new symmetrical four-roller bending (SFRB) process is introduced, which consists of feeding, pre-bending, reverse roll bending, second bending, and forward roll bending and unloading. A control strategy is proposed for the process, including on-line monitoring of curvature, on-line identification of the springback law, on-line prediction of final reduction, and control strategy. A convenient and reliable on-line curvature monitoring method is proposed. The quantitative relationship between the reduction and the curvature, in the form of a quadratic function, was established by physical experiments and numerical simulation, and the online identification of the springback law was realized. An on-line prediction method of the final reduction is proposed, and the determination principle of the reduction of three pre-bending processes is given. Finally, the control strategy of the SFRB process was verified by physical experiments. The relative error of the curvature radius of the final formed parts can be controlled within 0.8%. This research provides new insights into intelligent rolling.

Development and performance evaluation of a web-based feature extraction and recognition system for sheet metal bending process planning operations

ABSTRACT Sheet metal bending manufacturing companies require changeable and adaptable process planning systems to shorten the production cycle time and reduce operations costs. This is due to globalisation and the rapid change in market demands for sheet metal products. In light of this, this paper proposes a web-based feature extraction and recognition system. The system would ensure automated planning of various processes used by a bending machine to produce varieties of sheet metal products. The algorithms were implemented using C++ to produce the geometric and feature models used to extract, and recognise the bending features in various CAD files acquired from literature. Five (5) CAD files of various sheet metals were utilised to test the functionality of this system. The results from the feature recognition process have proven to be precisely what the user has designed and saved in the model file. Bend radius and bend angle. Finally, the developed system is able to transform a STEP file into a feature model and display the 3D CAD model within the least time. It is a cost-efficient standalone system that provides data storage, allows collaboration and data sharing. can be used anywhere where there is internet access.

Towards Automatic Part Identification in Sheet Metal Workshops

Pallets and forklifts equipped with Radio-Frequency Identification (RFID) technology can be a suitable option for bridging the information gap between cutting and bending stages in sheet metal production. However, a decision on how tagged pallets can be assigned to their content needs to be made. In this paper, a reactive and a proactive approach for the near-automatic identification of parts on pallets after cutting are discussed and their performance is evaluated through a series of simulations. In both approaches, the nesting information along with the measured net weight of the pallets are used to determine the parts on top of each pallet. The influence of the alternative solutions problem on the performance is investigated for both approaches. It is concluded that the actual decision on the approach selection depends on the time that is required for each recalculation and each pre-allocation. Those times are workshop dependent and, therefore, a decision should be made for each workshop specifically.

A Method for Simultaneous Optimization of Blank Shape and Forming Tool Geometry in Sheet Metal Forming Simulations

This paper presents a numerical method for simultaneous optimization of blank shape and forming tool geometry in three-dimensional sheet metal forming operations. The proposed iterative procedure enables the manufacturing of sheet metal products with geometry fitting within specific tolerances (surface and edge deviations less than 0.5 or 1.0 mm, respectively) that prescribe the maximum allowable deviation between the simulated and desired geometry. Moreover, the edge geometry of the product is affected by the shape of the blank and by an additional trimming phase after the forming process. The influences of sheet metal thinning, edge geometry, and springback after forming and trimming are considered throughout the blank and tool optimization process. It is demonstrated that the procedure effectively optimizes the tool and blank shape within seven iterations without unexpected convergence oscillations. Finally, the procedure thus developed is experimentally validated on an automobile product with elaborated design and geometry which prone to large springback amounts owning to complex-phase advanced high strength steel material selection.

Development of modes for straightening of hot-rolled strip in order to obtain rolled products for high-tech processing

Modern requirements for the quality indicators of hot rolled sheet steel are associated with maintaining high flatness of sheet metal during further processing by high-tech methods, for example, by laser or plasma cutting. When laser cutting a sheet it may bend due to the release of residual stresses that are unevenly distributed over the volume. The final stage in the production of hot rolled steel is straightening on roller straightening machines under cyclic alternating deformation. The solution to the problem is the optimal control of residual stresses at the main final stage of hot rolled sheet production when straightening strips on roller levelers under cyclic alternating deformation. The existing numerous approaches of calculating the parameters of the straightening on roller straightening machines do not allow determining the optimal modes that eliminate the initial inhomogeneous stress state of the hot rolled strip and ensure the minimum level of residual stresses in the rolled product. The paper substantiates the relevance of developing a methodology for selecting a strip straightening mode, which provides an expansion of the possibilities of the straightening process on roller straightening machines and obtaining hot rolled sheets with a minimum level of residual stresses and potential energy, suitable for plasma and laser cutting. The article describes the implementation of the method for selecting the mode of hot rolled strip straightening process based on the results of finite element modeling, confi rmed by experimental data obtained during leveling and subsequent cutting of sheets. The modes of straightening of strips with a thickness of 4 mm, 8 mm and 10 mm of steel grade S355MC have been calculated on 13-, 15- and 17-roller straightening machines of Severstal, providing minimum residual stresses, potential energy in sheets after straightening and deviations from the flatness of sheets during high-tech cutting. Based on industrial tests, the method for calculating straightening modes was introduced into production, the developed modes were accepted for use at Severstal. The proposed improvements of technology of the production of hot rolled sheet metal in the conditions of Severstal made it possible to obtain products suitable for laser cutting.

Investigation of Different Illumination Scenarios for the Evaluation of Thermally Cut Edges with Convolutional Neural Networks using a Mobile Device

In sheet metal production, the quality of a cut edge determines the quality of the cut itself. Quality criteria such as the roughness, the edge slope, and the burr height are of decisive importance for further application and quality determination. In order to be able to determine these criteria analytically, the depth information of the edge must be determined at great expense. The current methods for obtaining the depth information are very time-consuming, require laboratory environments and are therefore not suitable for a fast evaluation of the quality criteria. Preliminary work has shown that it is possible to make robust and accurate statements about the roughness of a cut edge based on images when using an industrial camera with a standard lens and diffuse incident light, if the model used for this purpose has been trained on appropriate images. In this work, the focus is on the illumination scenarios and their influence on the prediction quality of the models. Images of cut edges are taken under different defined illumination scenarios and it is investigated whether a comprehensive evaluation of the cut edges on the evaluation criteria defined in standards is possible under the given illumination conditions. The results of the obtained model predictions are compared with each other in order to make a statement about the importance of the illumination scenario. In order to investigate the possibility of a mobile low-cost evaluation of cut edges, cheap hardware components for illumination and a smartphone for image acquisition are used.

High-quality sheet metal production using a model-based adaptive approach

Abstract Automatic panel benders of Salvagnini Maschinenbau GmbH enable high-quality and high-efficient production of sheet metal components. To achieve the steadily increasing requirements on precision, a model-based adaptive concept has been developed controlling the complete production process as a digital twin, from CAD data to the final sheet metal part. First, an overview of the underlying simulation models with different levels of detail is given. The models consider the elastoplastic deformation of the metal sheets as well as the elastic machine components and mechatronic models of the powertrain. Secondly, an overview is given of the adaptive production concept allowing the real-time adaption of the machine to changing process parameters like material properties. Finally, all production steps are controlled by a digital twin based on this model-based adaptive strategy. The paper demonstrates the successful transfer of scientific results to an industrial application.

СИСТЕМА ДИНАМИЧЕСКОГО ПЕРЕРАСПРЕДЕЛЕНИЯ СКЛАДСКИХ РЕСУРСОВ ПРОМЫШЛЕННОГО ПРЕДПРИЯТИЯ

The article addresses the problem of redistribution of warehouse resources when working in a virtual organization or when changing the logistics structure of the enterprise. A two-stage model of providing warehouse resources to a common access to participants of a virtual en-terprise is considered. An automated system for managing redistribution of resources for the stage of disconnecting from a virtual enterprise or when closing your own warehouses was developed. 
 A description of the control object - a distributed warehouse system of an industrial enterprise specializing in the production of sheet metal. A formalized description of the technological process for the production of cold-rolled steel, including the stages of stockpiling, has been developed. The task of managing the distribution of resources is posed, the functional structure of the software complex is designed. Information, mathematical and algorithmic support for solving the problem of redistributing resources is presented. The architecture of information support includes a database containing regulatory and reference information and document management of the enterprise. The database information is used by the algorithmic support of four functional modules: management of normative and reference information, management of receipts and sales, management of warehouse movements, management of multi-turn packaging. The result of the work is presented by the system of dynamic redistribution of warehouse resources and implemented on the 1C: Enterprise platform, which allows solving the problems of the operational movement of material resources between the enterprise’s warehouses, also under the conditions of the virtual enterprise functioning. Absolute and relative distribution criteria are formed. The first group includes absolute criteria: volume, quantity, amount, weight. The second group consists of relative distribution criteria: quantity/volume, amount/volume, weight/volume. Testing the system using the example of criteria from each group showed the operability of all types of support using the example of a warehouse complex of an enterprise manufacturing metal rolling. Flexible customizable system structure allows you to expand the application of the proposed algorithmic support to other types of resources.