Sheet Metal Blanking Research Articles

Experimental Analysis and Optimization of Clearance between Punch and Die in Sheet Metal Blanking Process for Soft Steel

Blanking process is commonly used process in production of sheet metal industries to fabricate components. The Global market of sheet metal production is facing highly competition. Due to unavailability of skilled operators and shortage of affordable CAD/CAM systems, it is difficult to predict optimum clearance between punch and die to obtain high quality in small scale industries. Blanking is metal fabricating process and it is characterized by complete material separation. The simulation of the shearing process is complicated as the shear band formed is narrow and fracture criterion is inappropriate. The effect of potential parameters like thickness of sheet, punch-die clearance, tool wear, and punch geometry are studied to investigate their interactions on blanking process. It is important to select process leading parameters which can lead the process such that two similar products from two separate materials can be manufactured on same mold with high quality. This study will help to investigate the effect of thickness of sheet, clearance between punch and die and type of material on blanking process and will help to predict optimal set of parameters to obtain reasonable quality. A mathematical model of blanking process is developed and design of experiments method is used to predict optimum punch-die clearance for soft steel which will result into high quality of component.

Finite element simulation of the complete sheet metal blanking cycle: Effect of blanking clearance on force curve and cut edge quality

Sheet metal blanking process is a manufacturing process that is widely used in sheet metal forming and particularly in the electronics and automotive industries. The outcome and quality of the blanked parts are affected by various parameters such as the blanking clearance, the sheet metal mechanical properties and the wear of tools. However, experimental campaigns to assess the effects of these parameters on the process outcome can be prohibitively expensive for the industry. As a result, numerical simulation of the blanking process is becoming increasingly important to gain insight into the process and study these effects.The present paper provides a novel finite element (FE) simulation procedure to predict the complete blanking cycle including sheet metal cutting, sheet metal springback, punch penetration in die, and stripping phases. A blanking force curve showing the punch force at all phases can thus be obtained. The commercial finite element code ABAQUS® has been chosen to develop this procedure using ABAQUS/Explicit® code for the cutting phase and ABAQUS/Standard® code for the remaining phases. Based on this procedure, the influence of the blanking clearance on the punch force-displacement curve and on the cut edge quality has been studied. The obtained results have been compared to previous literature results and experimental findings.

Technology and equipment of roll straightening of sheet metal

The features of the editing technology, possible defects of sheet metal and piece blanks of complex configuration are presented. The main schemes and designs of sheet‑straightening machines are considered, as well as the main directions of improvement of LSM designs and editing technologies are highlighted. The analysis of the process of roll straightening is presented taking into account the phenomena occurring in a metal undergoing alternating loading with decreasing amplitude (interaction of elastic and plastic deformation, Bauschinger effect, etc.). The parabolic dependence of the residual curvature on the yield strength is noted. The obtained data were used in the design of the roll straightening complex and the technology of straightening sheet blanks of complex configuration.

An Investigation of Punch Radius and Clearance Effects on the Sheet Metal Blanking Process

In this study, the effects of punch edge radius and blanking clearance on product quality and blanking process in blanking of AISI 304 stainless steel sheet were investigated by using the fi-nite element analysis method. The blanking analyzes were performed at four different punch tip radii (0.01, 0.25, 0.5, 1 mm) and three different blanking clearance (1 %, 5%, 10%). As a result of the analysis, rollover, burr length increased, smooth sheared / fractured surface ratio and blanking force decreased with the increase in blanking clearance. Depending on the increase in the amount of punch tip radius, the blanking force, and burr length also increased, and the smooth sheared / fractured surface ratio decreased compared to the blanking process with flat punches.

Influence of Sheet Metal Pre-forming on Edge Crack Sensitivity using an AHSS Steel Grade

Especially in the automotive sector, high-strength sheet materials are processed in the manufacturing industry. These steels often show a pronounced sensitivity to edge cracks. Because of this, many edge crack testing methods for a wide variety of stress conditions have been developed to describe the edge crack sensitivity of a material. Only the hole expansion test according to ISO 16630 has been standardized. However, the standardization has some gaps in the process description, which has resulted in test modifications. Another disadvantage is the dependence of the results on the machine operator. In the past, the influence of the shear cutting parameters die clearance, cutting edge geometry, and type of cutting line on the edge crack sensitivity was only calculated for undeformed sheet materials. Not only are shear cutting operations carried out on undeformed sheet blanks in the context of the manufacturing of sheet metal components, but more and more pre-formed sheets are mechanically separated and subsequently further formed. Therefore, it is essential to consider the influence of the type and amount of pre-forming introduced on the sensitivity of a material to edge cracks. The discrete types of pre-forming, uniaxial tension, plane strain, and equi-biaxial stretch forming were introduced to sheet metal blanks using dual-phase steel. The Edge-Fracture-Tensile-Test was used to identify the residual formability of the undeformed and pre-formed specimens. The Edge-Crack-Sensitivity-Factor{K}_{mathrm{ec}}, which can be used to predict edge cracks in a finite element forming simulation, was determined from the recorded major strains for selected parameter configurations.

Perspectives on data-driven models and its potentials in metal forming and blanking technologies

Today, design and operation of manufacturing processes heavily rely on the use of models, some analytical, empirical or numerical i.e. finite element simulations. Models do reflect reality as best as their design and structure may appear, but in many cases, they are based on simplifying assumptions and abstractions. Reality in production, i.e. reflected by measures such as forces, deflections, travels, vibrations etc. during the process execution, is tremendously characterised by noise and fluctuations revealing a stochastic nature. In metal forming such kind of impact on produced product today in detail is neither explainable nor supported by the aforementioned models. In industrial manufacturing the game to deal with process data changed completely and engineers learned to value the high significance of information included in such digital signals. It should be acknowledged that process data gained from real process environments in many cases contain plenty of technological information, which may lead to increase efficiency of production, to reduce downtime or to avoid scrap. For this reason, authors started to focus on process data gained from numerous metal forming technologies and sheet metal blanking in order to use them for process design objectives. The supporting idea was found in a potential combination of conventional process design strategies with new models purely based on digital signals captured by sensors, actuators and production equipment in general. To utilise established models combined with process data, the following obstacles have to be addressed: (1) acquired process data is biased by sensor artifacts and often lacks data quality requirements; (2) mathematical models such as neural networks heavily rely on high quantities of training data with good quality and sufficient context, but such quantities often are not available or impossible to gain; (3) data-driven black-box models often lack interpretability of containing results, further opposing difficulties to assess their plausibility and extract new knowledge. In this paper, an insight on usage of available data science methods like feature-engineering and clustering on metal forming and blanking process data is presented. Therefore, the paper is complemented with recent approaches of data-driven models and methods for capturing, revealing and explaining previously invisible process interactions. In addition, authors follow with descriptions about recent findings and current challenges of four practical use cases taken from different domains in metal forming and blanking. Finally, authors present and discuss a structure for data-driven process modelling as an approach to extent existing data-driven models and derive process knowledge from process data objecting a robust metal forming system design. The paper also aims to figure out future demands in research in this challenging field of increasing robustness for such kind of manufacturing processes.

Stretch flange forming of steel alloys through FEM simulation

In sheet metal operation flanging is a common process in which one edge of the sheet is bent to the desired angle or the desired contoured shape and the other end keep in control either itself or by blank holder or pad force. Stretch flanging involves stretching the metal circumferentially while the bending line is concave. In the stretch flanging process, the initial flange length is a critical factor. Using commercial finite element software programmed Abaqus, a finite element simulation of the stretch flanging process was performed in this research. The impact of initial flange length on the radial strain, circumferential strain, and flange thickness distribution along the free edge of rectangular-shaped sheet metal blanks is investigated in this work. Aside from maximum radial strain, maximum circumferential strain and maximum thinning in the flange are also explored as effects of initial flange length. With a reduction in initial flange length along the free edge up to the punched centre, circumferential strain and flange thickness drop while radial strain increases. With increasing initial flange length, maximum radial strain, maximum circumferential strain, and maximum thinning are observed to rise. The formability of the stretch flanging process is shown to be considerably influenced by the initial flange length.

The effects of punch angle in noise and force formation for sheet metal blanking process

The paper is concerned with the effect of punch angle (0°, 4°, 8°, 16°), sheet thickness (0.8, 2 mm), and punch speed (25, 37.5 mm / min) on the force formation and noise in the blanking of DP600 dual-phase steel sheet. The blanking experiments were carried out in a modular blanking die. The blanking force and noise variables were obtained simultaneously during the blanking using a load cell and noise measuring device, respectively. It was determined that the blanking force significantly decreased with an increasing punch angle, while noise formation decreased. The increase in the punch speed slightly increased the amount of noise while it did not affect the blanking force significantly.

МОДЕЛЮВАННЯ ПРОЦЕСІВ ВИРУБКИ-ПРОБИВКИ ПЕРЕДАВАЛЬНИМИ СЕРЕДОВИЩАМИ

During improvement of the quality of products and reducing its cost, sheet metal stamping production, being the basis for the aerospace industry, should more intensively introduce modern production technologies, especially design. There are a large number of factors influencing the stamping process (especially parts with complex geometry), more comprehensive consideration of which would allow to optimize such processes, thereby reducing the manufacturing cost and improving the quality. Currently the processes of forming and separation of complex parts by of an elastic pad are of interest from the point of view of optimization and the final determination of the nature of the behavior of the material. This includes the refinement of such parameters as the maximum permissible thinning, the strength of the die. Clarification of these and other parameters will significantly reduce energy required. Determination of these and other parameters of sheet metal stamping is possible due to application of the modern analysis methods. For numerical studies in the sheet stamping production, the variational method or FEM is the most suitable. Computer modeling makes it possible to investigate the behavior of the material, the kinematics of the workpiece movement during forming process, select the correct loading scheme for the workpiece, and also makes it possible to consider several options for the location of the workpiece in the die, which is very important for stamping thin sheet metal blanks. It provides a significant reduction of the time and costs for carrying out natural experiments, and decrease of technological preproduction preparation of sheet metal stamping. The development of a mathematical model based on the FEM makes it possible to determine not only the required parameters of the process, but also to consider the forming process during its certain stages, to determine the stress-strain state, indicating at the same time the problem zones of excessive thinning, loss of stability, the need to apply a die with a back pressure for cutting of thin sheet metal blanks. It allows to evaluate the quality of a ready product according to the calculated parameters, to use the results obtained for the design of elastic pad

EXPERIMENTAL AND FINITE ELEMENT ANALYSIS OF NONAXISYMMETRIC STRETCH FLANGING PROCESS USING AA 5052

This paper deals with experimental and finite element analysis of the stretch flanging process using AA- 5052 sheets of 0.5 mm thick. A parametrical study has been done through finite element simulation to inspect the influence of procedural parametrical properties on maximum thinning (%) within the stretch flanging process. The influence of preliminary flange length of sheet metal blank, punch die clearance, and width was examined on the maximum thinning (%). An explicit dynamic finite element method was utilized using the finite element commercial package ABAQUS. Strain measurement was done after conducting stretch flanging tests. A Mesh convergence examination was carried out to ascertain the maximum percentage accuracy in FEM model. It is found through finite element simulation that the width of sheet metal blanks has a greater impact on the maximum percentage of thinning as compared to preliminary flange length, and clearance of the punch dies.

Improvement of Sheet Metal Properties by Inducing Residual Stresses into Sheet Metal Components by Embossing and Reforming

In sheet metal forming, combination of embossing and reforming allows the mechanical properties of sheet metal materials to be specifically improved. Here, local property modification is achieved by the residual stresses induced as a result of the one-sided embossing process followed by a reforming step. The residual stresses induced in this specific way can lead to a significantly increase in the fatigue strength of processed sheet metal components. However, in order to ensure this kind of component optimization in continuous operation, the induced stresses have to be homogeneous. In this respect, the main objective of the study reported about in this paper was to identify a forming strategy, consisting of the process steps embossing and reforming, that generates preferably homogeneous residual stress distributions into sheet metal blanks. For this, numerical and experimental investigations were carried out with samples of the stainless steel (X6Cr17) having a thickness of 1.5 mm. It was found that embossing and reforming, integrated into a conventional forming process, is a novel approach to specifically induce very localized homogeneous compressive residual stresses in sheet metal materials. This eliminates the need for costly post-processing by means of surface treatment.

On appropriate Finite Element discretization in simulation of gas-based hot sheet metal forming processes

Gaseous medium is being used for sheet metal forming at elevated temperatures, especially for lightweighting purposes. These processes enable forming of high strength alloys of a wide range of thickness due to low material flow stress as well as improved formability. In these processes, the resulting component properties are an interplay of numerous parameters. Instead of cost and time intensive experiments, FEM aids an effective and economic process optimization and enables a better understanding of the influence of process parameters on the component properties. In the current study, the importance of appropriate discretization of the workpiece within a gas-based hot sheet metal forming process is investigated based on a laboratory scale component. AA6010 sheet metal blanks of different thicknesses are studied numerically and experimentally. Simulations with different types of elements are performed and the evolution of process parameters as well as their influence on the final component thickness are analysed. Different element types resulted in noticeable difference in the simulation results and this difference also varies with the initial sheet thickness. Upon further experimental validation, the suitable element type for workpiece discretization is suggested, which enables practitioners to get reliable results via FE simulation of these processes.

Design of thermomechanical treatment of high strength steels

Reducing the level of COx and NOx emissions from combustion engines is an important goal in the automotive industry. One way to reduce the emissions is to use lightweight parts in the car construction. High-strength steels are one of the successful choices for body parts. Their strengthening mechanisms provide them with better mechanical properties, which translates into thinner sheet metal blanks and ultimately reduced weight of parts. The main strengthening mechanisms include TRIP (TRansformed Induced Plasticity) and TWIP (TWinning induced plasticity). This paper outlines processing of high-strength steels, from forging to round bars and heat treatment to determination of phase transformations and temperature profiles for thermomechanical processing in an innovative tool. The experimental materials contained manganese, silicon and different aluminium levels. Their compositions were selected with a goal to observe the properties of advanced multiphase high strength steels during processing.

The Frictional Force between Slug and Die in Shear Cutting after Material Separation

Frictional forces in sheet metal blanking are central in different aspects, e.g. in wear prediction, validation of simulation models or in so called slug pulling. The latter is a phenomenon where the slug is pulled out of the die by the punch after the sheet metal is separated. This leads to process disturbances reaching from a blocked belt feeder up to severe tool damage caused by the simultaneous cutting of the slug and the sheet metal strip. A sufficiently high frictional force between the slug and the die prevents this effect. Despite its importance, this force and its causes have not yet been investigated in detail. A method was developed in this paper to measure the frictional force between slug and die. A shear cutting tool with an integrated piezoelectric load cell and an inductive position sensor was used on a stamping press to cut sheet metal made of CuSn6 (R350, thickness 1 mm). The die clearance, the punch edge radii and the lubrication conditions were varied. A larger die clearance resulted in a lower frictional force while a larger punch edge radius increased it significantly. Lubrication reduced the frictional force, especially for small die clearances. Finally, the cause of the frictional force was investigated by identifying the relevant springback modes of the slugs. This was carried out by correlating the slugs' deflection, oversize, and clean cut height with the frictional force. Especially the slug oversize, i.e. the difference between the slug's diameter and the die's inner diameter, revealed a strong correlation. Calculations showed that the deformation in radial direction is the main cause of the frictional force between slug and die. It suggests that the slug oversize is a good measure for the magnitude of the frictional force.

Achieving Accuracy Improvements for Single-Point Incremental Forming Process Using a Circumferential Hammering Tool

The paper presents a novel solution for improving the accuracy of the wall area of parts manufactured by single point incremental forming. Thus, a forming tool with a special design that works according to the principle of circumferential hammering is deployed, with a direct improving effect of the forming conditions and consequently of the dimensional accuracy of the part. The research is focused on an experimental study of frustum-of-cone shapes manufactured from sheet metal blanks of DC05 deep drawing steel of 1 mm thickness. A typical customary technological setup is used for the single point incremental forming process, without any additional elements, and two forming tools, a hemispherical and a special one, which use the circumferential hammering effect. Several preliminary tests using both tools were performed in order to prove that part accuracy can be significantly improved by using the circumferential hammering tool. The research was further expanded to investigate the influence on part wall dimensional accuracy of three factors: tool spindle speed, tool feed rate and part dimensional configuration. Using a full factorial plan of experiments the results of 32 test runs were processed. All parts were machined adequately, free of any material fracturing. Based on the achieved machining accuracy of the part walls, precision mathematical models were developed for the prediction of part dimensional accuracy in those areas. The mathematical models were validated by practice, as the predicted accuracies were matched by the experimental results.

Numerical investigation of bipolar plates manufactured using hydroforming process

Simulations of forming processes using LS-DYNA and other nonlinear finite element software packages enables manufacturers to optimise processes without the attending waste associated with performing multiple actual processes. The goal of this study was to use finite element analysis to investigate microscale sheet hydroforming (MSSH) of annealed AISI 304 stainless steel for producing bipolar plates for proton exchange membrane fuel cells (PEMFC) based on the material properties of the blank that were obtained from hydraulic bulge testing. Two die geometries were used to investigate the effect of hydroforming pressure and channel width on the distribution of stress and strain across the flow field of the hydroformed channels, sheet thinning and the thickness distribution for the annealed AISI 304 sheet metal blanks. The simulation results were verified using experimental results. The results show that FEA technique accurately predicts the behaviour of the AISI 304 bank formed using MSSH.

Numerical investigation of bipolar plates manufactured using hydroforming process

Simulations of forming processes using LS-DYNA and other nonlinear finite element software packages enables manufacturers to optimise processes without the attending waste associated with performing multiple actual processes. The goal of this study was to use finite element analysis to investigate microscale sheet hydroforming (MSSH) of annealed AISI 304 stainless steel for producing bipolar plates for proton exchange membrane fuel cells (PEMFC) based on the material properties of the blank that were obtained from hydraulic bulge testing. Two die geometries were used to investigate the effect of hydroforming pressure and channel width on the distribution of stress and strain across the flow field of the hydroformed channels, sheet thinning and the thickness distribution for the annealed AISI 304 sheet metal blanks. The simulation results were verified using experimental results. The results show that FEA technique accurately predicts the behaviour of the AISI 304 bank formed using MSSH.

ПРИСПОСОБЛЕНИЕ И ИНСТРУМЕНТ ДЛЯ ИЗГОТОВЛЕНИЯ ОБРАЗЦОВ ИЗ ПОЛИМЕРНЫХ КОМПОЗИЦИОННЫХ МАТЕРИАЛОВ НА СТАНКЕ С ЧПУ (обзор)

The article discusses devices for fixing sheet metal blanks from PCM: a perforated vacuum table, its design features, advantages and disadvantages. Based on these data, the upper part of the vacuum table was made for cutting samples for Iosipescu tests and dielectric tests. The article describes various types of tools for PCM processing and an experiment on the wear resistance of a diamond-like coated rasp cutter when milling carbon fiber reinforced plastic, carried out by foreign researchers.

Numerical Simulation on Edge Crack of Advanced High-Strength Steel Considering Blanking Induced Damage

Sheet metal blanking is an indispensible process for stamping process widely used in automotive industry and home appliances. The damage induced by blanking becomes an important factor that may affect the sheet metal formability and cause edge crack. Conventionally, blanking process is simulated by solid element, while forming processes are simulated by shell element, and it is necessary that the damage legacy data transfer from blanking process simulation to forming process simulation so that the forming processes, especially edge crack can be simulated more accurately. In the present work, a new simulation method is proposed to predict edge crack in stamping of advanced high-strength steels considering blanking history. Blanking simulation is first conducted to obtain residual damage values near the blanked edge area, which will be further mapped onto the shell elements near the blanked edge in forming simulations. Several 3D numerical models of hole-expanding and drawing based on shell element are established to investigate crack during stamping and verified by experiments. The results show that the proposed method can efficiently predict the edge crack more accurately.

Symbiotic Circularity in Buildings: An Alternative Path for Valorizing Sheet Metal Waste Stream as Metal Building Facades

This study suggests an alternative approach to valorize non-hazardous industrial solid waste flow into construction materials, in particular as metal facade systems by quantifying the creative reuse of consistent and predicated sized scrap metal cutouts (known as Offal) that were generated from the automotive sheet metal stamping and blanking manufacturing processes. This study is an expansion on two papers presented at the 10th International Conference on the Environmental and Technical Implications of Construction with Alternative Materials (WASCON). Automotive sheet metal waste stream was transformed into two novel building facade system designs and a “cradle to gate” Life Cycle Assessment was carried out to analyze their environmental impacts and its resultant effect on design, manufacturing and economy. A Material Design Circularity Factor was introduced to compare both facade systems. Design #1 had greater impacts for all indicators except for operational energy due to the possibility of infiltration. Economically, design #1 had almost double the savings of design #2 at approximately four million dollars annually. The avoided carbon emissions made it evident that the creative reuse of Offal had significant environmental impacts. The two facade systems avoided 7.8 and 5.3 million kg CO2-eq. of greenhouse gas emissions for design #1 and design #2 respectively. Industrial Symbiosis is a viable concept that can lead to the adoption of circular economy principles to activate reuse over recycling for industrial by-products, which was promoted by creativity, saved manufacturing energy and the reduced costs of production of construction materials. This study proved that reusing automotive metal scrap for building envelopes is environmentally optimal and economically affordable.