Blanking Clearance Research Articles

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.

Effect of the individual layer thickness and relative blanking clearance on micro-blanking for Cu/Nb multilayer composite sheets

In this study, two types of Cu/Nb multilayer composite sheets with individual layer thicknesses of 11.11 μm and 0.35 μm, respectively, were first prepared and then tested by micro-blanking. The results show that the sheets of 0.35 μm exhibit higher ultimate tensile and shear strengths, and greater elongation, compared to those with an individual layer thickness of 11.11 μm. The sheet with an individual layer thickness of 11.11 μm achieves optimal blanking accuracy at a relative blanking clearance of 7%. Additionally, when the relative blanking clearance is 3%, it exhibits a significant proportion of smooth areas on the shear surface. Investigation of the shear surface at different ratios of punch stroke to sheet thickness (h/t) reveals that the Cu/Nb multilayer composite sheet experiences significant extrusion and bending during the micro-blanking process. Furthermore, the laminated structure exhibits remarkable continuity and deformation mobility, delaying crack formation. This study provides theoretical support for the plastic micro-blanking technology of multilayer composite.

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.

Optimum blanking clearance choice method by an approach coupling experimental trials and simulations

Blanking process of sheet metal is accomplished by a shearing action on a thin plate placed between two sharp cutting edges, known as “punch” and “die”. The main problem of this sheet metal cutting technology, that causes major shutdowns of the press machine, is the punch wear. Among all blanking parameters, the clearance set between the punch and the die has the major influence on tool wear. In this context, our study focuses on identifying the optimum blanking clearance that guarantees a maximum abrasion and chipping wear reduction for different sheet metal materials and different blanking operations. The developed approach combines experimental blanking tests and numerical simulation of blanking processes. Based on assumptions made in this paper, links are established between the stripping force and the abrasive wear behaviour of punching tools and also between the maximum pressure on the face of the punch and the risk of chipping. Using these links, criteria have been developed allowing to propose an optimum blanking clearance for all the configurations tested in this paper. A next step of this study consists on applying the optimum punch-die clearances in a variable way along a complex blanking shape and realizing experimental tests to compare the results (tool life and edge quality) with a constant blanking clearance.

Analysis of the influence of the blanking clearance size to the burr development on the sheet of mild steel, brass and aluminium in blanking process

Purpose: This research aims to analyse the influence of blanking clearance size on the burr development for mild steel sheet, brass and aluminium. The main reason for this research is estimating the burr size on blank parts. It is still significant since the quality of the products is determined by evaluating the amount of allowable burr in the parts. Design/methodology/approach: For the blanking process on the 3.00 mm thick sheets, various sizes of blanking clearance for a 20 mm diameter of the die opening are employed, as is the technique for obtaining the parts. Then the height of the burr on each product was measured using a micrometre and toolmaker microscope. The height of burr for each size of blanking clearance have been recorded and compared using a graph. Comparison made to identify which measure of blanking clearance and which type of material will produce a small size of burr. Findings: For mild steel, brass, and aluminium, blanking clearance 0.15 mm produced burr heights of 0.088 mm, 0.015 mm, and 0.024 mm, and blanking clearance 0.13 mm produced bur heights of 0.192 mm, 0.055 mm, and 0.046 mm, respectively. The brass had a lower burr height than mild steel and aluminium, according to the results. More significant blanking clearance (0.15 mm) produced a smaller size of burr compared to a smaller blanking clearance (0.13 mm). Practical implications: This study focuses on burr height rather than the wear of the punch and die cutting edge; burr height can affect punch and die sharpness. It also can guide practitioners in estimating blanking clearance and the burr height of mild steel, brass and aluminium. Originality/value: This paper demonstrates that the gap between the punch and die influences the burr height. The material strength also affects the burr height, with a high tensile strength resulting in a larger burr.

Feasibility of Mass Production Verified by Cut Surface Quality and Tool Load in Negative Clearance Blanking

Feasibility of Mass Production Verified by Cut Surface Quality and Tool Load in Negative Clearance Blanking

Effect of blanking on magnetic and mechanical properties of non-oriented electrical steel

World-wide blanking is the most popular technique for producing the non-oriented electrical steel lamination. However, blanking has a great effect on magnetic property and mechanical property, such as the introduction of uneven residual stress, the deterioration of magnetic properties and the increase of micro-hardness. In this research, non-oriented electrical steel sheets are investigated via blanking test by 3 kinds of punches. The blanking edges are examined by the optical microscopy and micro-hardness test to visualize the distribution of micro-hardness. The magnetic properties are also measured. The results show that the blanking clearance has a great influence on magnetic properties and mechanical properties of the blanked material.

Blanking induced damage in thin 3.2% silicon steel sheets

The cores of electrical motors and transformers are made by blanking, piercing and stacking of thin metallic sheets having various features cut from the original blank. The material experiences local plastic deformation near the cut edge due to the blanking operation. The quality and efficiency of the produced products are directly affected by the mechanical and magnetic properties of the blanks at the cut edge. The effects of the blanking process on deformation evolution in thin sheets of high Si electrical steels was investigated. In-situ blanking experiments together with the digital image correlation (DIC) technique were used to quantify local deformation evolution during thin sheet blanking operations. Magnetic hysteresis losses were measured using a purpose-built single sheet tester and linked to the measured deformation maps. The residual stresses were qualitatively assessed by means of nano-hardness measurements while the local microstructural properties and dislocation generations were determined using EBSD analysis of the blanked parts. The results indicated that for the tested materials with 0.1t blanking clearance, electrical steel sheets with 0.2 mm thickness experiences larger deformation prior to fracture during blanking compared with samples having 0.35 mm thickness. This has a direct relationship with the measured hysteresis losses. However, the dislocation maps indicated that dislocations of GNDs are more pronounced for thicker samples that aligns with the effect of dislocations on magnetic power losses rather than hysteresis losses measured in this research.

Investigations on edge quality and its effect on tensile property and fracture patterns of QP980

Advanced High Strength Steel (AHSS) sheet metals have been widely used in automotive structures due to its safety performance and lightweight potentials, and some AHSS materials have been found more sensitive to edge crack during the stamping process. The tensile property of the sheared edge has great influence on flangability for AHSS. In the present work, the effects of the blanking clearance and shear angle on the quality of the sheared edge and subsequent tensile property for QP980 have been investigated experimentally by microscope and sheared-edge tension test based on digital image correlation (DIC) technology. In addition, the tensile properties of the specimens prepared by wire electrical discharging machining (Wire-EDM) and laser cutting were tested as well. The results show that promising and stable sheared edge quality, and tension with postponed fracture can be achieved if the clearance ratio is set as 7% or 11% for QP980. During blanking with 5° or 10° oblique edge, the ratios of burnish zone and burr zone decrease simultaneously, and the subsequent tensile performance increases significantly. The oblique edge blanking obtains smaller and smoother burr, and the sheared surface benefits from less void damage. In addition, based on the fracture surface morphology and the tracking of the fracture process with DIC technology, two typical fracture patterns (oblique crack and transverse oblique crack) in tension test are illustrated. Oblique crack occurring on the specimens with good edge quality shows obvious necking phenomenon and belongs to the typical ductile fracture. While transverse oblique crack exhibiting with high frequency on the sheared specimens is typical edge fracture and shows mixed characteristics of ductile fracture and brittle fracture.

Optimum clearance determination in blanking coarse-grained non-oriented electrical steel sheets: experiment and simulation

Blanking process plays a critical role in the deterioration of magnetic properties of coarse-grained non-oriented electrical steel of motors. With the decrease of grain number in the thickness direction, the deformation behavior in blanking process becomes different and complex. In this paper, the high-grade non-oriented electrical steel is selected for blanking tests within the relative blanking clearance range. The results show that there exists an optimum clearance which leads to the high-quality sheared edge for the application. Nevertheless, the exact value of optimum clearance cannot be provided by experiments. Therefore, a novel Voronoi-based FE model is established to analyze the blanking deformation behaviors of individual grains. The flow stresses of surface and internal grains are identified through the widely applied surface layer theory. The proposed FE model is an appropriate prediction tool for simulating the blanking process of non-oriented electrical steel sheets. Meanwhile, through the new proposed model, an exact optimum clearance determination method is established. The proposed methodology predicts that the optimum clearance for the investigated sheet is 13.8%t, which is further verified by the experimental data.

Influence of Grain Size and Blanking Clearance on Magnetic Properties Deterioration of Non-Oriented Electrical Steel

In motor manufacturing, blanking process of non-oriented electrical steel inevitably induces plastic deformation and residual stress near the blanked edge and thus leads to the deterioration of magnetic properties. However, as for the newly developed non-oriented electrical steel, the scale of grain size is close to both blanking clearance and thickness. Grain size integrated with blanking clearance thus significantly affects the blanked edge quality. In order to reveal the effects of grain size and blanking clearance on magnetic properties deterioration, systematic blanking tests have been conducted using various non-oriented electrical steel sheets (same chemical composition, three thicknesses, and three grain sizes) in a considered clearance range. The blanked edges are characterized by means of optical microscopy, scanning electron microscopy, and micro-hardness tests. Magnetic domain structures are also observed by magnetic force microscopy. The iron losses are measured by single sheet tester method. The burnished ratio decided by clearance and grain size can be taken as the indicator to assess the deterioration of magnetic properties. The blanked edge with larger burnished ratio leads to lower increase of micro-hardness, less degradation of domain structure, and less deterioration of iron loss. In this paper, about 5.8% iron loss can be reduced by optimization of blanking clearance, which is quite pronounced for energy saving. In further study, an approximate linear function of the ratio of optimum clearance to gain size with $D^{-1/2}$ is empirically proposed to demonstrate the grain size dependence on optimum clearance determination. This paper thus provides an in-depth understanding and guidance for reducing the deterioration of magnetic properties caused by the blanking process.

Grain Size Effect on Optimum Clearance Determination in Blanking Non-Oriented Electrical Steel Sheet

Non-oriented electrical steel, as the core magnetic material, is firstly blanked into lamination in motor manufacturing. As for the newly developed steel, there is a general tendency toward thinner and coarser-grained. Due to blanking clearance and thickness are both down to the sub-millimeter scale, grain size becomes an important role in formation of blanked edge quality, which mainly determines the deterioration level of magnetic properties. This paper aims to systemically investigate the influence of blanking clearance and grain size on blanked edge quality. In this research, non-oriented electrical steel sheets of the same chemical composition, 3 thicknesses and 3 grain sizes are prepared for blanking tests over the conventional relative blanking clearance range. The blanking edges are quantitatively examined by means of optical microscopy to visualize the distribution of plastic deformation. The results show that there exists an optimum clearance that leads to a fine blanked edge. In further study, an approximate linear equation of the ratio of clearance/grain size (c/D) vs. D is found for optimizing the blanked edge quality. This research thus provides an in-depth understanding and guidance for optimum blanking clearance determination influenced by size effect.

Effect of strain gradient on stretch flange deformation limit of steel sheets

The effect of strain gradient on the stretch flange deformation limit of steel sheets was investigated by hole expansion test under some forming conditions and by FEM. Hole expansion ratio was changed by changing initial hole diameter and punch shapes. It was clarified that a limit stretch flange deformation strain basically depends on not the initial hole diameter and the punch shape by themselves but the strain gradient in the radial direction. The strain gradient along the direction toward the maximum principal strain did not affect limit deformation strain. The limit deformation thickness strain of the stretch flange portion could be changed by changing strain gradient. These results suggest that the formability of stretch flange deformation area should be determined from not only the maximum principle strain but also the strain gradient and blanking clearance.

A microstructure-based macro-micro multi-scale fine-blanking simulation of ferrite-cementite steels

The fine-blanking process of ferrite-cementite steels was simulated with a macro-micro multi-scale approach. In the macroscopic simulation, the effects of material and blanking clearance were investigated by evaluating the damage work density of the material in the center of the fine-blanking shearing zone. A series of microstructure-based models with different particle fraction and distribution were generated as sub-models for the microscopic simulations. Microscopic damage in the sub-models was predicted with the damage work model. The simulation results indicated that an increase in particle fraction and the existence of carbide banding accelerated the microscopic damage of the material in the shearing zone during fine-blanking. Micro cracks appeared and extended along the carbide band. In addition, an increase in blanking clearance speeded up the microscopic damage accumulation at the microscale and caused early fracture of the material in the shearing zone at the macro scale. The SEM observations of various fine-blanking specimens substantiated the predictions of the simulations and suggested that severe carbide banding would change the macro crack path in the sheets, adversely affecting the quality of the blanking surface.

음의 클리어런스를 갖는 AL6061-T6 포일 블랭킹의 유한요소해석

음의 클리어런스를 갖는 AL6061-T6 포일 블랭킹의 유한요소해석

Investigation of Scar Formation in Fine Blanking Processes and their Prediction in 3D ALE Simulations

Scar formation in fine blanking was investigated by means of a particularly developed fine blanking tool and experimental evidence about significant the process parameters chamfer size of the blanking tools, V-Ring usage and clearance is given. Furthermore, a special purpose Finite Element code using the Arbitrary-Lagrange-Eulerian method with a process specific mesh generation is demonstrated and used for the determination of relevant parameters for prediction crack formation in 3D fine blanking simulations. The simulations shown, that a commonly used description of fracture strain as a function of stress and deformation state is not sufficient. In order to simulate scar occurrence on the blanking surface, the significant increase of fracture strain due to temperature rise because of plastic heat generation has to be taken into account. A possible way of measuring the temperature effect was shown in torsion tests at different initial temperature levels.

Effects of Parameters on Fine Blanking of Steel Synchronizer Ring Teeth

The influences of parameters on fine blanking of steel synchronizer ring teeth have been studied in this paper. Based on the finite element (FE) analysis software DEFORM-3D, a three-dimensional FE model of fine blanking of steel synchronizer ring teeth was established. By analyzing the distribution of hydrostatic stress, the length of smooth cut surface and the height of die-roll, the influence of parameters (i.e., counterforce, blanking clearance and V-ring indenter form) on the cut surface of synchronizer ring teeth were discussed. The quantitative relationships between parameters and the cut surfaces were established. The results show that: Increasing counterforce, decreasing blanking clearance and V-ring indenter located on die are conducive to increase the length of smooth cut surface and to decrease the height of die-roll. These results have a certain guiding significance on the production process of fine blanking of steel synchronizer ring.

Finite Element Simulation and Experimental Research in Insulation Spacer Blanking

Blanking finite element analysis model of non-metallic material PET insulation spacer was established, and the influence of process parameters on blanking quality of insulation spacer was analyzed. The results show that the qualified cross-section quality, the high dimensional accuracy and the little bending distortion of blanking workpiece can be obtained by the reasonable blanking clearance and the higher blanking speed. The corresponding experiment was carried out, the results show that the process parameters of insulation spacer blanking obtained by numerical simulation are feasible, and the qualified insulation spacer was produced by the simulation results.

Three Dimensional Finite Element Simulation of Sheet Metal Blanking Process

The shearing process such as the blanking of sheet metals has been used often to prepare workpieces for subsequent forming operations. The use of FEM simulation is increasing for investigation and optimizing the blanking process. In the current literature a blanking FEM simulations for the limited capability and large computational cost of the three dimensional (3D) analysis has been largely limited to two dimensional (2D) plane axis-symmetry problems. However, a significant progress in modelling which takes into account the influence of real material (e.g. microstructure of the material), physical and technological conditions can be obtained by using 3D numerical analysis methods in this area. The objective of this paper is to present 3D finite element analysis of the ductile fracture, strain distribution and stress in blanking process with the assumption geometrical and physical nonlinearities. The physical, mathematical and computer model of the process are elaborated. Dynamic effects, mechanical coupling, constitutive damage law and contact friction are taken into account. The application in ANSYS/LS-DYNA program is elaborated. The effect of the main process parameter a blanking clearance on the deformation of 1018 steel and quality of the blanks sheared edge is analyzed. The results of computer simulations can be used to forecasting quality of the final parts optimization.

Shearing Edging Investigation in High-Speed Blanking Process Applying Precision Progressive Die

The high-speed blanking process applying precision progressive die represents the one of the highest level of today’s stamping technology, mainly is used for the production of the ultra-thin, small, complex electronic components. An orthogonal experiment scheme with three factors (including blanking clearance, surface roughness of the die, stamping speed) was established in this paper based on the actual production. The high-speed blanking process experiment applying precision progressive die was carried out base on this scheme. The quality of the shearing edging of blanking parts was used to evaluate the different influence degree of three factors. The result showed that the surface roughness of the die affected the quality of the shearing edging more than that of the other two. The higher the die surface accuracy, the better the quality of the shearing edging. The result also showed that the high speed can reduce the quantity of the burr of the blanking of the ultra-thin sheet metal.