Blank Holder Gap Research Articles

Analysis and Experiment of Blank Holder Gap in the Cylindrical Cup Deep Drawing of Low Carbon Steel to Prevent Cracking-Wrinkling

This paper aims to investigate Blank Holder Gap (BHG) in order to prevent wrinkles and crack defects in the deep drawing process of cylindrical cups with a diameter of 30 mm, using low carbon steel grade SPCC that is 0.7 mm thick. Mathematical and experimental approaches were applied to study the effect of BHG on wrinkle wave height and product quality. The analytical approaches used were the slab method and the Forming Limit Diagram (FLD) to determine the final thickness of the product specimen and the height of the wrinkling wave, respectively. Each method in this study had been compared to each other. Punch-die dimensions were determined based on the standard tool designed. According to the research, BHG is set 100% to 114% of the thickness of the initial material or equivalent about 0.70 to 0.80 mm. By using the value of this gap, the height of wrinkles can be avoided, the magnitude of the drawing force is still below the critical limit, and the product specimen does not experience wrinkles and cracks. The results of this study are applicable to the deep drawing of cup products on SPCC material with a thickness of no more than 1 mm.

A study on forming limit diagram and laminated stamping of paperboard

Abstract Coated paperboard not only has the advantages of traditional paper such as low density and cleanliness, but also overcomes its disadvantages such as poor barrier performance and sensitivity to moisture. It is more and more widely used in forming packaging containers. The current research on mechanical performance and inelastic deformation of paperboard mainly focus on its physical properties and simplified single-blank forming, but the studies on the forming limit diagram (FLD) of paperboard are relatively rare. In this paper, Nakajima tests have been carried out to determine the FLD curves of the polyethylene-coated paperboard blank along the machine direction, cross direction, and diagonal direction. A laminated stamping method for multi-blank is proposed and investigated by experiment and numerical simulation. Up to 5 blanks can be overlapped and stamped in a single punch stroke, and 5 bowl-shaped packaging containers can be formed simultaneously. Compared with the single-blank stamping process, the production efficiency can be greatly improved, but the flange area of the forming parts is easier to wrinkle. However, the wrinkling risk can still be controlled by optimizing the process parameters, such as friction factor and blank holder gap.

Optimizing the Process Parameters of Hydro-Deep Drawing of Cylindrical Parts Using Fiber Metal Laminates

Forming Fiber Metal Laminates (FMLs) is still challenging. There are some inherent limitations to forming smaller and complex-shaped FML parts. In particular, the process parameters have a major impact on the final FMLs part. In this paper, several investigations were conducted to optimize these process variables. In the investigations, different Blank Holder Gap (BHG) thicknesses were used to predict the optimal range; variable Blank Holder Force (BHF) and Cavity Pressure (CP) were chosen to make the results more convincing. Based on the numerical analysis, it is found that the optimum BHF should be between 10 to 15 KN; CP has a range from 8 to 10 MPa; optimum BHG should be 1.0 mm. And through using these predicted process parameters, a successful Glare cup has been formed. Furthermore, the forming performance of the Glare material is improved and the laminate has shown better formability. Finally, optimized process variables can be used for mass production of FMLs parts.

An Analysis of Process Parameters in the Hydroforming of a Hemispherical Dome Made of Fiber Metal Laminate

Even though fiber metal laminates (FMLs) were developed many years ago, existing forming approaches are not well qualified to produce intricate and small thin geometry. There are great difficulties in the deep drawing procedure, even for low forming depth. These difficulties are mainly related to the fiber layers limited elongation compared to the metals, and the process parameter selection during the deep drawing, which needs to be chosen very carefully. This research presents a numerical and experimental study on the influence of the hydroforming process parameters on FML hemispherical dome. The Aluminum 2024-T3 and prepreg glass fiber were used to produce the FML blanks. The parameters covered in this investigation were cavity pressure (CP), blank holder force (BHF), die entrance radius (DR), blank holder gap (BHG), and punch speed (PS). Taguchi’s design of experiments determined the effects of the input parameters on wrinkling and thinning. Results indicated that the BHG has the most significant impact on thinning and wrinkling. Optimization was conducted, and the optimum selected process parameter values were 80 kN for BHF, 15 MPa for CP, 8 mm for DR, 1.1 mm for BHG, and 30 mm/min for PS. Results revealed that FML cups formed by the optimized parameters could improve the utilization of the FMLs in mass production.

Investigation on the effect of blank holder gap in the hydroforming of cylindrical cups, made of fiber metal laminate

Although fiber metal laminates (FMLs) were invented a few decades ago, large-scale manufacturing, especially the forming process of small and complex-shaped products, has not been matured yet. The forming difficulty comes with the limited strain rate of the fiber layers compared to the metallic layers. As a result, the conventional approaches to form FML parts are not very suitable. Understanding the material behavior during the forming process is critical to find a new technique for relatively intricate and smaller FML parts. The blank holder gap (BHG) is one of the effective parameters to control the material flow in the deep drawing process, but in the case of the FMLs, the situation is completely different due to the laminate constituent. The compression of the fiberglass and thermo-plastique resin to the blank holder force (BHF) is not the same as the metals. The resin acts like a rubber, which decreases the thickness of the laminate and affects the friction between the laminate layers, especially when forming semi-cured laminates, which makes it hard to define an ideal BHF. This paper presents the results of numerical and experimental investigation of the effect of the BHG on the hydromechanical deep drawing (HDD) of a cylindrical cup made with 2/1 Glare sheets. It is found that the optimized BHF and cavity pressure (CP) with a BHG of 1.1 mm, smaller than the laminate’s initial thickness of 1.2 mm, resulted in a good part with a significant depth improvement of 35 mm. Results also exhibited that FML parts manufactured by considering the BHG can enhance its applications and lead to a reduction of time and effort spent in mass production.

Process Control Improvement in Deep Drawing of Hemispherical Cups Made of GLARE Material

Controlling the material flow under the blank holder in hydroforming is a delicate point that can be controlled by the blank holder force (BHF), cavity pressure (CP) and the blank holder gap (BHG). BHG is one of the effective parameters to control the material flow. A numerical and experimental approach studied the impact of the BHG on the Hydromechanical Deep Drawing (HDD) of a hemispherical cup made with 2/1 Glare sheets, including another two factors, CP and BHF. BHGs with different thickness was used in the experiments to form Glare Laminate. Simulation and experiment illustrate that an optimized value of these parameters has a good effect on the forming quality and depth of the final product. Finally, an appropriate value of the BHG is projected and the explanations of the failure modes are discussed.

An Investigation into Process Parameters Effect on the Formability of GLARE Materials Using Stamp Forming

The use of laminates allows an optimization of the material properties, these hybrid materials can unravel some problems in the industrial sector, particularly in aerospace, and advanced automotive industry. Fiber Metal Laminates (FMLs) can be produced both by laminating and by forming. Flat laminates are easier to produce by the lay-up process, for small and relatively complex shapes with low thickness there are significant challenges in the forming process even for small drawing ratios, In this investigation, a cylindrical GLARE cup was chosen, this shape with sharp curves and vertical geometrical walls, still face numerous difficulties in the forming procedure. Numerical simulations have been used and compared with the experimental results in the stamp forming to achieve good forming quality with higher depth. An extensive investigation of the effect of process variables has been done such as blank-holding force, and blank holder gap and the curing condition. Also, their roles in wrinkles formation, tearing and thinning, as well as formability have been performed. The results show a good agreement between the experiments and the numerical simulation and show clearly that the application of blank holder force and blank holder gap within specified limits has a positive effect on the quality of the formed cup and leads to higher depths. Understanding these parameters and the GLARE forming conduct and having a decent choice of these parameters can give the advantage to achieve smaller and more complex shapes with higher depth, especially for large scale manufacturing. Finally, this investigation can expand the modern application regions of the FMLs and GLARE parts.

Influence of Process Variables on the Stamping Formability of Aluminum Wing Nose Rib

Ribs are the forming components of the framework of an airplane wing. The nose ribs studied have a U-shaped geometry that consisted of a flat plate, a curved flange with various radius of curvature, and straight flange, and were produced by a stamping process. During stamping, some defects such as thinning, thickening, wrinkling, and springback may occur. To design a forming tool that produces good quality, it was essential to understand the influence of process variables. This study evaluated the influence of stamping process variables on the formability of the nose rib for prevention of excessive thinning and control of the springback phenomenon. Three important process variables namely, blank holder gap, die corner radius, and clearance between the die and the punch were analyzed during an Al-2024-O nose rib stamping. The stamping simulation was a nonlinear problem in nonlinear behavior of solid materials and contacts, which was applied to an elastic–plastic material employed with contact behavior conditions. A DOE design matrix was generated by a full factorial design with every combination of the design variables. The main process variables affecting the multi-objective function, i.e., thickness reduction ratio and springback amount were suggested through main effect analysis, along with the stamping simulation. An experiment was performed to verify the validity of the simulation results. Results indicated that the thickness reduction rate and the springback amount predicted by the simulation were in good agreement with the experimental results. The locations where the maximum thickness reduction occurred, the maximum deformation amount caused by springback, the blank holder force, and the initial blank shape were suggested in this paper. The influence of the process variables will be considered as a reference for improving the quality of the nose rib.

Simulation and Experimental Studies on Hydrodynamic Deep Drawing of 2198 Aluminum Lithium Alloy

The process of hydrodynamic deep drawing of Al2198 was investigated by finite element (FE) simulation and experimental works. The effects of die cavity pressure, blank holder gap and pre-bulging pressure on the forming process and the thickness distribution were evaluated. The results indicate that the pressure inside the liquid chamber and the blank holder gap or blank holder force are the main factors affecting hydrodynamic deep drawing process. In addition, appropriate pre-bulging pressure is beneficial to form good quality parts with a relatively uniform wall thickness.

Deformation and Defects in Hydroforming of Stainless Steel Ripple Plate with Controllable Corrugated Quantity and Depth

Hydro-forming can effectively solve the forming problem of complicated components. Aiming at the difficulty of stamping problem and poor forming quality for an aerospace deployable structure with ripple characteristics, hydro forming process is designed by analyzing deformation and defects. Combined with numerical simulation, defects of punch round corner region during hydro-forming are studied. Cavity pressure loading path, blank holder gap, corrugated quantity and depth are also optimized. The results show in the process the punch round corner is the weakest region, wrinkles will particular appeared in the blank holder zone. The corrugated quantity is in inverse proportion to the corrugated depth. In this paper, the finite Element Analysis model of corrugated quantity and depth is presented and calculated by the Dynaform program. This work is of directive significance to the optimal design and operation of ripple plate forming.

ANALISIS DAN EKSPERIMEN BLANK HOLDER GAP MINIMUM PADA PROSES RECTANGULAR CUP DEEP DRAWING

This paper aims to investigate the magnitude of minimum blank holder gap to prevent wrinkles and cracks defects of the rectangular cup with T4 material Tin Plate CA. Punch-die domensions are determined based on the standard tool designed. The methods of this research are an analytic, finite element (FE), and experimental approach, respectively. Each method in this study had been mutually compared to other methods. According to the research, minimum blank holder gap is recommended by 120% to 130% of the thickness of the initial material (about 0.24 A· 0.26 mm). By using the value of this gap, the height of wrinkles is very small, and the magnitude of the drawing force is still below the critical limit, so the product does not occur wrinkles and cracks.

Research on technological parameters of pressure forming with hot granule medium on AA7075 sheet

Hot granule medium pressure forming (HGMF) process is a new process in which granule medium replaces the medium in existing flexible-die hot forming process, such as liquids, gases or viscous medium. Hot forming of light alloy sheet parts can be realized based on the properties of granule medium, such as withstanding high temperature and pressure, filling well, sealing and loading easily. In this work, the forming of AA7075 cylindrical parts by HGMF process is taken as an example to establish the constitutive relation and forming limit diagram (FLD) of AA7075 sheet which is related to temperature by hot uniaxial tensile test of sheet metal. Based on the assumption that granule medium is applied to extended Drucker-Prager linear material model, the finite element model of HGMF process is established and the effect of technological parameters, such as forming temperature, blank-holder gap and drawing ratio, on the sheet metal formability, is studied. The limit drawing ratio curve of AA7075 cylindrical parts at forming temperature of 175−300 °C is obtained by HGMF process test, and the limit drawing ratio reaches the maximum value of 1.71 at 250 °C. The results of numerical simulation are consistent with the results of process test, and the forming force, distribution of wall thichness and form of instability are predicted correctly, which provides reference for the application of HGMF process.

마이크로 딥 드로잉 공정에서 박판소재의 크기효과 및 성형성에 관한 실험적 연구

This study investigates the effects of the size of copper sheets on the plastic deformation behavior in a microscale deep drawing process. Tensile tests are conducted on the copper sheets to study the flow stress of the materials with different grain sizes before carrying out the microscale deep drawing experiments. After the tensile tests, a novel desktop-sized microscale deep drawing system is used to perform the microscale deep drawing process. A series of microscale deep drawing experiments are subsequently performed, and the experimental results indicate that an increase in the grain size results in the reduction of the deformation load of the copper sheets due to the effects of the surface grain. The results also show that the blank holder gap improves both the formability of copper sheets and the material flow.

Hot granules medium pressure forming process of AA7075 conical parts

High strength aluminum alloy plate has a low elongation at room temperature, which leads to the forming of its components need a high temperature. Liquid or gas is used as the pressure-transfer medium in the existing flexible mould forming process, the heat resistance of the medium and pressurizing device makes the application of aluminum alloy plate thermoforming restricted. To solve this problem, the existing medium is replaced by the heat-resisting solid granules and the general pressure equipments are applied. Based on the pressure-transfer performance test of the solid granules medium, the feasibility that the assumption of the extended Drucker-Prager linear model can be used in the finite element analysis is proved. The constitutive equation, the yield function and the theoretical forming limit diagram(FLD) of AA7075 sheet are established. Through the finite element numerical simulation of hot granules medium pressure forming(HGMF) process, not only the influence laws of the process parameters, such as forming temperature, the blank-holder gap and the diameter of the slab, on sheet metal forming performance are discussed, but also the broken area of the forming process is analyzed and predicted, which are coincided with the technological test. The conical part whose half cone angle is 15° and relative height H/d 0 is 0.57, is formed in one process at 250°C. The HGMF process solves the problems of loading and seal in the existing flexible mould forming process and provides a novel technology for thermoforming of light alloy plate, such as magnesium alloy, aluminium alloy and titanium alloy.

A hybrid NN-FE approach to adjust blank holder gap over punch stroke in deep drawing process

In deep drawing process, the blank holder plays a key role in adjustment of metal flow into the die cavity. Moreover, the quality of drawn parts is extremely affected by this flow. There are two methods of treating the blank holder in deep drawing and its simulation. One is blank holder force (BHF) and the other is blank holder gap (BHG), defined as the fixed distance between the blank holder and the die surface. In previous studies, a large number of experimental techniques have been used to study BHF; however, the amount of theoretical and numerical simulation work to study BHG is insufficient. In the present study, the concept of BHG profile, i.e., variation of BHG over punch stroke is introduced and it is shown that a properly selected BHG profile can improve the section thickness of formed part and result in the drawing of deeper parts. Here, two methods for the optimization of BHG profile are devised, i.e., the local optimization and the global optimization methods. In the first approach, the best BHG in each punch step is determined and finally, the local optimized BHG profile is achieved. In the second method, however, the empirical model for the prediction of final minimum section thickness in terms of BHG profile is obtained using design of experiments and neural networks. In the next stage, the proposed model is implanted into a simulated annealing optimization procedure to identify a proper BHG profile that can produce the desired blank thickness. Afterward, the BHG profile approach is applied to a variety of initial thicknesses, blank diameters, and materials in order to examine the robustness of method. In this paper, ABAQUS finite element package is used to gather finite element (FE) data and several experiments are performed to verify the FE results.

Lubricant Research on SGMF of Magnesium Alloy Sheet

The non-isothermal drawing test in SGMF of the ordinary commercial AZ31B sheet metal was conducted to research the influence of lubricating condition on the drawing performance. And the experimental results have demonstrated that the lubricating condition has a great effect on the sheet drawability, furthermore, the work-piece with LDR of 2.4 was successfully produced when the water-based molybdenum disulfide with appropriate proportion was employed as lubricant, wherein the conditions were set as temperatures of the sheet metal and the granule medium respectively 290~310°C and 150~190°C, the blank holder gap 1.3mm and the drawing speed 1mm/s.

J122011 Optimization of Segmented Blank Holder Shape and Its Variable Blank Holder Gap in Deep-Drawing Process

J122011 Optimization of Segmented Blank Holder Shape and Its Variable Blank Holder Gap in Deep-Drawing Process

Optimization of Segmented Blank Holder Shape and Its Variable Blank Holder Gap in Deep-Drawing Process

Optimization of Segmented Blank Holder Shape and Its Variable Blank Holder Gap in Deep-Drawing Process

2111 Study on Effect of Blank Holder Gap on Cylindrical Cup Deep Drawing Process

This research is aimed to study on effects of Blank Holder Gap (BHG) on deep drawability, that has been investigated for a cylindrical cup deep drawing process from square blank shape. The BHG is an effective way to control material flow into the die cavity during forming process. The effects of BHG on deep drawing of circular cup are studied by using numerical simulation method with commercial code named LS-DYNA. The BHG is defined as a distance between die and blank holder surface (clearance). In this study the BHG is ranging from 1.05 to 1.60 mm when initial blank thickness is 1.00 mm. For failure (wrinkling and tearing) detection of deep drawing process Forming Limit Diagram (FLD) under Swift and Hill's criterion and Wrinkling Limit Diagram (WLD) are used. In order to find out an optimum BHG, and objective function of this research is defined as risk of tearing. From numerical simulation results, the BHG has a great effect on the forming quality of formed product. As ranging of BHG from 1.05 to 1.60 mm, a suitable BHG for deep drawing of circular cup for given tooling and material is tried to design. Moreover, a simple closed-loop algorithm had been developed in order to determine the variable BHF trajectory for constraint BHG during forming process.

Finite element simulation and model optimization of blankholder gap and shell element type in the stamping of a washing-trough

Wrinkling is the predominant failure and may be eliminated by appropriate control of blank holding force (BHF) in stamping of sheet metal parts. A new scheme for BHF was introduced in order to apply more realistic BHF in simulation. Different blankholder gaps (BHG) were used to simulate the blank holding process. The optimum BHG was determined through a systematic approach. It is found that the wrinkling in the flange region of the blank increases with the augmentation of the BHG. And the BHF varies owing to the variety of the stiffness of the flange sheet metal. Different shell element types based discrete Kirchhoff theory and Mindlin theory were used to simulate the deep drawing process with the optimum BHG. A comparison of the thickness and flange contour between the simulation results and experiment shows that the 4-node thin shell element based discrete Kirchhoff theory is better in the simulation of the sheet metal forming process and also has merit in not requiring much time.