Punch Height Research Articles

Study on Press Formability and Properties of UV-Curable Polyurethane Acrylate Coatings with Different Reactive Diluents.

UV-curable coatings have numerous advantages, including environmental sustainability due to 100% solid content, economic feasibility attributable to relatively fast curing time, decent appearance, mechanical properties, chemical resistance, and abrasion resistance. However, UV-curable polyurethane acrylate coatings on metals apparently restrict their engineering applications owing to low mechanical properties and poor thermal stability, giving UV-curable coatings less flexibility and formability. In this study, we evaluated the property change of films according to the type of reactive diluents that lowers the viscosity of UV-curing coatings for pre-coated metal and has a substantial effect on the curing rate, viscoelastic properties, adhesive properties, and flexibility of the film. Moreover, there are many changes in the properties of coatings according to varied curing conditions in order to evaluate the oxygen inhibition phenomenon during the curing process in the atmosphere. In particular, to evaluate the effect of reactive diluents on forming formability, which is the most crucial property for the pre-coated metal, this study used conventional formability tests, such as t-bending or the Erichsen test. Moreover, a cross-die cup drawing mold with a similar form as failure and Safety Zone was utilized in order to obtain clearer information on its actual formability. The analysis on the effect of failure and safety zone on the material used in press forming was conducted by assessing limit punch height and forming a limit diagram of the manufactured film according to varied reactive diluents.

Performance Evaluation of Planar Anisotropy Yield Criteria for Aluminum Sheet Forming Analysis

The present work aims making a step by identifying a set of standardized accuracy measures based on laboratory experiments. Uniaxial tension, plane strain tension, hemispherical dome, and square cup tests were conducted for a 6000 series aluminum sheet used as automotive panels. Principal strain distribution, punch height at fracture, draw-in, and wrinkling were measured and compared with numerical simulation predictions. The performance of the five yield criteria, Barlat89, BBC2005, Hill48, Vegter2017, and YSD6 (Yoshida 6th order polynomial function) was measured and evaluated using the conventional accuracy index and the proposed accuracy indexes that represent manufacturing defects encountered in practice. It is found that state of the art material models such as BBC2005, Vegter2017 and YSD6 are fully able of representing standardized material test results, which is also well reflected in the predictive accuracy of simulated hemispherical dome and square cup tests. Because earlier models such as Hill48 and Barlat89 lack in capturing a high number of experimentally determined data points, they should be used with caution even Barlat89 shows good performance in the hemispherical dome tests.

Microstructured SiOx/COP Stamps for Patterning TiO2 on Polymer Substrates via Microcontact Printing.

Microcontact printing (μCP) techniques have sparked a surge of interests in microfabrication since they help produce arrays on a wide range of target substrates in a facile and efficient manner. Polydimethylsiloxane (PDMS), as a well-established material for stamps, has constraints resulting from its hydrophobicity and softness, and the replication of PDMS stamps usually requires rigid masters or processes using a photoresist. Herein, a novel μCP stamp based on cyclo-olefin polymer (COP) is produced through vacuum ultraviolet (VUV) lithography. 2,4,6,8-Tetramethylcyclotetrasiloxane is selectively deposited at the affinity-patterns on the COP surface, and these patterned siloxane films are converted into SiOx meanwhile protecting the COP beneath them from the VUV photoetching. By this means, a patterned relief is fabricated on the COP plates, resulting in a hydrophilic SiOx/COP μCP stamp with punch heights of ∼180 nm. The novelty arises from the simplicity of the master- and photoresist-free microstructuring, and the higher stiffness of SiOx/COP stamps prevents the deformation during pressing. Finally, an example μCP is given to transfer titania precursor gel and produce TiO2 micropatterns on flexible polymer substrates. The SiOx/COP stamps and the μCP of TiO2 provide simple and cost-effective patterning techniques, which should contribute to the future design and creation of flexible devices.

ANALISIS KETINGGIAN TOOL PUNCH RIVET TERHADAP HASIL RIVET ING CONTACT PADA SWITCH LAMPU REM MOTOR TIPE C8EA

The product of CBEA Terminal B / B2 Assy is one of the C8EA type Switch components used for brake light switches on two-wheeled vehicles. In the manufacturing process often experience Contact Crack. Contact Crack problems occur in the rivet ing process. This study aims to reduce / eliminate the contact Crack problem, the method used is to conduct research on variations in the height of the punch in the rivet ing process. The initial height of the punch before the research is 49.10 mm, in this study the height of the punch to be examined is 48.60 mm, 48.70 mm, 48.80 mm, 48.90 mm and 49.00 mm. The results obtained for the most appropriate punch height are the height of 48.60 mm with the contact Crack ratio of 3/20, the size of the Crack & contact size entered into the standard, the flexural strength is still standard and the average hardness produced is 92.52 HV which is included in the maximum standard.

Experimental and numerical studies on joining steel tubes by end forming

The present article is focused on the development of a novel method of joining two steel tubes of different diameters at their ends by plastic deformation. A single stroke environmental friendly joining process consisting of tube end inversion and tube end beading has been developed. The proposed technology has the potential to replace the existing methods of joining such as welding, adhesive bonding, and joining by fasteners. The process has been modeled and analyzed in Abaqus finite element code, and the influence of important parameters on the joining formation has been identified. A number of criteria have been developed which can predict the quality of the joint at the shop floor. Demonstration of few selected cases on lab scale enhances the feasibility of the operation at the industrial level. The load-displacement behavior has been predicted, and validated with experiments. Out of all the parameters, projected height of punch, and circular arc radius are more influencing parameters. Mechanical testing of fabricated joints has been done using pull-out tests and compression tests. The strength of the fabricated joints compared well with the tube-to-tube joint made by arc welding. An alternative solution for joining of longer tubes has also been developed.

Surface quality and shape accuracy of multi-point warm press forming Corian sheets

The advantages of multi-point warm press forming Corian sheet are fewly studied. In this study, the principle of multi-point warm press forming process and the geometrical relationship between multi-point punch elements and objective surface were firstly illustrated. The multi-point CAD/CAM software was used for punch height calculation and punch location adjustment. The effects of elastic cushion, forming temperature and forming force on the forming accuracy, were studied through multi-point warm press forming experiments. Then, the Corian sheets for spherical and saddle-shaped parts based on suitable forming parameters were formed through multi-point warm press forming process, and the shape errors between experimental parts and objective ones were compared. The high surface quality and shape accuracy of both spherical and saddle-shaped parts were obtained at 165 °C with the forming force of 100 kN. It confirms that the multi-point warm press forming process is feasible for manufacturing Corian sheets.

NUMERICAL INVESTIGATION OF THE INFLUENCE OF PUNCH TIP RADIUS AND INTERPOLATOR TYPE IN MULTI-POINT FORMING

Multi-point forming (MPF) is a new flexible forming technology in which the fixed shape of conventional dies is replaced by a pair of opposed matrices of movable punch elements called "punch group".By using multi-point die a variety of three dimensional sheet parts of different shapes can be produced. However due to the discrete contacts between the work piece and punches the dimple defects occurred. In this paper, B-spline technique was used to represent the profile of the final product shape by adjusting the punch height of reconfigurable die. Finite element code (ANSYS 11) was used to simulate the MPF process and to investigate the influence of punch tip radius the interpolator type on the stress distribution, thickness variation and dimpling defect .The simulation results show that the large tip radius and (4mm) rubber interpolator have a great effect in reducing the stress concentration, thickness variation and also prevent the dimpling defect.

Sheet Metal Forming Processes – Recent Technological Advances

The sheet metal industry has seen more technological advances than any other since the last century. Right from hand-forming processes to finite element based simulation, the transformation is very significant. They have prominent industrial applications especially in automotive industries. This may be attributed to the ease with which the final component with desired shape and appearance can be produced using simple tools. Due to wide range of applications, the process of forming the sheet metal into various shapes leads to classification of the forming processes based on specific operation. This classification involves bending, blanking, stretch forming and deep drawing. Each process has some parameters that define the quality of the work achieved. This paper aims at scattering light on the recent research and developments in the sheet metal forming processes over the last two decades. Most of the literature available on sheet metal forming focuses on the parameters that influence the quality and economic factor of the final product. The influence of process parameters based on geometry such as punch nose radius, blank temperature, and blank holding force, tooling dimensions, blank thickness and punch depth is significant. Similarly, the parameters based on the material properties like elastic strength, yield strength, plasticity and anisotropy have as much influence as the geometry based parameters. The literature raises the issue of defects in the formed parts. Defects such as wrinkling, tearing, springback, local necking and buckling in regions of compressive stresses have been analysed using both experimental and simulation techniques. Springback, the most predominant defect, has been researched thoroughly while considering sheet thickness, punch force, nose radius, binder force, die opening, punch velocity, punch height, sheet anisotropy, clearance, elastic limit and yield strength of the blank material as input parameters. Lastly, this paper also aims at reviewing the finite element based tool design, experimental and numerical investigations into sheet metal forming processes.

Microstructure Correlation with Formability for Biaxial Stretching of Magnesium Alloy AZ31B at Mildly Elevated Temperatures

Magnesium AZ31B sheets of 2 mm thickness were stretch formed with a 101.6-mm-diameter punch at temperatures from 25°C to 150°C, in 25°C increments. Surface strains were measured with a digital image correlation method. The punch height versus load curve was found to be the same for temperatures of 25°C and for 50°C, whereas at 75°C and above, the load for a given punch height started to decrease, indicating a potential change in deformation mechanism. Electron backscatter diffraction was used to quantify features of the microstructure in the tested specimens. In particular, the gradual decrease in twinning activity as a result of easier thermally activated slip with increasing temperatures is quantified across this range. Moreover, twin activity was found to predominantly involve the formation of $$ \left\{{10\bar{1}1} \right\} $$ compression twins that rapidly transform to create secondary twins for easier strain accommodation.

The effect of mechanical properties on hole flangeability of stainless steel sheets

This study investigates the effect of mechanical properties on hole flangeability of stainless steel sheets. Four different stainless steel sheets, SUS202, SUS304L, SUS316L, and SUS430, with a thickness of 3.0 mm, were evaluated. To estimate the hole flangeability, hole expansion ratio, punch load, flange height, and lip thickness were experimentally investigated. The degree of circumferential strain along the periphery of the expanded hole is important in determining the hole expansion ratio. For materials with higher work hardening exponent and anisotropy, there is an increased resistance in wall thickness reduction, which accelerates local strain concentration along the periphery of the expanded hole in the circumferential direction and lowers hole expansion ratio. The main factors controlling punch load, lip thickness, and height were evaluated through correlation analysis. The flangeability of stainless steel sheets is strongly dependent on both the work hardening exponent and the material anisotropy.

Effects of mechanical properties and geometric conditions on stiffness of Hyperboloid Shallow Shell

The experiment models based on the hyperboloid shallow shells that represent automobile panel's surface features are established. The effects of material properties and geometric conditions condition on the stiffness of hyperboloid shallow shell are investigated experimentally. The influences of panel thickness and geometric conditions on stiffness are very obvious. Stiffness increases with increasing of the panel thickness, and stiffness doubled as increasing in thickness with 0.1 mm. The effect of thickness on stiffness is far greater than that of blank holding force. The greater the arc height of punch, the greater the stiffness. And stiffness increases nearly by five times with arc height of punch is from 3mm to 9mm. The effect of arc height of punch on stiffness is far greater than that of materials mechanical properties. The stiffness is varied with different panel material properties by the same forming and stiffness test conditions. The decrease of yield strength is beneficial to the panel stiffness. The appropriate choice of materials and forming process condition is important in meeting necessary requirements for the energy-saving, lightweight and reducing wind resistance design in automotive industry.

Flexible Die Design and Springback Compensation Based on Modified Displacement Adjustment Method

Springback in metal forming process often results in undesirable shape changes in formed parts and leads to deterioration in product quality. Even though springback can be predicted and compensated for through the theories or methodologies established thus far, an increase in manufacturing cost accompanied by a change in die shape is inevitable. In the present paper, it is suggested that the cost accompanied with springback compensation can be minimized while allowing the processing of various three-dimensional curved surfaces by using a flexible die composed of multiple punches. With the die being very flexible, the iterative trial-and-error method can be readily applied to compensate for the springback. Thus, repeated designing and redesigning of solid or matched dies can be avoided, effectively saving considerable time. Only some adjustments of punch height are required. Detailed designs of the flexible die as well as two core algorithms to control the respective punch heights are described in this paper. In addition, a closed-loop system for the springback compensation using the flexible die is proposed. The amount of springback was simulated by a finite element analysis and the modified displacement adjustment (DA) method as the springback compensation model was used in the closed-loop system. This system was applied to a two-dimensional quadratic shape problem, and its robustness was verified by an experiment.

Numerical simulation of multi-point forming accuracy for polycarbonate sheet

Multi-point forming is an advanced flexible manufacture technology, which has been used in many fields successfully. In order to provide a flexible method for forming a polymer, multi-point forming is applied to the manufacture of polycarbonate sheet. An optimized DSGZ constitutive model is established to describe the stress–strain relation of polycarbonate sheet, and its parameters are determined according to experimental data. The multi-point forming process of polycarbonate sheet is introduced briefly, and a simple calculating scheme of punch height is developed. Numerical simulations of spherical and saddle-shaped parts are carried out by dynamic explicit finite element analysis, and the effects of punch number and punch radius on the surface accuracy and shape accuracy are studied. The multi-point forming experiments of polycarbonate sheet are done, and the comparisons of shape error between experimental parts and objective parts are conducted, which show that the polycarbonate products have good surface accuracy and shape accuracy.

Study of multi-point forming for polycarbonate sheet

The multi-point forming (MPF) process of polycarbonate (PC) sheet is introduced briefly, geometrical relationship between objective surface and punch element is determined, and a simple calculation scheme of punch height is developed. Numerical simulations of spherical and saddle-shaped parts are carried out by dynamic explicit finite element analysis; the effects of forming temperature, forming pressure, punch matrix, and punch radius on the forming quality are investigated, and the suitable forming parameters are determined. Then, the MPF experiments of PC sheet for spherical and saddle-shaped parts based on the forming parameters are done, and the comparisons of shape error between experimental parts and object surfaces are carried out. Consequently, the PC products have good shape accuracy, which confirms that MPF used for forming PC sheet is feasible and the forming parameters obtained by numerical simulation are sensible.

유한요소법을 이용한 가변스트레치공정 성형변수에 따른 성형오차 경향분석

A shape error of the sheet metal product made by a flexible stretch forming process is occurred by a various forming parameters. A die used in the flexible stretch forming is composed of a punch array to obtain the various objective surfaces using only one die. But gaps between the punches induce the shape error and the defect such as a scratch. Forming parameters of the punch size and the elastic pad to prevent the surface defect must be considered in the flexible die design process. In this study, tendency analysis of shape error according to the forming parameters in the flexible stretch process is conducted using a finite element method. Three forming parameters, which are the punch size, the objective curvature radius and the elastic pad thickness, are considered. Finite element modeling using the punch height calculation algorithm and the evaluation method of the shape error, which is a representative value for the formability of formed surface, are proposed. Consequently, the shape error is in proportion to the punch size and is out of proportion to the objective curvature radius and the elastic pad thickness.

A study on thick plate forming using flexible forming process and its application to a simply curved plate

In this study, design and fabrication of a flexible forming machine are carried out for the purpose of manufacturing a prototype of curved plate block for hull structure used in shipbuilding industry. Flexible forming dies which consist of numbers of punches in an array form for upper and lower sides are designed in view of thick plate forming. A punch has formation of male and female screws to adjust its length with regard to a given surface, and all punches are supported by each other in punch housing. Software for process configuration and punch control are developed to operate the novel flexible forming machine. The software are composed of the punch height calculation part which uses an offset surface scheme. Prior to manufacturing of a prototype, numerical simulations for a saddle-typed thick plate forming process including metal forming and spring-back analyses are carried out to predict the forming performance. Experiments are also carried out to validate and confirm the feasibility of flexible forming technology in view of practical application of thick plate forming process. Curvature radii observed in the simulation and experiment are investigated and compared. Consequently, development and practical application of flexible forming technology to the thick plate forming process are described from design of the forming machine to manufacturing of the prototype. It is confirmed that the flexible forming technology suggested in this study has enough feasibility in new application of thick plate forming in shipbuilding structures which has been formed through expensive and laborious conventional line heating.

Application of flexible forming process to hull structure forming

The conventional line heating method has been applied for the manufacture of various curved blocks used for hull structures in the ship-building industry. However, it has low economical efficiency and productivity because most of its processes are based entirely on the skillful experience of experts. In this study, a flexible forming process is proposed and utilized to substitute for the conventional manual process. In the proposed process, numbers of punches which have round shapes on the contact tip are adopted to configure an equivalent forming surface according to the arbitrarily curved objective surface. A simple punch height determination algorithm that considers the discrete surface and its spatial planar equations is applied to determine the discrete forming surface composed of the adjusted punches. Punch height data are transferred to a numerical simulation model using ANSYS parametric design language, and finite element analysis is conducted to check the formability of the process. Further, experimental investigations are carried out to verify the feasibility of the process using a flexible forming apparatus. Consequently, it is confirmed that a double-curved thick plate could be obtained by the flexible forming process.

Finite element analysis of punch height effect on V-bending angle

Considering the advantages of the V-bending die, the economical set-up time and the fabrication of a wide range of part size and complex shape, the V-bending die is generally used, especially in the Press Brake machine. However, the punch heights in the partial V-bending die affected the bending angle. In this study, the finite element method (FEM) was used to investigate the effects of punch height. The FEM simulation results revealed that the effects of punch height on the bending angle were clearly theoretically clarified based on the material flow analysis and stress distribution. The punch height affected the gap between the workpiece and the die, as well as the reversed bending zone, which resulted in a non-required bending angle. Therefore, applying a suitable punch height created a balance of compensating the gap between the workpiece and the die, and the stress distribution on the bending allowance and the reversed bending zone. This resulted in achieving the required bending angle.

A study of surface deflection in pressed automobile panels

There is no perfect evaluation criterion presently that can satisfy the needs of the engineering and the research on the surface deflection of automobile outer panels. A convenient 2D and 3D evaluation criterion that can quantitatively measure the magnitude and the location of surface deflection is developed mathematically. The surface deflection is shown by comparing the curvature variations between the pressed panel and the punch. The evaluation criterions tested by example are correct. The surface deflection is investigated through the experiment of the double-curved shallow shell drawing parts. The mechanism of surface deflection and the effects of forming conditions on surface deflection are analyzed. And the influence law of forming conditions on surface deflection is achieved, such as binder force, curvature radius (arc height of punch), sheet thickness, materials property and draw-beads.

Stamp Collapse in Soft Lithography

We have studied the so-called roof collapse in soft lithography. Roof collapse is due to the adhesion between the PDMS stamp and substrate, and it may affect the quality of soft lithography. Our analysis accounts for the interactions of multiple punches and the effect of elastic mismatch between the PDMS stamp and substrate. A scaling law among the stamp modulus, punch height and spacing, and work of adhesion between the stamp and substrate is established. Such a scaling law leads to a simple criterion against the unwanted roof collapse. The present study agrees well with the experimental data.