• Transactions of the Korean Society of Mechanical Engineers
• /
• v.13 no.5
• /
• pp.886-900
• /
• 1989

The purpose of this paper is to obtain the effect of blankholding force in deep drawing process. Flange deformation is analysed by theoretical approach in order to apply the optimum blankholding force to the blank. As the result, the upper and lower blankholding force is determined in terms of variables in deep drawing process. Experiment are carried out with the high stiffness spring-type blankholder system. Theoretical upper blankholding force are relatively good agreement with experimental result and the range of initial blankholding forces for various materials tested are found by experiment.

• Transactions of Materials Processing
• /
• v.23 no.8
• /
• pp.489-494
• /
• 2014

Micro forming is an appropriate process to manufacture very small metal parts which can be employed in the field of electronic devices or electrically controlled mechanical systems. The purpose of the current study was to investigate the influences of both blankholding force and blank diameter for the deep drawing of very small cups. It is essential to control the blankholding force because improper force can result in defects such as wrinkles in the flange or cracks in the corner of the drawn cups. In the current study blankholding force was controlled by springs connected to the blankholder of a press die. Exchangeable bushing dies with various die-corner radii were also used. To obtain the limit drawing ratio for each working condition several sizes of circular specimens were prepared using blanking tools. Beryllium copper(C1720) alloy sheet of $50{\mu}m$ thickness was chosen for the experiments. The maximum limit drawing ratio of 2.1 was achieved experimentally for the conditions of the blankholder force(BHF)=5.3kgf and Rd=0.3mm. Both thickness and hardness along the central section of drawn cups were measured and compared for different drawing conditions. It was found that the deviation of measured data in the thickness and hardness distribution increases with increasing blankholder force and blank diameter.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.5 no.3
• /
• pp.50-57
• /
• 1996

This study was performed the blankholding force and Vee-ring effects on blanking characteristics, such as maximum blanking force, burnish, dish-shape, hardness. etc. in fine-blanking die by the experimental method. Two types of aluminum (Al.1050-O, Al, 5052-H) Such as annealed and unannealed materials were used for the experiment. In order to get a hydrostatic pressure effect, the clearance was set to 0.5% of the thickness of strip, and the counter punch and stripper plate with Vee-ring was set-up. While this experiment was carry8ing out, the average blanking velocity was constant (37.5mm/sec). As a result of this study, we got a good surface roughness and a dimensions, the good squareness and the reduction of dish-shape could be obtained, and also the additional results obtained were such that the hardness of shear plane was increased and the maximum blanking force was reduce in the condition of Vee-ring height of 1.0~1.5mm, and blankholding force of 1200kg.

• Journal of the korean Society of Automotive Engineers
• /
• v.11 no.4
• /
• pp.35-42
• /
• 1989

The major purpose of this paper is a study on the effect of die profile radius on the formability of spring-type blankholder system in deep drawing process. By drawing the various materials, formability is studied by means of checking the drawing force, blankholding force variation, limiting drawing ratio and wall wrinkling phenomenon. As the die profile radius increases, the maximum drawing force and maximum blankholding force decrease regardless of lubrication condition. Because better lubrication induces blankholding force to rise, spring type blankholder system is better to protect flange wrinkling phenomenon than constant pressure type. And wall wrinkling phenomenon was not detected in experimental die radius range, so the Miyakawa's upper wrinkling limit is understimated in case of material tested.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2010.11a
• /
• pp.165-166
• /
• 2010

• Journal of the korean Society of Automotive Engineers
• /
• v.11 no.3
• /
• pp.49-59
• /
• 1989

The purpose of this paper is to obtain the effect of die lubrication in deep drawing process. The flange wrinkling is analysed by a moment equilibrium method in order to apply the optimum blankholding force to the blank. The experiment has been carried out with the high stiffness spring-type blankholder system. As the result, blankholding pressure is determined in terms of variables in deep drawing process. In the range of frictional coefficient which has been found in this experiment, there was a little difference in required blankholding force but a great difference in drawing force. It was found that the stiffness of blankholder was the major factor which influences on flange wrinkling in spring-type blankholder system.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1997.10a
• /
• pp.24-27
• /
• 1997

In the present work, rigid-plastic continuum elements employing the shape change and anisotropic effects are derived for the purpose of applying more realistic blankholding force condition in three-dimensional finite element analysis of sheet metal forming process. In order to incorporate the effect of shape change effectively in the derivation of finite element equation using continuum element for sheet metal forming, the convected coordinate system is introduced, rendering the analysis more rigorous and accurate. The formulation is extended to cover the orthotropic material using Hill's quadratic yield function. For the purpose of applying more realistic blankholding force condition, distributed normal and associated frictional tangent forces are employed in the blankholder, which is pressed normal and associated frictional tangent forces are employed in the blankholder, which is pressed against the flange until the resultant contact force with the blank reaches the prescribed value. As an example of sheet metal forming process coupling the effect of planar anisotropy and that of blankholding boundary condition, circular cup deep drawing has been analyzed considering both effects together.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2004.05a
• /
• pp.57-61
• /
• 2004

in order to improve the quality of the sheared surface in cutting of sandwich sheet metals the cut-off operation is mainly investigated which is the typical shearing process in sheet metal forming technology. For experiments the cut-off die is made which can be easily adjusted by die design variables such as blankholding force, pad force, and clearance. The sheet metals chose as specimen are clad304(STS304-Al1050-STS304) and anti-vibration sheet metal. The shearing process is visualized by the computer vision system installed in front of the cut-off die and the sheared surface before and after cut-off operation is measured and quantitatively compared with the help of the optical microscope. From test results the good sheared surface was shown when the clearance gets small with large blankholding force.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1996.03a
• /
• pp.188-193
• /
• 1996

This study was performed the blankholding force and vee-ring effects on Blanking characteristics, such as maximum blanking force, burnish, dish-shape, hardness. etc, in fine-blanking die by the experimental method. Two types of aluminum (Al. 1050-0, Al 5052-H) Such as annealed and unannealed materials were used for the experiment. In order to get a hydrostatic pressure effect, the clearance was set to 0.5% of the thickness of strip, and the counter punch and stripper plate with Vee-ring was set-up. While this experiment was carrying out, the average blanking Velocity was constant (37.5mm/sec) As a result of this study, we got a good surface roughness and a glassy shear plane(burnish) of the sheet over 90% thickness, and such as the excellent accuracy of dimensions, the good squareness and the reduction of dish-shape could be obtained, and also the additional results obtained were such that the hardness of shear plane was increased and the maximum blanking force was reduced in the condition of Vee-ring height of 1.0~1.5mm, and blankholding force of 1200kg.

• Transactions of Materials Processing
• /
• v.20 no.1
• /
• pp.36-41
• /
• 2011

Meso-scale or micro-scale forming of sheet metal parts has been recently considered as one of the important forming technologies with growing demand on meso/micro products for electric or medical devices. Experimental investigation on the cylindrical meso-cup drawing with hemispherical punch is carried out to examine the limit drawing ratio and thickness distribution of drawn cups. The working parameters chosen in this study are blank diameter, die-corner radius and blankholding force. It is found from the experiments that the limit drawing ratio of 2.4 can be achieved in the case of hemispherical cup drawing and uniform thickness distribution in wider region can be obtained compared with the results of conventional cup drawing.