• Journal of Korean Society for Quality Management
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• v.44 no.4
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• pp.935-949
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• 2016

Purpose: This study attempts to find out the optimum condition of the rotary cutter making pellet in the footwear outsole process. The pellets are used in the process of outsole rubber fabrication to reduce cycle time and save raw material. Methods: Computer simulations are used to analyze the maximum stress in the rotary cutter after designing a variety of cutter shapes. Taguchi method is used to identify the robust condition of the cutter. In $L_{18}$ orthogonal array, the control factors such as knife width, twisted angle, number of knives, diameter, knife depth and supported angle are considered and noise factors like assembly tolerance and amount of antifriction are allocated. Results: It is found that the most important factors to reduce maximum stress in the cutter are supported angle and diameter. Using Tacuchi's results, we can reduce 70% cycle time and 9% raw material compared to the traditional method using cutting die. Conclusion: When designing the rotary cutter, the best conditions are the diameter at its maximum allowable value and supported angle in the boundary of machine inner space.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.11
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• pp.977-982
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• 2015

This study uses finite element analysis to evaluate the forming load of tool entrance angle of the cold forward extrusion molding process of helical gear; this can replace the spur gear applied to the Electronic Parking Brake (EPB) system. A cold forging process is often used in the automobile industry as well as in various industrial machines due to its high efficiency. Finite element analysis is frequently used when interpreting results of the forging process. Formality was evaluated by calculating tooth profile filling rate of helical gear. Change in required forming load was investigated when the entrance angle of forward extrusion tool die was changed from $30^{\circ}$ to $60^{\circ}$, also by finite element analysis. We suggest suitable tool entrance angles.

• Transactions of Materials Processing
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• v.23 no.8
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• pp.501-506
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• 2014

Progressive shearing with blanking dies is commonly employed to produce large quantities of tiny sheet metal electronic parts. Sheet metal pins, which are narrow and long, that are sheared with a progressive die set are often twisted. The twist in the sheet metal pins, which usually occurs in the final shearing operation, generally decreases with increasing blank holding force. The blank holding forces in all shearing operations are not the same because of different shearing positions and areas. In the current study, the optimal layout of the springs in a progressive die set to minimize the twist of the sheet metal pin is proposed. In order to find the holding force acting on the tiny narrow blanks produced with the proposed springs during the shearing process, the equivalent area method is used in the structural analysis. The shearing of the sheet-metal pin was simulated to compute the twist angle associated with the blank holding force. The constraint condition satisfying the pre-set blank holding force from the previous shearing operations was imposed. A design of experiments (DOE) was numerically implemented by analyzing the progressive die structure and by simulating the shearing process. From the meta-model created from the experimental results and by using a quadratic response surface method (PQRSM), the optimal layout of the springs was determined. The twist of sheet metal pin associated with the optimal layout of the springs found in the current study was compared with that of an existing progressive die to obtain a minimal amount of twist.

• Restorative Dentistry and Endodontics
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• v.20 no.1
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• pp.152-163
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• 1995

This experiment was performed to observe the adhesion pattern and microleakage in the gingival margin according to variation in the resin cement thickness which results from thickness of Die spacer. which is considered to effect the adaptability of the composite resin inlays. Clearfil CR inlays were fabricated on stone models with CR Sep applicated once and Nice fit twice, 4 times, and 6 times each. After 2nd curing within the CRC-100 oven, CR inlays were cemented with CR inlay cement. Dye(2% methylene blue) penetration and adhesion pattern were evaluated after sectioning of gingival margin into :3 pieces. The results were as follows ; 1. The thickness of resin cement showed unevenchanging pattern with that of die spacer, namely, it was increased until 4 times' application of Nice-Fit but was decreased with 6 times' application of that. 2. The degree of dye penetration wasn't affected by cement thickness within a limited value. 3. Most of dye penetration was shown through the interface between cement and enamel rather than the interface between cement and CR inlay. This shows that the affinity of resin cement for CR inlay was superior to the adhesive strength with tooth structure. 4. No gap was found at the interface between enamel and cement but some showed separation between dentin and cement. It is concidered that the contraction force of cement was less than the bond strength with the enamel. 5. Lots of voids were found in the CR inlay and resin cement. There was a pooling tendency of bonding agent and cement in the axiogingival line angle portion. 6. In some specimens, cracks were shown in enamel margin. From this it could be considered that cavity preparation and surface treatment weakened the tooth structure.

• Journal of the Semiconductor & Display Technology
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• v.22 no.4
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• pp.32-37
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• 2023

For the potential applications in large-area OLED lightings, hydrogen fuel cells, and secondary batteries, we have performed an intermittent coating of high-viscosity polydimethylsiloxane using roll-to-roll slot die coater. During intermittent coating, dead zones inevitably appear where the thickness of PDMS patch films becomes non-uniform, especially at the leading/trailing edge. To reduce it, we have coated the PDMS patches by varying the process parameters such as the installation angle of the slot die head, coating speed, and patch interval. It is observed that the PDMS solution flows down and thus the thickness profile is non-uniform for horizonal intermittent coating, whereas the PDMS solution remaining on the head lip causes an increase in the PDMS thickness at the leading/trailing edges for vertical intermittent coating when the coating velocity is low. As the coating speed increases, however, the dead zone is shown to be reduced. It is addressed that the overall dead zone (the dead zone at the leading edge + the dead zone at the trailing edge) is smaller with horizontal intermittent coating than with vertical intermittent coating.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.3
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• pp.262-268
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• 2002

Statement of problem. In-Ceram system is one of the all-ceramic crowns that can be used in anterior 3 unit fixed partial dentures and posterior single crowns. The alumina core used in In-Ceram system is manufactured using slip-casting technique. The slip-casting technique is difficult and technique sensitive. To improve this problem, tape-casting method was introduced into dentistry. There were no studies to examine the effect of margin design on the margin fitness of all-ceramic crowns fabricated from alumina tape. Purpose. The purpose of this study was to compare the marginal fitness of glass infiltrated alumina core fabricated from aqueous-based alumina tape according to different margin types ($90^{\circ},\;110^{\circ},\;135^{\circ}$ shoulder margin). Material and method. Three upper central resin incisors were prepared with $90^{\circ},\;110^{\circ}$, and $135^{\circ}$ shoulder margins for all-ceramic crowns, respectively. The resin teeth were duplicated and master die and special plaster die were made as usual. After alumina cores were fabricated from aqueous-based alumina tape, cores were cemented to each 15 epoxy dies replicated from three resin teeth with resin cement. These cemented cores were embedded in epoxy resin. Specimens were cut mesiodistally and buccolingually. Marginal gap and discrepancy were measured under microscope. Results. The marginal gap and discrepancy of $90^{\circ}$ marginal angle was $75.1{\mu}m,\;86.6{\mu}m,\;110^{\circ}$ marginal angle was $41.5{\mu}m,\;50.7{\mu}m$ and $135^{\circ}$ marginal angle was $51.7{\mu}m,\;54.2{\mu}m$, respectively. The smallest value was seen in 110 (angle, which was statistically significant compared to that of $90^{\circ}$ angle (p<0.05). Conclusion. Marginal fitness of alumina cores made of alumina tape with $110^{\circ}$ shoulder margin was best and others were clinically acceptable.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.03b
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• pp.40-47
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• 1996

An upper bound solution of tube drawing process using a fixed tapered plug has been obtained , which reduces to an solution for tube sinking by setting friction factor between tube and plug at zero. Effects of various process paraments have been discussed based on the solution.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.5
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• pp.583-594
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• 2000

Dislodgement of a crown or extension bridge and the loosening of a retainer of a bridge is a serious clinical problem in fixed restoration. Generally these problems are considered to be associated with deformation of the restoration. During biting, the restoration is subjected to complex forces and deforms considerably within the limit of its elasticity. Deformation of the restoration under the occlusal force induces excessive stress in the cement film, which then leads to the cement fracture. Such a fracture may eventually cause loss of the restoration. Because most of the past retention tests for full veneer crown were done without fatigue loading, they were not exactly simulating intraoral environment. And the purpose of this study was to evaluate the effect of cyclic cantilever loading on the retentive strength of full veneer crowns depending on different type of cements and taper of prepared abutment. Steel dies with $8^{\circ}\;or\;16^{\circ}$ convergence angle were fabricated through milling and crowns with the same method. These dies and crowns were divided into 8 groups. Group 1 : $16^{\circ}$ taper die, cementation with zinc phosphate cement, without loading Group 2 : $16^{\circ}$ taper die, cementation with zinc phosphate cement, with loading Group 3 : $8^{\circ}$ taper die, cementation with zinc phosphate cement, without loading Group 4 : $8^{\circ}$ taper die, cementation with zinc phosphate cement, with loading Group 5 : $16^{\circ}$ taper die, cementation with Panavia 21, without loading Group 6 : $16^{\circ}$ taper die, cementation with Panavia 21, with loading Group 7 : $8^{\circ}$ taper die, cementation with Panavia 21 without loading Group 8 : $8^{\circ}$ taper die, cementation with Panavia 21, with loading After checking the fit of die and crown, the luting surface of dies and inner surface of crowns were air-abraded for 10 seconds. The crowns were cemented to the dies, with cements mixed according to the manufacturer's recommendations. A static load of 5kg was then applied for 10 minutes with static loading device. Twenty-four hours later, group 1, 3, 5, 7 were only thermocycled, group 2, 4, 6, 8 were subjected to cyclic loading after thermocycling. Retentive tests were performed on the Instron machine. From the finding of this study, the following conclusions were obtained 1. Panavia 21 showed significantly higher retentive strength than zinc phosphate cement for all groups (p<0.05). 2. There was a significant difference in the retentive strength between $8^{\circ}\;and\;16^{\circ}$ taper for zinc phosphate cement(p<0.05), but no significant difference for Panavia 21 (p>0.05). 3. Cyclic loading significantly decreased the retentive strength for all groups(p<0.05). 4. For zinc phosphate cement, there was 35% reduction of the retentive strength after loading in the $16^{\circ}$ taper die, 25% in the $8^{\circ}$ taper die, and for Panavia 21, 21% in the $16^{\circ}$ taper die, 18% in the $8^{\circ}$ taper die.

• Transactions of Materials Processing
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• v.8 no.4
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• pp.364-373
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• 1999

For material characterization of semi-solid materials, backward extrusion process, which has been used in forming of hollow-sectioned products, was analyzed by the upper bound analysis in the current study. The existing kinematically admissible velocity field was applied to steady state at which there was no change in the assumed regions of velocity field. For unsteady state, new velocity field, as a function of dead zone angle, was proposed. Through the whole analysis, fiction between die and workpiece was also considered. It has been studied how the process variables, such as friction factor and punch velocity, and material parameters, such as strength coefficient, strain rate sensitivity could affect on analysis results. Finally, by the comparison with the finite element analysis, the reliability and efficiency of the proposed velocity field were discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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• pp.493-503
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• 1998

The sectional forming analysis considering bending effects from the geometrically deformed shape of two linear membrane finite elements(called super element) was performed under plane strain assumption for analyzing forming processes of an arbitrarily shaped draw-die. For the evaluation of bending effects, the bending equivalent forces are calculated from the bending moment computed using the changes in the interior angle at the middle node of super element, and are agumented to the membrane stretch forces. In order to verify the validity of the bending formulation, the simulation results for the stretch, draw, and bend sections were compared with membrane analysis results and measurements.