• Design & Manufacturing
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• v.17 no.1
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• pp.56-63
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• 2023

In this study, the vibration signal of the mold was measured and analyzed to monitor the process information and characteristics during the press molding process. A necklace-type picture frame mold was used for press molding, and the vibration signal was measured by GY-61 acceleration sensor module attached to the surface of the upper (movable) mold base. The change of the vibration signal of the mold according to press speed was analyzed. As a result, the vibration signal had a large change at five sections: "Holder contact", "Punch contact and start of pressing", "End of pressing", "Mold open", and "Demolding". The time difference between "Punch contact and start of pressing" and "End of pressing" means the pressing time which is the actual time the material is molded under pressing pressure. The time intervals for each section, represented by the time interval between "Holder contact" and "Punch contact and start of pressing", can be used to compare and evaluate the press speed applied to the process. By comparing the vibration signals at 60 rpm and 90 rpm, the amplitude at the section of "Punch contact and start of pressing" increased as the press speed increased. This result means that as the press speed increases, more force and pressure is applied to the material. Also, the peak values of the other sections were found to increase as the press speed increased. It was found that the pressing time, the time interval between "Punch contact and start of pressing" and "End of pressing", decreases as the pressing speed increases. Similarly, press speed factor, the time interval between "Holder contact", and "Punch contact and start of pressing", is found to be shorter. Therefore, based on the result of this study, the pressing time, press speed, pressing(punching) pressure of each cycle can be monitored by measuring the vibration signal of the mold. Also, it was confirmed that the level and trend of process information and characterization can be evaluated as the change of the mold vibration during press molding.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.5
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• pp.128-134
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• 2021

A press-fitted shaft is an essential part used in industrial machines, and it is generally used to transmit large quantities of power. Very high contact pressure occurs at the end parts of the contact between the shaft and boss, which are press-fitted shaft components. Such contact pressure not only damages the contact surface of a press-fitted shaft but also reduces its fatigue strength. To improve a press-fitted shaft's fatigue strength, the contact pressure on the contact surface, which directly affects the fatigue strength, should be minimized. Thus, in this study, the design configuration optimization of the end part of the boss was based on the approximate optimization method and was aimed at minimizing the contact pressure at the end of a press-fitted shaft. Comparison of the contact pressure and the contact stress of a conventional press-fitted shaft with those of the optimized press-fitted shaft showed that the boss design of the optimized press-fitted shaft effectively improved the fatigue life.

• Composites Research
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• v.27 no.6
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• pp.254-259
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• 2014

In this study, a device and pressure press process that is able to substitute autoclave process is developed. This process complements disadvantages of autoclave process which are long process-time and high production cost. The developed device provides air pressure as well as the vacuum which are greatest feature of autoclave process. The device is sealed using hydraulic pressure to keep the air pressure inside the mold. The transfer of the heat is designed to be direct. The heating and pressure charging time are decreased by reducing the interior space. Tooling cost is reduced dramatically compared to autoclave process. Spring-back phenomenon is measured and compared. The temperatures of several parts of the mold during molding are measured. The fiber volume fraction of the parts molded by autoclave process and by the developed process are compared.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.3
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• pp.356-363
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• 2013

Mechanical molding press which is used for transformation process during semiconductor manufacturing process has structural deformations by pressure. If these deformations have over limit range, life of the press itself can be reduced and it will be exerted on a bad effect for quality of the semiconductor. In this research, the main plates and links of a press are analyzed in relation to the structural deformations caused by pressure excluding thermal deformations. After modifying the modeling, the analysis is performed again to determine optimal design of the press, and this design is introduced to ensure that most of the stresses on the main plates are within safe allowable limits. As a result, an optimal design method for the structure is investigated to produce the desired pressure even when the size of the main structure is minimized.

• Journal of the Korean Wood Science and Technology
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• v.23 no.2
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• pp.55-69
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• 1995

The primary objective of this research was to investigate optimum manufacturing condition of thin composite panels composed of sawdust, polyethylene film and polypropylene net. At the study the experiment was designed to make thin board in which sawdust offers effectiveness as core composing material, polyethylene as adhesive with added urea resin, and polypropylene as stiffness and flexibility in the composition panel. 100 types of thin composite panels were manufactured according to press-lam and mat-forming process of various hot pressing conditions(pressure, temperature and time). They were tested and compared with control boards on bending properties(MOR, MOE, SPL, WML), internal bond strength, thickness swelling, linear expansion and water absorption. At the same time the visual inspections of each types of panels were accomplished. The physical and mechanical properties of composite types passed by visual inspection were analyzed by Tukey's studentized range test. From the statistical analysis, the optimum manufacturing condition of thin composite panels were selected. Compared with two manufacturing processes, mat-forming process performed better than press-lam process in all tested properties. The optimum manufacturing conditions resulted from the experiment and statistical analysis were able to determine as following: the press temperature was shown the most good result at 130$^{\circ}C$ in mat forming process and 140$^{\circ}C$ press lam process, the press time 4 min in both processes, but the press pressure was 25-10kg/$cm^2$ in mat forming and 15k/$cm^2$ press lam process.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.4
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• pp.85-90
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• 2012

Wet pressing process has great influence not only on the paper properties but also on the efficiency of total manufacturing process including energy efficiency. The slow drainage propensity of old corrugated container(OCC) might require more complicated control of wet pressing process. In this study, the change in press efficiency and in structure of wet sheet by the various condition of laboratory roll press simulator were evaluated to provide background information about wet pressing of OCC. The higher pressure and the slower machine speed resulted in higher efficiency of wet pressing but the change trends of dryness depending on the wet press pressure and machine speed were shown differently according to OCC treatment. The effects of water contents of felt on the wet press efficiency and sheet structure were also investigated. The higher contents of water in felt resulted in less removal of water generally and the crushed structure of wet sheet were appeared especially at higher pressure.

• Transactions of Materials Processing
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• v.19 no.6
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• pp.378-386
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• 2010

Nowadays there has been great interest in using heat treated cast material for press dies due to several advantages like reduction in die production costs. However, in hot press forming processes H13 forged tool steel is mostly used. Cooling performance of dies in hot press forming processes is considered as an important factor of study and also the IHTC parameter between cast material die and sheet metal should be considered as an essential. In the present study, the IHTC was calculated for the sheet metal in the hot press forming process with cast and forged material dies. The temperature measurements were performed for the sheet metal, casting and forged material dies by applying various contact pressure in hot press forming. IHTC was calculated and studied by adopting the inverse heat convection method in DEFORM-2D. Each IHTC was considered as a function of contact time and contact pressure. The experimental data were compared with calculated data obtained from the proposed equation and references.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.101-104
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• 2002

The influences of the powder packing density on the Bi-2223/Ag tape have been investigated. For packing powder, both method of uniaxial press and packed rod form made by cold isostatic press(CIP) have been applied. As the pressure of cold isostatic press(CIP) is increased, fill factor and critical current (Ic) of Bi-2223/Ag tape is increased. At a pressure of 2000kgf/cm$^2$, fill factor reach ∼3l% and this sample has the engineering current density(Je) value of ∼8.5kA/cm$^2$(Ic ∼77A, Jc ∼ 30kA/cm$^2$). The tape sample packed by uniaxial press method shows more sawsaging effect than the sample processed by cold isostatic press(CIP), resulting from inhomogity of powder distribution produced by the process of uniaxial press.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.5 no.3
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• pp.22-30
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• 1996

In order to compensate for out-of-straightness of shafts, an automatic straightening process composed of an automatic measuring module, an automatic control unit and operating softwares was developed with a hydraulic press. The out-of-sraightness of each shaft was measured automatically in the measuring stage. An optimal pressure point was determined to minimize TIR value of the shaft according to press count of 3-points bending process. In the geometric adaptive control procedure, punch stroke and springback of the shaft were predicted by an observer using on-line measured values of press force and deflection amount I each press count. An automatic straightening machine was realized with the measuring module, the GAC module, PLD, IBM-PC and the operating software on the hydraulic press. the validity of the proposed straightening process was confirmed through a series of experiments with cam shafts.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.6
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• pp.81-86
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• 2017

The high-pressure resin transfer molding (HP-RTM) process has a very effective for the mass production of carbon fiber reinforced plastic (CFRP) for light weight in the automotive industry. In developing robust equipment, new process and fast cure matrix systems reduces significantly the cycle time less than 5 minutes in recent years. This paper describes the cavity pressure, temperature and molding characteristics of the HP-RTM process. The HP-RTM mold was equipped with two cavity pressure sensors and three temperature sensors. The cavity pressure characteristics of the HP-RTM injection, pressurization, and curing processes were studied. This experiment was conducted with selected process parameters such as mold cap size, maximum press force, and injection volume. Consequently, this monitoring method provides correlations between the selected process parameters and final forming characteristics in this work.