• International Journal of Precision Engineering and Manufacturing
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• 제4권5호
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• pp.34-40
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• 2003

This paper presents the inertial force problem of ultrahigh-speed injection molding machine using linear motors, and presents its solutions. To make very thin products by injection molding, very high injection speed is required, and linear motors are used for this purpose. However, direct drive by linear motors may cause brief nozzle separation from the sprue bushing because of the inertia force which is as large as the total output thrust of the linear motors, and this momentary separation can cause molten plastic to leak. In this paper, two solutions are proposed for this inertia force problem. One is the mechanical cancellation of the inertia force, and the other is to increase the nozzle contact force. With the latter solution, the stationary platen bending worsens, so a new nozzle contact mechanism is also proposed, which can prevent the stationary platen bending.

• 한국정밀공학회지
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• 제19권10호
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• pp.171-177
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• 2002

This paper presents the inertial force problem of ultrahigh-speed injection molding machine using linear motors, and presents its solutions. To make very thin products by injection molding, very high injection speed is required, and linear motors are used for this purpose. But direct drive by linear motors may cause brief nozzle separation from the sprue bushing because of the inertia force as large as the total output thrust of the linear motors, and this momentary separation can cause molten plastic leakage. In this paper, two solutions are proposed for this inertia force problem. One is the mechanical cancellation of the inertia force, and the other to increase the nozzle contact force. With the latter solution, the stationary platen bending worsens, so a new nozzle contact mechanism is also proposed, which can prevent the stationary platen bending.

• Design & Manufacturing
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• 제17권1호
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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.

• Tribology and Lubricants
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• 제12권1호
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• pp.22-28
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• 1996

This study was undertaken to investigate the dry wear characteristics and mechanism of KP-4M steel for plastic molding against SKD 61 hardened by heat treatment. The wear test was carried out under different conditions such as sliding speed, contact pressure, sliding distance, with frictional tester of pin on disc type. The wear loss on variation of sliding speed was little in lower speed range below 0.5 m/sec and in higher speed range above 1.5 m/sec,'but wear loss was high in intermediate speed range. The critical sliding speed, which showed the maximum value of specific wear rate, became lower with increased contact pressure. Increasing the contact pressure, the critical sliding distance Lcr which the wear mechanism changes from severe wear to mild wear was increased due to the decrease of oxidation reaction velocity. Through this study we suggested a model of generation and elimination process of wear debris of KP-4M steel for plastic molding.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.212-220
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• 2000

Single flighted screw extrusion is the most cost effective method for the production of film, sheet, pipe and the fundamental step in other processes including blow molding and injection molding. The temperature of polymer melts and injection pressure play a very important role in the injection molding machine. Thermal distortion and displacement of screw by temperature difference and injection pressure difference cause adhesive wear by metal-to-metal contact. In this paper we analyze thermal distortion and stress of screw includes pressure and temperature distributions by finite element analysis to understand dynamic characteristics of screw.

• 한국산학기술학회논문지
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• 제14권11호
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• pp.5366-5370
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• 2013

본 연구에서는 볼트의 원활한 성형이 이루어지도록 볼트의 성형 공정 중 2단계에서 시행하던 압출공정을 4단계로 옮기고 2단계와 3단계에서는 볼트 머리부 성형만 이루어지도록 공정을 조정하여 해석하였다. 그 결과 약간의 수정으로 원활한 성형이 이루어 졌으며 접촉압력은 수정 전보다 1단계에서는 감소하고 2단계에서는 증가하였으며, 최대유효응력, 유효변형율, 성형력은 수정전보다 1, 2단계에서 모두 증가함을 알 수 있었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1563-1565
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• 2008

Hydrophobic plastic plates employing nano surface features are injection molded using thermoplastic materials. A variotherm molding process is devised for filling the nano pores and releasing the molded nano features from the master. The size of the molded nano surface features are about 100nm in diameter and 200nm in height. The size of the molded plate is about 30mm x 30mm and the thickness is 1mm. As molding materials, Polypropylene, PMMA, COC and PC are employed, which are all typical commodity thermoplastic materials. The mold temperature(stamper temperature) is investigated as a major processing parameter for molding high aspect ratio nano surface features. Almost fully molded nano features are fabricated above a certain level of mold temperature depends on the employing material. The contact angles on the injection molded plates are measured to estimate the hydrophobicity and found to have higher contact angle up to 180% compared to the blank plate with no surface features.

• 한국생산제조학회지
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• 제21권6호
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• pp.1008-1012
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• 2012

Injection molds are fabricated by assembling a number of plates in which mold core and cavity components are inserted. The assembled structure causes a number of contact interfaces between each component where the heat transfer is affected by the thermal contact resistance. However, the mold assembly has been treated as a one body in numerical analyses of injection molding, which has a limitation in predicting the mold temperature distribution during the molding cycle. In this study, a numerical approach that considers the thermal contact effect is proposed to predict the heat transfer characteristics of an injection mold assembly. To find the thermal contact conductance between the mold core and plate, a number of finite element (FE) simulations were performed with the design of experiment (DOE) and statistical analysis. Thus, the heat transfer analyses using the obtained conductance values can provide more reliable results than conventional one-body simulations.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.367-370
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• 2003

In this study, application of SAM (self-assembled monolayer) to nano replication process as an anti-adhesion layer was presented to reduce the surface energy between the nano mold and the replicated polymeric nano patterns. The electron beam lithography was used for master nano patterns and the electorforming process was used to fabricate the nickel nano stamper. Alkanethiol SAM as an anti-adhesion layer was deposited on metallic nano stamper using solution deposition method. To analyze wettability and adhesion force of SAM, contact angle and LFM (Lateral Force Microscopy) were measured at the actual processing temperature and pressure for the case of nano compression molding and at the actual UV dose for the case of nano UV molding. It was found that the surface energy due to SAM deposition on the nickel nano stamper markedly decreased and the quality of SAM on the nickel stamper maintained under the actual molding environments.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.248-251
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• 2005

Graphite reinforced conductive polymer composites for PEMFC bipolar plates were fabricated by the compression molding technique. Graphite powder was mixed with an phenol resin to impart electrical property in composites. In this study, conductive polymer composites with high filler $loadings(>60wt.\%)$ were manufactured to accomplish high electrical conductivity above 100S/cm. The level of compaction is important because graphite powder increase electrical conductivity of composites by direct physical contact between particles. The optimum molding pressure according to filler was proposed experimentally. Various tests(electrical conductivity, flexural strength, compressive strength, leach test, etc) were carried out to verify the performance of fabricated composites for PEMFC bipolar plates. Fabricated composites have good electrical conductivity and mechanical strength. The results of leach test and contact angle measurement showed similar characteristics compared with commercial bipolar plates.