• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.422-425
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• 2008

Recently, electronic products and related parts are required to have thin thickness because of small form factor. To go with the trend, LGP(light guide plate) of LCD BLU(Liquid Crystal Display Back light unit: It is one of kernel parts of LCD) for cell phone has the thickness of 0.3 mm and the battery case of cell phone has 0.25 mm. Accordingly, high speed injection molding is required to make products which have thin thickness. High speed injection molding means that the resin is injected into the cavity at higher than normal speed avoiding short shot. In the case of hydro-mechanical high speed injection machine, it requires the design for hydraulic unit to make high injection speed and the design for control unit to control hydraulic unit. In the present paper, we concentrated on the molding stability of hydro-mechanical high speed injection machine to make an LGP of 0.3 mm thickness.

• Design & Manufacturing
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• 제10권2호
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• pp.1-5
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• 2016

High-speed and high-torque performance is required in the ultra-high speed electric injection molding machine field. To implement this performance, the big-size inverter is needed and the corresponding converter should be used. In this case, the whole cost for configuring the system will be increased. In this paper, we introduce a method which is able to reduce the energy and the cost for configuring the system using the energy regeneration. The energy regeneration method is based on reusing the regeneration power generated at the electric motor during decelerating the injection motion. In this paper, we demonstrate the effectiveness of the method by using the ultra-high speed injection motion.

• 소성∙가공
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• 제17권8호
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• pp.657-661
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• 2008

Recently, products of electronic industry and related parts are required to have the thickness thinner and thinner to reduce the part weight. To go with this trend, LGP(light guide plate) of LCD-BLU(Liquid Crystal Display-Back Light Unit: It is one of kernel parts of LCD) for cell phone has the thickness of ${\sim}0.3mm$ and the battery case of cell phone has ${\sim}0.25mm$. Accordingly, high speed injection molding is required to mold products which have thinner parts. To achieve high speed injection and proper control of hydraulic unit, various design was applied to conventional injection unit. In the present paper, we concentrated on the molding stability of hydro-mechanical high speed injection machine to make an LGP of 0.3mm thickness.

• 소성∙가공
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• 제23권1호
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• pp.41-48
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• 2014

The light guide plate has become the major component for the backlight module in general information technology products (e.g. mobile phones, monitors, etc.). High speed injection molding has been adopted for thin walled LGP giving advantages such as weight, shape, size, and reduction in production costs. In the current study, the rheological characteristics of high liquidity plastic resin PC(HL8000) were measured using a capillary rheometer to improve the reliability of the numerical analysis for high speed injection molding. With the measured viscosity and PVT of PC(HL8000), numerical analysis of injection molding was conducted using the simulation software(Moldflow). Filling time and deflection were predicted and compared with those of traditional PC resins(H3000, H4000). The results show that PC(HL8000) has significantly different rheological characteristics during high speed injection molding. Hence proper properties of the resin should be used to improve the accuracy of numerical predictions.

• 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.

• 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.

• Design & Manufacturing
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• 제11권1호
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• pp.14-18
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• 2017

Recently, the injection-molded products are lighter, and thinner than ever. In this work, Injection molding simulation was conducted to analysis the filling pattern imbalance in high speed injection molding process for thin-wall injection component, 8 inches LGP. Numerical analysis shows that shear heated polymer near the side wall causes filling imbalance between center and side of cavity. Short shot experiments were conducted and compared with simulation results. Filling imbalance ratio showed a tendency to increase for wider fan gate.

• Design & Manufacturing
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• 제9권2호
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• pp.20-24
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• 2015

Recently, the light guide plate (LGP), a component of the BLU, becomes thinner and larger than ever. In industrial field, specialized injection molding technique is applied to mold the ultra-thin LGP such as a ultra-high speed injection molding. Usually very high melt temperature is used for low viscosity. High injection speed and melt temperature lead to yellowing of LGP. In the present paper a series of injection molding experiment was performed under various injection molding conditions. Yellow index, CIE xy, spectral transmittance of sample were measured using the UV-Visible spectrophotometer. Systematic decrease of spectral transmittance in UV-B range was found as the melt temperature was higher. Yellow index and CIE xy were became higher near the gate location in LGP. From the result of analysis of variance, the main factor to affect for yellow index was mold temperature and that for spectral transmittance(at 315 nm) was melt temperature.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.259-264
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• 2005

The shrinkage of the product in injection molded part occurs due to the volume change with variation of temperature and pressure and is influenced by the processing conditions of injection molding. Mold designers greatly concerns the shrinkage of parts for a high dimensional accuracy. In this study, bar type HIPS specimen with 15x19 grid on the surface was tested. The amount of shrinkage of flow and transverse directions was examined with respect to the injection molding conditions such as melt temperature, injection speed, holding pressure, mold temperature and cooling time. As the packing pressure increased, the difference of shrinkage of both directions is decreased and the absolute shrinkage value also decreased.