• 폴리머
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• 제38권6호
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• pp.708-713
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• 2014

대부분의 플라스틱 제품은 사출성형을 통해 생산된다. 사출성형에서 성형수축은 피할 수 없으며 이는 제품에 휨이나 뒤틀림을 유발하여 제품의 치수정밀도를 떨어뜨리는 요인으로 작용한다. 사출성형 시 발생하는 휨이나 뒤틀림은 성형조건이나 제품의 형상에도 영향을 받지만 수지의 물성에 따라서도 다양하게 나타난다. 본 연구에서는 제품의 휨을 제어하기 위해 폴리카보네이트를 유리섬유로 보강하여 물성을 예측하였으며, 이를 이용하여 사출성형해석을 실시하였다. 사출성형해석을 통해 유리섬유로 보강된 수지에서 제품의 휨이 감소하는 것을 확인할 수 있었다. 본 연구방법의 타당성과 신뢰성을 검증하기 위하여 사출실험을 실시하여 수지의 물성에 따른 휨 값을 분석하였으며 해석과 실험에서 유사한 경향의 휨이 발생하는 것을 관찰할 수 있었다. 결론적으로 본 연구에서 수행한 바와 같이 해석 프로그램을 통해 수지의 물성을 설계하고 이를 통한 휨의 제어가 가능함을 확인할 수 있었다.

• The Journal of Advanced Prosthodontics
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• 제11권1호
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• pp.55-64
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• 2019

PURPOSE. The accuracy of denture bases was compared among injection molding, milling, and rapid prototyping (RP) fabricating method. MATERIALS AND METHODS. The maxillary edentulous master cast was fabricated and round shaped four notches were formed. The cast was duplicated to ten casts and scanned. In the injection molding method, designed denture bases were milled from a wax block and fabricated using SR Ivocap injection system. Denture bases were milled from a pre-polymerized block in the milling method. In the RP method, denture bases were printed and post-cured. The intaglio surface of the base was scanned and surface matching software was used to measure inaccuracy. Measurements were performed between four notches and two points in the mid-palatal suture to evaluate inaccuracy. The palatine rugae resolution was evaluated. One-way analysis of variance was used for statistical analysis at ${\alpha}=.05$. RESULTS. No statistically significant differences in distances among four notches (P>.05). The accuracy of the injection molding method was lower than those of the other methods in two points of the mid-palatal suture significantly (P<.05). The degree of palatine rugae resolution was significantly higher in the injection molding method than that in other methods (P<.05). CONCLUSION. The overall accuracy of the denture base is higher in milling and RP method than the injection molding method. The degree of fine reproducibility is higher in the injection molding method than the milling or RP method.

• Design & Manufacturing
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• 제14권3호
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• pp.8-16
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• 2020

In this study, the vibration signal of the mold was measured and analyzed to monitoring the process time and characteristics during injection molding. A 5 inch light guide plate mold was used to injection molding and the vibration signal was measured by MPU6050 acceleration sensor module attached the surface of fixed mold base. Conditions except for injection speed and packing pressure were set to the same value and the change of the vibration signal of the mold according to injection speed and packing pressure was analyzed. As a result, the vibration signal had a large change at three points: "Injection start", "V/P switchover", and "Packing end". The time difference between "injection start" and "V/P switchover" means the injection time in the injection molding process, and the time difference between "V/P switchover" and "Packing end" means the packing time. When the injection time and packing time obtained from the vibration signal of the mold are compared with the time recorded in the injection molding machine, the error of the injection time was 2.19±0.69% and the error of the packing time was 1.39±0.83%, which was the same level as the actual value. Additionally, the amplitude at the time of "injection start" increased as the injection speed increased. In "V/P switchover", the amplitude tended to be proportional to the pressure difference between the maximum injection pressure and the packing pressure and the amplitude at the "packing end" tended to the pressure difference between the packing pressure and the back pressure. Therefore, based on the result of this study, the injection time and packing time 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 variables such as the injection speed, maximum injection pressure, and packing pressure can be evaluated as the change of the mold vibration during injection molding.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.57-61
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• 2009

In recently industry, with the miniaturization and high-precision of machine part, the development of mold manufacturing technology for mass production is accompanied by the development of new industrial field such as IT, NT and BT. The metal injection molding(MIM) process combines the well-known thermoplastic injection and powder metallurgy technologies to manufacture small parts for IT, NT, BT industrial. In this study, the bar type MIM mold with a 800um thickness is made for influence of feedstock material and injection parameter through an experiment.

• Design & Manufacturing
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• 제9권1호
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• pp.27-30
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• 2015

The injection molding is used in more than 70% of total production of plastic products. Weld line in injection molded part is one of the defects in injection molding process. Weld line deteriorates not only appearance quality but also mechanical property. In this study, tensile strength about material such as ABS, PP, PA and PS was tested. as the results, the first result appears that weld's strength retention ratio's are 0.90, 0.84, 0.85, 0.76 and the second result apeears that weld depth decrease as processing temperature increased.

• Design & Manufacturing
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• 제8권1호
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• pp.23-26
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• 2014

The injection molding is used in more than 70% of total production of plastic products. Weld line in injection molded part is one of the defects in injection molding process. Weld line deteriorates not only appearance quality but also mechanical property. In this study weld quality has been examined according to the injection processing temperature, materials and mold designs. We selected four different materials such as PA, PP, ABS and PS as experimental materials. Weld quality increased as injection processing temperature increases. It was more dependent on materials flow ability. As a result, weld quality incase of rectangular core is better than circular core.

• Design & Manufacturing
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• 제6권2호
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• pp.1-5
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• 2012

Weld line in injection molded part is one of the defects in injection molding process. Weld line deteriorates not only appearance quality but mechanical property. In this study, ABS and PP were used as experimental materials. And weld line length, depth and strength have been examined according to the injection molding conditions. As the results of experimental studies, weld line length increased as flow rate increases for all materials. And the flow rate is most influenced to the creation of weld line length. Also weld line strength increased, as flow rate and melt temperature increase for all materials. The whole experiment results was similar to CAE analysis results.

• 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.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.375-378
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• 2003

In the present study, a new approach to predict the strength of sintered materials has been carried out and a new framework combining neck growth model and ideal pore model has been established based on the results of tensile tests on powder injection molded specimens with the various porosity. Powder injection molding (PIM) uses the shaping advantage of injection molding but is applicable to metals and ceramics. PIM delivers structural materials in a shaping technology previously restricted to polymers. 17-4 PH stainless steel powders with average diameters of 10 $\mu\textrm{m}$ were injection-molded into flat tensile specimens sintered at the various temperatures ranging from 900 to 1350$^{\circ}C$ for 1h. The relationships between strength and porosity were applied to the experimental results and verified.

• 소성∙가공
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• 제20권2호
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• pp.173-178
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• 2011

Environmental Stress Cracking(ESC) is one of the most common causes of unexpected brittle failure of thermoplastic polymers. The exposure of polymers to liquid chemicals tends to accelerate the crazing process, initiating crazes at stresses that are much lower than the stress causing crazing in air. In this study, ESC of acrylonitirile butadiene styrene(ABS) was investigated as a function of the molding conditions such as injection velocity, packing pressure, and melt temperature. A constant strain was applied to the injection molded specimens through a 1.26% strain jig and a mixture of toluene and isopropyl alcohol was used as the liquid chemical. In order to examine the effects of the molding conditions on ESC, an experimental design method was adopted and it was found that the injection velocity was the dominant factor. In addition, predictions from numerical analyses were compared with the experimental results. It was found that the residual stress in the injection molded part was associated with the environmental stress cracking resistance (ESCR).