• IE interfaces
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• v.13 no.4
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• pp.591-598
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• 2000

In this paper, an efficient algorithm is proposed to find parting lines(PL) and generate parting surfaces(PS) for an injection mold design. We used a Face-Edge Graph which can be made by B-rep information of solid model. The graph is useful for finding the peripheral-loop edges for PL and the inner-loop edges for hole-patch. The PS can be generated automatically by selecting pre-defined direction lines. We can create a core and cavity molds by trimming the raw stock block with the PS and the upper/lower faces of a product model. We implemented proposed method with Unigraphics API functions and C language, and tesed on Unigraphics V15.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.270-273
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• 2017

Productivity through reduced defects in plastic injection molding and reduced cycle times is a long-standing need in the injection industry. In particular, productivity is very urgent for the domestic injection industry, which is caught between the pursuit of latecomers such as China and technological gap with Germany and Japan which will not be narrowed down. Through 30 years of research and experience in the domestic injection industry, we have found that controlling the surface temperature of injection molds is the key of quality control. There have been various attempts to utilize advanced control techniques such as PID control, but the productivity against leading companies in Germany and Japan is still insufficient. Using Approximation Algorithm - "Knapsack" and "Minimum Makespan Scheduling", We want to show how to efficiently control objects with periodic repetitive data patterns that are difficult to solve with PID control. In addition, We want to propose that the control by Approximation Algorithm is effective enough to improve the productivity of the product by analyzing the data extracted from actual injection site.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.3
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• pp.1045-1050
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• 2011

This study proposed the new pressing method under heat for the plastic automotive interior part in order to make embossing on the skin of the raw material of the part. The raw material is laid on the lower mold and it is pressed by the upper one with embossing shape. The air is suctioned from the inside of both molds for producing tension and making embossing shapes on the skin of the part without its breakage. The corresponding molds and test machines are made and the proposed manufacturing process is validated.

• Design & Manufacturing
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• v.13 no.3
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• pp.41-47
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• 2019

In conventional machining, the use of cutting fluid is essential to reduce cutting heat and to improve machining quality. However, to increase the performance of cutting fluids, various chemical components have been added. However, these chemical components during machining have a negative impact on the health of workers and cutting environment. In current machining, environment-friendly machining is conducted using MQL (minimum quantity lubrication) or cryogenic air spraying to minimize the harmful effects. In this study, the injection nozzle that can combined injecting minimum quantity lubrication(MQL) and cryogenic gas was designed and the shape optimization was performed by using computational fluid dynamics(CFD) and design of experiment(DOE). Performance verification was performed for the designed nozzle. The diameter of the sprayed fluid at a distance of 30 mm from the nozzle was analyzed to be 21 mm. It was also analyzed to lower the aerosol temperature to about 260~270K.

• Design & Manufacturing
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• v.2 no.5
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• pp.16-20
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• 2008

Almost all injection molds have multi-cavity runner system for mass production, which are designed with geometrically balanced runner system in order to accomplish filling balance between cavity to cavity during processing; However, even though geometrically balanced runner is used, filling imbalances have been observed. In these day, the CAE has been used widely in injection molding. However, CAE with fusion mesh can't indicate such as jetting, flow mark and filling imbalance in multi cavity mold. In this study, we investigated the filling imbalance according to runner shapes by CAE analysis. As a result in CAE, in case of binary branch runner system, filling imbalance was indicated between cavity to cavity, but the flow pattern of each cavity uniformed in unary branch runner system.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.6
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• pp.847-851
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• 2010

It was attempted to develop an auto part by over molding injection mold that produces precision products in high productivity with use of an eco-friendly TPE substitute material for NBR. NBR is currently used in motor gear cover, one of the key parts in motor module for auto doors. Gear cover is composed of plastics and rubber mostly today, which requires a two (2) step process for production using two presses of different types. A hot press is used at this time for forming the rubber, which has drawback of requiring a rather long forming time of 400 seconds for one forming process. Even though this difficulty is overcome by reducing production time through employment of multi-cavity molds, time for forming process must be shortened for improvement of the productivity eventually, and the existing method of insert injection for products that have been formed with plastic material must be outgrown. In this point of view, over molding injection using TPE has a big advantage. Forming time is shortened to 54 seconds, and working the two (2) processes in series by one (1) press could solve the durability problem caused by deflection of the plastics, not to mention shortening the process time. Enhancement of productivity by almost 80% and improvement in the accuracy of the product could thus be achieved.

• Journal of Practical Engineering Education
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• v.9 no.2
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• pp.119-124
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• 2017

In injection molding process, the runner system of the mold is a flow path for filling the cavity of the molded part during the advance of the screw by the force of the hydraulic cylinder, which involves the filling and packing process of the molten resin. Thus, the sprue, runner and gate greatly affect the appearance of the molded part, the physical properties of the resin, the dimensional accuracy and the molding cycle etc. Feed systems with incorrect runner and gate designs cause various molding defects, So it is important to maintain the optimum runner balance to prevent these defects. In order to improve the knowledge of practical mold technology, which is applied to the manufacturers of injection molds, a training model of the mold technology process is presented based on the technical guidance on the technical difficulties.

• Design & Manufacturing
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• v.15 no.3
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• pp.7-12
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• 2021

Plastic injection molds used for rapid heating and cooling must minimize surface damage due to friction and maintain excellent thermal and low electrical conductivity. Accordingly, various surface treatments are being applied. The properties of Al₂O₃ coating and DLC coating were compared to find the optimal surface treatment method. Al₂O₃ coating was deposited by thermal spray method. DLC films were deposited by sputtering process in room temperature and high temperature PECVD (Plasma enhanced chemical vapor deposition) process in 723 K temperature. For the evaluation of physical properties, the electrical and thermal conductivity including surface hardness, adhesion and wear resistance were analyzed. The electrical resistance of the all coated samples was showed insulation properties of 24 MΩ/sq or more. Especially, the friction coefficient of high temp. DLC coating was the lowest at 0.134.

• Korean Journal of Materials Research
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• v.31 no.6
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• pp.331-338
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• 2021

Ti-Al-Si target and Cr-Si target are sputtered alternately to develop a multi-layered nitride coating on a steel mold to improve die-casting lifetime. Prior to the multi-layer deposition, a CrN layer is developed as a buffer layer on the mold to suppress the diffusion of reactive elements and enhance the cohesive strength of the multi-layer deposition. Approximately 50 nm CrSiN and TiAlSiN layers are deposited layer by layer, and form about three ㎛-thickness of multi-layered coating. From the observation of the uncoated and coated steel molds after the acceleration experiment of liquid metal injection casting, the uncoated mold is severely eroded by the adhesion of molten metallic glass. On the other hand, the multi-layer coating on the mold prevents element diffusion from the metallic glass and mold erosion during the experiment. The multi-layer structure of the coating transforms the nano-composite structured coating during the acceleration test. Since the nano-composite structure disrupts element diffusion to molten metallic glass, despite microstructure changes, the coating is not eroded by the 1,050 ℃ molten metallic glass.

• Design & Manufacturing
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• v.16 no.4
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• pp.24-33
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• 2022

Fiber-reinforced plastics(FRPs) have excellent specific stiffness and strength, so they are usually used as automotive parts that require high rigidity and lightweight instead of metal. However, it is difficult to predict the mechanical properties of injection molded parts due to the fiber orientation and breakage of FRPs. In this paper, the fiber orientation characteristics and mechanical properties of injection molded specimens were evaluated in order to fabricate automotive transmission side covers with FRPs and design a rib structure for improvement of their rigidity. The test molds were designed and manufactured to confirm the fiber orientation characteristics of each position of the injection molded standard plate-shaped specimens, and the tensile properties of the specimens were evaluated according to the injection molding conditions and directions of specimens. A gusset-rib structure was designed to improve the additional structural rigidity of the target products, and a proper rib structure was selected through the flexural tests of the rib-structured specimens. Based on the evaluation of fiber orientation and mechanical characteristics, the optimization analyses of gate location were performed to minimize the warpage of target products. Also, the deformation analyses against the internal pressure of target product were performed to confirm the rigidity improvement by gusset-rib structure. As a result, it could be confirmed that the deformation was reduced by 27~37% compared to the previous model, when the gusset-rib structure was applied to the joining part of the target products.