• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.303-306
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• 2001

To shorten the delivery time for new products, a lot of prototype plastic parts manufacturing technologies have been developed including injection molding, vacuum casting, thermal forming and so on. Among them, RIM is becoming one of a important soft tooling methods to produce prototype and mass production parts within short time. Further more, as the rapid prototyping technology based tooling methods are playing an important role in prototype manufacturing industry, the utility of the RIM is increasing. But few analyses and mold design techniques have been developed so far due to its chemical and mechanical complexity during the packing and curing process. This research suggests mold gate design criteria to prevent bobbles from molded parts through simplified mathematical model and change of bubble sizes according to the geometry of the molded parts through experiments. Also this study shows the differences of bobble generation mechanism between RIM and injection molding.

• 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.

• Journal of Korean Society for Quality Management
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• v.29 no.3
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• pp.86-96
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• 2001

The objective of this research is to develop a robust design methodology for plastic injection molded parts wherein warpage will be minimized by a complex method which is a kind of a simple direct search method. The design space considered for optimization is divided Into two sub-design space : mold and process conditions. Warpage is quantified using the Moldflow injection molding simulation software. The design methodology was applied to an actual part of a fax machine, the Guide-ASF model, through two different design policies. The significance of this study is the synthesis of a computer simulation of injection molding process and optimization technique to determine the optimal robust design solution.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.1
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• pp.44-50
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• 2015

This paper presents a heuristic process-optimization procedure for minimizing warpage in injection-molded parts based on the dynamic robust design methodology. The injection molding process is known to have intrinsic variations of its process conditions due to various factors, including incomplete process control facilities. The aim of the robust design methodology advocated by Taguchi is to determine the optimum design variables in a system which is robust to variations in uncontrollable factors. The proposed procedure can determine the optimal robust conditions of injection molding processes at a minimum cost through a trade-off strategy between the degree of warpage and the packing time.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.737-740
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• 2000

Injection molded plastic parts have many appearance imperfections: weld line sink mark flow mark, gloss, shading, scratching, etc. Because these appearance faults have not accepted esthetically, so pastic parts are produced through painting or texturing. The purpose of this paper is to develop a paintless molded part of TV Mask Front, using numerical simulations and experiments. In order to minimize problems of injection, this study carried out computer aided injection mold filling simulations using MF/FLOW. Based on these numerical results we developed FR(Flame Retardant) HIPS and estabilished guidelines of part design, mold design, and processing conditions. We took effects of cost savings, inprovement of productivity, and utilization of recycling by eliminated painting process.

• Transactions of Materials Processing
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• v.8 no.3
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• pp.276-283
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• 1999

This study focuses on part quality and cycle times under gas-assisted injection molding (GIM) of box shape molded parts. The position of the gas channel was established near to parting line at the end of last locations to fill. Applied hot runner and valve gates, the gas was introduced directly into the mold cavity via gas pin. As GIM was applied, the conclusion reached as follows. I) The quality of appearance was improved by reducing sink marks and scratches of texture. ii) The reliability was improved by preventing warpages and reinforcing rigidity through optimum gas channel layout. iii) It is enable to use small size of injection molding machine step by step as GIM was accomplished low pressure and reduced clamp forces against CIM. iv) The productivity were improved by reducing cycle times.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.265-268
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• 2005

Thermoplastic elastormer (TPE) has many advantages such as high flexibility, high elasticity and high elongation, etc. TPE is easily molded such as plastic materials, therefore, many TPE parts are applied as home appliances and mechanical parts. However, if TPE is once molded, its mechanical properties are changed by injection molding conditions such as melt temperature, mold temperature, injection pressure and holding pressure, etc. In this study, the influences of the injection molding condition on the mechanical properties of thermoplastic vulcanizates(TPVs), which is one of the TPE, were investigated. By the injection molding experiment, as increasing the melt temperature, the tensile strength, shrinkage and hardness decreased. By the scanning electron microscope (SEM) analyzing the TPVs' crystallization, the morphology was affected by the melt temperature.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.3
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• pp.172-176
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• 2003

In this paper, we studied the effects of mold temperature on the microstructure of injection molded parts. The weld line decreases in length and width as mold temperature increases. We investigated the dimensional stability of the parts made of two kinds of resin(polypropylene and polystyrene) by varying the mold temperature. As the mold temperature is high, both the shrinkage ratio and the thickness difference for the PS parts decreases. But the observation of PP parts shows a tendency to increase. The easiness of cavity filling and transcription of the mold texture is improved as the mold temperature is high.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.811-814
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• 2001

Warpage analysis of bobbin, molded by injection molding process was performed. Concerned with a mold design, cooling system was designed based on Taguchi method, the distance between cavity wall and cooling channel was most influent factor amongst four design variables like an inlet temperature of coolant, a coolant flow rate, a diameter of cooling channel, and the distance between cavity wall and cooling channel. Optimal packing processes to reduce the warpage of molded part was analyzed based on the response surface method by considering holding pressure. Their optimal processing conditions were 9.4 seconds, 5.3 seconds, 15.2 seconds, and 85MPa, respectively.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.4
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• pp.99-104
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• 2011

In this paper the approach of neural network was proposed which detects a variety of defects in the molded parts. In an attempt to improve the response of the system, It is designed to minimize the use of memory via LookUp table in software. The goal of these methods was to extract the features of samples in learning of neural networks, overcoming the algorithms of defects detection and classification. Through the learning of 500 sample patterns of molded parts, defects of 3% molded parts was detected and classified as the incorrect diameter parts. We expect that proposed approach is an effective alternative to save test time and cost for defect detection of a fine pattern within the molded parts.