• Transactions of the Korean hydrogen and new energy society
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• v.31 no.3
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• pp.328-336
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• 2020

In the Francis turbine, the leakage flow through the runner gaps which are between the runner and the stator structure influences the internal flow and hydraulic performance. Thus, the investigation for the flow characteristics induced by the runner gaps is important. However, the runner gaps are often disregarded by considering the time and cost of the numerical analysis. Therefore, in this study, the flow characteristics according to runner gaps of the Francis turbine model were investigated including the leakage flow of the runner cone. The three-dimensional unsteady Reynolds-averaged Navier-Stokes analyses were conducted using a scale-adaptive simulation shear stress transport as a turbulence model for observing the influence of the leakage flow on the internal flow and hydraulic performance. The efficiencies were decreased slightly with runner gaps; and the complicated flows were captured in the gaps.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.10
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• pp.1021-1028
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• 2015

Subminiature lenses are currently widely used in mobile phone cameras and are usually produced by injection molding. The lens molding process has the unique feature of a runner volume that is much larger than the part volume, and this feature should be considered when determining the mold design and molding conditions. In this study, a shell-type runner was proposed as an alternative to the conventional cylindrical runner used for lens molding. An injection molding simulation was performed by applying the proposed shell runner, and the simulation results were compared with those from the cylindrical runner case. It was found that the shell runner could considerably reduce the runner cooling time with only a slight increase in the injection pressure. The effect of the runner thickness was then investigated numerically in terms of the mold filling and cooling characteristics, from which an optimal runner thickness could be determined.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.716-719
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• 1997

This paper describes the runner and gate design capabilities of the RAMEDS system, which is a specialized CAD system for injection mold design, dcvcloped using the application procedure interface of the Unigraphics system. In this system, runners lying on sculptuted partlng surface can be modeled by projecting the runner trajectory on the surface and sweeping a selected cross section along the projcctcd trajectory. In addtion, the system provides solid modeling capabilities for three types of gates currently.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.370-373
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• 2009

The runner-valve is an effective solution for the filling balance of the multi cavity molds. Automation of the runner-valve system is necessary for more efficient and accurate control of the filing balance. We designed an automatic runner-valve actuator for the automation and characterized the actuator by experiment. We obtained a linear relationship between motor-driving time and the height of the runner-valve. However, the motor-driving times for upward and downward directions were different due to the frictional characteristics of the actuators. Also we obtained the motor-driving times for backlashes of the 4 actuators. The results were used to formulate the relationship between the resin-arrival time and the flow rate change of the runner-valve with the theoretical equation that was derived in the previous research.

• Design & Manufacturing
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• v.1 no.1
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• pp.45-50
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• 2007

Recently, the study for filling imbalance in thermoplastic polymer has gradually been increased. However, it is hard to find the researches for filling imbalance of thermoplastic elastomer(TPE). The experiment of filling imbalance was conducted for thermoplastic vulcanize(TPV) and PP, ABS polymers in the mold with un-geometrically balanced runner system(Branch Type Runner System). In this experiment, the effects of the melt temperature, injection pressure and injection speed on the filling imbalance were investigated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.10
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• pp.1575-1582
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• 2001

Injection molding is widely used in producing various plastic parts due to its high productivity, and the demand for injection molded products with high precision is increasing. To achieve successful product quality and precision, the design of gating and runner system in injection mold is very important because it influences the melt flow into the cavity. Some deflects, such as weld lines and overpacking, can be effectively controlled with proper selection of gate locations. In the present study, the design of gate locations in injection molding of a dashboard fur automobiles was carried out with CAMP mold, a PC-based simulation system for injection molding. A dummy runner system was developed to simulate a runner system in order to increase the efficiency of the analysis procedure. The numbers and locations of gates were iteratively determined in the present investigation. In this procedure, an acceptable design was obtained in terms of reducing the maximum pressure and clamping force.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.04a
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• pp.33-39
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• 2003

Injection molding is widely used in producing various plastic parts due to its high productivity and the demand for high precision injection molded products is ever increasing. To achieve successful product quality and precision, the design of gating and runner systems in the injection mold is very important since it directly influences melt flow into the cavity. Some defects such as weld lines and overpacking can be effectively controlled with proper selection of gate locations. In the present study, the design of gate locations in injection molding of a dashboard for automobiles was carried out with CAMPmold, a PC-based simulation system for injection molding. A dummy runner was developed to simulate a runner system in order to increase the efficiency of the analysis. The numbers and locations of gates were varied in the present investigation as that an acceptable design was obtained in terms of reduced maximum pressure and clamping force.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1724-1727
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• 2005

Injection molding process is one of the processes that can mold plastic product as low cost. However, manufacturing process of automobile bumper mold has lots of trial and error. Especially, desiging of a huge mold such as bumper mold is needed to establish a design standard for runner system. In this study, CAE was conducted to observe the variation of melt-flow by changing runner and gate type in automobile bumper mold as preceding study for a standard design of runner system.

• Journal of Korea Foundry Society
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• v.37 no.3
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• pp.71-77
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• 2017

Casting defects produced during the casting process seriously affect the mechanical properties of the resulting products, reduce the performance capabilities of the product, and also result in economic losses. Therefore, this paper mainly investigates the causes of defects and methods by which to reduce these defects stemming from molten metal flows in a runner system of the type widely used in the sand mold casting process. The flow characteristics of a molten alloy are difficult to observe during the actual casting process. For this reason, a water model was used to observe the flow in the casting process, and the flow in each case was recorded using high-speed cameras as part of the experimental process of this study. Several repetitive experiments were performed to improve the accuracy of the experimental results. The traditional casting system was modified according to the design rules proposed by Campbell, and the system was termed flow-adaptive gating system with a water model. Comparing the flow characteristics of traditional and adaptive gating systems with a water model shows that the bubbles in the water in the latter case are reduced more significantly than in the former case. A ceramic filter system was adapted to the flow-adaptive gating system to minimize the instability of the flow during filling, which occurs as the fluid velocity in the runner increases. In additional, the flow behavior with and without the filter system were compared. The water model system in this work was shown to be able to verify that the adaptation of the filter system brings improvements by stabilizing the flow and reducing the amount of bubbles in the runner system. Moreover, using the flow-adaptive runner system with the filter system leads to considerably stable flows in the runner system.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.192-203
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• 2001

The design of gate and runner(delivery system) is one of the most important subject in injection molding. Delivery system is a channel to flow the polymer melt from the injection molding machine to the mold cavities. Also, delivery system affect quality and productivity of the part. The synthesis of delivery system of injection molding has been done empirically, since it requires profound knowledge about the moldability and causal effects on the properties of the part, which are not available to designers through the current CAD systems. GATEWAY is a knowledge module which contains knowledge to permit non-experts as well as mold design experts to generate the acceptable geometries of gate and runner far injection molded parts. A knowledge-based CAD system is constructed by adding the knowledge module, GATEWAY, to an existing geometric modeler. A knowledge-based CAD system is a new tool which enables the concurrent design and CIM with integrated and balanced design decisions at the initial design of injection molding.