Microfluidic chips have become a critical component in advanced applications such as biochemical analysis, medical diagnostics, drug development, and environmental monitoring because of their ability to precisely control fluid flow at the microscale. The functionality of these chips is highly dependent on the precision and dimensional stability of microchannel structures formed on them. While injection molding is an efficient method for a mass production of microfluidic chips, it is required to minimize undesirable deformation due to thermal and mechanical stresses, which can degrade the overall performance. This study investigated global (Macro-scale) and local (Micro-scale) deformation behaviors of injection-molded microfluidic chips. Effects of processing parameters, including mold temperature, melt temperature, filling time, and packing pressure, were investigated. The Taguchi-based design of experiments approach was employed to systematically analyze these effects and to determine optimal conditions to minimize deformation.
Recently, with the expansion of application of polymer composite materials, high levels of deformation compensation actions have been developed. However, there is a problem of high-temperature viscoelasticity that occurs over time after completing the injection molding process. In this study, changes of mechanical properties of the Moldflow program for injection molding were analyzed to verify the viscoelasticity phenomenon through deformation analysis. In addition, deformation analysis of plastic injection molded products according to arrangement of three ribs was conducted and two products with different geometric shapes of the same function were compared. As a result, it was possible to reflect the viscoelastic effect by reducing the elastic modulus and shear modulus of the material. It was confirmed that the geometric shape with thick ribs formed in multiple longitudinal directions was mainly responsible. On the surface of the product where the rib arrangement was parallel and perpendicular to the flow direction, the orientation was orthogonal to the linear direction and the maximum residual stress was 81.17 MPa, which showed the largest value. It was judged that viscoelastic phenomena could be predicted and that an arrangement of parallel and perpendicular ribs that might intersect should be avoided.
SFT, which has a high glass fiber content, is one of the effective methods to replace metal and secure weight reduction and price competitiveness. Also, paintless injection molding in which a functional pattern is applied to the mold surface can eliminate the cost of painting. In this study, three types of SFTs were manufactured by adding round glass fibers measuring Φ7 and Φ10 μm and flat glass fiber measuring 27 × 10 μm for the experiment. DOE (Design of Experiment) was conducted to confirm the change in the warpage of the product and the gloss of the micro pattern due to the cross-sectional shape of glass fibers and the major injection conditions. Based on the results, it was identified that the flat SFT had a very small warpage compared to the round SFTs, and the holding pressure was the main factor in the warpage of all three SFTs. The Φ7 μm SFT had the largest gloss value, and the Φ10 μm SFT and the flat SFT had similar average values. All SFTs demonstrated an enormous change in gloss according to the change in mold temperature. The flat SFT had the smallest standard deviation in both warpage and gloss.
SFT, which has a high glass fiber content, is one of the effective methods to replace metal and secure weight reduction and price competitiveness. This study evaluated the effect of glass fiber shape on mechanical properties in injection molding by fabricating SFT with a glass fiber content of 60%. Three types of SFTs were manufactured by adding round glass fibers of Φ7 μm and Φ10 μm and flat glass fibers of 27 × 10 μm. DOE (Design of Experiment) conducts to confirm the change in tensile strength due to changes in significant injection conditions. As a result of the experiment, Φ7 μm SFT and flat SFT have similar tensile strength and Φ10 μm SFT showed the lowest tensile strength value. As for the standard deviation of strength value, the Φ7 μm SFT had the largest standard deviation, and the Φ10 μm SFT showed the slightest change in the injection conditions. In flat SFT, it confirms that the tensile strength increased as the molding temperature increased. The fracture surface observes using SEM. It founds that the tensile strength lowers due to the small glass fiber density and many pullouts at the fracture surface of Φ10 μm with weak strength.
Citations
Citations to this article as recorded by
Enhancing Adhesive Strength between Metal and Plastic in Smartphone Applications Moon-Soo Kim, Jin-Hyung Park, kang-Suk Choi, Seon-Mi Park, Seong-Dae Choi Journal of the Korean Society of Manufacturing Process Engineers.2025; 24(9): 82. CrossRef
As a heating method for RHCM (Rapid Heating Cycle Molding) various heating technologies such as high frequency induction heating, IR heating, gas heating, and high temperature steamare applied, but these methods are not satisfying high productivity due to low energy efficiency. Research has been actively conducted on RHCM based on planar heating elements with high heating efficiency, such as carbon nanotubes, which are applied. To apply the CNT web film to the RHCM, a heating element must be applied inside the injection mold and power must be applied. As electricity is directly applied to the CNT web film to generate heat, all mold parts in contact with the CNT web film must be insulated, and high heat transfer is required for rapid heating performance. Thus, in this study, a multi-layer structure mold module for insulation and high heat transfer was designed to enable rapid heating by applying a CNT web film as a heat source. To this end, we intend to present a research direction for the commercialization of rapid heating molds, by identifying the main variables of rapid heating through heating experiments by the mold metal and insulator materials, and reflecting them in the mold design.
Injection molding is one of most widely-used polymer processing technologies in which hot polymer fills a mold cavity, and is solidified during the subsequent cooling process. In the mold filling stage, the mold temperature should be high to improve flow characteristics, and low to reduce cooling time during the cooling stage. To fulfill these objectives, rapid mold heating technology has been developed to raise mold temperature, without significant increase in cycle time. While the conventional rapid heating technologies required dedicated facilities such as steam heating or high-frequency induction heating system and has a limitation in uniform heating, the purpose of this study was to develop a facile and conformal mold heating unit that uses a carbon nanotube (CNT) film heater. The CNT film heater was used to heat a curved mold with high temperature uniformity, by maintaining uniform distance from the mold surface. The developed conformal heating technology was then applied to a singly curved mold and a multiply curved mold. Considering that the resulting temperature uniformity is superior to the conventional oil heating, the conformal mold heating technology using the CNT film heater can be used to improve part quality and productivity in various molding processes.
The design of the injection mold cooling system is important. The cooling time consumes 70-80% of the injection molding cycle, so a well-designed cooling system can shorten the molding time and improve productivity significantly. Recently, many studies have been conducted for rapid cooling of a hot-spot area using CO₂ in injection molding. In this study, a cooling module based on CO₂ was designed and manufactured for uniform and rapid cooling of an injection mold with a large cavity, and cooling characteristics were investigated through experiments. As the CO₂ supply pressure increased, the cooling effect increased significantly, while the cooling uniformity decreased relatively. In the case of using the heat exchanger, the cooling effect increased by 10oC on average compared to the case without the heat exchanger, whereas the effect on the cooling uniformity was insignificant. When the CO₂ was injected from both sides, the cooling effect increased by approximately 8oC on average compared to the case of injection from one side, and the cooling uniformity was approximately 10% higher. By using a heat exchanger and applying CO₂ bidirectional supply, a cooling rate of up to 5.78℃/s and an average of 4.9℃/s could be achieved.
The main function of aircraft ejection system is that it separates the store from the aircraft. The ejection force is important for the safety of the aircraft when the store is ejected, because the store can be lifted by air flow affected by the aircraft’s speed. If the ejection force is low, the aircraft can be damaged by the floating store. The ejection force of the suspension system should be designed in order to release the store safely. In this study, the ejection force of the pyrotechnic suspension using the cartridge to eject the store was researched. This research was performed, based on the precedent study about the over-center linkage mechanism and the pressure drop by the orifice. The ejection force was calculated, after analyzing mathematical fundamentals about the pressure in the system of the suspension and analyzed through AutoDyn and ADAMS software. Finally, the theoretical results were compared with the ejection test results of the suspension system.
The purpose of this study was to develop an efficient mold heating technology by an embedded heating unit. To localize the heating effect in the mold core and prevent heat transfer to surrounding mold plates, the core module with embedded heating unit was assembled to a mold plate in a detachable manner. The detachable core module was then separated from the mold plate when the mold was opened, and thus could be rapidly heated by the embedded heater. The heated core contacted with the mold plate when the mold was closed, and could be cooled by heat conduction to the mold plate of which thermal inertia was much larger than that of the core module. To verify thermal efficiency of the proposed structure, heat transfer simulation was performed with an experimental validation. Mold filling simulation was also performed to investigate the effect of mold heating on improving flow characteristics through a thin and narrow channel. Injection molding experiments were also conducted by adopting the proposed embedded heating module.
Citations
Citations to this article as recorded by
Analysis of Rapid Heating Performance in Multi-Layered Injection Mold System for CNT Surface Heating Element Application Hyeon Min Lee, Young Bae Ko, Woo Chun Choi Journal of the Korean Society for Precision Engineering.2022; 39(7): 461. CrossRef
Energy Saving of Rubber Forming by Direct Heating Press Mold Development Young Tae Cho Journal of the Korean Society for Precision Engineering.2022; 39(7): 485. CrossRef
A Study on Conformal Heating of Curved Mold Using CNT Film Heater Seo-Hyeon Oh, Eun-Ji Jeon, Hyeon-Min Lee, Yeong-Bae Ko, Keun Park Journal of the Korean Society for Precision Engineering.2022; 39(7): 469. CrossRef
Conformal Mold Heating and Cooling Using a Carbon Nanotube Film Heater and Additively Manufactured Cellular Metamaterial Jeong-Hee You, Jun-Won Lee, Seo-Hyeon Oh, Keun Park International Journal of Precision Engineering and Manufacturing-Green Technology.2022; 9(6): 1463. CrossRef
A Study on the Heat Transfer Characteristics of a Glass Lens Mold Heating Block according to Design of a Heat Radiating Block Bo Min Seo, Dong Yean Jung, Keun Park, Chang Yong Park Journal of the Korean Society for Precision Engineering.2022; 39(7): 493. CrossRef
First
Prev
