Glass Molding Process Research Articles

유리 렌즈의 열 성형 공정 조건 도출을 위한 수치해석 연구

유리 렌즈의 열 성형 공정 조건 도출을 위한 수치해석 연구

Studies on Protective Coatings for Molding Tools Applied in a Precision Glass Molding Process for a High Abbe Number Glass S-FPM3

Precision glass molding (PGM) is an efficient process used for manufacturing high-precision micro lenses with aspheric surfaces, which are key components in high-resolution systems, such as endoscopes. In PGM, production costs are significantly influenced by the lifetimes of elaborately manufactured molding tools. Protective coatings are applied to the molding tools to withstand severe cyclic thermochemical and thermomechanical loads in the PGM process and, in this way, extend the life of the molding tools. This research focuses on a new method which combines metallographic analysis and finite element method (FEM) simulation to study the interaction of three protective coatings—diamond-like carbon (DLC), PtIr and CrAlN—each in contact with the high Abbe number glass material S-FPM3 in a precision glass molding process. Molding tools are analyzed metallographically using light microscopy, white light interferometry, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The results show that the DLC coating improved process durability more than the PtIr and CrAlN coatings, in which the phenomenon of coating delamination and glass adhesion can be observed. To identify potential explanations for the metrological results, FEM is applied to inspect the stress state and stress distribution in the molding tools during the molding process.

Study of Heat Transfer Strategy of Metal Heating/Conduction Plates for Energy Efficiency of Large-Sized Automotive Glass Molding Process

In recent years, as an important functional material, glass has been widely used in architecture, electronics, optics, and other fields. As an emerging glass processing technology, the glass molding process (GMP) has received widespread attention and research in recent years. In this paper, we study the modeling and analysis of different heat transfer strategies for the energy efficiency of large-sized automotive instrument glass. The heat transfer model of the metal heating plate–conducting plate mold is established, the thermal energy efficiency in the forming process of large automobile glass is analyzed, and the energy efficiency of the mold in the heating stage is compared. The energy consumption per piece generated by the GMP heating device is reduced from 4865.2 to 4668.5 kJ, a reduction of 4.04%. By optimizing the heat flow density, the energy consumption per piece generated by the GMP heating device was reduced from 4865.2 to 4625.5 kJ, a reduction of 4.92%, meeting the sustainable manufacturing requirements.

Optimization of precision molding process parameters of viscoelastic materials based on BP neural network improved by genetic algorithm

Micro-structured optical components (MOC) are popular due to their unique optical and mechanical properties. Glass molding processing (GMP) is currently the main method of MOC manufacturing. In GMP, the process parameters determine the efficiency and quality of the glass processing. However, the optimization of their multi-objective molding process parameters has not been studied comprehensively enough. In this paper, a thermocompression model of a viscoelastic material and a mold is developed using coupled thermal-structural analysis in Abaqus. In addition, the data was analyzed to investigate the influence of process parameters on GMP performance. Then, a BP neural network model was built, and the model was trained and tested. A prediction model that can reasonably reveal the relationship between the process parameters and the molding effect was obtained. A multi-objective optimization algorithm GA was used to optimize the design of the hot-pressing process parameters. At last, a set of process parameters with the best forming effect was obtained. This study provides valuable insights into optimizing glass molding process parameters for practical production.

유리렌즈 성형 금형에서 방열블록 형상에 따른 금형 가열부의 열전달 특성 연구

The purpose of this study is to propose a better contact surface pattern of a heat radiating block in a progressive GMP (Glass Molding Process) heating assembly. In this study, a simulation model based on FEM was developed to perform a thermal analysis for the heating assembly. It was verified by comparing experimental results. The temperature distribution on the heating block surface and heating energy consumption was analyzed with the change of contact surface pattern and area of a heat radiating block. The considered pattern on the contact surface was cross (+) and straight (-) shape. The contact area ratio was changed from 16 to 100%. The simulation results show that the heating energy consumption increased to reach a target temperature with the increase of contact area ratio. The straight-shaped patterns on a heat radiating block presented more uniform temperature distribution on the mold heating surface than the cross shaped surface, whereas it resulted in a slightly higher energy consumption of up to 9%. This study shows that the contact surface pattern on a heat dissipating block can control the temperature distribution on the mold heating surface.

Two-Step Glass Molding Process for Forming Glass Edges with Obtuse Angles for Mobile Displays.

The domain of edge displays with 2.5D or 3D curved designs has been expanded to improve user convenience. The currently available 3D cover glass offers a limited curvature radius of at least 5 mm and a curvature less than 88°, due to limitations in the undercuts and formability of parts. The development of a full 3D cover, applicable to next-generation displays, requires cover glass molding technology with a curvature exceeding 90°. Here, a mold design and molding process, which addresses the current limitations by dividing the existing glass molding press (GMP) process into two stages, is proposed. The bending geometry of the glass prepared on the basis of the proposed mold design plan during single-step compression forming and two-step compression forming was predicted using commercial analysis software. A molding product with a curvature radius of 2.5 mm and an angle of curvature of 138.9° was produced when process conditions with bending by up to 180° with no damage were applied during actual forming experiments. Further research on annealing and cooling processes of GMP is expected to enable the design and process implementation to manufacture curved glass with a single curvature of at least 90° and multiple curvatures.

Study on Mechanism of Glass Molding Process for Fingerprint Lock Glass Plates

Curved glass is widely used in 3C industry, and the market demand is increasing gradually. Glass molding process (GMP) is a high-precision, high-efficiency 3D glass touch panel processing technology. In this study, the processing parameters of fingerprint lock glass panels were deeply analyzed. This paper first introduces the molding process of the glass panel, discusses the glass forming device, and explains the heat conduction principle of the glass. Firstly, it introduces the forming process of the glass panel, discusses the glass forming device, and explains the heat conduction principle of the glass. Secondly, the simulation model of a fingerprint lock glass plate was simulated by MSC. Marc software. The stress relaxation model and structure relaxation model are used in the model, and the heat transfer characteristics of glass mold are combined to accurately predict the forming process of glass components. The effects of molding temperature, heating rate, holding time, molding pressure, cooling rate and other process parameters on product quality characteristics (residual stress and shape deviation) were analyzed through simulation experiments. The results show that, in a certain range, the residual stress is inversely proportional to the bending temperature and heating rate, and is directly proportional to the cooling rate, while the shape deviation decreases with the increase of temperature and heating rate. When the cooling rate decreases, the shape deviation first decreases and then increases. Furthermore, a verification experiment is designed to verify the reliability of the simulation results by measuring and calculating the surface roughness of the formed products.

A comprehensive review of theory and technology of glass molding process

With the development of aerospace, military, medical, and 3C industries, the design of aspherical optical component has attracted more and more attention. As a substitute for the traditional manufacturing process for glass materials, the glass molding process (GMP) has the advantages of high forming accuracy, short production cycle, low cost, and non-pollution. This paper presents an overview of recent progresses of theory and technology in the glass molding process. The existing theoretical models (stress relaxation and structural relaxation) of glass material in GMP are introduced, and the most recent applications of these theoretical models are discussed. In addition, the latest advancements in theory of applying both high-frequency microwave and ultrasound-assisted techniques in GMP are detailed. Moreover, the implementations of both apparatus (heating source, ultrasonic vibration auxiliary device, molds, and measurement and controller) and whole machine of GMP are compared in detail. Lastly, the reasonable ranges and change rules of molding conditions, such as molding temperature, molding pressure, and holding time, are reviewed, and effects of GMP on performances (temperature distribution, stress, curve deviation) are discussed.

Fabricating Microstructures on Glass for Microfluidic Chips by Glass Molding Process.

Compared with polymer-based biochips, such as polydimethylsiloxane (PDMS), glass based chips have drawn much attention due to their high transparency, chemical stability, and good biocompatibility. This paper investigated the glass molding process (GMP) for fabricating microstructures of microfluidic chips. The glass material was D-ZK3. Firstly, a mold with protrusion microstructure was prepared and used to fabricate grooves to evaluate the GMP performance in terms of roughness and height. Next, the molds for fabricating three typical microfluidic chips, for example, diffusion mixer chip, flow focusing chip, and cell counting chip, were prepared and used to mold microfluidic chips. The analysis of mold wear was then conducted by the comparison of mold morphology, before and after the GMP, which indicated that the mold was suitable for GMP. Finally, in order to verify the performance of the molded chips by the GMP, a mixed microfluidic chip was chosen to conduct an actual liquid filling experiment. The study indicated that the fabricating microstructure of glass microfluidic chip could be finished in 12 min with good surface quality, thus, providing a promising method for achieving mass production of glass microfluidic chips in the future.

Numerical study on fabricating rectangle microchannel in microfluidic chips by glass molding process

This paper studied the glass molding process (GMP) for fabricating a typical microstructure of glass microfluidic chips, i. e., rectangle microchannel, on soda-lime glass by finite element method. More than 100 models were established on the platform of Abaqus/Standard. The influence of parameters, i. e., temperature, aspect ratio, side wall angle and friction coefficient on deformation were studied, and the predicted morphology of the molded microchannel were presented as well. The research could provide fundamental experience for optimizing GMP process in the future.

Study the Formation Process of Cuboid Microprotrusion by Glass Molding Process †

This paper investigates the formation process of a typical microstructure in the glass microfluidic chip, i.e., cuboid microprotrusion, by the soda-lime glass molding process (GMP). The finite element models on the platform Abaqus/Standard were established for simulating the glass molding process. The glass viscoelasticity at pressing temperature was described by the General Maxwell model. The influence of the temperature, aspect ratio and side wall angle on the replication ratio was investigated, and the corresponding predicted molded profiles were demonstrated as well. The established simulation model was verified by experimental results eventually. It could provide a fundamental experience for optimizing glass molding parameters to fabricate microstructures on glass chips.

Numerical Modeling of Cooling Stage of Glass Molding Process Assisted by CFD and Measurement of Residual Birefringence

Process parameters of Precision Glass Molding (PGM) are often sought by Finite Element (FE) simulation. Mechanical as well as thermal boundary conditions (BCs) are necessary for FE simulation in which mechanical BCs are usually known or easily determinable. However, most of the thermal BCs are generally assumed in the FE simulation as they cannot be measured directly. The focus of this article is to propose a novel method for evaluating the thermal BC of glass–N2 gas. FE simulations as well as thermal cycling experiments are carried out for a glass disk specimen for three different cooling rates. CFD analysis of N2 flow in the PGM machine is performed to understand the heat extraction mechanism. Based on this, adhoc values for equivalent heat transfer coefficient (heqv) are obtained by lumped system analysis. A novel methodology is then proposed for obtaining accurate heqv values by measurement of integrated residual birefringence in glass using digital photoelasticity. FE simulation is repeated for different values of heqv until the integrated birefringence based on simulation matches with that of the experiment. For the same cooling rates, two aspherical glass lenses are molded and their residual birefringence is measured and compared with the glass disk specimen.

Study on High-Temperature Glass Lens Molding Process Using FEM Simulation

The glass molding process (GMP) can press glass perform into a shape of finished lens under high pressure and temperature conditions, and it is easy to achieve mass production. So, it has emerged as a promising alternative way to produce complex shapes lens. It is well known that viscoelastic is one important properties of glass at high temperature. In this study, A 4-pair generalized maxwell model was used to express viscoelastic of glass, and model parameters were obtained by fitting the relaxation curve obtained from experiment. The finite element models were established by MSC.MARC, the correctness of the FEM models and its used model parameters were verified by the cylindrical compression experiments. Finally, the simulations of glass lens forming stage were performed under different conditions. Stresses distribution were predicted by FEM, it was found that the maximum stress at the edge of lens, which make lens rupture easily at this zone. It was also discovered that the molding temperature is higher, the less stress, and the molding velocity is higher, the higher stress.

Glass biochip fabrication by laser micromachining and glass-molding process

Due to their low cost, small size, and high-speed performance, biochips are often used in various bio-experiments. Compared with polymer-based biochips, glass-based substrates are less sensitive to heat and organic environments. This study presents a hybrid processing approach that uses laser micromachining (LMM) and precision glass molding (PGM) techniques to mass-produce glass-based biochips. A silicon carbide (SiC) mold with an outside diameter of 20 mm was used to hot emboss biochip channels measuring 200 μm wide and 185 μm deep. This study also identifies the optimal conditions for glass molding when processing soda-lime glass for biochip applications, and discusses the influence of the major processing parameters on biochip channel depth. This study uses the Taguchi method to assess the effects of several molding parameters on larger-the-better performance characteristics. The experiments in this study consider the effects of several molding parameters, such as molding temperature, pressing force, moving speed, temperature holding time, and vacuum environment, to achieve optimum characteristics for biochip channels. Orthogonal array analysis indicates that the optimal process parameters includes a 620 °C molding temperature, 1 kN pressing force, 5 mm/min moving speed, 60 s temperature holding time, and a vacuum-free environment. This study also investigates the surface roughness of glass biochip channels.

실험계획법에 의한 GMP용 비구면 광학유리의 성질에 미치는 조성의 효과 연구

In this study, the composition of optical glass for GMP(glass molding process) was designed with ‘Design of Experiments’ method. All the composition batch was performed by ‘Create Factorial Design’ method. Particularly, SiO₂, BaO and Al₂O₃ were chosen major parameters for investigating the effects of components on optical and thermal properties. BaO and Al₂O₃ strongly influenced on optical and thermal properties, respectively. Finally, the approximate values of desired optical and thermal values were obtained by microtuning of compositions. At the composition of BaO:Al₂O₃:SiO₂=10:4:48 (molar ratio), refractive index(nd) was 1.5833, coefficient of thermal expansion(CTE) was 104×10 -7 /℃.

The glass-molding process for planar-integrated micro-optical component

This paper presents a precision glass-molding process to fabricate planar-integrated micro-optical components (PIMOC) applied to a micro projection display system, optical interconnection system and optical storage system. The PIMOC was designed based on wave propagation theory, and fabricated using a glass molding process. Experimental results are discussed in this article. The experiment showed that the PIMOC fabricated in a vacuum environment meets the design value with precision glass-molding technology (PGMT) at a molding force of 2.75 kN, a molding temperature of 750 °C and a cooling rate of 49 °C/min.

Investigation of the Interfacial Reaction between Optical Glasses and Various Protective Films and Mold Materials

The glass molding process (GMP) is regarded as a very promising technique for mass producing high precision optical components such as spherical/ aspheric glass lenses and free-form optics. However, only a handful of materials can sustain the chemical reaction, mechanical stress and temperature involved in the glass molding process. Besides, almost all of these mold materials are classified as hard-to-machine materials. This makes the machining of these materials to sub-micrometer form accuracy and nanometer surface finish a rather tough and expensive task. As a result, making mold life longer has become extremely critical in the GMP industry. The interfacial chemical reaction between optical glass and mold is normally the main reason for pre-matured mold failure. This research aimed to investigate the interfacial chemical reaction between various optical glasses, different anti-stick coating designs and several mold materials. The results showed that glass composition, coating design (composition, microstructure, thickness), environment (vacuum, air or in protective gas), reaction temperature and time could all have profound effects on the interfacial chemical reaction. Based on the results, a design developed specially for certain glasses is more likely to be the viable way of optimizing the effect of the protective coating.

The Effect of TaN Interlayer on the Performance of Pt-Ir Protective Coatings in Glass Molding Process

The glass molding process provides great potential for mass production of precise glass optical components at low cost. The key issue for achieving a low production cost is to extend the service life of the expensive mold inserts. The precious metal based alloy is one of the coating materials for the molds which provides excellent glass anti-sticking results. However, the inter-diffusion between the WC/Co mold materials and precious metal coatings will deteriorate the coatings which needs to be resolved. It is essentially to deposit an interlayer as the diffusion barrier to improve the inter-diffusion problem. A thin layer of TaN was deposited on the WC/Co substrate as the diffusion barrier using a magnetron sputtering system, and followed by the deposition of Pt-Ir layer as the protective layer. Low Tg Glass gobs (L-BAL 42) were placed on the coated substrate to investigate inter-diffusion between the substrate and coating at high temperature. The surface interaction between the glass gobs and protective coatings was also examined. The obtained TaN and Pt-Ir multilayer had a dense nano-crystalline structure. High temperature wetting tests showed that the TaN film could effectively resist the cobalt and tungsten diffusion into the precious metal protective layer and, as a result, minimized the possibility of oxidation and interaction between glass and protective coating. The coated substrates retained a good surface finish and the glass gobs stayed fully transparent after 6 hours reaction test at 700°C.

Fabrication of a Solid Immersion Mirror and Its Optical Evaluation

We report the optical design of a solid immersion mirror (SIM) incorporated with a flying slider – called a SIM slider – for a near-field recording (NFR) system, its fabrication process, and optical evaluation. To achieve diffraction-limited performance ∼λ/14 (rms), a two-step glass-molding process was employed to fabricate the SIM. The numerical aperture of the SIM slider was 1.29. The rms value of the total wavefront aberration was 0.0679λ. The fabricated SIM slider achieves the optical performance estimated by calculation with the fabrication errors considered, and even diffraction-limited performance. However, an rms value of 0.035λ–0.04λ for the total wavefront aberration is generally assigned for condensing optics for practical use because not only condensing optics but also other optical elements are involved in a practical optical disc system. Therefore, the aberration caused by the fabrication errors in the molding process should be reduced to at least 59% of the present level, if the SIM is to be applied to a practical NFR system.

Finite element analysis of a coating architecture for glass-molding dies

Finite element analysis (FEA) is being used as an integral part of an overall research program that is being conducted to develop a non-sticking, oxidation- and wear-resistant coating system for glass-molding dies and forming tools. This non-linear thermomechanical FEA consists of two parts: (1) a global analysis using a coupled thermomechanical model of the complete die to predict the locations where the die experiences extreme stress/strain condition during molding cycles; and (2) a local analysis of the die coating used to protect the die at those positions where extreme conditions were predicted by the global analysis, to analyze the stresses generated in the coating system during a simulated glass-molding process. This paper outlines the methodology developed in this work, which can be used to explore the effects of die geometry, die material, and coating materials on the integrity, reliability and performance of a coated die. This methodology may also be helpful for investigation of the mechanisms relating to the thermal fatigue problem. The preliminary results presented here demonstrate that it is possible to find an optimized coating architecture with optimal stress transition from the substrate to the outmost working layer by selecting appropriate coating materials and engineering the compositional gradients of the functionally graded material (FGM) intermediate layer.