Vacuum-assisted precision molding of 3D thin microstructure glass optics

Vu, Anh Tuan; Vogel, Paul-Alexander; Dambon, Olaf; Klocke, Fritz

doi:10.1117/12.2307060

Cited by 9 publications

(9 citation statements)

References 13 publications

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“…Accordingly, further growth of the contact area is occurred, until these surrounding spots contact with the mold surface become “frozen”. Similar study on the simulation of nonisothermal hot glass forming of microstructure optics demonstrates this observation . Such glass filling behavior into the microscale cavities of the mold surface explains the slight increase of the contact coefficient during the period of holding force.…”

Section: Results and Validationsupporting

confidence: 76%

“…Similar study on the simulation of nonisothermal hot glass forming of microstructure optics demonstrates this observation. 23 Such glass filling behavior into the microscale cavities of the mold surface explains the slight increase of the contact coefficient during the period of holding force. However, only a steady state, rather than a time-dependent deformation model is used.…”

Section: Simulation Results and Validationmentioning

confidence: 98%

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Numerical and experimental determinations of contact heat transfer coefficients in nonisothermal glass molding

Helmig

et al. 2019

J Am Ceram Soc

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Heat transfer at the interfacial contact is a dominant factor in the thermal behavior of glass during nonisothermal glass molding process. Recent research is developing reliable numerical approaches to quantify contact heat transfer coefficients. In most previous studies, however, both theoretical and numerical models of thermal contact conductance in glass molding attempted to investigate this factor by either omitting surface topography or simplifying the nature of contact surfaces. In fact, the determination of the contact heat transfer coefficient demands a detailed characterization of the contact interface including the surface topography and the thermomechanical behavior of the contact pair. This paper introduces a numerical approach to quantify the contact heat transfer by means of a microscale simulation at the glass‐mold interface. The simulation successfully incorporates modeling of the thermomechanical behaviors and the three‐dimensional topographies from actual surface measurements of the contact pair. The presented numerical model enables the derivation of contact heat transfer coefficients from various contact pressures and surface finishes. Numerical predictions of these coefficients are validated by transient contact heat transfer experiments using infrared thermography to verify the model.

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Section: Results and Validationsupporting

confidence: 76%

Section: Simulation Results and Validationmentioning

confidence: 98%

Numerical and experimental determinations of contact heat transfer coefficients in nonisothermal glass molding

Helmig

et al. 2019

J Am Ceram Soc

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“…The latter is influenced both by process parameters, e.g. temperature and molding force (e.g., Maxwell [15,16] or Burgers' models [17,18]), the heat transfers at the glassmold interface [19][20][21] and by system variables such as the geometry of the blank and that of the mold, as well as the surface properties [22]. Another challenge is the control of shrinkage, which is also significantly influenced by thermal and system parameters [23].…”

Section: Fig 4 Process Chain Of the Wafer Scale Processmentioning

confidence: 99%

Enabling Sustainability in Glass Optics Manufacturing by Wafer Scale Molding

Strobl

Vogel

et al. 2022

KEM

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Numerous optical applications have rising demands for ever increasing quantities from lighting and projection optics for modern vehicles to home or street lighting using LED technology. Glass is the material of choice for most of those application fields. It has several advantages over polymers, including heat and scratch resistance as well as longevity and recyclability. Non-isothermal glass molding has become a viable hot forming technology for mass production of optics. The major challenge is enabling a scalable replication process allowing the optical glass elements to be manufactured with high form accuracy and at low-cost production with low reject rates. This work introduces recent developments in glass optics manufacturing that allow the fulfilment of seemingly contradicting criteria: the economic growth and the need for less consumption of resources and energy. While single cavity non-isothermal molding is state-of-the-art, a manufacturing innovation through wafer-scale molding enables an exponentially increasing number of optics to be produced per production shift, allowing a significant reduction of unit costs. In parallel, as multiple optics are produced in one manufacturing cycle, the energy consumption and the consequent CO2 emission can be reduced. In contrast, the technological development arises several challenges that will be discussed in this work. Besides the selection of suitable mold concepts and materials, the challenges also include the temperature control of the mold and the blank up to the optimization of flow and shrinking mechanisms of the glass during rapid forming. Another difficulty in the non-isothermal glass molding is to maintain the low form deviation required for precision optics, repeatability, and low failure rates through process optimization. Finally, detail calculations of cost, energy and CO2 consumption, in comparison with conventional fabrication of glass components using grinding and polishing as well as single cavity molding, will be demonstrated. The non-isothermal wafer-level glass molding is a new technological solution for the sustainable manufacturing of optics at large-scaled production.

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“…An earlier study of the author has indicated that the Burgers model precisely predicts the creep displacements of B270i glass in a wide molding temperature range, which correspond to viscosity η = 10 11.7 − 10 7 Pas. 36 Second, it is emphasized that because the Burgers model consists of a Maxwell and a Kelvin element, it is capable of representing both creep and stress relaxation phenomena. As a result, the relaxation function can be directly computed from the fitting parameters obtained from the creep compliance.…”

Section: Determination Of Relaxation Modulusmentioning

confidence: 99%

Modeling of thermo‐viscoelastic material behavior of glass over a wide temperature range in glass compression molding

Grunwald

Bergs

2020

J Am Ceram Soc

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In glass compression molding, most current modeling approaches of temperature‐dependent viscoelastic behavior of glass materials are restricted to thermo‐rheologically simple assumption. This research conducts a detailed study and demonstrates that this assumption, however, is not adequate for glass molding simulations over a wide range of molding temperatures. In this paper, we introduce a new method that eliminates the prerequisite of relaxation functions and shift factors for modeling of the thermo‐viscoelastic material behavior. More specifically, the temperature effect is directly incorporated into each parameter of the mechanical model. The mechanical model parameters are derived from creep displacements using uniaxial compression experiments. Validations of the proposed method are conducted for three different glass categories, including borosilicate, aluminosilicate, and chalcogenide glasses. Excellent agreement between the creep experiments and simulation results is found in all glasses over long pressing time up to 900 seconds and a large temperature range that corresponds to the glass viscosity of log (η) = 9.5 – 6.8 Pas. The method eventually promises an enhancement of the glass molding simulation.

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Vacuum-assisted precision molding of 3D thin microstructure glass optics

Cited by 9 publications

References 13 publications

Numerical and experimental determinations of contact heat transfer coefficients in nonisothermal glass molding

Numerical and experimental determinations of contact heat transfer coefficients in nonisothermal glass molding

Enabling Sustainability in Glass Optics Manufacturing by Wafer Scale Molding

Modeling of thermo‐viscoelastic material behavior of glass over a wide temperature range in glass compression molding

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