Thermoforming mechanism of precision glass moulding

Liu, Weidong; Zhang, Liangchi

doi:10.1364/ao.54.006841

Cited by 21 publications

(30 citation statements)

References 32 publications

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“…The chamber of the PGM machine is evacuated with an inert gas, such as nitrogen, before heating the preform and mold up to the required molding temperature above the glass T g . This will make the glass viscosity be in the range of 10 7 to 10 8 Pa·s [40]. The process is then conducted by applying either a constant compression force or a pressing velocity within a period of time selected.…”

Section: Typical Pgm Proceduresmentioning

confidence: 99%

“…At the end of the molding, the lens is first cooled down with a small rate, during which the compressive force remains until the glass temperature has dropped to a specific temperature corresponding to the strain point of glass (h = 10 13.5 Pa·s). The demolding process can then take place associated with a higher cooling rate for a higher production efficiency [40,41].…”

Section: Typical Pgm Proceduresmentioning

confidence: 99%

“…In PGM, mold deterioration and shape and optical property variations of molded lenses are major problems [33,40,[44][45][46][47]. The manufacture of a quality optical mold is the costliest part in the PGM production chain.…”

Section: Performance Of Molded Optical Lensesmentioning

confidence: 99%

“…This technique is based on the softening of glass in its super-cooled liquid region which is above the glass transition temperature T g [40]. With this, once the surface of a mold cavity is made to have the required dimensions, geometries and features, in a single production step a precision glass lens can be thermally formed to copy the cavity geometries and features of the mold.…”

Section: Introductionmentioning

confidence: 99%

“…A PGM process involves heating, soaking, molding, first cooling, demolding and final cooling, through which both the glass and mold experience complicated thermo-mechanical deformation. For example, in a very narrow temperature range the viscosity of glass undergoes a change of several orders of its magnitude, which brings about significant challenges for the production of high precision lenses by PGM [40]. As a result, the quality of the molded lenses is still not as good as those manufactured by precision machining processes, although the production cost of the former is only half of that of the latter [42].…”

Section: Introductionmentioning

confidence: 99%

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Precision glass molding: Toward an optimal fabrication of optical lenses

Zhang

Liu

2017

Front. Mech. Eng.

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It is costly and time consuming to use machining processes, such as grinding, polishing and lapping, to produce optical glass lenses with complex features. Precision glass molding (PGM) has thus been developed to realize an efficient manufacture of such optical components in a single step. However, PGM faces various technical challenges. For example, a PGM process must be carried out within the super-cooled region of optical glass above its glass transition temperature, in which the material has an unstable non-equilibrium structure. Within a narrow window of allowable temperature variation, the glass viscosity can change from 10 5 to 10 12 Pa$s due to the kinetic fragility of the super-cooled liquid. This makes a PGM process sensitive to its molding temperature. In addition, because of the structural relaxation in this temperature window, the atomic structure that governs the material properties is strongly dependent on time and thermal history. Such complexity often leads to residual stresses and shape distortion in a lens molded, causing unexpected changes in density and refractive index. This review will discuss some of the central issues in PGM processes and provide a method based on a manufacturing chain consideration from mold material selection, property and deformation characterization of optical glass to process optimization. The realization of such optimization is a necessary step for the Industry 4.0 of PGM.

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Section: Typical Pgm Proceduresmentioning

confidence: 99%

Section: Typical Pgm Proceduresmentioning

confidence: 99%

Section: Performance Of Molded Optical Lensesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Precision glass molding: Toward an optimal fabrication of optical lenses

Zhang

Liu

2017

Front. Mech. Eng.

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P‐52: Novel Forming Technology of 3D Cover Glass with Induction Heating System for Curved‐Corner Display

Kim

Seo

Nam

et al. 2022

Symp Digest of Tech Papers

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This paper talks about new thermal forming method of 3‐dimensional box‐type cover glass with double curvature for mobile phone application. Induced heating of glass forming molds was successfully employed around edge area in order to minimize typical surface wrinkle and dent defects commonly appearing in conventional direct mold heating with heating plates. The results showed better surface qualities compared to conventional heating by optimizing mold temperature, loading pressure and 2‐dimensional initial preform shape.

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High-temperature friction characteristics of N-BK7 glass and their correlation with viscoelastic loss modulus

Zhou

Zhu

et al. 2021

Ceramics International

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Thermoforming mechanism of precision glass moulding

Cited by 21 publications

References 32 publications

Precision glass molding: Toward an optimal fabrication of optical lenses

Precision glass molding: Toward an optimal fabrication of optical lenses

P‐52: Novel Forming Technology of 3D Cover Glass with Induction Heating System for Curved‐Corner Display

High-temperature friction characteristics of N-BK7 glass and their correlation with viscoelastic loss modulus

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