Final Shape of Precision Molded Optics: Part II—Validation and Sensitivity to Material Properties and Process Parameters

Ananthasayanam, Balajee; Joseph, Paul; Joshi, Dhananjay; Gaylord, Scott W.; Petit, Laëticia; Blouin, Vincent Y.; Richardson, Kathleen; Cler, Daniel; Stairiker, Matthew; Tardiff, Matthew

doi:10.1080/01495739.2012.674838

Cited by 34 publications

(38 citation statements)

References 2 publications

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“…The large deviations near the center and the edge of the lens are due to the cooling-induced shrinkage and edge effect, respectively [40]. For a precision lens, the allowed center thickness change is about 25 mm [41], and the maximum deviation of overall surface shape should be within several micrometers or smaller [77,78]. Thus, the above numerical analysis [40] has demonstrated that mold compensation is essential; otherwise the lenses by PGM are not usable.…”

Section: Mechanisms Of Lens Distortionmentioning

confidence: 99%

“…It has also been reported [77,78], based on a parametric study on the formation mechanism of shape deviation, that Fig. 7 (a) The evolution of a lens shape in PGM; (b) the deviation with respect to the mold cavity geometry; (c) the relationship between H/R and r/R [40] the structural relaxation of glass is the primary reason for lens distortion in PGM [78].…”

Section: Mechanisms Of Lens Distortionmentioning

confidence: 99%

“…Recently, a method was proposed for identifying the shear relaxation modulus and the structural relaxation function via measuring the time variation of the glass plate thickness [80]. The CTE variation was often modeled by the ToolNarayanaswamy-Moynihan (TNM) model [77,78], the parameterization of which needs structure relaxation tests and thermal expansion tests. It is clearly complicated to establish a constitutive model using these methods.…”

Section: Constitutive Modeling Of Optical Glassmentioning

confidence: 99%

“…Based on the shoving model [83], the temperature-dependent viscosity of optical glass can then be directly linked to its shear modulus, and the CTE of glass can be predicted through modulus based on a phenomenological TNM model [77,78], in which the parameters needed in TNM model can be determined by the modulus changes along with the temperature in the impulse excitation method. The above constitutive model with the measured/derived parameters has been verified and programmed into ABAQUS as a user material (UMAT) [40].…”

Section: Constitutive Modeling Of Optical Glassmentioning

confidence: 99%

“…To obtain sophisticated solutions and useful guidelines for process optimization, the finite element (FE) method has been widely used to reveal the mechanism of geometry deviation and residual stresses [77,78]. This involves an accurate constitutive description of optical glass, the instantaneous property change of optical glass during the heating-cooling cycle in PGM, and lens distortion characterization.…”

Section: Property and Deformation Of Optical Glassmentioning

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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