A complete qualification methodology for coatings of precision glass molding tools

Klocke, Fritz; Georgiadis, Kyriakos; Dambon, Olaf; Bouzakis, K.‐D.; Gerardis, S.; Skordaris, G.

doi:10.1117/12.892802

Cited by 3 publications

(2 citation statements)

References 19 publications

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“…Recently, a quick testing facility [72,73] was proposed to assess the service life of mold coatings for PGM. It was noticed that in PGM a long period of time in the heating-cooling process is without mechanical stresses or chemical influence.…”

Section: Selection Of Mold Materialsmentioning

confidence: 99%

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: Selection Of Mold Materialsmentioning

confidence: 99%

Precision glass molding: Toward an optimal fabrication of optical lenses

Zhang

Liu

2017

Front. Mech. Eng.

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“…The mold material is commonly composed of tungsten carbide (WC) due to its high strength and hardness at high temperatures as well as its ability to be precisely machined by means of grinding and polishing [8][9][10]. To protect the WC molding tools from degradation caused by harsh process conditions, a surface protective coating is applied [11,12]. Three groups of surface protective coatings are commonly used [13]: precious metal coatings [14], ceramic hard coatings [15], and carbon-based diamond-like carbon (DLC) coatings [16].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2023

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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.

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