Ultra-precision grinding is primarily used to generate high quality and functional parts usually made from hard and difficult to machine materials. The objective of ultra-precision grinding is to generate parts with high surface finish, high form accuracy and surface integrity for the electronic and optical industries as well as for astronomical applications. This keynote paper introduces general aspects of ultra-precision grinding techniques and point out the essential features of ultra-precision grinding. In particular, the keynote paper reviews the state-of-the-art regarding applied grinding tools, ultra-precision machine tools and grinding processes. Finally, selected examples of advanced ultra-precision grinding processes are presented.

Ultra-precision grinding

This study provides a global substance flow analysis for gallium (Ga), germanium (Ge), and indium (In) for 2011, quantifying the amount of metal lost during extraction, beneficiation/smelting/refining, manufacturing of intermediate products, and the amount embodied in end-use products. Thus far, studies illustrating their cradle to end-use life cycle on a global scale are either missing or outdated, and thus opportunities to increase their supply remain unknown and/or not quantified. The results illustrate the losses and inefficiencies stages, thereby identifying potential additional supply by process improvement, recovery, and recycling. Results show that there are significant opportunities to meet future demand of Ga and Ge by concentrating recovery efforts in the extraction and beneficiation/smelting/refining stages. Further, 1.4% Ga, 0.7% Ge, and 54% In of the theoretical available amount in the attractor ores are extracted to meet the primary refined demand in 2011. Of the 9,065 tonnes (t) of Ga embodied in the Bayer liquor (from aluminum production), only 263 t are refined. This is owing to low capacities of Ga refining, combined with a refining efficiency of 60%. Ge presents a similar case for the same reasons, in which only 43 t of Ge of the 7,636 t of Ge available from zinc leach residue are refined. Meeting future In demand, on the other hand, will require greater efforts in increasing end-of-life recycling. Process efficiencies for Ga (46%), Ge (56%), and In (78%) demonstrate further potential. We quantify the flows into use by distinguishing among dissipative and nondissipative end uses, as well as the recyclable fraction for each metal for 2011

Global substance flow analysis of gallium, germanium, and indium: Quantification of extraction, uses, and dissipative losses within their anthropogenic cycles

Investigation on the viscoelasticity of optical glass in ultraprecision lens molding process

With the recent development of less costly uncooled detector technology, expensive optics are among the remaining significant cost drivers. As a potential solution to this problem, the fabrication of IR lenses using chalcogenide glass has been studied in recent years. We report on the fabrication of a molded chalcogenide-glass lens for car night vision and on the evaluation of the lens. The moldability of chalcogenide glass was characterized through transcription properties of the mold's surface. In addition, both IR transmittance and x-ray diffraction patterns of the molded chalcogenide-glass lens were evaluated to verify the compositional and structural stability of the glass material under the given molding conditions.

Fabrication of molded chalcogenide-glass lens for thermal imaging applications.

Ga–Sb–S Chalcogenide Glasses for Mid‐Infrared Applications

We examine the effect of temperature on the molding of chalcogenide glass for infrared (IR) lens fabrication and evaluate a molded chalcogenide glass lens. Both the adhesion of the chalcogenide glass to the mold's surface and lens breakage depended on the initial heating temperature and on the molding temperatures in the glass molding process. In addition, the molded chalcogenide glass lens was evaluated based on transcription characteristics of the mold's surface, IR transmittance, and x-ray diffraction patterns. From the analysis results, we verified that the chalcogenide glass lens for IR imaging application could be fabricated by well-controlled temperature conditions.

Effect of temperature on the molding of chalcogenide glass lenses for infrared imaging applications.

This study investigated the following two issues using the design of experiment (DOE): (1) grinding conditions of tungsten carbide (WC) mold to fabricate aspheric glass lenses for the megapixel camera phone module and (2) pressing conditions in the molding process using the mold fabricated under the optimum conditions found by DOE. The optimization of the grinding and the pressing conditions with respect to the surface roughness (Ra) of the ground WC and the form accuracy (PV) of the molded lens, respectively, were ascertained by employing factorial design method. As a result of the analysis of variance (ANOVA) and P-value (significance level), it was verified that the depth of cut in the grinding process and, in case of the pressing, the time of pressing step 2 represent the most significant operative variables that affect the corresponding response variable. The WC mold was fabricated under the optimum condition found by DOE and it shows a PV of 0.181 µm in aspheric surface. In the optimum condition, pe...

A Study of Mold Grinding and Pressing Conditions in the Molding of Aspheric Glass Lenses for Camera Phone Module

In this research, the optimal grinding condition has been obtained by design of experiment(DOE) for the development of aspheric lens for the 3 Mega Pixel, 25x optical zoom camera-phone module Also, the WC mold was processed by the method of ultra precision grinding under this optimal grinding condition The influence of DLC coating on form accuracy (PV) and surface roughness(Ra) of the mold was evaluated through measurements after DCL coating using ion plating on the ground mold Also, aspheric glass lens was molded by before and after the use of the mold of DLC coating, respectively The optical characteristics of each sample, which were molded by the different mold, were compared with each other

Optical Properties of Aspheric Glass Lens Using DLC Coating Mold

Recently, with increasing lightness and miniaturization of high resolution camera phones, the demand for aspheric glass lens has increased because plastic and spherical lenses are unable to satisfy the required performance. An aspheric glass lens is fabricated by high temperature and pressure molding using a tungsten carbide molding core; so precision grinding and coating technology for the molding core surface is required. In this paper, Aspheric glass lens for 5 megapixel 4 time zoom camera phone modules was developed. The grinding condition of the tungsten carbide molding core was found after applying design of experiments (DOE). Also, the ultra-precision grinding process was investigated under this condition by experiment. Rhenium-iridium (Re-Ir) coating was applied on the ground surface of the tungsten carbide molding core. The influence of Re-Ir coating was compared and evaluated. The surface roughness of the molding core were improved by application of Re-Ir coating on the surface of the tungsten carbide molding core. Aspheric lenses were also molded with the non-coated molding core and the Re-Ir coated molding core. The surface roughness of the aspheric glass lens improved by about 0.4 nm (aspheric surface) and 0.5 nm (plane surface).

Jeong-Ho Kim

Papers

Fabrication of molded chalcogenide-glass lens for thermal imaging applications.

Effect of temperature on the molding of chalcogenide glass lenses for infrared imaging applications.

A Study of Mold Grinding and Pressing Conditions in the Molding of Aspheric Glass Lenses for Camera Phone Module

Optical Properties of Aspheric Glass Lens Using DLC Coating Mold

Rhenium-iridium coating effect of tungsten carbide mold for aspheric glass lens