In the optical systems field, key components such as spectroscopic elements often require the use of optical materials with high-refractive indices to achieve miniaturization and lightweight characteristics. However, high-refractive index optical materials have low machinability due to their brittle characteristic. In this study, we investigated the changes in surface characteristics during precision pattern machining of high-refractive index materials; specifically, a low fracture toughness, for use in grating spectroscopic elements. The experiment involved diamond turning for the primary machining, and for the secondary pattern machining, the tool rake angle, tool feed rate, and depth of cut were set as variable conditions. Surface roughness measurements and surface quality analyses were carried out using a white-light interferometer and tool microscopy. The results provide insights into the influence of conditions on the surface properties during the machining of high-refractive index materials for grating spectroscopic components. Under the machining conditions with a tool rake angle of -65o, tool feed rate of 5,000 mm/min, and a depth of cut 10 nm, the surface roughness of Ra 8.0 nm was achieved. Based on these findings, we plan to conduct further research on the mechanical fabrication of the blaze angle for grating spectroscopic components.
Zinc sulfide (ZnS) is a widely used material in far-infrared and near-infrared imaging systems due to its exceptional optical transmittance properties. Through a hot isostatic compression process, during manufacturing, ZnS undergoes crystal structure modifications, resulting in increased transmittance across the visible and infrared spectra. However, ZnS exhibits low fracture toughness and irregular crystal orientations, making it prone to brittle fracture during the conventional cutting processes. Such brittleness often leads to surface defects that scatter light, diminishing optical transmittance. Therefore, understanding the conditions conducive to ductile processing is critical and necessitates a thorough brittle fracture analysis. This study introduces a novel quantitative analysis method to determine the occurrence of ductile processing and brittle fracture in ZnS materials after the turning process. To validate the efficacy of this approach, experimental machining was conducted through diamond turning and magnetorheological fluid polishing processes. Subsequently, a comprehensive quantitative assessment of brittle fracture was performed. Additionally, the relationship between brittle fracture and optical transmittance was explored using the proposed analysis method.
Here in, a high-quality automotive camera lens was developed based on an ultra-precision diamond turning core and cyclic olefin polymer (COP) injection molding process. To improve surface roughness and achieve the accuracy of plastic injection molding lens, systematic mold core machining process was developed and demonstrated using the diamond turning machine. The cutting tool path was generated by using NanoCAM 2D, and it was partly revised to prevent interference between the cutting tool and the workpiece. After the initial machining using the generated tool path, the compensation-cutting process was conducted based on the measured surface profile of an initially machined surface. After two times of compensation machining, the fabricated core mold showed a shape error of 100 nm between peak to valley (PV) and Arithmetic mean roughness (Ra) of 3.9 nm. The performance of the fabricated core was evaluated using an injection molding test. Injection molded aspheric plastic lens showed contrasts that were higher than 55% at 0.0 F, 30% at 0.3 F, and 20% at 0.7 F without any moiré phenomenon that meets the specification for automotive vision module with 1MP and 140° field of view.
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Research progress on grinding contact theory of axisymmetric aspheric optical elements Wenzhang Yang, Bing Chen, Bing Guo, Qingliang Zhao, Juchuan Dai, Guangye Qing Precision Engineering.2026; 97: 24. CrossRef
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Performance enhancement of material removal using a surface-refinement model based on spatial frequency–response characteristics in magnetorheological finishing Minwoo Jeon, Seok-Kyeong Jeong, Woo-Jong Yeo, Hwan-Jin Choi, Mincheol Kim, Min-Gab Bog, Wonkyun Lee The International Journal of Advanced Manufacturing Technology.2024; 135(11-12): 5391. CrossRef
We present Error Compensation Software (ECS) which uses a decic polynomial model and three-dimensional surface measurement data for the fabrication of high precision freeform mirrors. ECS is designed based on a graphic user interface that includes an error calculation mechanism and surface distribution maps, and it accepts the Ultrahigh Accurate 3D Profilometer (UA3P) measurement data of the fabricated mirror surface. It exports surface coefficients and tool paths for the Single Point Diamond Turning (SPDT) machine which allows engineers to utilize the software during the compensation process. The ECS is based on Visual C++ and runs on the Windows operating system. The error compensation process with ECS has been applied to the 90 mm diameter aluminum freeform mirrors for usage in view infrared satellites, and the root mean square and peak-to-valley surface errors were reduced from 1.52 to 0.11 μm, and from 7.05 to 1.99 μm, respectively, satisfying the requirement of the infrared camera.
The study focused on the development of the CAM system restricted to the fabrication of variable pitch screws by using turning centers. To develop the dedicated CAM system at a low cost, open source programming language was used as much as possible. A commercially available 3D-CAD system was used to model variable pitch screws. The edge data of the variable pitch screw was extracted from 3D-CAD data of the variable pitch screw, and then a number of the edge data were copied by the amount of feed in the longitudinal direction of the screw to make a cutter path. The successive cutter path was repeatedly generated by reducing the size of the edge data. The advantage of this method of generating the cutter path is very simple and easy to use, compared with the conventional CAM systems. During the cutter path generation, the system can detect the collision between the cutting tool and the workpiece. As a result, the validity of the developed CAM system for variable pitch screws fabrication was confirmed from several examples of the cutter path generation.
This paper is a study of the machining characteristics, cutting force and surface roughness of a turning center by laserassisted machining. The laser-assisted machining (LAM) is an effective method to improve the machinability of difficult-tocut materials. The LAM has recently been studied for various machining processes, but the research on the threedimensional and turning-center machining is still insufficient. In this study, a machining experiment of the turning-center process was performed by the laser-assisted machining with Inconel 718. Before the machining experiment, performed to thermal analysis was for a selected to effective depth of cut. The cutting force and surface roughness were compared and analyzed. The machining experiment confirmed that the machinability was improved in the LAM.
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The surface roughness and cutting forces are the important factors for the machine-part quality during the hard-turning process. The aim of this paper is to optimize hard-cutting conditions via implementation of response surface methodology (RSM). The experiments were conducted for the hard-turning process with the Box-Behnken design. The validation of the surface roughness and cutting forces was performed with the obtained 2nd order polynomial regression model. The results showed that the surface roughness was strongly dependent upon the RPM. The diminution of the cutting force was attributed to the low feed rate and the depth of cut. On the basis of the RSM, optimized cutting conditions of RPM, feed rate, and depth of cut are 3440, 0.0352 [mm/rev], and 0.03 [mm]. In this optimal cutting condition, the surface roughness can be around Ra= 0.202 μm.
Titanium alloy has been widely used in the aerospace industry because of its high strength and good corrosion resistance. During cutting, the low thermal conductivity and high chemical reactivity of titanium generate a high cutting temperature and accelerates tool wear. To improve cutting tool life, cryogenic machining by using a liquid nitrogen (LN2) jet is suggested. In cryogenic jet cooling, evaporation of LN2 in the tank and transfer tube could cause pressure fluctuation and change the cooling rate. In this work, cooling uniformity is investigated in terms of liquid nitrogen jet pressure in cryogenic jet cooling during titanium alloy turning. Fluctuation of jet spraying pressure causes tool temperature to fluctuate. It is possible to suppress the fluctuation of the jet pressure and improve cooling by using a phase separator. Measuring tool temperature shows that consistent LN2 jet pressure improves cryogenic cooling uniformity.
Recently, titanium alloys have been widely used in aerospace, biomedical engineering, and military industries due to their high strength to weight ratio and corrosion resistance. However, it is well known that titanium alloys are difficult-to-cut materials because of a poor machinability characteristic caused by low thermal conductivity, chemical reactivity with all tool materials at high temperature, and high hardness. To improve the machinability of titanium alloys, cryogenic cooling with LN2 (Liquid Nitrogen) and nanofluid MQL (Minimum Quantity Lubrication) technologies have been studied while turning a Ti-6Al-4V alloy. For the analysis of turning process characteristics, the cutting force, the coefficient of friction, and the surface roughness are measured and analyzed according to varying lubrication and cooling conditions. The experimental results show that combined cryogenic cooling and nanofluid MQL significantly reduces the cutting forces, coefficients of friction and surface roughness when compared to wet condition during the turning process of Ti-6Al-4V.
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