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1. Influence of clamping technique on the resulting surface roughness in diamond machining of CaF2

   Adam, B.; Riemer, O.; Rickens, K.; Lucca, D.A.; Tunesi, M. (June 2022, Proceedings of the 20th euspen International Conference and Exhibition)

   Single crystal calcium fluoride (CaF2) is widely used for transmissive optics in the ultraviolet and vacuum ultraviolet (UV and VUV) spectral regions because of its high optical transmission. Optical components made of CaF2 are usually manufactured by precision machining to generate high quality surfaces with low surface roughness. However, the influence of the clamping technique on the resulting surface roughness of diamond machined CaF2 has not been reported. In this research, two clamping techniques, vacuum clamping and gluing with wax, are used in off-axis diamond turning experiments with zero degree and negative rake angle diamond tools. Surface characterization by white light interferometry and atomic force microscopy show surfaces with low surface roughness. Furthermore, a significant influence of the clamping technique on the generated surface topography is observed. 

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2. Ultra-Precision Machining: Cutting With Diamond Tools

   https://doi.org/10.1115/1.4048194  

   Lucca, D. A.; Klopfstein, M. J.; Riemer, O. (November 2020, Journal of Manufacturing Science and Engineering)

   null (Ed.)

   Abstract This article is written as a tribute to Professor Frederick Fongsun Ling 1927–2014. Single-point diamond machining, a subset of a broader class of processes characterized as ultraprecision machining, is used for the creation of surfaces and components with nanometer scale surface roughnesses, and submicrometer scale geometrical form accuracies. Its initial development centered mainly on the machining of optics for energy and defense related needs. Today, diamond machining has broad applications that include the manufacture of precision freeform optics for defense and commercial applications, the structuring of surfaces for functional performance, and the creation of molds used for the replication of a broad range of components in plastic or glass. The present work focuses on a brief review of the technology. First addressed is the state of current understanding of the mechanics that govern the process including the resulting forces, energies and the size effect, forces when cutting single crystals, and resulting cutting temperatures. Efforts to model the process are then described. The workpiece material response when cutting ductile and brittle materials is also included. Then the present state of the art in machine tools, diamond tools and tool development, various cutting configurations used, and some examples of diamond machined surfaces and components are presented. A discussion on the measurement of surface topography, geometrical form, and subsurface damage of diamond machined surfaces is also included. 

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3. Face Turning of Single Crystal (111)Ge: Cutting Mechanics and Surface/Subsurface Characteristics

   https://doi.org/10.1115/1.4057054  

   Zare, A.; Tunesi, M.; Harriman, T. A.; Troutman, J. R.; Davies, M. A.; Lucca, D. A. (July 2023, Journal of Manufacturing Science and Engineering)

   Abstract Single crystal Ge is a semiconductor that has broad applications, especially in manipulation of infrared light. Diamond machining enables the efficient production of surfaces with tolerances required by the optical industry. During machining of anisotropic single crystals, the cutting direction with respect to the in-plane lattice orientation plays a fundamental role in the final quality of the surface and subsurface. In this study, on-axis face turning experiments were performed on an undoped (111)Ge wafer to investigate the effects of crystal anisotropy and feedrate on the surface and subsurface conditions. Atomic force microscopy and scanning white light interferometry were used to characterize the presence of brittle fracture on the machined surfaces and to evaluate the resultant surface roughness. Raman spectroscopy was performed to evaluate the residual stresses and lattice disorder induced by the tool during machining. Nanoindentation with Berkovich and cube corner indenter tips was performed to evaluate elastic modulus, hardness, and fracture toughness of the machined surfaces and to study their variations with feedrate and cutting direction. Post-indentation studies of selected indentations were also performed to characterize the corresponding quasi-plasticity mechanisms. It was found that an increase of feedrate produced a rotation of the resultant force imparted by the tool indicating a shift from indentation-dominant to cutting-dominant behavior. Fracture increased with the feedrate and showed a higher propensity when the cutting direction belonged to the <112¯> family. 

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4. Development of a manual multi-axes workpiece adjustment system for ultraprecision diamond machining

   Shizuka, H.; Rickens, K.; Riemer, O.; Lucca, D.A. (July 2019, Proc. 19th Int. Conference & Exhibition of the European Society for Precision Engineering & Nanotechnology)

   This paper describes the development and performance evaluation of a manual multi-axes workpiece adjustment system for ultra-precision diamond machining that is capable of holding a CaF2 specimen with high positioning accuracy without pre-machining. Experiments revealed that the specimen alignment system developed in this study has sub-micrometer adjustment resolution and demonstrates a stiffness that can withstand diamond cutting forces. Applying this system to diamond cutting of CaF2 produced an error of nominal cut thickness of at most 10 nm on both ends of the 10.5 mm cutting length and achieved a defect-free finished surface. 

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5. Studying mechanism of anisotropic crack generation on C-, R-, A-, and M-planes of sapphire during ultra-precision orthogonal cutting using a visualized slip/fracture activation model

   https://doi.org/10.1063/10.0026318  

   Kwon, Suk Bum; Min, Sangkee (December 2024, Nanotechnology and Precision Engineering)

   Duan, Xuexin; Fu, Richard; Guan, Weihua; Guan, Yingchun; Sun, Shuhui (Ed.)

   With the growing demand for the fabrication of microminiaturized components, a comprehensive understanding of material removal behavior during ultra-precision cutting has become increasingly significant. Single-crystal sapphire stands out as a promising material for microelectronic components, ultra-precision lenses, and semiconductor structures owing to its exceptional characteristics, such as high hardness, chemical stability, and optical properties. This paper focuses on understanding the mechanism responsible for generating anisotropic crack morphologies along various cutting orientations on four crystal planes (C-, R-, A-, and M-planes) of sapphire during ultra-precision orthogonal cutting. By employing a scanning electric microscope to examine the machined surfaces, the crack morphologies can be categorized into three distinct types on the basis of their distinctive features: layered, sculptured, and lateral. To understand the mechanism determining crack morphology, visualized parameters related to the plastic deformation and cleavage fracture parameters are utilized. These parameters provide insight into both the likelihood and direction of plastic deformation and fracture system activations. Analysis of the results shows that the formation of crack morphology is predominantly influenced by the directionality of crystallographic fracture system activation and by the interplay between fracture and plastic deformation system activations. 

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