Papers by Keyword: Surface Generation

Abstract: In ultra-precision diamond turning (UPDT), axial spindle vibration (ASP) plays a crucial role influencing nanometric surface quality. In this study, a simplified model for ASP is proposed to study its effects on surface generation in UPDT as the spindle is idealized as a mass-spring-damper system. Significantly, the model successfully explains that ASP induces radial patterns at a machined surface. More importantly, this proposed model can be employed to easily predict and understand the effects of ASP on surface generation in UPDT.

Abstract: The examination of the main machining methods applied in manufacturing processes from machine building and based on material removal from workpiece highlights essentially the existence of distinct processes able to generate material. An analysis of certain machining methods able to develop processes of material removal from workpieces was initiated by taking into consideration the principle machining schema and the capacity of generating machined surfaces. One concluded that within distinct machining processes, various phenomena are applied in order to obtain material removal from workpiece.

Abstract: Reflecting lens is an important component of optical systems, such as high-resolution cameras, large space telescopes and meteorological satellites etc. Among the lens materials, Silicon Carbide (SiC) has attracted a lot of attention as an important optical material because of its excellent mechanical and physical properties. Apart from the form accuracy, the attainment of a consistently high optical quality in polishing SiC is still of a concern. There are advanced ultra-precision polishing machines that can correct geometrical errors and surface finish of the workpiece. These include surface roughness and waviness. However, the hardness of SiC material itself put an challenge for polishing process. In this paper, A computer controlled ultra-precision polishing (CCUP) method based on mechanical polishing is used to produce the SiC lens. Experiments are being designed on a 7-axis ultra precision polishing machine (Zeeko IRP200). As it is difficult to find out slurry which is harder than SiC so that the conventional polishing slurry is be used. It provides a nice consequence that it also efficient when the polish powder is softer than the machined materials. The tool pressure, polishing head speed and the feed rate are varied and optimized to obtain the best reflectivity of the lens being polished. A pilot experiment will be conducted for the corrective polishing for the form error of the optical surface made of SiC. The result from the study will provide an important means to optimize the process for machining SiC reflective lens using the CCUP process.

Abstract: Plasticfilms with Embossed Micro-Structured Patterns have been Widely Used Inbacklight Guide Panels. the Mass Production of these Films Demands Forultra-Precision Roller Embossing of Micro-Structured Patterns on Plastic Filmsby Precision Pattern Rollers. due to the Heavy Workload and High Precisionrequirements, Ultra-Precision Rollers with Microstructures are very Difficultto be Machined in the Level of Submicrometer Form Accuracy and Surface Finishin Nanometer Range. this Paper Presents Theoretical and Experimental Studies Ofultra-Precision Machining of Precision Rollers with Microstructures. Themachining Mechanism for Precision Roller is Firstly Explained, and Hence Astudy of Effect of Cutting Strategies on Surface Generation in Ultra-Precisionmachining of Micro-Structured Pattern Rollers is Presented. this Includes Thestudy of Different Cutting Trajectories, Length-to-Diameter Ratio of Therollers, Mounting Method for the Rollers, the Number of Cuts in the Formationof the Micro-Structured Patterns, as well as the Time Budgeting for Adoptingdifferent Cutting Trajectories in Ultra-Precision Machining of Micro-Structuredpattern Rollers. the Results of the Study Provide an Important Means Forenhancing the Surface Quality and Optimizing the Time for Machining Precisionrollers.

Abstract: The elliptical vibration cutting (EVC) technique has been found to be a promising technique for ultraprecision machining of various materials. Researchers have proved that the EVC technique prevails over both conventional cutting and 1D vibration cutting techniques in most aspects in terms of cutting performances. However, during the EVC process, vibration marks or cusps are generated by the elliptical vibration locus and can result in an increase in the overall roughness of machined surface, which is undesirable for achieving high-quality mirror surface. Although researchers have developed a calculation method for the height of the cusps, only the effects of vibration frequency on surface generation were studied, and the effects of the other vibration and machining parameters have not been investigated in detail by previous researchers. Hence, in the present study, in order to deeply understand surface generation process along nominal cutting direction under the EVC technique, which is critical for its performance improvement and application, an experimental study comprising a series of grooving tests was carried out. The effects of nominal cutting speed on the surface generation at two different thrust-directional vibration amplitudes are investigated. Analysis is given for the comparison between the theoretical and experimental roughness values, showing that there exists a critical nominal cutting speed, below which the measured roughness value is quite small and the vibration marks are almost undetectable.

Abstract: In this paper we propose a new mathematical model for micro milling operations. To achieve the desired quality of the final product or the desired structure on the product's surface the process kinematics as well as tool-workpiece interaction are considered. The presented model takes into account the relative motion between tool and workpiece. We consider the input infeed rate which is reduced by the elastic deflection of the tool due to the cutting forces appearing during the process. The tool wear and surface texture depend on the cutting force; therefore the analysis of the forces plays an important role in characterizing the cutting process. Moreover, the analyzing these forces during the simulation we can calculate the effective cross-sectional area of the cut in each time step of the process. This gives us a forward model for the full production chain. This model is extended in order to include a surface generation model as well as quality parameters for the resulting micro-milling surface.

Abstract: Surface reconstruction and NURBS surface generation based on 3D surface mesh partitioning are more essential today. In this paper, we present a new method of automatic partitioning complex surface meshes into the bounded regions with four corner points (quadrilateral regions) based on using control points (notches) for NURBS surface generation. The procedure of this method consists of 4 major steps: (1) the 3D polygons mapping into 2D polygons; (2) convex decomposition of the polygons in the 2D space; (3) subdivision of each polygons into quadrilateral regions; (4) mapping the received 2D regions onto the 3D original surface mesh. Main contribution in this paper is automatic partitioning of the 3D segmented parts of complex surfaces into quadrilateral regions based on combination of segmentation, mapping, and subdivision techniques. Automatic partitioning allows us to create not rectangular but quadrilateral regions without using any user-dependent parameters for further NURBS surface generation.

Abstract: Chip formation and surface generation were investigated when ultra-precision turning of SiCp/2009Al and SiCp/ZL101A composites using Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) tools. The results showed that the machined surfaces took on many defects of pits, voids, microcracks, grooves, protuberance, matrix tearing etc. It was noticed that most of these defects had an intimate relationship with the removal process of SiC particle. The surface finish was much better when the SiC particles were removed by cut through or in-situ pressed into mechanisms. Material swelling and side flow, tool-workpiece relative vibration, feed rate and tool nose radius, removal mode of SiC particles were these main mechanisms of surface generation. Generally, a saw-toothed chip was formed when ultra-precision turning this kind of material and the mechanisms of this type of chip were dynamic microcrack behavior and strain concentration, which induced by the non-uniform deformation of the workpiece material.

Abstract: For defects of low-plastic, brittle damage and micro-crack, brittle-hard materials are often collapsed and ruptured, and processing surface was made by complicated micro grooves after repeated processing. In order to know the complex rules of surface generation, series tests of diamond abrasives scratching glass with different processing paths and depth of cut were done. Cutting force and acoustic emission signal were collected. Crack generation, path interference, dynamic characteristic of glass processing were observed.

Abstract: This paper presents a study of effect of cutting conditions on surface quality in FTS machining of optical microstructures such as micro-lens array. A power spectrum analysis is proposed to characterize the surface quality in FTS machining. It is found that there is a strong relationship between the surface roughness and the power spectrum of the surface profile. This provides an important means for the characterization of surface quality in FTS machining of optical microstructures.