Papers by Author: Wei Min Lin

Abstract: According to the sharp rheological characteristics of magnetorheological fluid in the magnetic field, the principle and mechanism of magnetorheological finishing is analyzed. Based on the Preston equation, the Reynolds equation and its boundary conditions, the two-dimensional material removal model is built and simulated. Furthermore, a series of MRF experiments are carried out, and the influence of the immersed depth and material kinds on material removal rate are clarified respectively. The experimental results are compared with the modeling results of material removal rate to confirm the mechanistic model validity.

Abstract: In this study, grinding of Si3N4, SiC, and Al2O3 ceramics under the condition of electrolytic in-process dressing (ELID) system was investigated. The surface appearances of these engineering ceramics during the ELID grinding process were attentively observed to describe the formation of finely finished surfaces. Based on the analysis of material properties and detailed micro-observation of ground surfaces, it can be concluded that the material removal mechanism of engineering ceramic is closely related to its mechanical properties. The silicon nitride ceramic was most easily machined to precision surface among these three engineering ceramics.

Abstract: A new CAD system, which is called Volume-CAD (VCAD) have been developed. We carried out research and development of VCAD fabrication process based on VCAD/CAM precision control. In this study, a developed V-CAM had been used for a polishing fundamental experiment of a free form surface. The relationship between NC resolution and form accuracy of polished surface are discussed.

Abstract: In the present study, surface roughness after grinding with different mesh size diamond wheels were measured to study the surface roughness characteristics of engineering ceramics. According to the surface behaviours and measured surface roughness, the relation between the surface roughness and the properties of these brittle materials was described. Coupled with the micro-observation of ground surfaces, it was concluded that the grinding condition and material properties led to the differences of surface roughness characteristics of brittle materials. The silicon nitride ceramic was the most easily machined to ductile surface among these ceramics.

Abstract: In ELID (Electrolytic In-process Dressing) operations, the setting of starting point is quite important for reducing waste of time and for achiving high quality surface. In this study, the authors proposed a new describing mode for ELID grinding. The oxide layer formed on the wheel surface was divided to four sub-layer: porous-layer, polishing-layer, grinding-layer and interface-layer. The influence of the oxide layer on material removal rates and surface properties was investigated. It was found that, olny the oxide layer with thickness less than 24'm has capability of material removal. In ELID grinding, optimal thickness of the oxide layer is about 8~9'm. And the oxide layer with thickness of 4~9'm is suitable for grinding.

Abstract: In the present study, zirconia ceramic, crystal and two typical natural granites were ELID ground on a precision grinding machine under the same condition. The surface appearances during the grinding process with different mesh size metal bonded diamond wheels were examined to describe the formation of finely finished granite surfaces. According to the detailed micro-observation of ground surfaces, it can be concluded that the material removal mechanism of the main mineral components for natural granites are really similar to other brittle materials during ELID grinding process. However, the differences of material performances cause the granite materials to be larger critical grain depth of cut and more ductile during finely grinding.

Abstract: Ultraprecision optical components require ultra-fine smooth surface quality of sub-nanometer or sub-angstrom in Ra. To satisfy these requirements, ultraprecision on-machine measurement system is very important, by which the profile measurement and evaluation is conducted on the machine. The form accuracy is improved by compensating machining when the form accuracy is not enough. Ultraprecision on-machine measurement systems were developed for measurement with high-accuracy and high-efficiency. It was confirmed that the on-machine measurement with AFM was possible for surface roughness or complex form for local areas. In addition, a laser probe unit with a maximum resolution of 1nm, a measuring range of 10mm, a repeatability of 5.6nm and a maximum measurable angle of 60 degrees was developed. The possibility of the non-contact on-machine form measurement was confirmed for global form accuracy control.

Abstract: This paper describes an ultra precision polishing method of aspherical mirrors, and the fundamental research on polishing characteristics. The aspherical mirrors with a diameter of about 30mm made by fused silica glass and CVD-SiC were ELID (electrolytic in-process dressing)-ground to high form accuracy with #4000 cast iron bonded diamond wheel, and then polished with a small polishing tool. As the result, final surface roughness of 1.4nmRa and form accuracy of 1.2 μm was obtained.

Abstract: In V-groove ELID grinding process, to achieve optimal grinding performance and satisfactory surface quality and profile accuracy, metal bonded diamond grinding wheels need to be carefully sharpened. In this paper, we applied the proposed new micro-truing method consisting of electro-discharge truing and electrolysis-assisted mechanical truing to sharpen the edge of large grinding wheels. The minimum wheel tip radiuses of 6.3 and 8.5µm were achieved for the #4000 and #20000 grinding wheels. The truing mechanisms and sharpening performance are also discussed.