Papers by Keyword: Ultra-Precision Grinding

Abstract: During grinding a large number of micrometer or sub-micrometer grains remove material from the surface of a workpiece, acting as cutting tools. As the grains perform the material removal process, the alterations on the workpiece surface are correlated to the grain characteristics, as well as process parameters. In the case of nano-grinding, only several atomic layers are removed and surface quality of nanometer level is attained. For this process, simulations can be carried out with Molecular Dynamics method, with a view to determine its characteristics. In the present study, the case of peripheral nano-grinding of a copper substrate with multiple abrasive grains is investigated for various depths of cut (namely 0.35, 0.54 and 0.72 nm) and results concerning grinding forces, temperature and workpiece deformation are presented and discussed. Cutting forces, temperature and workpiece deformation was observed to increase between the cases with 0.54 and 0.72 nm depth of cut to a greater extent than between the cases with 0.35 and 0.54 nm depth of cut.

Abstract: Large aperture lenses with high surface quality are demanded for professional imaging products such as single-lens reflex cameras and astronomical telescopes. Large aperture optical lenses are shaped by ultra-precision grinding and finished by prolonged polishing. However, the prolonged polishing process leads to deterioration of the form accuracy. In order to reduce the amount of polishing, ductile-mode ultra-precision grinding is demanded. In this study, a rubber bonded wheel, which has a low elastic modulus, is used for grinding of spherical glass BK7, and influence of the hardness of the rubber bonded wheel and abrasive chip thickness on brittle fracture and surface roughness are experimentally investigated.

Abstract: Electrolytic in-process dressing (ELID) grinding is drawing more and more attention by the researchers for its smart method of in-process dressing of the grinding wheel. Many researches place emphasis on study of in-processing dressing and oxide layer. In this study, the effects of three grinding factors, including wheel speed, load applied on workpiece and eccentricity of three parts in one holder, on surface roughness (Ra) and material removal rate (MRR) were investigated in a single-side ELID grinding experiment. Each factor has three levels. The experimental results show that each factor has different influence: 1. Applied load is the main factor which significantly affects the Ra and MRR; 2. the speed of grinding wheel doesn’t show much influence; 3. eccentricity has a great influence on roughness but not on material removal rate.

Abstract: Ultra-precision grinding is an effective method to machine the optical micro v-groove, which is one of microstructures applied to the fiber-optics connectors, displays and other photonics devices. The ultra-precision grinding technology directly obtains high surface quality for brittle materials when the grinding process is under the ductile mode. This paper introduces general aspects of ultra-precision grinding technology in the fabrication of the micro v-grooves structures and introduces the essential features of ultra-precision grinding. The process of the manufacturing of the optical micro v-grooves components is presented in this paper. It contains the prediction models of surface roughness and form accuracy in the ultra-precision grinding and the optimization model under the consideration of the influences of grinding parameters,grinder factors and the material properties on the surface quality and machining efficiency. This study therefore contributes to providing a further understanding on the mechanisms of material removal and surface generation in ultra-precision girnding.

Abstract: The demand for large aperture lenses with high surface quality and form accuracy used for single-lens reflex cameras has been increasing. Generally, large aperture glass lenses are produced by ultra-precision grinding. Considering the increasing global competition, the grinding process has to be improved. However, highly efficient grinding causes worse surface quality, which leads to much polishing and ultimately results in lower form accuracy. Thus in this study, aiming at the realization of highly efficient and precise grinding of glass lenses, cross grinding of optical glass BK7 is carried out. As a first step of the study, the influence of grinding conditions on the surface quality is investigated experimentally.

Abstract: In traditional manufacture of grinding wheel, a key problem is the randomly arrangement of the diamond abrasives, which results in randomly distribution of surface roughness. In this paper, through controlling the magnetic field during the forming process of the grinding wheel, arrangement of diamond abrasives is orderly to obtain a more orderly surface roughness. The forming process of diamond fine grinding wheel is studied under magnetic field controlling. The grinding experiment for aspherical mold was carried out on the tungsten carbide YG8 and the surface quality after grinding was also analyzed

Abstract: Taking ultraprecision grinding of silicon nitride ceramic as an example, this paper mostly introduces some influences of diamond wheel’s specialties on the grinding process and surface quality during ELID (electrolytic in-process dressing) grinding of hard and brittle materials. Research indicates that grain size and concentration of abrasive material should be reasonably selected based on the surface roughness. And Inhomogeneity of concentration distribution along wheel circumference will result in heterogeneity of insulator layer state, which will bring difference in the number of abrasive grain in the grinding area, thereby changing the actual cutting depth of every abrasive grain. Dynamic balancing of grinding wheel should be accurately adopted to reduce eccentric mass, furtherly to avoid generating waveness on the workpiece surface. For the purpose of reflecting rightly compositive effect from eccentricity of wheel shape, roundness of the wheel and periodical vibration derived from eccentric mass, actual radial runout of grinding wheel should be well and truly measured and controlled based on the wheel’s surface profile during wheel is rotating at working speed.

Abstract: This paper reported a deterministic method to predict geometrical interferences between grinding wheel and workpiece on ultra-precision grinding for micro aspherical lens mould. An inclined axis grinding mode controlled by B axis is considered and investigated. For avoiding the interference between the grinding wheel and the workpiece, the relationship of the radius of the grinding wheel should be analyzed in the grinding process. In this paper, a geometrical mathematical model for avoiding interferences between grinding wheel and workpiece is built up, and three interference conditions are analyzed. The maximum diameter of the cylindrical grinding wheel is computed and obtained for grinding axisymmetric aspheric surface.

Abstract: Surface characteristics of CZT wafers machined using wire sawing, free abrasives lapping and polishing and ultra-precision grinding were investigated. Wire sawing resulted in the removal of material in both ductile and brittle regimes, but both polishing and grinding led to a ductile removal. The grinding produced very smooth surfaces free of embeddings and scratches, which is thus considered to have better machinability than the free abrasive machining. The nanoindentation and nanoscratch on MCT wafers at nanometric scales resulted in considerable plastic deformation, but no fracture features. The hardness of the MCT wafer was 500 to 550 MPa, and the coefficient of friction was particularly high, ranging from 0.45 to 0.55.

Abstract: During the silicon wafer grinding, the different process parameters could cause the silicon wafer shape greatly different. Based on the rotational coordinate principle of kinematics, a theoretical model of the ground wafer shape in rotational grinding process is developed, in which many critical factors are considered in this paper. These factors mainly include the parameters of the dressing vacuum chuck and wafer grinding etc. And the mathematical equation of the ground wafer shape is derived. Moreover, as one of the important indexes, TTV(total thickness variation) is researched and analyzed. The equation of TTV is given. The built model can offer a theoretical foundation for further experimental researching. The research results are significant to effectively control the ground wafer shape in a certain.This paper applied the Autonomous Intelligent System(AIS) to deal with the intelligent activities intelligently and automatically, and thereof provided a new method for the Supply Chain Management(SCM) on MC manufacture. First, a new supply chain model based on E-HUB was presented according to the requirements of MC manufacture, and then the structure and operation of AIS were designed to support that SCM. Finally, the development technology of AIS was discussed.