Advanced Materials Research Vols. 24-25

Abstract: This paper presents the processing flow and results of optical fabrication for an optical correcting lens with a free-form surface, namely a free-form lens. Because a correcting lens has no rotation axes of symmetry and its surface cannot be expressed by a continuity equation, its processing technology is different with that of general aspheric lenses. The correcting lens was firstly formed from a glass workblank with flat face using diamond abrasion wheel with spherical shape, and then loose abrasive lapped and polished with oblique axis spherical tools to decrease the surface roughness and increase the surface accuracy based on the measuring result after forming. At the lapping and polishing stages, two processing methods are employed. One is to control the processing pressure, and the other is based on dwell time. Since high precision fabrication is closely related with high precision measuring, this paper also presents a high precision non-contact optical measuring method based on image transforming for correcting lenses. The effectiveness of the processing flow and technology is confirmed by an experiment in which a workblank is processed into a satisfying correcting lens.

Abstract: Based on the analysis of various disfigurements of carbon fiber reinforced plastics formed in drilling process, the formation model of disfigurement is built up, and analysis results shows that the main reason of disfigurement is the exceeding cutting force. By focusing on these problems, new-type drill—super-hard electroplated abrasive drill is developed, and some experiments were carried out. Compared with the traditional sintered-carbide drill in drilling, the super-hard electroplated abrasive drill has lower drilling force, better drilling quality, higher machining efficiency, and longer life-span. A conclusion that super-hard electroplated drill is more suitable for drilling CFRP is gained.

Abstract: Utilize the characteristic that magnetic force line may penetrate the non-magnetic material, using the magnetic abrasive finishing (MAF) method complete to the non-magnetic small workpiece surface precise processing. In order to enhance polishing efficiency, usually with the magnetic particles and abrasive particles mixes together in the sinter method or the cementation method, the cost is higher; the variety is not also complete. Therefore, use the simply mixed method mixed the ferromagnetism iron particles, the alumina particles and the lipin, directly participates in magnetism polishing, already obtained the good processing effect through the experiment. This paper analysis and explanation the best experimental condition such as the granularity proportion of the ferromagnetism iron particles and the alumina particles etc.

Abstract: Sintered NdFeB permanent magnet is widely used because of its excellent magnet property. But there is few report of machinbility of it. This paper presents an experimental investigation of the machining characteristics of sintered NdFeB permanent magnet using a combination process of electro-discharge machining (EDM) with ultrasonic machining (USM). The EDM / USM machining mechanisms are integrated to improve the machining efficiency. During the experiments, concentration of abrasive in the dielectric fluid is changed to explore its effect on the material removal rate (MRR). MRR of EDM /USM, conventional EDM and tool vibration aided EDM are compared, REWR and machined surface characteristics are also compared between them. From the experimental results, it is concluded that the combination EDM/USM process can increase the MRR and decrease the thickness of the recast layer. In the combination process, an appropriate abrasive concentration can improve its machining efficiency.

Abstract: Considering the shock between the press head and press disk in high speed lapping is more serious, this paper proposes a new method to reduce this shock. By this method a hole is machined for air passing on the press head axis. The topper of the hole is connecting with a pressure air resource. Thus an air cushion between the press head bottom and press disk on the workpiece is produced. With the distance between them reducing gradually, the damping of air cushion on the press head increases gradually. This makes speed of the press head approaching the workpiece decrease gradually and until reach zero. The pressure of the press head acts on the press disk increases gradually from zero to working pressure, which can reduce the shock between the press head and workpiece effectively, prevent weak workpiece from destroying in lapping and improve machining accuracy and quality. This method possess the advantages of easy to carry out, simple to operate and convenient to apply.

Abstract: In order to improve the surface quality and machining efficiency for mold polishing. Digital automatic Polishing is a good method, MasterCAM is the software that often is used for CAM machining, path layout and building method are emphasized according to the MasterCam’s curved surface processing path setting method, and aimed at the different curved surface use different polishing path building method, at last, the rationality of the polishing path building was validated.

Abstract: In this paper, mixed slurries containing silica abrasives and polystyrene (PS) polymer particles in deionized water at pH 10.5 have been evaluated for silicon wafer polishing. By applying the theory of electric double layer model, the effect of the particle interactions in mixed slurry is investigated. Zeta potential measurements and TEM images have been used to show the formation of composite particles. The polishing mechanism with composite particles slurries is discussed. Polishing experiments with the mixed slurries formed by coating smaller (~30nm) abrasives onto softer and larger (~2000nm) polymer particles have shown the superior characteristic with higher removal rate and high surface quality.

Abstract: Since almost large die surfaces are free-form surfaces, currently, these are almost manually implemented. In order to overcome this barrier, floating polishing is a feasible polishing technology. The contact pressure between grain and workpiece is a key problem of floating polishing technology. This paper focuses on contact pressure between grain and workpiece. At first, study the friction bound condition between grain and workpiece by ANSYS analysis software, then, compare with the analysis results of slip-line field theory and the test results of single grain. The results show the feasibility of the hypothesis of full friction condition. Finally, study the contact pressure between polishing disk and workpiece using the analysis results of single grain. The research achievements will be used for developing the floating polishing.

Abstract: In the design of ultrasonic honing equipment, it is hard to accurately get the natural vibration frequency of the ultrasonic vibration with the regular computing technology, which takes great inconvenience during designing of the device and puts it into production. This paper studies the ultrasonic vibration honing vertical equipment of φ150mm that is designed by the North University of China and carried on the natural vibration frequency analysis and corresponded numerical simulation, which got excellent achievement. In the paper the mathematical model is set up, which uses the MARC software to accomplish the numerical simulation and corresponds the vibration modal of the tool head of the devise, this paper also carries on the dynamic response analysis and solves the related difficult problem successfully. In the end, the proof test is done to support the theory.

Abstract: In this study, the influences of carbides and alloy additives on ground surface characteristics of several high Chromium (Cr) steels and abrasive grains of working surface were discussed. In the grinding using metal bonded CBN wheel, almost constant values in ground surface roughness and high grinding ratio were shown. 5% Cr steel with Vanadium, 8% Cr steel and 10% Cr steel showed a rougher surface than Cr steels with 3%, 4% and 5% due to the carbide inclusion. The grinding ratio of 5%Cr steel could be raised considerably by adding sulfur to it.