Advanced Materials Research Vols. 126-128

Abstract: For the precision engineering ceramics parts, semi-ductile regime machining technologies are usually adopted to obtain the final surface. It is very important to research the brittle-ductile material removal characteristics and corresponding monitoring technology in ultrasonic aided lapping of engineering ceramics to obtain better surface quality. A series of lapping tests were carried out in the paper and the influence law of lapping parameters on the ductile percentage of ultrasonic lapped surface was achieved, which enables to off-line identify the material removal characteristics. Though the material removal characteristics can be online judged through monitoring the ratio of lapping component forces qualitatively, the monitoring effect is worse just because of lower response frequency of dynamometer and the relativity of lapping force. In this paper, a novel online monitoring technology of material removal characteristics is put forward based on AE technology. Through the wavelet package analysis of AE signals, the discrimination index and standard of material removal characteristics can be obtained. It is proved that this technology can realize online identification of the brittle-ductile material removal characteristics in ultrasonic aided lapping of engineering ceramics effectively.

Abstract: Viscoelastic polymers are used as one of coating materials for protecting the products from scratches. Presently, the repair of the coating surface for removing dust or extraneous matters has been performed through several polishing processes. However, it becomes increasingly difficult to polish its surface by only applying good skill and experience of skilled worker because a leading-edge viscoelastic polymer for coating is further scratch-resistant. Thus, based on quantitative evaluation of relation between polishing process and finished surface, it is necessary to make the polishing process appropriate for the leading-edge viscoelastic polymers. In this study, we attempt to establish the evaluation method of the polished surface and clarify the surface condition with invisible scratches.

Abstract: The purpose of this research is to establish a way to realize the axisymmetric free-form polishing by controlling the scanning speed of the rotating polishing tool. The scanning speed was determined by comparing the measured result of the polished shape with the target shape. Experiments with the proposed method were carried out and the effectiveness of the method was verified.

Abstract: This study proposes an innovative sphere-like tool for polishing process in the machining center. It can be applied not only z-axis rotation but also spinning rotation so that multidirectional polishing can be performed simultaneously. One of important polishing parameters is polishing force. It should be constant to prevent over or under polishing. In this paper, sliding control theory is proposed to achieve constant polishing force. Polishing process was modeled as a single degree of freedom of mechanical system including mass, spring, and damper. Control law has been determined based on polishing process model using sliding surface equation. Based on this control law, single and multi desired polishing force simulations were conducted. From the simulation results, it can be shown that the procedure to design control law has effective performance.

Abstract: This paper investigates the effects of some chemical factors on the material removal rate (MRR) in chemo-mechanical polishing (CMP) of Si (100) wafers. The CMP was carried out in alkaline slurry using alumina and ceria particles with hydrogen peroxide. When using the alumina particles, the MRR initially decreases with increasing the slurry pH value until pH = 9. Nevertheless, the application of the ceria particles increases the MRR before the pH of the slurry reaches 10. A higher slurry flow rate brings about a greater MRR.

Abstract: The service properties and lives of mechanical parts and components are closely related to their surface quality and precision, and many of the frictional surfaces are required to be finished thereby improving the surface quality and precision. In electrochemical mechanical finishing (ECMF) processes, the surfaces of metal parts are removed through the electrochemical anodic dissolution to obtain the desirable dimensions and surface finish. ECMF is characterized by the independence of the hardness of workpiece and little wear in tools. As a result, it has received more and more attention in the research area of polishing and finishing for mechanical parts. This article reviews the practical works in ECMF technologies from the aspects of surface quality and precision characteristics. Not only excellent surface quality but also high precision dimensions of parts can be obtained with ECMF. It has wide applications in machining precision mechanical parts and components.

Abstract: Electrically conductive polycrystalline composite diamond (EC-PCD), which consists of electrically conductive diamond grits, has recently been developed for the purpose of providing the material with both excellent tool property and good machinability. This paper deals with an investigation of machinability of EC-PCD by EDM with a copper (Cu) electrode. As a result, it was found that the EDM speed (Material removal rate) for EC-PCD was higher than that of the standard PCD. Although the surface roughness of the standard PCD was 13µm Rzjis at set current ip=3A, the surface roughness of the EC-PCD was 5µm Rzjis at the same current condition. Furthermore, it was observed that the EC diamond particle in EC-PCD was machined by single discharge EDM. Moreover, it was confirmed that EC-PCD was able to be applied a fine discharge profiling or a making fine holes using a rotating electrode.

Abstract: In the past half century, EDM (electrical discharge machining) is one of the most popular methods for manufacturing casting and plastic injection molds. Unlike other traditional mechanical cutting methods, EDM removes materials away by sparks, which leads to high temperature and pressure. As a result, it has no restriction to hardness because of its non-contact property. However, there will be recast layers on the surface of work-pieces and thus the surface need improved. In order to decrease the surface roughness, we added different powders into dielectric to become ERF (electrorheological fluid). By rotating spindle, the chain structures of ERF can improve surface of SKD11. The result shows that, when the gap is 100μm and electrode φ2, starch has 61% improvement rate and Al2O3 has 14.97%.

Abstract: Gears’ surface quality and modification characteristic have an important influence on its working performance. Pulse Electrochemical Finishing (PECF) could get excellent surface topography. In this project, PECF with a scanning cathode is used to finishing the cylinder gear. Tooth profile modification is realized by PECF with an uneven interelectrode gap distribution along the tooth profile and tooth lead modification is realized by PECF with a variable moving velocity of the cathode. The experimental results show that the tooth surface roughness could be decreased from Ra 3.9μm to Ra 0.35μm, which means that the PECF process possesses the finishing ability for the raw surface tooth, and the difference of material removal of PECF with an uneven interelectrode gap distribution could be 46μm and the material removal could be controlled by regulating the moving velocity of the cathode, which means tooth profile and lead modification could be realized by PECF.

Abstract: This paper presents a new polishing pad with polishing silicon surface composed of a layer of Ethylene-vinyl acetate (EVA) adhesive pad coated with SiC grits. A set of polishing parameters: coating SiC grit size, concentration of SiC grit in slurry, polishing load, polishing wheel turning speed, and absorption time of polishing pad were identified with the Taguchi Methods for optimum polishing effect in terms of roughness of polished silicon surface. A surface roughness of 0.026 μm Ra can be obtained with the following values: grit size at 1.2 μm (both coated on pad and mixed in slurry), concentration of SiC grit in slurry at 25%, polishing load at 50 gram, turning speed at 10,000 rpm, absorption time of polishing pad at 15 minutes.