Advanced Materials Research Vols. 126-128

Abstract: The use of cutting fluid containing nano particles in wet grinding and MQL grinding of Ti-6A1-4V is studied. For comparison purpose, experiments by applying the general purpose water-based cutting fluid are also conducted. The loading of the grinding wheel and morphology of the ground surface are observed, and the grinding forces and roughness of the ground surface are measured for analysis. It is found that the use of cutting fluid containing nano particles results in less loading of the wheel and better ground surface as compared with those with the use of the general purpose water-based cutting fluid because of smaller grinding forces and coefficient of friction originated from “lotus effect” of nano particles. MQL leads to better results than wet grinding. This is attributed to the possibility of more nano particles to effectively reach the grinding zone by the assistance of the high pressure air of MQL, which in turns enhances the functions of nano particles in alleviating wheel loading and decreasing coefficient of friction. Based on the experimental results, it is concluded that the use of cutting fluid containing nano particles has positive effects on grinding. Especially the MQL, not only can it achieve the best performance, it is also cost effective and environmentally attractive.

Abstract: Grinding forces during grinding silicon wafer have great influences on the accuracy, surface quality and grinding yield of the wafer. It is necessary to develop an accurate and reliable grinding dynamometer for measuring and monitoring the grinding process of the large and thin wafer. In this work, a new 3D (three-dimensional) grinding dynamometer using piezoelectric sensors is designed and developed, which is used for a wafer grinder based on wafer rotating grinding method. The calibrating experiments of the 3D grinding dynamometer are carried out. The FEA and modal analysis are made and compared with the results of mode testing. Furthermore, the static performance parameters of the dynamometer are obtained from the loading experiment. The experiment results indicate that the 3D grinding dynamometer can measure axial, radial and tangential grinding force of grinding wheel with high sensitivity, good linearity, good repeatability and high natural frequency, and fully satisfied requirement for measuring and monitoring of the grinding force in wafer grinding process.

Abstract: This study investigates surface formation characteristics in elliptical ultrasonic assisted grinding (EUAG) of monocrystal sapphire. During EUAG process, the workpiece is imposed to ultrasonically vibrate in two directions, i.e., vertical and parallel to work-surface, by using an elliptical ultrasonic vibrator. In our previous work, the vibrator has been produced by bonding a piezoelectric ceramic device (PZT) on a metal elastic body. When two alternating current voltages with a phase difference are applied to the PZT at the same frequency that is close to the resonant frequency of the longitudinal and bending mode of the vibrator, two dimensional ultrasonic vibrations are generated simultaneously, resulting in an elliptical motion on the end face of the vibrator. In this paper, to clarify the work-surface formation characteristics in EUAG of sapphire material, grinding experiments are carried out involving sapphire substrate. In experiments, work-surface roughness is measured, and the ground work-surface morphology is examined by scanning electron microscope (SEM). The experimental results are summarized as: (1) Compared with conventional grinding (CG), the elliptical vibration leads to a decrease of surface roughness up to 25% in EUAG; (2) The surface roughness has a monotonously increasing trend with the increasing wheel depth of cut in both EUAG and CG, but has little variation with the worktable feed rate. As the wheel speed increases, the surface roughness decreases until it reaches a minimum, and then increases in a monotonous trend in both EUAG and CG; (3) The surface quality in EUAG has a significant improvement, and it is prone to achieve the ductile regime grinding of sapphire compared with CG. These indicate that the elliptical ultrasonic assisted grinding is an efficient technique for high performance machining of monocrystal sapphire.

Abstract: In order to fabricate micro geometrical shapes by EDM process, micro electrodes as tools are needed. At present, micro electrodes are generated by grinding and/or on-machine EDM operations and then it is well known that efficient productivity of micro electrodes cannot be realized. In this study, a new micro EDM method is proposed, in which, micro electrodes generated in turning operation controlling thrust forces to be zero are utilized. As the results of some experimental evaluations, productivities and availabilities of proposed micro EDM are confirmed.

Abstract: The Taguchi Method was applied in this study to discuss the mechanical strength of heterogeneous plastic materials by ultrasonic-aided spin welding. Two heterogeneous plastic workpieces were rotated by a high speed motor, to make the top of conducting energy angle generate the high temperature due to friction. When the thermoplastic material reached the heat distortion temperature, a proper pressure was exerted on another material, the surface would be welded in a semi-melted state. Then the process conditions of ultrasonic welding were arranged by using the standard orthogonal table of Taguchi Method, and the temperature of the contact friction surface could be increased by the excitation of ultrasonic transducers as well as magnified and displaced by sound wave welding head. The optimal value of tensile strength was obtained by using the Large-the-Best characteristic of the Taguchi Method to obtain the important control factors of this experiment; a validation experiment was carried out by using the adjusted factors.

Abstract: This paper deals with laser forming procedure to bend pure titanium sheets along arbitrary curved shape. In preliminary experiments, single straight-line bending was carried out and the relationship between bending angle and laser irradiation conditions was investigated. It was clarified that the bending angle was able to control with scanning velocity and the number of scanning passes. With use of obtained experimental formula for the bending angle, we tried to bend the Ti sheet along given parabola shape with a multi straight-line bending. The experimental result was corresponding to the target shape well. This paper proposed a laser forming procedure for curved shapes which include both convex curve and concave curves. It was confirmed that it was able to curve a titanium sheet along arbitrary curved surface with proposed method.

Abstract: In this study, a method for the fabrication of microstructures on the surface and inside photosensitive glass (Foturan glass) by femtosecond laser-induced modification was developed. This technique was followed by heat treatment to crystallize the modified area, and the specimen was then placed in an HF acid solution for chemical etching. The fabricated microstructures were observed using scanning electron microscopy (SEM). Two examples: (a) a U-shaped microchannel and (b) an arc-type microchannel formed inside glass are presented.

Abstract: Fused silica is an important material for optics of ultraviolet laser transmission. It is difficult to be ground in ductile mode because of a high brittleness. In this paper, ductile mode grinding was achieved by a taper grinding method when the initial surface was a polished surface. However, when the initial surface was an unpolished surface, ductile mode grinding could not be realized because of the existence of surface and subsurface damages. The damages on the ground fused silica surface were repaired by CO2 laser irradiation with optimal laser power and scanning velocity. The optimal parameters were determined by studying the viscosity of fused silica and etching depth of laser irradiated groove. Besides laser processing parameters, surface roughness of laser irradiated surface is also greatly influenced by the initial surface roughness.

Abstract: Dry Electrical discharge machining (Dry EDM), using gas as dielectric, has been developed to solve problems against environment. It has both advantages of high material removal ratio (MRR) and low relative electrode wear ratio (REWR). We investigated the effect of duty factor, peak current, and reference ratio of gap voltage on MRR and REWR of Dry EDM, respectively. Moreover, trying to prove the attachment on electrode surface could decline REWR. It is considered that melting material of work-piece was sputtered and stuck onto electrode surface, and to become a protection layer as result in low REWR. However, the attachment will be removed under the condition of high peak current and high discharge frequency. But the amount of attachment just has little change when discharge number and arc discharge ratio are both decrease.

Abstract: Rising demand for sustainable development motivated our eco-friendly polishing method. In this study, fixed-abrasive polishing using a compact robot was proposed based on a new approach that includes the idea of secondary tools. The effectiveness of using a compact robot was investigated by life cycle assessment for eco-friendly polishing processing. The actual polishing process was carried out with low pressure to determine the potential of the proposed polishing method. As a result, low-environmental-load processing was achieved by machine downsizing without affecting the processing results by designing an independent pressure mechanism along the equipment’s main axis. The nano-surface could also be obtained with this method for glass material.