Materials Science Forum Vols. 505-507

Abstract: An automatic pipe cutting/welding robot with a magnetic binder, which is named APCROM, is developed and its tracking control is studied in this paper. Using magnetic force the four-wheeled mobile robot binds itself to the pipe and executes automatic pipe cutting/welding process. As APCROM rotates around the cylindrical pipe laid in the gravitational field, the gravity effect on the movement of the robot varies. The varying gravitational effect deteriorates the tracking performance of the robot and degrades the quality of the pipe cutting/welding process. To maintain a constant velocity and consistent cutting/welding performance, the authors adopt a repetitive learning controller, which learns through practice the required effort to cancel the tracking errors. Analysis results and experimental results verify the effectiveness of the proposed control scheme.

Abstract: The gap control problem in hole-machining of Pyrex® wafer by electrochemical discharge machining (ECDM) to obtain a smooth quality and acceptable material removal rate is studied. Analysis of the pulse signals shows that the average current pulse interval is constant, and it is mainly related to the ion translation conditions, such as the electrolyte concentration and the flushing strategy. The most steady and intense average current density can be obtained if the voltage on-time is around 3 times the average current pulse interval and the voltage off-time is 1/4 of the on-time for bubble film dissipation. The utmost allowable feed rate at each depth is recorded as the reference of the feed rate in real continuous machining to avoid the damage to the wafer. By applying 80% of the extreme allowable feed rate, 99.9% quality-proved holes can be acquired. The diametric error at the entrance or exit is within 6%. Besides, there is no crater-like problem around the hole that facilitates the succeeding bonding process. This study contributes to the successful production of reusable optical biological chips with integrated micro fluidic channels.

Abstract: In this study, experiments were conducted to reveal effects of polishing parameters on surface characteristics and removal rate when polishing glass-ceramic based rigid disk. The parameters studied including rotational speed, applied pressure, and abrasive concentration. Experimental results show that surface roughness, waviness and removal rate could be improved by adjusting the levels of polishing parameters.

Abstract: Presently, the loose abrasive wire saw is the most commonly used technique for slicing hard and brittle materials. However its productivity is relatively low. A diamond wire saw has been developed for slicing brittle materials such as silicon wafer. The objects of this paper is to make the thin diamond wire saw apply to high cost production in semiconductor industries with the effective processing parameters such as machined surface roughness, material removal rate, the wear of the wire and the kerf width of the slicing. Effects of processing parameters on the performance of the diamond wire sawing processes are investigated by using the Taguchi method for this design of experiment (DOE). The analysis of the result shows that the optimal combinations for good surface roughness are small grain size, high wire speed, and low feed rate. Wire speed and feed rate are positively related to material removal rate.

Abstract: Diamond has been well recognized a strategic engineering material. It possesses excellent physical and chemical properties including the highest hardness and thermal conductivity, and good resistance to chemical erosion. Although CVD diamond film has good potential outstanding properties, its industrial applications have been limited by the non-uniform thickness and rough surface. In the current study, the CVD diamond film is polished by the chemical-assisted mechanical method with different slurries. These slurries contain strong oxidation chemical and diamond powder. During the process, the diamond film was held against the rotational ceramic plate with transverse oscillation at 90 °Cor lower. The profilometer, atomic force microscope and scanning electron microscope were used to evaluate the surface integrity of the diamond films before and after polishing. Based on the experimental results, the slurry containing potassium persulfate (K2S2O8) produces the highest material removal rate while potassium permanganate (KMnO4) develops the best local surface roughness. The strategy of using potassium persulfate for coarse polishing followed by potassium permanganate for fine polishing yields the diamond films of the best global surface roughness. The average surface roughness of the diamond film produced by the proposed technique is below 10 nm after 5 hours.

Abstract: This paper describes the performance of an atomizer coupled with a substrate which produces metal powder and spray forming materials simultaneous in the spray chamber. Ultra fine metal powders are produced from this process. The melt is atomized by a twin-fluid atomizer with internal mixing mechanisms. The molten spray injected from the swirling chamber of the atomizer is then impinged upon the substrate to form the two phase impinging flow. The deposition rate of the molten spray on the substrate is controlled by the diameter of the substrate, the height of the substrate ring and the distance of the substrate from the outlet of the atomizer. This in turn determines the powder production rate of the spraying processes. Experimental results indicate that the deposition rate of the spray forming material decreases as the distance between the substrate and the atomizer increases. For example, the deposition rate decreases from 48% to 19% as the substrate is placed at a distance from 20cm to 40cm. On the other hand, the metal powder production rate and its particle size increases as the substrate is placed far away from the atomizer. The production of metal powder with mean particle size as low as 3μ m level has been achieved, a level which is not achievable by the conventional gas atomization processes.

Abstract: Ultra high precision positioning is an important issue in modern manufacturing industries. As it comes to positioning it is widely believed that friction is detrimental to high precision. As a result, people usually use special mechanical systems such as air-bearing guides and/or hybrid drives in a high precision positioning system to avoid the influence of friction. These strategies, however, increase the operational cost and system complexity. In this paper, it describes how to apply the Precision-Limit Positioning (PLP) technique introduced in [1] to a standard linear motor system with the existence of friction. The position resolution is designed to equal to the resolution of the position sensor used in the feedback loop, which is 2nm/count. It is further requested that the repeatability and steady state vibration of the system are stable enough so that the table is capable of doing count-by-count operation.

Abstract: This paper described design, fabrication and study of micro electrospray chips. The micro electrospray chips are fabricated by using micro-electro-mechanical system (MEMS) technology. The micro electrospray techniques can be used in many applications, including high viscous fluid dispenses for 3D rapid prototyping and biological sample analysis in mass spectrometer. In this study, micro electrospray chips with different wedge angels are investigated by using microscopic visualization techniques. Four spray modes are identified at various operation voltages and currents. It is found that the voltage for stable cone-jet mode decrease as wedge angle becomes smaller. On the other hand, it is also found that stable cone-jet mode represent a constant current range in current (I)-voltage(Ф) curve. It allows us to easily identify if the micro electrospray chips operate at cone-jet mode.

Abstract: Generally, rapid prototype system, it bases on the operation principle to process layer by layer, and has several kinds of hardware already. The input of STL file format has become the de facto standard in rapid prototyping. With the application of complex material, the variety of product-type using RP technology will be dramatically extended and, no more, be limited in model production. However under the structure of 3D printing, large item production will be possible only if specific support were applied. This study proposes the hardware and software integrated method with the subject of the three-dimensional printing. The hardware utilizes ink-jet of general two-dimensional printer and combines with the traversing mechanism and the process controls and model material, and piles up in accordance with default layer thickness. As the supporting structure in STL-file format is generated through the concepts of the 3D-printing support generating method which is carried out by performing projection and displacement of selected triangular surfaces and then the generated 3D model is further constructed by Open GL and saved in STL-file format. As STL file is read, and then builds adjacency to store into the topology data structure. After the operation of direct slicing rule, hundreds of contours in each layer are obtained by using Visual C ++ programming language and OpenGL library to implement the algorithm above. It can confirm exactness that the software output and systematic feasibility of integrating the hardware through the result of system integration test on the 3D printer.