Advanced Materials Research Vols. 941-944

Abstract: Possibility of creation of systems of power supply for autonomous consumers based on the new hydrogen technologies using local waste as an energy resource is shown. Amount of consumed gas for production 1 Cl of electricity at supply of hydrogen obtained by electrolysis and hydrogen-containing mixture with the residual content of methane at an identical oxidizer and pressure of fuel supply are commensurable. The possibility of effective operation of a fuel cell module on hydrogen-containing fuel (received from biogas) with the residual content of methane and the possibility of reach modes of effective use of fuel were confirmed. The consumption mixture with residual methane (2% vol.) is comparable (within 5%) with the required amount of hydrogen produced by electrolysis to generate the identical power at a predetermined time interval. The use of relatively cheap hydrogen-fuel derived from biogas from local secondary renewable resources can contribute to the creation of autonomous economical systems of power supply.

Abstract: Electrical discharge machining (EDM) has the capability of machining all conductive materials regardless of hardness, and has the ability to deal with complex shapes. However, the speed and accuracy of conventional EDM are limited by probability and efficiency of the electrical discharges. To improve the machining speed and accuracy, we developed a 3-DOF controlled, high-speed, high-precision, magnetic/piezoelectric hybrid drive actuator. For the actuator, a voice coil motor type of magnetic bearing having a positioning stroke of a few millimeters is used to control the motion of an electrode in the thrust direction in order to speedily maintain a suitable distance from the workpiece. Moreover, two piezoelectric elements having high response speed and high precision are used to achieve the vibration of the electrode in the radial direction in order to immediately remove the debris between the electrode and the workpiece. The positioning performance of the actuator is evaluated through experiments, and the experimental results show that the actuator possesses a positioning resolution of 1μm, a bandwidth of 120Hz and a positioning stroke of 2mm in the thrust direction, and a positioning resolution of 0.05μm, a positioning stroke of 10μm at 1000Hz in the radial directions.

Abstract: Micro EDM is used to machine micro features which are of the same size order as material microstructure of workpiece. Due to the difference of the thermal properties between the crystal grain and grain boundary, the machining performance of micro EDM varies with the crystal grain sizes of workpiece. This paper investigated on the influence of grain size and grain boundary on the machining performance of micro EDM. By drilling micro holes on two pieces of stainless steel 304 (SUS 304) which are different in grain sizes, test results revealed that the characteristics of micro EDM is influenced by grain sizes of workpiece materials significantly.

Abstract: In the Micro Electronic Discharge Manufacture (The diameter of electrode is no more than 0.5mm), the response frequency of the spindle in Z axis is too low to satisfy the requirement of rapid response. Considering this problem, a novel spindle apparatus based on the Magnetic Suspension drive principle is proposed in this paper, the basic structure and principle are introduced. At the same time, the Magnetic field distribution and they are analyzed by the finite element software Ansoft Maxwell. Theory conduction and simulation results indicates that the response frequency of the spindle and the electromagnetic forces satisfy the design requirement, the novel spindle can shift in a small range around the equilibrium position, and there is no magnetic coupling effect in each other degrees of freedom of the spindle, so the independent PID algorithm can be used in the control of each degree.

Abstract: The ability to machine advanced ceramic materials such as ZrO₂, SiC, and AlN is of high interest for various industries because of the extraordinary material properties that these ceramics possess. Once sintered, these ceramics are characterized with high mechanical strength, high thermal stability and high chemical inertness. Therefore it is extremely difficult to machine these ceramics with dimensions in few microns using traditional techniques. Electrical discharge machining (EDM) is an electro-thermal machining process used to structure conductive materials. By applying a conductive layer on top of the non-conductive material, the EDM process can also be used to machine the non-conductive material. This paper presents a study on the effect of tool polarity and tool rotation on the material removal rate and electrode wear ratio during the EDM process of non-conductive SiC, ZrO₂ and AlN ceramics. The reasons for the variation in the material removal rates among the different ceramics are examined by comparing the material properties. Relatively lower value of flexural strength, fracture toughness and melting temperature is the reason for AlN ceramic to have the higher MRR than SiC and ZrO₂ ceramics.

Abstract: The ultra-precision master gears have important application in calibrating high precision gear measuring instruments or coordinate measuring machines and in military industry. Firstly based error interference of the angle-transferring curve, the periodical translocation technique (PTT) of gear-grinding to improve the indexing accuracy of ultra-precision gears is proposed. The conclusions are drawn by precision experiment: (1) controlling 2/3~3/4 of total teeth participating in regrinding process can obtain the smaller total cumulative pitch deviation; (2) with increasing of the number of teeth participating in regrinding processes, the effects on single pitch deviation is more obvious. Finally, the total pitch deviation F_p of the specimen reaches to 0.79 μm (2.7′′), and the single pitch deviation f_p reaches to 0.30 μm (1.0′′) by adopting PTT technique and both of them reaches to submicron level.The precision gear-grinding experiments show the efficiency and practicability of the PTT technique.

Abstract: Basing on an inert perforated metal mask, a hybrid electrochemical fabrication combining electroforming and mask electrochemical machining was proposed to manufacture metal through-hole array with double tapered openings. The feasibility of this novel process was investigated experimentally. The effects of pattern parameters of inert metal mask, such as wall angle, α, substrate thickness, H, hole spacing, L and hole size, D, on profiles of the resulting holes were analyzed. The experimental results show that the hybrid fabrication is able to manufacture high-aspect-ratio double tapered hole array with good surface quality.

Abstract: Combining the latest achievements of scientists to study cosmology, the machining accuracy of microelectronic devices is not the limit size of hyperfine micro-machining processing. In the future, it will develop a novel micro-machining method using dark energy and dark matter, and setup a new era. The paper introduces the Planck scale and the Heisenberg uncertainty relation into the Newtonian gravity for the model simplification. Newtonian gravity can be separated into two parts that is Dark Matter and Dark Energy. Every part is inverse relation to the distance.

Abstract: Microfluidic chips with micro-pillar array to capture cancer cells in a small volume were designed and fabricated in this paper. The structure includes two parts. This chip has a glass slide bonded to a silicon structure, and both of them contain twelve micro-channels with patterned chevrons or U-triangle-bones, micro-pillar array is completed on silicon wafers using wet chemical etching method on the substrate. To monitor cell capture tendency of the structure, the rows of capture structure were modeled using the finite element method (COMSOL Multiphysics). The results show that this structure can decrease the impact force to half or even less, the fluid can go through the micro-pillar array equably and the subjects in the flow can be sizing by the structure.

Abstract: Thermal accumulation in micro droplet deposition manufacturing (MDDM) has a significant influence on geometric profile and microstructure of the fabricated metal micro-parts. In this paper, thermal behavior of a new aluminum droplet on the deposit surface was investigated using one-dimensional heat transfer model. Then several thin-walled aluminum cubic pipes were fabricated by MDDM to verify the numerical analysis result. The result shows that the thermal accumulation would increase gradually with the increase of the deposit height. It associated with thermal input and output on the top surface of the deposit, which could be controlled or eliminated by optimizing processing parameters such as deposition frequency.