Micro electrical discharge machining（EDM） deposition process is a new micro machining method for fabrication of metal micro structures. In this process, the high level of tool electrode wear is used to achieve the m...Micro electrical discharge machining（EDM） deposition process is a new micro machining method for fabrication of metal micro structures. In this process, the high level of tool electrode wear is used to achieve the metal material deposition. Up to now, the studies of micro EDM deposition process focused mainly on the researches of deposition process, namely the effects of discharge parameters in deposition process on the deposition rate or deposition quality. The research of the formation of micro structures with different discharge energy density still lacks. With proper conditions and only by the z-axis feeding in vertical direction, a novel shape of micro spiral structure can be deposited, with 0.11 mm in wire diameter, 0.20 mm in outside diameter, and 3.78 mm in height. Then some new deposition strategies including angular deposition and against the gravity deposition were also successful. In order to find the forming mechanism of the spiral structures, the numerical simulation of the transient temperature distribution on the discharge point was conducted by using the finite-element method（FEM）. The results show that there are two major factors lead to the forming of the spiral structures. One is the different material removal form of tool electrode according with the discharge energy density, the other is the influenced degree of the movement of the removed material particles in the discharge gap. The more the energy density in single discharge is, the smaller the mass of the removed material particles is, and the easier the movements of which will be changed to form an order tendency. The fine texture characteristics of the deposited micro spiral structures were analyzed by the energy spectrum analysis and the metallographic analysis. It shows that the components of the deposited material are almost the same as those of the tool electrode. Moreover the deposited material has the brass metallic luster in the longitudinal profile and has compact bonding with the base material. This research is useful to understand the micro-process of micro EDM deposition better and helpful to increase the controllability of the new EDM method for fabrication of micro structures.展开更多
A new deposition method is described using micro electrical discharge machining （EDM） to deposit tool electrode material on workpiece in air. The basic principles of micro electrical discharge deposition （EDD） are...A new deposition method is described using micro electrical discharge machining （EDM） to deposit tool electrode material on workpiece in air. The basic principles of micro electrical discharge deposition （EDD） are analyzed and the realized conditions are predicted. With an ordinary EDM shaping machine, brass as the electrode, high-speed steel as the workpiece, a lot of experiments are carried out on micro EDD systematically and thoroughly. The effects of major processing parameters, such as the discharge current, discharge duration, pulse interval and working medium, are obtained, As a result, a micro cylinder with 0.19 mm in diameter and 7.35 mm in height is deposited. By exchanging the polarities of the electrode and workpiece the micro cylinder can be removed selectively. So the reversible machining of deposition and removal is achieved, which breaks through the constraint of traditional EDM. Measurements show that the deposited material is compact and close to workpiece base, whose components depend on the tool electrode, material.展开更多
High-power pulsed magnetron sputtering （HPPMS or HiPIMS） is an emerging coating technology that produces very dense plasmas and highly ionized sputtering atoms. This paper is focused on discharge properties, unbalan...High-power pulsed magnetron sputtering （HPPMS or HiPIMS） is an emerging coating technology that produces very dense plasmas and highly ionized sputtering atoms. This paper is focused on discharge properties, unbalanced features and temporal evolution of pulse current of the HPPMS discharge. A hollow cathode was used to suppress the scattering of charges. A coaxial coil surrounding the target was used to control the breakdownvoltage and pulse repetition frequency by varying the coil current. A Langmuir probe and an oscilloscope were used to simultaneously measure the floating potential, pulse voltage and pulse current signMs. The pulse power density in the discharge reached 10 kW/cm2 with frequencies as high as N40 Hz and a pulse width about 1~5 ms. The characteristics of the discharge evolution were analyzed using magnetron discharge dynamics.展开更多
The current advances of the solar sensor techniques are over reviewed. The amorphous material preparation, design and fabricating method, structure and performances, and experimental results of the amorphous silicon s...The current advances of the solar sensor techniques are over reviewed. The amorphous material preparation, design and fabricating method, structure and performances, and experimental results of the amorphous silicon solar sensors are described.展开更多
基金supported by National Natural Science Foundation of China(Grant No.50675049)
文摘Micro electrical discharge machining（EDM） deposition process is a new micro machining method for fabrication of metal micro structures. In this process, the high level of tool electrode wear is used to achieve the metal material deposition. Up to now, the studies of micro EDM deposition process focused mainly on the researches of deposition process, namely the effects of discharge parameters in deposition process on the deposition rate or deposition quality. The research of the formation of micro structures with different discharge energy density still lacks. With proper conditions and only by the z-axis feeding in vertical direction, a novel shape of micro spiral structure can be deposited, with 0.11 mm in wire diameter, 0.20 mm in outside diameter, and 3.78 mm in height. Then some new deposition strategies including angular deposition and against the gravity deposition were also successful. In order to find the forming mechanism of the spiral structures, the numerical simulation of the transient temperature distribution on the discharge point was conducted by using the finite-element method（FEM）. The results show that there are two major factors lead to the forming of the spiral structures. One is the different material removal form of tool electrode according with the discharge energy density, the other is the influenced degree of the movement of the removed material particles in the discharge gap. The more the energy density in single discharge is, the smaller the mass of the removed material particles is, and the easier the movements of which will be changed to form an order tendency. The fine texture characteristics of the deposited micro spiral structures were analyzed by the energy spectrum analysis and the metallographic analysis. It shows that the components of the deposited material are almost the same as those of the tool electrode. Moreover the deposited material has the brass metallic luster in the longitudinal profile and has compact bonding with the base material. This research is useful to understand the micro-process of micro EDM deposition better and helpful to increase the controllability of the new EDM method for fabrication of micro structures.
基金This project is supported by National Natural Science Foundation of China (No.50275038).
文摘A new deposition method is described using micro electrical discharge machining （EDM） to deposit tool electrode material on workpiece in air. The basic principles of micro electrical discharge deposition （EDD） are analyzed and the realized conditions are predicted. With an ordinary EDM shaping machine, brass as the electrode, high-speed steel as the workpiece, a lot of experiments are carried out on micro EDD systematically and thoroughly. The effects of major processing parameters, such as the discharge current, discharge duration, pulse interval and working medium, are obtained, As a result, a micro cylinder with 0.19 mm in diameter and 7.35 mm in height is deposited. By exchanging the polarities of the electrode and workpiece the micro cylinder can be removed selectively. So the reversible machining of deposition and removal is achieved, which breaks through the constraint of traditional EDM. Measurements show that the deposited material is compact and close to workpiece base, whose components depend on the tool electrode, material.
基金supported by National Natural Science Foundation of China(No.50407015)the Scientific Research Fund of the Liaoning Provincial Education Department of China
文摘High-power pulsed magnetron sputtering （HPPMS or HiPIMS） is an emerging coating technology that produces very dense plasmas and highly ionized sputtering atoms. This paper is focused on discharge properties, unbalanced features and temporal evolution of pulse current of the HPPMS discharge. A hollow cathode was used to suppress the scattering of charges. A coaxial coil surrounding the target was used to control the breakdownvoltage and pulse repetition frequency by varying the coil current. A Langmuir probe and an oscilloscope were used to simultaneously measure the floating potential, pulse voltage and pulse current signMs. The pulse power density in the discharge reached 10 kW/cm2 with frequencies as high as N40 Hz and a pulse width about 1~5 ms. The characteristics of the discharge evolution were analyzed using magnetron discharge dynamics.
文摘The current advances of the solar sensor techniques are over reviewed. The amorphous material preparation, design and fabricating method, structure and performances, and experimental results of the amorphous silicon solar sensors are described.
