Papers by Keyword: Ultra-Precision Machine

Abstract: Responding to the demand on the ultra-precision equipment for machining monocrystalline silicon, sapphire, zirconia ceramics and other large-size functional crystal substrates in the microelectronics and optoelectronics manufacturing, this study analyzes the current state-of-the-art of polishing technologies and the technical challenges to achieving high surface quality substrates. In this study, a planetary double-sided polishing machine is designed to solve the problem between achieving high polishing quality and efficiency. The machine is characterized by process stability, large polishing pressure and high polishing speed, etc. which is verified by polishing zirconia substrates with satisfactory results: material removal rate of 5 μm/h and the surface roughness Ra of 1 nm.

Abstract: In the respect of ultra-precision manufacturing of axisymmetric surface, the machine tool with tool swing feeding has less interpolation error sources compared to the conventional ultra-precision diamond turning machine tool. The installation errors of machine tool greatly affect the manufacturing accuracy of parts. Therefore, based on the multi-body dynamics theory , the structure characteristics of this machine tool, and the parts' relative positions of machine tool, in this paper we established the space geometric model and the integrated error model of machine tool integrated with the actual installation error of machine. The analysis results of the error model show that the relationship between the depth of axis (tool shaft and main shaft of machine) parallelism and the profile error is linear function; when the installation error of swing arm was lower than 150′′,the profile error of parts was less than λ/10.

Abstract: Micro/nano machining becomes more and more important and popular. Ultra-precision machines are the fundamentals. Aiming at design and developing an ultra-precision machine tool for micro/nano machining, the slide, one of the most important part of the machine has been analyzed by FEM. The software Abaqus has been used for the analysis. Based on the full load created by the coils and permanent magnet of the linear motors, the kinetics characteristics have been analyzed. According to the analytical results, the slide structure has been optimized to fulfill the requirements of the developed micro/nano machine tool.

Abstract: The manufacturing system developed in this paper is mainly used for the ultra-precision grinding of the hard-cutting materials, such as high strength steel and carbonized tungsten, which are characteristics with axisymmetric aspheric surface. Under the priority of accuracy and grinding rigidity to design the key components of multi-axis linked parallel grinding system of aspheric surface, such as high speed grinding spindle, B axis grinding rotary table, clamps and center high adjusting system. Maximum speed of the grinding spindle is 90,000rpm, spindle rotating accuracy is 0.1μm, rotation-angle-accuracy of B axis is , center height adjusting accuracy is 0.1μm, using the system can realize parallel grinding of aspheric surface[1].

Abstract: The requirement of the ultra-precision machine tools for ductile cutting of hard brittle materials was examined experimentally. One of the essential factors of achieving ductile mode cutting was not only high-resolution feedback control but also the dynamic performance of the machine tool in forming solid immersion lens of monocrystalline silicon. We also proposed newly developed method for ultra-precision machine tools, which does not have enough high dynamic performance in order to achieve ductile mode cutting of the hard brittle materials. An additional device consisted of air slider on the machine tool was applied to cutting of glass in order to keep stable ductile mode cutting. We fabricated high-value added structure, which are designed a diffraction grating, consisted of micro groove on a borosilicate crown glass surface with the developed device.

Abstract: Air Spindles have been used in ultra precision machines for several years due to their advantages such as high speed rotation, low friction, and low vibration, [1]. Air spindles are widely used in these machines for producing precise work pieces. Although, spindles function on a very complicated theoretical basis, [2, 3], their structure is very simple and consists of mainly a rotor and a stator. The rotor/stator could be made of different shapes. A cylindrical shape is the one commonly in use. The spindle designed in this work has a spherical configuration. It has been designed so that it could be moved without application of electric motor and only by a wind turbine system, [4]. The spindle studied in this research uses compressed air for rotor suspension, and has an air turbine for rotating its shaft. A thin air film acts as bearing layer between rotor and stator. In design procedure, operation parameters such as air inlet pressure for turbine, air inlet pressure for bearing, diameter of turbine nuzzles, diameter of bearing nuzzles, clearance between rotor and stator and etc. have been considered, [5]. A prototype spindle has been manufactured using design criteria. The influence of above mentioned parameters have been recognized through experiments.

Abstract: Ultra precision machine tools are used in nano machining technology. Two main assemblies creating rotational and linear motion, called air spindle and linear air table are used in these machines. The linear air table has been simulated experimentally like a linear air bearing. This bearing moves in the main direction, X, while it has straightness error motions in Y and Z directions. The error values vary due to different parameters. This investigation deals with the influential parameters and their proportion in the error value. As far as the two mating surfaces are separated by a thin layer of pressurized air, the air pressure, location and amount of external load, are some of the parameters which have been studied. Results show that the more air pressure, the more stability and stiffer table. There will be less error motions as well. The error amount is not the same in X and Y directions. Finally, in order to have linear stiffness, the optimum air pressure, external load, and load location have been decided.

Abstract: Air spindles in ultra precision machines produce rotational movements for the cutting tool or work piece. The common combination of a simple cylindrical rotor and stator is the design for most spindles. If the length of such a spindle is longer than usual, it will deviate from its stable situation and start vibrating during operation, especially in high rotational speeds. In order to overcome the vibration problem, one of possible solutions is the application of a spherical rotor and stator. The manufacturing and assembly limitations do not allow obeying the spherical shape exactly. Thus, the design has been committed according to a quasi-sphere. This form of the rotor will be more stable. The subsequent result of stability improvement will be less air pressure and power consumption. There are some specific characterizations of the spindle which must be calculated for the spherical case. For this purpose a computer model of the object was made. Then, the model was put under finite element study to find the best air pressure and air flow velocity condition.

Abstract: Ultra precision machines are used for very precise machining as well as small parts. Due to their application, the accuracy of products has been upgraded in recent years. Thus, dimensional accuracies could be compared with surface texture dimensions like roughness and etc. In order to attain dimensions with surface texture accuracy, usually micro/nano meter, it is necessary to adopt ordinary machining technologies with micro/nano techniques. This measuring by adoption leads to nano-machining. Nano-machining researches deal with all three basic components of, machine tools, work piece, and cutting tool, which have fundamental importance for development of this technique. Despite of wide range of possible researches, only part of design points of ultra precision machines have been considered in this report. Air operated systems, like air slide table, and air spindle are examples of ultra precision machine tool components. These two components have been analyzed for some of their characteristics. Experiments have been planed to extract the relationship between stiffness, employing some of the effective parameters such as air pressure and air gap. The results describe the performance condition of air table and air spindle under different loadings.

Abstract: An ultra-precision machine is developed to machine components made of KDP crystal with single point diamond fly cutting technique. This paper presents a compensating control algorithm of error disturbance feed-forward which enhances the stability of ultra-low speed motion of the semi-closed loop feed control servo system of the machine. The simulation results indicate that the values of the steady-state tracking error decreases to 1/10 after using the compensating control algorithm. The fluctuation ratio is less than 4% when machining KDP crystal with the feed rate of 60μm/s.