Ming-Fei Chen

Static behavior and dynamic stability analysis of grooved rectangular aerostatic thrust bearings by modified resistance network method

Abstract This paper begins with the development of the resistance network method (RNM) for designing an aerostatic rectangular bearing with X-shaped grooves. The Newmark integration method and the modified RNM, which takes into account the equilibrium of the mass flow rate and the squeeze film effect, are used to analyze the time-dependent dynamic behaviors at each time step. Finally, the stability properties as well as impulse responses of this type of bearing, which simulates variation in film gap caused by imperfect guideway geometry, are demonstrated in the current paper.

Research on the arc type aerostatic bearing for a PCB drilling station

This paper describes the development of the resistance network method (RNM) for analyzing the static behavior of arc type aerostatic grooved bearing. In this study the nonsymmetrical complexity geometry of gas film clearance and its influence on the bearing behaviors are taken into account when the misalignment takes place between shaft and arc type bearing due to the external nonsymmetrical load.

A fast positioning method with pattern tracking for automatic wafer alignment

The applicable wafer bonding process for semiconductor industry is usually administered in a three-dimensional oxides structure design. The bonding technology of the silicon-silicon wafer is an important process because the mechanical structure and the circuit layout of the wafer surface must be positioned accurately. This study focuses on the automatic alignment algorithms for the wafer bonding system, in which the crisscross marks on the surfaces of the two wafers aligned by pattern recognition and image processing technology and a fast positioning system with feedback control to achieve a fast and accurate wafer bonding process.

Investigation into the Finite Element Modeling and Dynamic Characteristics of the Assembly of Spindle and Motor Rotor

The electro-spindle is a core component of a high-speed machine tool, and motor-rotor mounted on shaft is an important factor which influences the dynamic characteristics of the electro-spindle. When the dynamic characteristics of the electro-spindle are analyzed, the finite element method is an important computation method. However, owing that fitting the spindle shaft with the motor-rotor is considerably complicated, there are often errors between the computational result of the finite element method and the result of modal testing. Such errors result from the differences between the finite element model and the actual system. In the present paper based on rotor dynamics proposes a finite element modeling method for the motor-rotor shaft, and then adjusts the finite element model by means of modal testing and optimization methods. The research results indicate that this modeling method is accurate and efficient. Besides, in the present paper, motor-rotors of different inner diameters are mounted onto shafts of the same size, and then modal testing and a finite element analysis are applied to obtain the dynamic characteristics of the motor-rotor shaft under different assembly tolerances. The research results can be used as a reference for the tolerance design of the motor-rotor shaft assembly.

Dynamic Behaviors Analysis of the Aerostatic Linear Guideway with a Passive Compensator for PCB Drilling Machine

Externally pressurized gas-lubricated linear guideway has been successfully used in the PCB drilling machine. In this paper, we analyze the performance of the grooved aerostatic thrust bearing with passive compensator and the dynamic behaviors of aerostatic linear guideway with compensating aerostatic thrust bearings. The Newmark integration method and the modified resistance network method (RNM), which consider the equilibrium of mass flow rate and the squeeze film effect, use to analyze the time-dependent dynamic behaviors. The results indicate that the passive compensator could maintain the thrust bearing in the suitable film gap. Therefore, the aerostatic linear guideway could achieve accurate straight motion and reduce vibration amplitude.

The Identification of Nonlinear Systems Using - Plane Coordinates

In order to instantaneously distinguish the (coefficient of viscous damping) and (coefficient of stiffness), which are both functions of time in an M.C.K. nonlinear system, a new identification method is proposed in this paper. The graphs of the - are analyzed and the dynamic behavior of M.C.K. systems in a - coordinate plane is discussed. This method calculates two adjacent sampling data, the displacement, velocity, and acceleration (which are obtained from the responses of a pulse response experiment) and then distinguishes and of an instantaneous system. Finally, this method is used to identify the aerostatic bearing dynamic parameters, C and K.

Effect of Optical Properties Characteristic Polymethylmethacrylate Using UV Laser Direct-Structuring

Polymethylmethacrylate (PMMA) material has excellent characteristics, such as being light weight, low cost, ease of machining, and optical quality, which are useful in numerous applications such as backlit LCD display panels, lens optics, and other photoelectric fields. Laser machining of polymerization material results in a superior machining quality, high accuracy, high speed, and high reproducibility, produces a small variety of products, reduces mold costs, and enables the rapid manufacture of products based on complex graphics by processing different depths and widths of the 3D structure. This paper presents the fabrication of symmetrical array microstructures on PMMA material by using a UV laser system. The PMMA material dimensions and thickness were 20 x 20 mm and 1 mm, respectively. Regarding the machining quality, the laser pulse energy, pulse repetition frequency, and fill spacing were adjusted. For the experiments, a semiconductor laser source (635 nm/5 mW/TEM00) and a beam profiler were used to measure the characteristics of a laser beam passing through the microstructures. The microstructure pitches and morphologies also affected the light uniformity. After laser machining, the surface morphology and the light transmittance were measured using a spectrophotometer.

Edge isolation of transparent conductive polymer (TCP) thin films on flexible substrates using UV laser ablation.

The purpose of this study was to directly use the writing techniques for the complex electrode edge isolation of transparent conductive polymer (TCP) thin films by a nanosecond pulsed UV laser processing system. The processing parameters including the laser pulse energy, the pulse repetition frequency, and the scan speed of galvanometers were examined to ablate the TCP films deposited on polyethylene terephtalate substrates of 188 microm thick. The thickness of TCP films was approximately 20 nm. The laser pulse repetition frequency and the scan speed of galvanometers were applied to calculate the overlapping rate of laser spots and to discuss the patterning region quality. Surface morphology, edge quality, and width and depth of edge isolated patterning structures after laser ablation process were measured by a three-dimensional confocal laser scanning microscope. In addition, the electrical conductivity of ablated TCP films was measured by a four-point probes instrument. After isolated line patterning was formed, the ablated TCP films with a better edge quality were obtained directly when the overlapping rate of laser spots, the scan speed, and the pulse repetition rate were 83.3%, 200 mm/s, and 40 kHz, respectively. The better surface morphology of electrode pattern structures was also obtained when the scan speed and the pulse repetition rate were 500 mm/s and 40 kHz, respectively.

Study on the Aerodynamic Effect and Misalignment Influence of Journal Gas Bearing for High Speed Electro-spindle

This paper analyzes the characteristics of the journal bearing, which include the angular misalignment of the shaft and the aerodynamic effect induced under high speed influencing the performance influence of the journal air bearing. The theoretical analysis uses the finite difference method to solve the Reynolds equation and considers the satisfaction of flow equilibrium through the restrictor, thus determining an unknown downstream pressure in the recess. Finally, the behaviors of a hybrid journal bearing which considers the aerostatic and aerodynamic effect as well as the influence of the tilt of the shaft are presented.

Research on Reverse Engineering for Rotor-Bearing Systems Using the Finite Element Method

The critical speed is one of the major dynamic parameters of a rotor-bearing system. Because the working speed of a rotor-bearing system continuously increases, problems of second-order and higher-order critical speed necessarily appear. The critical speed of the rotor-bearing system is obviously affected by these parameters, which include the rotors dimensions, materials, and the stiffness of its bearings and its coupling. Identifying the relationship between these parameters and the critical speed becomes extremely important. Therefore, this study obtains the critical speed and the bearing stiffness in the rotor-bearing system by employing a reverse engineering approach, combining analysis, modal testing and order tracking.First, the finite-element model of the rotor-bearing system is developed, and this can be identified by the results of the modal testing. The Campbell diagram and the critical speed map can be obtained by the correction model combined with the gyroscopic effect. Finally, the optimization method obtains the bearing stiffness by comparing the critical speed map and testing the results of the order-tracking. This investigation provides a method to determine the dynamic characteristics and critical speed map for the rotor-bearing system, and can be used to design and develop a high-speed rotating machine, including the spindles of machine tools, and the vacuum pumps.