Materials Science Forum Vols. 628-629

Abstract: The numerical control (NC) program files need re-generating if there is any tool dimension change or tool wear for multi-axis machining. If the tool is replaced to adapt this change there will be increased cost. To solute this problem, 3D cutter radius compensation method for 5-axis computer numerical control (CNC) machining is deeply researched. Taking five axes linkage machine tools of X, Y, Z, B, C form with rotary tables B and C as an example, coordinate transformation matrix (CTM) and the cutter compensation vector for 3D cutter radius compensation are derived. The discrimination methods for path joint pattern (PJP) are given. A controller with 3D cutter radius compensation function for 5-axis linkage CNC machine tools is developed based on this method. The controller is allocated to a 5-axis milling machine tool and experiments are done. The proposed algorithm is demonstrated using a practical example.

Abstract: A robust optimization approach of an accelerometer is presented to minimize the effect of variations from micro fabrication. The sensitivity analysis technology is employed to reduce design space and to find the key parameters that have greatest influence on the accelerometer. And then, the constraint conditions and objective functions for robust optimization and the corresponding mathematical model are presented. The optimization problem is solved by the Multiple-island Genetic Algorithm and the results show that an accelerometer with better performance is obtained.

Abstract: The current research about Power-MEMS is mentioned. A micro turbine-generator system which aims to generate ultra-high power density at a high speed about 105r/min is put forward. Its work-principle is adequately introduced. The performance-tests of the turbine-generator are accomplished on a test-bench which has been specially designed. It can be seen that the micro turbine-generator system is able to generate about 0.6W output-power and a maximal voltage about 12.5V. Moreover, the turbine-generator is tested in four conditions in order to investigate how the pressure, volume flow and temperature of inlet gas affect the system’s performance.

Abstract: A new 2-DOF positioning table of high speed and accuracy, directly driven by voice coil actuator, is put forward, which can be applied to IC packaging for wafer wire bonding equipment. With the help of a novel elastic decoupling mechanism, the driving element is mounted on the baseboard, diminishing its moving inertia, improving its dynamic performance. By establishing dynamic model of VCA and positioning table, an electromechanical coupling control system based on displacement PID controller is proposed. The prototype experiment shows that the new 2-DOF positioning system is of higher speed and higher accuracy than the traditional ones.

Abstract: Two methods of inertia simulation, energy compensation method and torque control method, using work of electromotor during brake application are discussed in comparison in this paper. Mathematical models are described. Experiment under various brake conditions unfolds the rule of some key factors of energy compensation including working period of electromotor, start point and ending condition of compensation. Comparison experiment shows advantages of the energy compensation method over its counterpart. Limitations as well as corresponding solutions are discussed in the end.

Abstract: The piezoelectric bone conduction auditory device (PBCAD) with a rectangular piezoelectric bimorph as a driving components was designed based on the principle of bone conduction(BC), the audio signal converted to a vibration signal stimulate the auditory nerve via the skull to create hearing. Finite element analysis of rectangular piezoelectric vibrator means to support and optimize the structure of the program and improve equipment sound effects in the regional auditory signals of low-frequency, the experiment of rectangular PBCAD chalks up the curve of structure parameters. Experimental studies show: rectangular piezoelectric BC unit can achieve better function of bone conduction auditory device (BCAD).

Abstract: A multiscale simulation model was built to study the nanometric cutting process of single crystal copper. This multiscale model distinctly reduces the degree of freedom of the whole system compared with full atomistic simulations. Through analyzing the fluctuations of tangential cutting force and strain energy with cutting distance, we confirm that the deformation mechanism of single crystal copper is plastic deformation caused by generation and evolution dislocation. The highest compressive stress locates in shear zone and highest tensile stress locates in the machined surface and subsurface. Simulation results show that there exists a high value of stress around dislocations, which reveals the local high value of stress is the main reason for the generation and evolution of dislocations in the workpiece material.

Abstract: Effect of plane strain machining parameters such as rake angle and cutting velocity on the formation of ultra-fine structure in several materials has been studied. The microstructure and hardness of chips generated by machining were characterized by optical microscopy, scan electron microscopy and hardness tester respectively. The experimental results indicated that chip materials with ultra-fine grained and high hardness can be produced with more negative tool rake angle at some lower cutting velocity. The rake angle has more important effect on the formation of ultra-fine grain chips than cutting velocity. The rake angle for getting chips of obvious refined and significant hardened is different for different materials respectively. While the temperature of shear plane and tool-chip interface are increased with the increasing cutting velocity which alleviates the increase of hardness produced by decreasing rake angle.

Abstract: Micro injection molding is competitive for fabrication of polymer-based micro-fluidic chips because of its high productivity. Unlike hot embossing, injection molding will not provide even molding condition for everywhere of the molded part. So the microchannels of an injection molded micro-fluidic chip need to be checked everyplace, while a hot embossed micro-fluidic chip can be checked only by one slice of the microchannels if only the micro protrusions of the mold stamp remain the same cross-sectional figure. Because an injection molded micro-fluidic chip has characteristics that its replication of the micro stamp protrusion is perfect in height but not satisfactory in width, especially for the width of the micro protrusion’s root which matches the molded microchannel’s opening, in this study micro flat photos of injection molded micro-fluidic chips were processed by our own image processing system developed from the image box of Matlab software. Measuring data about microchannels width from the micro flat photos were compared with measuring data obtained from a cross-sectional photo of one slice of the microchannels. Difference between data of these two measuring ways was less than 2% for opening width of the molded microchannel. So by image processing of the micro flat photos, rapid overall non-destructive testing of micro replication can be carried out for injection molded micro-fluidic chips.

Abstract: The research aims to develop an experimental equipment to carry out in depth research on micro electrochemical machining (micro-ECM). The mechanisms of ultra-short pulse current micro ECM are discussed. As a consequence, lower machining voltage, lower passivity electrolyte concentration, high frequency short pulse power supply and micro rotating tool electrode at high speed have been synthetically used to localize the dissolution area during micro-ECM. The machining gap can be kept at a very small value, and the better resolution of machined shape is achieved by using a novel designed electrode gap control system and the effective utilization of ECM for micromachining is fulfilled. The experiments on microstructure by micro-ECM milling on stainless steel plate are conducted. The micro structures milled on 304 stainless steel foil with 300μm thickness with high precision and high aspect ratio are achieved, and the width of micro beam is about 60μm.