Key Engineering Materials Vols. 364-366

Abstract: The surface topography characterization of MEMS device is very important to bonding technology of MEMS device. Motif characterizing method is a characterizing method of surface topography by graph. Aiming at the diversity and regionality of surface topography of MEMS device, in this study we have sampled the surface of MEMS device by 3-dimentinal grids using the surface profiler developed by us and characterizes the surface topography of MEMS device by the extended Motif characterizing method. The surface of MEMS device is divided into several Motif regions; the surface topography of every divided region can be evaluated respectively; the details of every region can be zoomed and these regions as a whole or every region can be revolved and projected; one of these regions can be as the reference of other regions. So the height, gradient and other characteristics of others regions of the whole MEMS device surface can be analyzed relative to the reference region; the whole and local surface topography of whole MEMS device can be analyzed.

Abstract: Passive film of stainless steels possesses good corrosion resistant property. However, the passive film formed in nature is not uniform and the quality is not consistent. It is the major causes for local corrosion. The pitting potential test is a traditional method to test local corrosion of stainless steels. The local corrosion is usually induced by the break-down of the passive film. Therefore, it can be utilized to evaluate the quality of the passive film. Also, because the pitting test is quick and inexpensive, many tests can be performed to evaluate the uniformity of the passive film. This study focuses on SS316 stainless steel. The specimens were treated with electropolishing processes. The original and the processed specimens were tested by pitting potential tests. From these results, the distribution and the uniformity of passive film could be evaluated. An efficient and inexpensive index of the uniformity of the passive film is proposed.

Abstract: The products of laser diode have been widely used, creating high profits. As there are only semi-auto-focus machines to do the focusing-jobs for the products of laser diode, it takes much work and increases the products’ cost. Therefore we developed a fully auto-focus machine for the products of laser diode to promote the quality of products and reduce the cost of the products. The AC servomotor was adopted to control the focus length. The image of the well-focused laser diode point can present more accurate information than the blurred laser point. It is helpful to get precise focus of laser diode. We adjusted the focus length of laser diode products by a fuzzy algorithm according to the feedback image information. The feedback image of laser diode spot was processed to distinguish the background, blurred region and bright region by a three-value thresholding method. The image information of the laser diode spot, the area of the bright region and the ratio between the blurred area and the bright area, were used as the criterion for the autofocusing job and to judge whether the focusing-job was well-done. In the meantime, we could also get the offsets in the x- and y- direction of the laser diode from the image of laser diode spot. Finally, we adjusted the focus length and the offsets of the laser diode products by a fuzzy imaging control algorithm to get the optimal focusing condition.

Abstract: This paper presents a cost-effective technique for achieving optical surface finish of thermally stable polycrystalline diamond (PCD) composites using dynamic friction polishing (DFP). The effect of polishing parameters on the material removal rate and surface characteristics of polished specimens were studied. The surface characterisation was carried out by optical microscopy, atomic force microscopy (AFM), scanning electron microscope (SEM) and its attached energy dispersive X-ray (EDX) analysis. It was found that optical surface finish of PCD with roughness Ra = 50 nm could be obtained efficiently with nearly a ten fold reduction in polishing time compared to the currently used method in industry.

Abstract: In this study, a Ni-P alloy electroforming nanostructure material with low surface roughness and low internal stress was developed by using a pulse current. Square-wave cathodic current modulation was employed to electrodeposit ultrafine-grained Ni-P films from an additivefree Sulfamate nickel bath. The effect of various factors, such as peak current density, duty cycle and pulse frequency on the roughness and internal stress were investigated. Pulse current significantly influences the microstructure of Ni-P alloys. The internal stress and roughness of Ni-P alloys increased as peak current density increased, but the internal stress of Ni-P alloys decreased as duty cycle decreased.

Abstract: This study performs an experiment to investigate the effect of process variables such as rotational cutting speeds of the wheel, feed rate of the work-table and grinding depth of cut on surface roughness and the fluctuations of grinding forces for Ti-6Al-4V titanium alloy. STP-1623 ADC surface grinding machine, grinding wheel with CBN material sintering and Ti-6Al-4V titanium alloy workpiece are used in the experiment. The roughness of the grinding surface was measured by the roughness measuring instruments and the fluctuations of grinding forces were measured through dynamometer after each surface layer ground from the workpiece in the experiment. The grinding performance can be ascertained from the signal fluctuations phenomena of the grinding forces both along normal and tangential directions, which may also be utilized as an index for the quality of surface finish judgment. The results show that excellent surface quality being always consistent with the stable grinding force fluctuations and can be obtained under the conditions of slow feed rate of the work-table, high revolutions of the wheel and shallow depth of cut.

Abstract: In this paper a novel constraint calibration technique for Stewart platform based Parallel Kinematics Machine(PKM) is presented. A commercial trigger probe and a developed double-ball bar gauge are employed to aid the calibration. In the measuring process the characterized errors can be obtained by comparing the nominal characterized size calculated by the function using the measuring data with the real size of the double-ball gauge. An optimization approach is used to calculate the PKM structural errors, and these errors can be finally compensated into the control model. The error transferring matrix with regard to the structural error of PKM can be formulated. The calibration efficiency can be improved by the automatic calibration operation with the doubleball bar gauge. The developed calibration system has been applied in the industry where the PKM is used for machining the turbine vane, and the machining quality can meet the requirements of the specifications. The presented calibration scheme is generic to be applied for the wide range of PKMs.

Abstract: Conventional machining is generally preferred in manufacturing metal components with 2½D features and/or 3D silhouettes. With the ever increasing demand for reduced sizes and increased accuracy, however, traditional machine tools have become ineffective for cutting miniature components. A typical example is gear manufacturing. It is known that gears are machined using the gear hobbing process in which the cutter axis and the workpiece axis are required to be synchronized to an accurate constant ratio. According to a market survey, only a few machine tools can make gears with the size of φ1.0 mm. This paper presents our effort in developing a PC-based millimeter scale CNC turning centre with gear hobbing capability to machine miniature gears. In this machine, the synchronization required by the gear hobbing process was achieved directly by controlling the AC servomotors. Experiment results show that the machine is able to machine high quality components with diameter as small as 0.075 mm and hob gears with module as small as 0.09.

Abstract: A diffractive laser beam shaper has been proposed as a lossless approach to transfer a Gaussian laser beam into a thin line beam with a uniform distribution along the line direction for scanning material processing or illumination application. With the consideration for the feasibility of fabrication, the optical performance of the diffractive beam shaper with its surface relief quantized at different levels has been analyzed with scalar diffraction theory, which shows that an 8 level solution is sufficient for keeping the uniformity in the line direction while the focusing function in the orthogonal dimension needs to be performed by an extra cylindrical lens.

Abstract: Nowadays some measurement tasks are usually made by the joint use of different systems, techniques, even sciences, trying to find the best results together with less work time. This is the case of close range photogrammetry and laser distancemeter. It is possible to find some works where they are applied together in so different sceneries as architectonic conservation, civil engineering, building, etc. One of the scopes where these techniques can be applied is in the measurement of facades of buildings in construction [1,2]. During the constructive process it is necessary to make periodic measurements, and also during the whole life of the building, as a control tool [3]. At the present day some of these measurements are hand-made, with the risk of having an industrial accidents in some situations. In this work we present a methodology based on a photogrammetric - distancemeter joining measure system, in order to semi-automate some measurement procedures in building construction. The system consists of a semi-rigid calibrated support putting up a laser distancemeter and a digital camera, called CaM-DisT®. The support was specifically designed for this kind of application. The development of the system was made in four steps: establishment of the mathematical background; design of the support; construction of the support; and calibration of the complete system. The calibration process was made by two different alternatives which are xpounded this contribution in detail.