Micro-punching process of stainless steel foil with micro-die fabricated by micro-EDM

Micro-punching has become a potential micro-manufacturing process due to the simplicity of the process, low cost, high production capability and accuracy. But the size of a punched micro-hole is limited due to the difficulties of tool fabrication. In the paper, we propose a design procedure according to buckling theory and a kind of micro-die fabrication method for micro-punching process. Micro-punch and female die with high dimensional accuracy were fabricated by micro-EDM with block electrode. Micro-punching processes of stainless steel foil were conducted with the micro-punch and female die equipped in the precision micro-punching tool. Micro-holes of 300, 150 and 100 μm in diameter were pierced with a good profile and high dimensional accuracy, which indicate that the micro-die fabricated by micro-EDM is suitable for micro-punching processes.     

Fabrication of a micro-tip array mold using a micro-lens mask with proximity printing

In this study, a mold for a micro-tip array is fabricated using a microlens array mask with proximity exposure. The micro-tip array uses a microlens array mask with geometrical optics. Light passing through a microlens is focused at the focal points. There is microlens on the mask and the pattern that results from the light passing through the mask is directly projected onto the photoresist surface. A concave profile is developed using a positive photoresist and the remaining photoresist microstructures are formed after the development process. By changing the distance between the mask and the photoresist and the radius of curvature of the microlens, various tip shapes can be fabricated. The exposure gap is calculated using the microlens array mask and the geometry of the mold of micro-tip array is established using the irradiance absorption maps for the different levels. These methods respectively use the model of the positive photoresist and optical software. When electroforming a metallic micro-tip copy of the patterned photoresist, masters are created. The metal micro-tip array is used membrane probe card.     

Flat panel detector based on a shadow mask plasma display panel

A flat panel detector based on the structure of a shadow mask plasma display panel is analyzed in terms of the electron amplification factor when used in the Townsend mode. The detector consists of a metal shadow mask and two ultra‐thin glass substrates with electrodes depositing on them. The shadow mask divides the detecting area into arrays of independent cells. The electron gain and linearity of the device are investigated by simulation based on the particle‐in‐cell/Monte Carlo collision model. Similar experiments are carried out. Both experimental and simulation results show that the linearity of the detector is significant. The applied voltages and the effective cathode area are parameters affecting its gain. As the avalanche process in the center of the cell with small electric field strength is much smaller than that near the shadow mask edge, the gain increases exponentially with the anode voltage but decreases with the negative shadow mask voltage. The balance between effective cathode area and high electric field intensity near the shadow mask edge provides room for future optimization of the detector. In conclusion, the flat panel detector is a promising component in a detection system for high energy radiation, and the wide application of the device is expected.     

Silicon shadow mask fabrication for patterned metal deposition with microscale dimensions using a novel corner compensation scheme

Pattern deposition of metals with controlled and microscale dimensions can be a challenging task if traditional photolithography is not a practical option. This is a particularly valid concern for the case of certain polymer substrates, which are gaining in importance in the microelectronics and related industries. Therefore, a novel design and process flow for batch fabricating low cost reusable silicon shadow masks was developed. Of note was the corner compensation scheme employed to avoid over-etching of the convex corners in the design. These shadow masks enabled deposition of metals or other suitable materials with feature sizes ranging from approximately 3 to 250 μm and were successfully utilized to form patterned metal heater lines and pads on various samples. The heaters, required for conducting thermal conductivity measurements of the underlying films/substrates using the three omega (3ω) method, showed resistance–temperature linearity, confirming theoretical estimates to within 0.2%. Moreover, the room temperature thermal conductivity of an amorphous SiO₂ film as well as a polyaniline thick film were measured, further validating the deposition through shadow mask technique.     

Fabrication of HARM structures by deep-X-ray lithography using graphite mask technology

The cost-effective fabrication process for high-aspect-ratio microstructures using X-rays depends largely on the availability and quality of X-ray masks. The fabrication of X-ray masks using commercially available graphite sheet stock, as a mask membrane is one approach that is designed to reduce cost and turnaround time. Rigid graphite offers unique properties, such as moderate X-ray transmission, fairly low cost, electrical conductivity, and the ability to be used with either subtractive or additive processes [1, 2]. This paper will demonstrate the potential of a cost-effective, rapid prototyping of high-aspect-ratio microstructures (HARMs) using graphite masks. The graphite wafer accommodates both the intermediate mask and the working mask. In order to allow a direct comparison of the graphite mask quality with other X-ray masks, the primary pattern was derived from a Ti X-ray mask using soft X-ray lithography (XRL). Received: 7 July 1999 / Accepted: 29 September 1999     

Novel pixel design for high‐resolution AMOLED displays with a shadow mask

Abstract— The bottlenecks in achieving high resolution for active‐matrix OLED (AMOLED) displays based on currently available manufacturing processes were evaluated and compared. The use of a shadow mask has proven to be viable for mass production, but the fabrication of high‐precision shadow masks becomes very difficult when the resolution exceeds 180 ppi. The latest breakthrough in increasing display resolution is presented. Without an increase in cost, the limitations of the conventional shadow‐mask process using novel subpixel designs have been successfully overcome. A high resolution reaching of 270 ppi has been successfully demonstrated on a 3‐in. VGA‐format AMOLED display, fabricated by using a shadow mask with a much lower resolution of 135 ppi. This innovative pixel design opens up the possibilities of manufacturing high‐resolution displays using a relatively low‐resolution shadow mask.     

Fabrication of intermediate mask for deep x-ray lithography

 This paper presents the fabrication of intermediate x-ray mask for deep x-ray lithography. In order to have working mask with absorbers thickness larger than 10 μm, the intermediate mask should have absorbers of 0.7 μm in thickness. To demonstrate intermediate mask fabrication, x-ray zone plates are fabricated on the 1.2 μm low-stress silicon-rich silicon nitride (SiN_x) membrane with the tri-layer Chromium-Tungsten-Chromium (Cr–W–Cr) as the x-ray absorbers. The chromium layers both 200 angstroms are used as adhesion and for stress relief. The SiN_x film is deposited with low pressure chemical vapor deposition (LPCVD) and the free standing membrane are formed by KOH silicon backside etching. With the e-beam lithography and reactive ion etching, width of 0.8 μm of outmost zone of the x-ray zone plates has been achieved on the membrane. The scanning electron microscopy (SEM) images of the x-ray zone plates and pictures of intermediate masks are demonstrated. Received: 25 August 1997/Accepted: 3 September 1997     

Multi-objective optimization of stainless steel 304 tube laser forming process using GA

Laser forming is one of the most recent forming processes developed which uses a laser beam to induce a deliberate thermal stress on a workpiece to form a sheet metal. Accordingly, bending tubes using laser beam have attracted the attention of many engineers. In this paper, we studied the effects of various laser beam parameters on the tube bending process. To investigate the effects of all the parameters, we performed a large number of analyses and generated applicable tube laser bending data. We utilized Taguchi design of experiment method to manage the finite element simulation of the laser forming process. Subsequently, to have an easier, but more flexible and more complete laser forming data bank, we employed artificial neural networks to predict the required tube bending parameters for the proposed forming criteria. Finally, we used genetic algorithm programming to solve the multi-objective optimization with respect to the laser forming parameters. The objectives include maximum bending angle, minimum ovality, minimum thickening, and minimum forming energy consumption. The results from this study indicate that we can use applied data tables to find the optimum tube laser forming parameters. The outcome of the numerical experiments is consistent with the existing literature on the laser forming process.

     

A method of solving a large-scale rolling batch scheduling problem in steel production using a variant of column generation

This paper presents a transparent model and a solution approach to solve a large-scale rolling batch scheduling problem. First, the problem is formulated as a multiple routes problem with multi-objective (MRMOP). By defining a hierarchical cost structure it is natural to decompose the MRMOP into several well-studied sub-problems, i.e. the multiple routes minimum cost problem (MRMCP), the knapsack problem (KP) and the linear assignment problem (LAP). Among these sub-problems the MRMCP is considered as the central one and is tackled first of all. The solution procedure for the MRMCP is based on a partial set-partitioning formulation. It makes use of a variant of column generation. Feasible column is generated as needed by solving a resource constrained elementary shortest path problem (RC-ESPP) by a mixed strategy combing an exact method and heuristics. Then a procedure called Adding-Node is introduced to implicitly solve the KP starting from the solution of the MRMCP. Finally, we solve the LAP with Hungarian algorithm to consider the total tardiness and earliness of the production. Computational results are presented compared with several promising methods on benchmark problems and production orders from Shanghai Baoshan Iron and Steel Complex. The results demonstrate the efficiency of the proposed algorithm.     

Fabrication of curved sub-micron Si structures by a combination of anisotropic etching using surfactant-added TMAH solution and FIB direct-drawn mask

Silicon anisotropic wet etching is applied for fabricating round-shaped micro-structures in a size range of sub-microns. In this work, we demonstrate that arbitrary 2-D mask patterns having curved profile can be successfully transferred to deep-etched cavity profiles on a Si {100} wafer. The sub-micron mask is directly drawn on the Si wafer by irradiating focused ion beam to the wafer surface. Anisotropy in etch rate of Si using tetra-methyl ammonium hydroxide solution was modified and controlled by adding a surfactant Triton X-100 to the solution. Etched profile was conformal to etch mask patterns having smooth curvatures.     

The Fast Intelligent Tracking (F!T) tube: A CRT without a shadow mask

Abstract— The F!T tube is a new type of CRT without a shadow mask. The primary function of the mask, color selection, is taken over by an electronic control system that guides the electron beams over the correct phosphor lines. The position of the beams is detected by means of dedicated structures on the faceplate. Proof of the principle has been shown in single‐ and triple‐beam 17‐ and 32‐in. tubes.     

Fabrication of microgratings on PMMA plate and curved surface by using copper mesh as X-ray lithography mask

We demonstrate experimentally the X-ray lithography technique to fabricate microgratings on a PMMA plate and on curved surfaces such as PMMA cylinder lens surfaces with X-ray lithography by copper mesh as mask. Some gratings with 12.7 μm pitches on the plate and on PMMA curved surface with large area (10 mm × 10 mm) by vertically moving or rotating the resist stage exposure are realized.     

The Fast Intelligent Tracking (F!T) tube: Electronic aspects of a CRT without a shadow mask

Abstract— The F!T tube is a new type of CRT without a shadow mask. Correct color selection is performed by an electronic system, measuring the landing positions of the electron beams, and correcting them through a dedicated deflection system. In this paper, we describe system aspects concerning the measurement system of the control loop and tracking signal reliability. Results are discussed as well.     

Fabrication of X-rays mask with carbon membrane for diffraction gratings

We have produced diffraction gratings for obtaining high resolution X-ray phase imaging, such as X-ray Talbot interferometer. These diffraction gratings were required to have a fine, high accuracy, high aspect ratio structure. Therefore, we decided to use the X-rays lithography technique that used synchrotron radiation of the directivity for a manufacture process. The accuracy of the completed structure depends largely on the accuracy of the X-ray mask. In our group, a resin material is conventionally used for the membrane of large X-ray masks. However, X-ray masks comprising a resin membrane have the disadvantage that, after several cycles of X-ray exposure, they crease and sag due to X-ray-derived heat. As a substitute for the conventional resin membrane, we experimentally fabricated a new X-ray mask using a carbon wafer membrane. The newly fabricated X-ray mask was subjected to X-ray exposure experiment. We succeeded in making the structure body which was almost shape. And the experimental results verified that the new mask did not deteriorate even when used repeatedly, demonstrating that it was highly durable.     

Micro-milling performance of AISI 304 stainless steel using Taguchi method and fuzzy logic modelling

In this study, micro-milling of AISI 304 stainless steel with ball nose end mill was conducted using Taguchi method. The influences of spindle speed, feed rate and depth of cut on tool wear, cutting forces and surface roughness were examined. Taguchi’s signal to noise ratio was utilized to optimize the output responses. The influence of control parameters on output responses was determined by analysis of variance. In this study, the models describing the relationship between the independent variables and the dependent variables were also established by using regression and fuzzy logic. Efficiency of both models was determined by analyzing correlation coefficients and by comparing with experimental values. The results showed that both regression and fuzzy logic modelling could be efficiently utilized for the prediction of tool wear, cutting forces and surface roughness in micro-milling of AISI 304 stainless steel.     

Mathematical modelling and parameter identification of a stainless steel annealing furnace

A new, comprehensive mathematical model of continuous annealing furnaces is developed, under consideration of both the radiative and convective heat transfer of the furnace components. Based on measured normal operating data from an industrial stainless steel plant, parameter identification is basically carried out using a nonlinear least-squares optimization algorithm for the whole annealing furnace, to estimate optimal values of uncertain parameters, such as emissivities. Due to the complexity of the model, a sequential approach for parameter identification is proposed and implemented, i.e. the parameter set is divided into different subsets, and the parameter estimation is carried out sequentially in several steps and iterations. The performance of the model with the estimated parameters is then evaluated on a different test data set. It is shown that the obtained model can predict temperature evolutions along the furnace in good agreement to measured data, under both steady-state and transient conditions. The presented model is suitable for controller design and process optimization.     

Injection molding of 316L stainless steel microstructures

Micro powder injection molding (PIM) is a promising process for low cost fabrication of three-dimensional microstructures. The PIM can be used for a wide range of metal and ceramic materials, combined with the potential for mass production. In this paper, initial study on the molding of 316L stainless steel microstructures was investigated. Three different micro-cavity shapes were used. Small powder with mean size of 4 m was used with two multi-component binder systems. Microstructures with dimension as small as 35 m could be injection molded. For successful molding, the binder system must provide high green strength to withstand ejection from the mold and suitable molding parameters used. For example, a high mold temperature is required and ejection speed must be reduced. The cross-sections of the microstructures are precisely replicated. The general shape in the depth direction is replicated although it is not as good as that for the cross-section. More work has to be conducted to realize the full potentials of the process.The authors would like to thank the Nanyang Technological University for awarding a research grant to conduct this research and Adeka Fine Chemicals (Tokyo) for the supply of PAN 250 binder.     

Post-buckling behavior of cold-formed thin-walled stainless steel beams

A numerical approach for predicting the post-buckling responses of cold-formed thin-walled stainless steel beams is presented. In the analysis, the nonlinear and unsymmetrical stress-strain relations in tension and compression for both flat and corner materials are considered. The effective width concept is used to account for the post-buckling strength of the thin compression flange of the beam. Using this concept, the value of the effective width varies with the stress borne by the flange edge. In view of the nonlinearities introduced by considering the material characteristics and the post-buckling behavior of the individual elements, an iterative procedure is employed to establish the nonlinear moment-curvature relation of a section. In a beam subjected to bending, the effective moment of inertia of the section varies from point to point along the length of the beam depending upon the magnitude of the moment at the point considered. In this analysis, the continuously flexible beam is replaced with a finite number of discrete rigid elements connected by flexible joints at which the continuously varied curvature is lumped through numerical integration. In the case of a continuous beam, it is further complicated by the fact that the bending moment distribution along the beam is not known a priori and its determination is part of the solution to the problem. An iterative algorithm is developed to obtain the approximate true moment distribution considering the compatibility conditions at the support. A computer program following th e above solution scheine has been developed and is capable of predicting the nonlinear responses of most of the common thin-walled sections encountered in light-gage steel design. Comparisons with some available experimental data are provided.     

A fast fingerprint image enhancement algorithm using a parabolic mask

The quality of fingerprint images (FIs) varies depending on the image taking method. The performance of automatic fingerprint recognition systems highly depends on the quality of the fingerprint images. In these images often are distorted areas, where the valleys and ridges are not clear and there are discontinuities at in the ridge flows. To overcome these unwanted defects fingerprint recognition systems employ enhancement algorithms to improve the quality of the images. Following, binarization, feature extraction, and matching algorithms are executed on the enhanced image. In real-time systems, the overall execution time has primary importance and therefore, especially the enhancement algorithm must be fast and effective. In this study, we propose a fast filtering method with a mask of parabolic coefficients based on the directions. The experiments executed on FVC2000 have proved that, the algorithm provides faster and better enhancements from those described in the literature.     

Multi-modal defect detection of residual oxide scale on a cold stainless steel strip

This work presents two initial approaches and a novel technique for the industrial inspection of residual oxide scale on a cold stainless steel strip. The research aims to develop real-time systems to detect 50-μm defects. Initially, a spectrophotometric analysis provides the wavelength regions where differences between stainless steel and residual oxide scale reflectance are highlighted. The multi-modal approach is based on laser techniques that comprise three different strategies to gradually achieve a robust stainless steel industrial inspection through the evaluation of their performance. First, an inspection system based on a single commercial laser has been designed with a dynamic threshold module. In the second approach, the inspection task is accomplished by volatilizing a reduced area of the stainless steel surface with short pulses of a high-power ultraviolet laser and then analyzing the generated plasma with an intensifier camera. The third technique consists of an innovative smart vision system for surface visual inspection based on laser diode diffuse illumination. This vision system can be configured to work with two laser illumination modes: the diffuse coaxial lighting and the diffuse bright-field lighting. These techniques aim to gradually improve surface defect detection of a cold stainless steel strip. Furthermore, some of the results of the defect detection level obtained with each approach are displayed and discussed.