Showing papers in "International Journal of Precision Engineering and Manufacturing in 2011"

A Review of Piezoelectric Energy Harvesting Based on Vibration

Abstract: This paper reviews energy harvesting technology from mechanical vibration. Recent advances on ultralow power portable electronic devices and wireless sensor network require limitless battery life for better performance. People searched for permanent portable power sources for advanced electronic devices. Energy is everywhere around us and the most important part in energy harvesting is energy transducer. Piezoelectric materials have high energy conversion ability from mechanical vibration. A great amount of researches have been conducted to develop simple and efficient energy harvesting devices from vibration by using piezoelectric materials. Representative piezoelectric materials can be categorized into piezoceramics and piezopolymers. This paper reviews key ideas and performances of the reported piezoelectric energy harvesting from vibration. Various types of vibration devices, piezoelectric materials and mathematical modeling of vibrational energy harvestings are reviewed.

Computer-aided porous scaffold design for tissue engineering using triply periodic minimal surfaces

Abstract: Recently, computer aided geometric design of triply periodic minimal surfaces (TPMS) has received considerable attention in the area of computer aided nano design on account of its ability to efficiently construct a large number of complex surfaces. In this paper, a TPMS is described with periodic surfaces composed of simple trigonometric functions, thus enabling easy generation of TPMS for use in various mechanical, chemical, and physical applications. We first describe a TPMS with mesh surface using conventional marching cube algorithm. We then propose various related algorithms for generating complete solid model for various applications, ranging from thickened solid, through voxel solid, to complexshaped solid. The validity of this new technique is demonstrated for a variety of TPMSs, including the P, G, D, I-WP, F-RD, L, and I2-Y** surfaces. Finally, a new control approach for pore size distribution in tissue scaffold design is presented based on the pore-making element composed of TPMS and conformal refinement of all-hexahedral mesh in order to show the practical applicability of the newly suggested modeling approach.

Applications of laser assisted metal rapid tooling process to manufacture of molding & forming tools — state of the art

Abstract: Recently, researchers related to the development of eco-friendly molding and forming tools have refocused on the laser assisted metal rapid tooling process to cope the global warming and the resource depletions. The advantageous inherent features of the laser assisted metal rapid tooling process, include an additive proves, switchable supply material and material deposition along an arbitrary trajectory, provide the tool designer and manufacturer with a chance to overcome the limitations of the conventional molding and forming tools from viewpoints of the energy consumption, the environmental impact and the material usage. This paper presents recent researches related to the application of laser assisted metal rapid tooling process to manufacture molding and forming tools. In addition, key technologies of important applications are discussed. Finally, the future issues of the laser assisted metal rapid tooling process related to the development of eco-friendly molding and forming tools are described.

Recent Researches in Micro Electrical Machining

Abstract: The demand for micro parts and moulds has been increasing in various fields. Among the various micro machining technologies, micro electrical machining is one of the most widely used because it can be applied for conductive or nonconductive materials. This paper discusses the recent studies that explore many ways to improve micro electrical machining performance. Many researchers proposed ways to improve productivity and accuracy through experimental or analytical studies. The improved-performance trends of micro electrical machining are expected to continue thanks to the miniaturization of manufactured goods in a high-tech industry.

Optimization of cutting parameters for turning Al-SiC(10p) MMC using ANOVA and grey relational analysis

Abstract: This paper presents the detailed experimental investigation on turning Aluminium Silicon Carbide particulate Metal Matrix Composite (Al-SiC -MMC) using polycrystalline diamond (PCD) 1600 grade insert. Experiments were carried out on medium duty lathe. A plan of experiments, based on the techniques of Taguchi, was performed. Analysis of variance (ANOVA) is used to investigate the machining characteristics of MMC (A356/10/SiCP). The objective was to establish a correlation between cutting speed, feed and depth of cut to the specific power and surface finish on the work piece. The optimum machining parameters were obtained by Grey relational analysis. Finally, confirmation test was performed to make a comparison between the experimental results and developed model and also tool wear analysis is studied.

Neural network based hybrid force/position control for robot manipulators

Abstract: This paper presents a neural network based adaptive control scheme for hybrid force/position control for rigid robot manipulators. Firstly the robot dynamics is decomposed into force, position and redundant joint subspaces. Based on this decomposition, a neural network based controller is proposed that achieves the stability in the sense of Lyapunov for desired interaction force between the end-effector and the environment as well as regulate robot tip position in cartesian space. A feedforward neural network is employed to learn the parametric uncertainties, existing in the dynamical model of the robot manipulator. Finally numerical simulation studies are carried out for a two link rigid robot manipulator.

Design of U-shape milled groove conformal cooling channels for plastic injection mold

Abstract: Besides the solid free-form fabrication technology, milling operation is an alternative applicable method to make complex cooling channels conform to the surface of the mold cavity. This paper presents the U-shape milled groove conformal cooling channels and proposes the design optimization process in order to obtain an optimal cooling channels’ configuration and target mold temperature. The relation between the cycle averaged thermal behavior of the mold cavity and the two-dimensional configuration of cooling channels was first investigated thoroughly by an analytical method. Design of experiment and 2D simulation were done to obtain the mold wall temperature and to check the feasibility of the analytical method. The optimization process of the free-form conformal cooling channels is based on the combination of both analytical method and 3D CAE simulation. The analytical step relies on explicit mathematic formulas, so it can approach the neighboring optimal solution quickly. Subsequently, the three-dimensional heat transfer simulation is applied to fine-tune the optimization results. A case study for a plastic car fender was investigated to verify the feasibility of the proposed method. The results show that conformal cooling channel gives a uniform cooling, reducing the cooling time and increasing the molded part’s quality with less effort of plastic designers and high computational efficiency.

Identification and measurement of geometric errors for a five-axis machine tool with a tilting head using a double ball-bar

Abstract: Geometric errors are one of the primary potential sources of error in a five-axis machine tool. There are two types of geometric errors: position-dependent geometric errors and position-independent geometric errors. A method is proposed to identify and measure the position-independent geometric errors of a five-axis machine tool with a tilting head by means of simultaneous multi-axis controlled movements using a double-ball bar (DBB). Techniques for identifying position-independent geometric errors have been proposed by other researchers. However, most of these are based on the assumption that position-dependent geometric errors (such as linear displacement, straightness, and angular errors) are eliminated by compensation, once the position-independent geometric errors have been identified. The approach suggested in this paper takes into account the effect of position-dependent geometric errors. The position-dependent geometric errors are first defined. Path generation for circle tests with two or three simultaneous control movements is then carried out to measure the position-independent geometric errors. Finally, simulations and experiments are conducted to confirm the validity of the proposed method. The simulation results show that the proposed method is sufficient to accurately identify position-independent geometric errors. The experimental results indicate that the technique can be used to identify the position-independent errors of a five-axis machine tool with a tilting head.

A review on research and development of laser assisted turning

Abstract: LAM(Laser assisted machining) is machining method that performs a machining for workpieces using a laser preheating process. By combining the LAM and CNC lathe using laser beam, it could be named LAT (Laser Assisted Turning). A machining process in LAT has been applied at 1200∼1400°C using a specific cutting tool, after preheating a workpiece using laser beam as about 2000°C. This study performed a review on the laser assisted turning and heat treatment through classifying these technologies into three categories; the device and mechanism for establishing LAT, the machining process and heat treatment for applying LAT, and the analysis and theoretical research, which are the most important issues in LAT.

Geometric optimization of micro drills using Taguchi methods and response surface methodology

Abstract: Micro drill-bits for halogen-free printed circuit boards were analyzed using Taguchi methods and response surface methodology (RSM). Since micro drills have many shape factors, which are not easy to describe exactly, Taguchi methods are one of the most common optimization approaches. However, Taguchi methods can only optimize among fixed variables. Using RSM, one can create a regression surface. Optimal shapes of micro drills were determined using a normalized sum of various measures of performance. It was suggested that RSM combined with other methodologies should be used with more shape factors to further analyze the performance of micro drill-bits.

Optimization of cutting conditions for surface roughness in CNC end milling

Abstract: The aim of this research is to develop an integrated study of surface roughness to model and optimize the cutting parameters when end milling of 6061 aluminum alloy with HSS and carbide tools under dry and wet conditions. A multiple regression analysis using analysis of variance is conducted to determine the performance of experimental measurements and to show the effect of cutting parameters on the surface roughness. The second-order mathematical models in terms of machining parameters have been developed for each of these conditions on the basis of experimental results. Genetic algorithm (GA) supported with the regression equation is utilized to determine the best combinations of cutting parameters providing roughness to the lower surface through optimization process. The value obtained from GA is compared with that of experimental value and found reliable. It is observed from the results that the developed study can be applied to other machining processes operating under different machining conditions.

Investigations into Performance of Dry EDM Using Slotted Electrodes

Abstract: Dry EDM is an emerging EDM technology, which uses gas as dielectric fluid. Due to low density of gaseous dielectric, the process experiences i) unconstrained plasma expansion thereby reducing the effective material removal rate (MRR) and ii) inefficient disposal of debris. This work proposes use of electrodes with peripheral slots to provide more space for the flow of dielectric for effective debris disposal and consequently improve MRR. In this regard, a comprehensive experimentation using Taguchi L16 orthogonal array has been planned initially to optimize the number of peripheral slots on the electrodes, and then to understand the effect of the slots on material removal, tool wear, oversize and depth achieved as a function of processing conditions. It is observed that the optimum number of peripheral slots on electrode for effective debris evacuation is four for the electrode configuration used in this work. The statistical analysis shows that in dry EDM, discharge current (I), gap voltage (V), rotational speed (N) and pulse off-time (Toff) control MRR. Also, use of slotted electrodes significantly reduces the electrode wear rate, and attachment of debris particles on the electrodes.

Direct machining of micro patterns on nickel alloy and mold steel by vibration assisted cutting

Abstract: Feasibility of direct machining of micro patterns for micro molds by 2-dimensional vibration assisted cutting or elliptical vibration cutting was investigated and its machinability was compared with the conventional cutting method. Micro patterns of successive V-grooves and micro pyramids were machined on workpieces of a pure nickel, nickel alloy and mold steels with single crystal diamond, cubic boron nitride and poly crystal diamond tools which move along a circular path with a diameter less than 2 μm at an excitation frequency of 18 kHz. It was observed that the utility of EVC, that is a decrease of cutting resistance and an improved machining quality, was retained regardless of materials of workpieces and tools, and the improvement compared to CCM was far clearer when machined with a worn cutting tool. The risk of catastrophic or fatigue failure of tool was, however, increased by the impulsive forces resulting from periodic contact making and breaking between the tool and workpiece of high strength and hardness.

Manufacturing of inchworm robot using shape memory alloy (SMA) embedded composite structure

Abstract: To design effective movement of robots, various locomotive mechanisms have been investigated. In this study, an inchworm robot was manufactured using shape memory alloy (SMA) which was embedded in composite materials. A Ni-Ti SMA wire was pre-strained and embedded in the glass fiber reinforced polymer (GFRP) strip laid on an ∩-shape mold. Then SMA embedded composite structure was cured at room temperature for 72 hours. Controlling DC current through the SMA wire, the SMA-composite structure, body, could be actuated by changing the radius of curvature. Two legs were attached to the end of body and the leg has two edges which have different coefficients of friction to provide directional movement. One stroke of inchworm provided 4.0 mm translational movement. Repeating on and off of DC current, the inchworm robot gives continuous movement. This mechanism can be applied to the soft morphing robotics, bio medical devices, airplane inlet, etc. instead of using traditional components for their movement.

Test and error parameter estimation for MEMS — based low cost IMU calibration

Abstract: A new method is presented to calibrate a low-quality, MEMS-based Inertial Measurement Unit (IMU). The proposed method consists of a novel dynamic test-setup with a combination of a single-axis rate-table and an attitude change mount, to overcome the limitations in the conventional calibrations with the static or quasi-static test-setups. A Fourier Transform method is deployed in the proposed scheme to estimate the error parameters including bias, scale factor, and misalignment of the accelerometers and rate gyros. Compared to the commonly used Recursive Least Squares method, the Fourier Transform method is more efficient in terms of the computation time, yet it resulted in comparable or improved results in the series of verification tests in this study.

A dexterous robot hand with a bio-mimetic mechanism

Abstract: This paper describes a development of bio-mimetic robot hand and its control scheme. This robot hand has four independently moving fingers, which are driven by four-coupled link mechanism with two linear actuators. By using the linear actuators, we make the hand similar to human hand in its structure and motion. The coupled link mechanism makes the hand compact in structure and efficient in power. The robot hand is designed considering the dexterity and the compact size suited for various tools and objects in daily life. The hand has tactile sensors mounted on the palm and the fingertips at each finger. With tactile sensor based feedback control and force closure method, the paper shows the control of the robot hand which is very stable in grasping and handling various objects.

Machining characteristics of micro EDM in water using high frequency bipolar pulse

Abstract: Micro EDM using conventional pulse generators such as the RC type or transistor type with water as the dielectric fluid suffers from poor accuracy of machined structures due to electrolytic corrosion. In this study, a new high frequency bipolar pulse generator for micro EDM in water was developed in order to prevent electrolytic corrosion. The new pulse generator produced a high frequency bipolar pulse possessing a positive pulse duration of several hundred nanoseconds with a high repetition rate provided to the machining gap. Discharge characteristics of micro EDM using the new pulse generator were investigated. Machining characteristics were also investigated according to machining conditions such as the repetition rate, positive voltage, capacitance and resistivity. Using the new pulse generator, micro holes without electrolytic corrosion were successfully fabricated in deionized water and tap water. Machining time, tool wear and clearance using the new pulse generator in deionized water decreased compared with those using the RC circuit in kerosene.

Experimental and numerical investigations of mode I delamination behaviors of woven fabric composites with carbon, Kevlar and their hybrid fibers

Abstract: This paper studied the effect of the hybridization of carbon and Kevlar fibers on mode I interlaminar fracture toughness and crack propagation behaviors with double cantilever beam (DCB) tests. The crack propagation characteristics, crack growth trend and rate, and fracture surfaces were observed using an optical microscope and SEM micrographs for the three different types of materials. Moreover, details of the stress distribution around the crack tip and the crack propagation pattern across the width of the DCB specimen were investigated using the finite element method, including a cohesive element. The mode I interlaminar fracture toughness of carbon-Kevlar hybrid/epoxy was nearly average for carbon/epoxy and Kevlar/epoxy. The maximum load predicted by the numerical method showed good agreement within an error of 5% with the experimental results.

Impact of traffic environment and cognitive workload on older drivers’ behavior in simulated driving

Abstract: As the use of in-vehicle technologies became more popular, there is concern about a concomitant increase in driver distraction arising from their use. While the introduction of voice recognition systems is intended to reduce the distraction due to manual operation of these units, a significant proportion of the distraction associated with their use may arise not from the manual manipulation but rather the cognitive consequences. It is also known that the risk of inattentive driving varies with age. In this study, the impact of cognitive workload and traffic environments on older drivers’ behavior was investigated in a driving simulator. To assess the impact of advancing age on driving performance degradation under a dual task condition, the performance of 63 drivers, divided into younger (20–29) and older (60–69) age groups, was evaluated. The authors also considered driving behavioral differences in the context of urban and highway driving, appropriately counterbalanced. At a specified location in the two scenarios, subjects were asked to complete a series of auditory tasks of increasing complexity. Comparisons of younger and older drivers’ driving performance, including forward velocity, speed control, standard deviation of lane position and steering wheel reversal rate, were conducted. Results indicated that age and traffic environment impact both driving performance and compensatory behavior during dual task conditions.

Study of Drop-on-Demand Printing Through Multi- Step Pulse Voltage

Abstract: This paper presents study of the Electrohydrodynamic Drop-on-Demand (DOD) phenomena by applying the multi-step pulse voltage. The multi-step voltage was generated through the high voltage power source connected with pulse generator. A DOD phenomenon was observed with the help of high speed camera. For study purpose the experiments were performed on ethanol by changing the operating parameters such as multi-step pulsed voltage, frequency of applied pulsed voltage and flow-rate. For DOD printing purpose conductive ink is used and patterns were made on the glass substrate and analyzed on different operating conditions. The minimum droplet diameter of approximately 40μm at 325Hz frequency was achieved on the glass substrate. The printed pattern exhibited the linear ohmic behavior and pattern material is characterized through XRD. This study will help in better understanding of the Electrohydrodynamic DOD phenomena for the printing purpose.

Improvement of formability for multi-point bending process of AZ31B sheet material using elastic cushion

Abstract: On multi-point forming process, one of the most obvious limitations is the need for a pliable interpolating material such as elastic cushion between punch element tips and sheet metal to prevent the formation of dimples on the surface of final part. In this study, numerical simulations of multi-point bending process in case of different thicknesses of elastic cushion are performed to obtain a specified final shape as a cylindrical surface with curvature radius of 434.65mm and centre angle parameter of 52.73° by using initial blank with length of 800mm, width of 600mm, and thickness of 2mm, respectively. To find the suitable thickness of the elastic cushion, four evaluating indicators including plastic dissipation energy, stress components, shape error and maximum ductile damage are introduced and analyzed. As the results, each value of four evaluating indicators is decreased, and their distributions become more uniform on the deformed blank by adopting the elastic cushion. Resultantly, it is summarized that the formability of AZ31B magnesium alloy can be improved by using the elastic cushion, and the most proper thickness of the elastic cushion is 4 mm for the multi-point bending process of AZ31B sheet with thickness of 2mm.

Thermo-Mechanical Finite Element Analysis of Hot Judder Phenomenon of a Ventilated Disc Brake System

Abstract: Hot judder characteristics of a ventilated disc brake system are discussed. Three dimensional finite element models of the ventilated disc, pads and pistons are created, and a fully coupled thermo-mechanical analysis of the hot judder phenomenon of the disc brake system is performed using SAMCEF. The brake dynamo test is carried out according to the high speed judder test mode. The evolution of the temperature distribution on the disc surface is described, and the hot spot generation process is investigated. The simulation results such as the maximum disc temperature, BTV are compared to the data from the dynamo test, and the reliabilities of the analysis technique and simulation model presented in this paper are verified.

A comparative study of the physical and mechanical properties of porous hydroxyapatite scaffolds fabricated by solid freeform fabrication and polymer replication method

Abstract: A novel porous scaffold designed for application as a bone substitute, with a structure containing three-dimensional (3D) pore channels in a hydroxyapatite (HA) scaffold, was fabricated using a combination of a solid freeform fabrication (SFF) and cast in a mold using freezing casting method. This study was performed to evaluate the physical and biomechanical properties of the HA scaffolds fabricated by SFF and using polymer replication method (PRM), one of the conventional methods. Although the phase composition and porosity of these two scaffolds are similar, their external shape and mechanical property were different. All of the fabricated scaffolds showed similar patterns through X-ray diffraction. The difference between porosities of two HA scaffolds were not statistically significant (P>0.05). However, the average compressive strength of the scaffold fabricated by SFF was 14.6 MPa, and that of the scaffold fabricated using polymer replication was 3.56MPa (P<0.05). It was confirmed that SFF fabrication could have a relatively higher mechanical property than PRM fabrication at the same porosity.

Pull-in instability analysis of electrostatically actuated microplate with rectangular shape

Abstract: As the size of the micro-electro-mechanical systems (MEMS) continues to decrease, the classical elasticity continuum theory may be inefficient to describe their mechanical behaviors. By introducing the strain gradient elasticity into the classical Kirchhoff plate theory, the size-dependent model for electrostatically actuated microplate-based MEMS is developed. The sixth-order partial differential equation (PDE), derived with the help of the principle of minimum potential energy, can be numerically solved by utilizing generalized differential quadrature (GDQ) method and pseudo arc-length algorithm. The model, with three material length scale parameters (MLSPs) included, can predict prominent size-dependent normalized pull-in voltage with the reduction of characteristic structural size, especially when the plate dimension is comparable to the MLSP (on the order of microns). This study may be helpful to characterize the mechanical properties of electrostatically actuated MEMS, or guide the design of microplate-based devices for a wide range of potential applications.

Comparison of gait and cognitive function among the elderly with Alzheimer’s Disease, Mild Cognitive Impairment and Healthy

Abstract: The purpose of this study was to compare gait pattern and cognitive function among elderly patients with Alzheimer’s Disease (AD), elderly people with Mild Cognitive Impairment (MCI), and Healthy Controls (HC). Twenty three elderly patients participated: 10 AD (77.2±6.84 yrs), 7 MC I(72.9±6.28 yrs), and 6 HC (71.6±5.78 yrs). Gait and Cognitive function were collected using an accelerometer attached to the foot and the Korean version of the Consortium to Establish a Registry for Alzheimer’s Disease (CREAD-K), respectively. To compare differences in gait performance among groups, mean stride time, magnitude and structure of gait variability and ratio of low frequency and high frequency (LF/HF ratio) of stride time sequence were used in this study. Results showed that gait variables (mean stride time, LF/HF ratio of stride time) were useful for classification between MCI and HC. Cognitive function (T1, T3, T4, T6, and T8 of CREAD-K) represented the difference between AD and HC. This study may provide a foundation for future work on progression of dementia.

A parametric dynamic study on hunting stability of full dual-bogie railway vehicle

Abstract: Analysis is performed on the hunting stability of a full railway vehicle system composed of a vehicle body, two bogie frames, and two wheelsets for each bogie frame. Incorporated into this analysis are the nonlinear heuristic creep and flange-rail contact models. The results show that the hunting speed is most sensitive to the primary longitudinal and lateral stiffnesses, and the nonlinear heuristic creep model plays a key role in confining the hunting speed within a physically reasonable range. Eigenanalysis is performed to investigate the dynamic behavior of the vehicle in the vicinity of the hunting speed. The results reveal that there exists not only the most dominant pair of complex conjugate roots, but also its shadowed roots. The roles of these two principal pairs of eigensolutions in the hunting motion are thoroughly explored via numerical studies using bifurcation analysis and an orbital representation. It is shown that the nonlinear hunting motions before the modal transition speed mainly refer to the principal mode, and those after the critical speed refer not only to the principal mode, but also to its shadowed mode, which supports the necessity of the dual-bogie railway vehicle model in the hunting analysis.

Polygon-based 3D surgical planning system for hip operation

Abstract: This paper presents a light-weight software system that enables virtual three-dimensional (3D) surgical planning of hip replacement surgery for extracting 3D surgical parameters such as the position and the orientation of femoral resection plane, the interference-free trajectory of prosthesis implantation, and the final assembled position. According to the specification of an individual patient, the system allows the surgeon to design a hip prosthesis that most closely recovers the original function of the joint. Since it is based upon the 3D anatomy, the system overcomes a geometrical mismatch between prosthesis-bone interfaces which is the main limitation of 2D-based approach. The closely customized prosthesis-bone fit appears to increase the durability of hip prosthesis, and enhances the load distribution and the stability. Detailed steps of the system are described, and typical example is presented to validate the methodology. The result shows that the proposed pilot surgical planning system is applicable.

Investigation of Cutting Parameters Effect for Minimization of Sur face Roughness in Internal Turning

Abstract: Minimizing the surface roughness is one of the primary objectives in most of the machining operations in general and in internal turning in particular. Poor control on the cutting parameters due to long boring bar generates non conforming parts which results in increase in cost and loss of productivity due to rework or scrap. In this study, the Taguchi method is used to minimize the surface roughness by investigating the rake angle effect on surface roughness in boring performed on a CNC lathe. The control parameters included besides tool rake angle were insert nose radius, cutting speed, depth of cut, and feedrate. Slight tool wear was included as a noise factor. Based on Taguchi Orthogonal Array L18, a series of experiments were designed and performed on AISI 1018 steel. Analysis of variance, ANOVA, was employed to identify the significant factors affecting the surface roughness and S/N ratio was used to find the optimal cutting combination of the parameters. It was concluded that tool with a high positive rake angle and smaller insert nose radius produced lower surface roughness value in an internal turning operation. It was also concluded that high feedrate and low cutting speed has produced the lowest surface roughness.

Parameter optimization using a regression model and fitness function in laser welding of aluminum alloys for car bodies

Abstract: The objective of this paper is to determine the optimal welding conditions in terms of the productivity and weldability for laser welding of aluminum alloy AA5182 using filler wire AA 5356. The experiments were performed with laser power, welding speed, and wire feed rate as control factors. Tensile tests were carried out in order to evaluate the weldability under each welding condition. In order to estimate the tensile strength, three regression models are proposed. One is a multiple linear regression model, another is a second order polynomial regression model, and the last is a multiple nonlinear regression model. Of the three models, the second order polynomial regression model had the best estimation performance with respect to ANOVA (analysis of variation) and average error rate. Also, this study defines objective functions for tensile strength, which represents weldability, and for the welding speed and wire feed rate, which represent productivity. In addition, fitness functions are obtained using the objective functions and a weight matrix which shows the importance of each objective function. The steepest descent method is used to find the optimal point where the fitness function was maximized. Optimal welding conditions were found at a filler wire feed rate of 2.7 m/min, laser power of 4 kW, and welding speed of 7.95 m/min.

Micro-patterning on non-planar surface using flexible microstencil

Abstract: A method for fabrication of flexible stencil was studied. Flexibility of the stencil allows micropatterning on a curved surface by material deposition or material removal (etching) through patterned hole of the stencil. In this study, low mechanical stability of the thin stencil membrane was improved by bonding the membrane with rim supporter which is thick and strong enough for easy handling of the stencil. Both of the membrane and rim structure were made of elastomer, PDMS using molding process from SU-8 master mold. The application test of shadow deposition and etching on underlying nonplanar surface using the fabricated flexible stencil mask showed the feasibility of the suggested technique into micro- patterning on a curved surface.