Dry Micro Research Articles

Simulation and experimental study on effect of surface residual stresses in dry orthogonal micro turning sample

ABSTRACT Turning is a drastically favoured machining process for producing cylindrical components with required dimensions. Prediction of chip formation is essential when damages caused by chips are into consideration during machining. A high amount of residual stresses are generated in the machined component due to a large number of forces and temperature distribution during machining. The scope of this paper is to investigate the percentage of residual stresses induced in a component during the dry micro turning process. Hence, in this work, Inconel 718, A2024-T351, and AISI D2 (62HRC) are selected as a workpiece materials and WC as tool material, simultaneously comparison studies of chip morphology have been carried out. Also, cutting speed and power consumption were investigated experimentally by opting varied tool rake angles (positive, negative, and zero) and a depth of cut. Residual stresses, nose wear, and chip morphology were found experimentally while machining Inconel 718. From the simulation and experimental results obtained, one can adopt a suitable tool rake angle to minimise power consumption during the micro turning process which leads to a sustainable machining process.

Experimental evaluation of surface generation and force time-varying characteristics of curvilinear grooved micro end mills fabricated by EDM

Conventional cutting fluids as coolants and lubricants are being widely used in various machining processes, but these cutting fluids give rise to biological and environmental problems. The advantages of implanting micro texture on macroscopic cutting tools have been proved widely in implementing sustainable machining. But seldom studies focused on preparing micro texture on the surface of micro end mill with diameter less than 1 mm. In this study, an attempt has been made to create curvilinear grooved micro textures on the rear surface of double helical micro end mills with diameter of about 800 μm by electrical discharge machining (EDM) method for lowering specific milling energy and forces. Then, dry micro milling experiments were performed on aluminum alloy material using micro end mills with or without curvilinear grooved micro textures. The surface generated mechanism, force time- varying characteristics, specific milling energy, chip capacity and tool wear form of curvilinear grooved micro end mills in dry micro milling are revealed. Besides, the effects of structural parameters of micro textures and process parameters on specific milling energy and dry micro milling forces are discussed. Experimental results disclosed that the average specific cutting energy involved in dry micro milling process of aluminum alloy material machined by micro end mill with curvilinear grooved micro textures is decreased by 21.35%. The normal and tangential forces are significantly reduced compared to ordinary micro end mill. The voids and stomatal located in micro textures fabricated by EDM method are found to be conductive to store and accommodate some extrusion chips. For micro end mill with curvilinear grooved micro textures, the oxidative wear is more serious but the adhesion wear is slighter than ordinary micro end mill. This research is expected to prepare and optimize micro textured micro end mills suitable for dry micro milling process, which has important theoretical significance and engineering application value.

Experimental Investigation on Machinability of Aluminum Alloy during Dry Micro Cutting Process Using Helical Micro End Mills with Micro Textures.

Aluminum alloy material is widely used in the electronics, weapons, aviation and aerospace industries, due to its medium strength, good corrosion resistance, good toughness and excellent oxidation properties. With the trend of product miniaturization, micro cutting has become the mainstream technique for fabricating micro parts and components, so it is very meaningful and vital to work on removing the cutting fluid from the micro cutting process and make it totally sustainable and eco-friendly. In this work, an attempt has been made to fabricate micro textures onto the rear surface of helical micro end mills with diameters of less than 1 mm. Micro textures in the form of grooves were fabricated using a noncontact low speed wire electrical discharge turning technique. Dry micro cutting experiments were carried out on an aluminum alloy material using helical micro end mills with micro textures and the dry micro cutting surface quality and tool wear have been investigated. The influence of dry micro cutting parameters on the surface roughness parameters were also investigated. Experimental results showed that the Sa and Sq can be reduced to be about 1.56 μm and 2.08 μm, respectively. Contrasting results indicate that the implantation of micro textures does not deteriorate the dry micro cutting surface but improves the machined surface consistency of an aluminum alloy workpiece. The tool wear on helical micro end mills with micro textures involved in the dry micro cutting process of Al 6061 mainly include rear frictional wear, oxidation wear and diffusion wear.

Analysis of Corner Radius in Dry Micro WEDM

Dry micro WEDM is a machining process where gas is used as the dielectric medium instead of liquid. This process favored for its environmental friendly nature and its ability in machining complex intricate shapes with great precision. Regardless of its high precision, the machining precision of cutting sharp corners cannot be satisfied. Therefore, the purpose of this paper is to analyze the process parameters; gap voltage, wire tension, and air dielectric pressure to find the optimal parameters to minimize the radius during the sharp corner cutting of stainless steel workpiece. Compressed air was used as the dielectric fluid, whereas the electrode was a 70 micrometer tungsten wire. The experiments were design using full factorial method while the data were analyzed using analysis of variance (ANOVA). Based on ANOVA, gap voltage and wire tension had a major influence on the corner radius. The optimum parameters for minimum corner radius were found to be 85 V gap voltage, 0.16 N wire tension, and 0 MPa dielectric pressure.

Investigation of Taper Angle in Dry Micro Wire EDM

Dry micro wire EDM have been introduced to fabricate complex micro parts with high accuracy. It is a process where gas is used instead of liquid as the dielectric fluid. However, in order to achieve high accuracy, taper angle remains as one of the critical issues. Hence, this paper investigates the effect of process parameters; gap voltage and wire tension; on taper angle in dry micro wire EDM on stainless steel using compressed air as dielectric fluid and tungsten as wire electrode. Empirical model using general factorial method was developed for the estimation of taper angle. Based on the ANOVA, gap voltage has major influence on taper angle. The optimum machining parameters for minimum taper angle were found to be 85 V gap voltage and 14 % wire tension.

Influence of dry micro abrasive blasting on the physical and mechanical characteristics of hybrid PVD-AlTiN coated tools

The current study investigates the effect of the micro abrasive blasting (MAB) on the physical and mechanical characteristics of the cutting tools before and after coating deposition. Cutting tools were subjected to micro blasting by alumina (Al2O3) grains at varying pressure so as to improve the efficacy of the coating process. AlTiN coating of thickness 1.45 μm was deposited onto the tool surface by arc enhanced high power impulse magnetron sputtering (HiPIMS) hybrid deposition technique. The coatings were characterized using nano indentation, atomic force microscopy and micro scratch test. The results of nano indentations on the coated surface revealed the influence of the micro abrasive blasting technique and pressure on the superficial hardness. Surface morphology results showed better-adhered surface in case of cutting tools subjected to micro abrasive blasting before the deposition due to an increase in density of the nucleation sites for growth of aluminum which can be judged with the help of higher aluminum content in the energy dispersive x-ray analysis. The film adhesion of the coating onto the tool substrate is observed to be improved significantly with an increase in blasting pressure in the case of the samples subjected to micro abrasive blasting before coating. Additionally, X-ray diffraction analysis was performed to investigate crystallographic phases. The attained results provide insight concerning the optimum selection of micro abrasive blasting technique along with the pressure, for enhancing the cutting performance of coated tools during the machining of nickel-based superalloy Nimonic C 263.

Precision Control of Kerf in Metal Cutting Using Dry Micro WEDM: Issues and Challenges

Micro dry wire EDM is a process where gas is used as the dielectric fluid instead of a liquid. In this process certain modifications of a wire EDM are needed during the machining operation to achieve stable machining. Optimizing kerf to get high dimensional accuracy is one of the critical issues in micro dry wire EDM. The fundamental modelling for optimum kerf using micro dry wire EDM has not been formulated yet. Due to the complex phenomenon, the prediction of optimum kerf in a micro dry wire EDM process is rather difficult. Hence, the main objectives of this research are to improve the micro dry wire EDM process and to develop mathematical models for optimum kerf using micro dry wire EDM. During the process improvement of micro dry wire EDM, various machining setup will be involve in order to achieve the most stable process. The most stable machining process will be used to prove the developed mathematical models. A mathematical relationship between kerf and process parameters is anticipated. The mathematical models in conjunction with experimental data will eventually produce the desired theory. The developed process and mathematical model of kerf is a breakthrough in fabricating products such as micro tools, molds etc. with optimum kerf and high dimensional accuracy. The successful completion of this research will contribute to the environmental friendly micromachining process.

Dimensional Accuracy in Dry Micro Wire Electrical Discharge Machining

Dimensional accuracy is important in fabricating miniaturized product in order to reduce the material waste and machining cost as well as to achieve a better quality product. This paper presents the analysis and modelling of dimensional accuracy in dry micro wire electrical discharge machining with control parameters of gap voltage and wire tension. The investigation was performed on stainless steel using integrated multi-process micro machine tools DT 110 with compressed air as the dielectric fluid and tungsten as the wire electrode. The dimensional accuracy was determined through kerf width differences of the machined slots. The kerf width was measured using scanning electron microscope. Full factorial was used to design the experiment while analysis of variance (ANOVA) was used to analyse the results as well as to evaluate the adequacy of the developed model. Based on ANOVA, both parameters; gap voltage and wire tension have high influence on kerf width differences. The optimum machining parameters for minimum kerf width differences were found to be 85 V gap voltage and 10 % wire tension. The developed model is adequate since the percentage error (2.13 %) is relatively small. It is recommended that different type of gases should be used for further investigation in order to determine the accuracy of the dry micro wire EDM.

Geotechnical Study of the Aptian Limestone of the Kef Region, Northwestern Tunisia: Evaluation for Industrial Use

This study aims to the initial characterization of Aptian sedimentary limestones in the Kef region located in the North-West of Tunisia in order to use in industrial fields. The limestone samples were collected from three outcrops respectively named Jebel Jerissa, Jebel Hmeima and Jebel Harraba. A geochemical characterization highlights a variation of the weight percentage (wt%) as follows: CaO (53 - 55), MgO (0.04 - 0.28), Al2O3 (0.07 - 0.51), Fe2O3 (0.41 - 2.87), and a loss on ignition (41.62 - 43.35). The other oxides (K2O, SO3, Na2O) are in trace amounts. Mineralogical analysis revealed that limestones contain more than 95% of calcite and the clay impurities are the minor phases detected. Petrographic study showed that these limestones are packestone-wakestone type. The hardness of Aptian limestones crosses the upper limit of the hard domain. Geotechnical tests reveal a Dry Micro Deval (MDS) coefficient varying from 23% to 33%, a Wet Micro Deval (MDH) coefficient with values oscillating around 26% to 36%, a Los Angeles coefficient (LA) about 25% against a value of the compressive strength ranging from 593 Kg/cm2 to 866 Kg/cm2. The gravimetric tests highlighted a flexural strength value from 106 Kg/cm2 at 208 Kg/cm2, while the ultrasonic coefficient oscillates from 4876 m/s to 5233 m/s, indicating the low porosity of these limestone (0.5% to 1%). The density recorded an average value of 2.50 g/cm3. The various properties studied have proved that the limestone studied can be used in various industrial fields such steel industry, aggregate, cement industry and marble.

Inhaled dry salt micro particles in the treatment of bronchopulmonary dysplasia: a five case series report

Background. Despite current medical ad-vances, to this day there is no single medi-cal intervention to effectively prevent or treat bronchopulmonary dysplasia (BPD) in both preterm and term infants. Along with protective ventilation strategies, vari-ous drugs are being used or are being re-searched at this very moment, with the sole purpose of improving the general outcome for these patients. Inhaled dry salt micro particles therapy is now one of them. Materials and methods. This report pre-sents five patients, diagnosed with severe BPD. All of them received, complemen-tary to classical BPD management and respiratory support, continuous inhaled dry salt micro particles, via SaltMed car-tridges, for a period of 12 to 30 days. After only 24 hours of administration, we were able to observe a significant improvement in respiratory function and dynamics. It was possible to use a lower fraction of in-spired oxygen (FiO2), mean airway pres-sure (MAP) and peak inspiratory pressure (PIP) in all mechanically ventilated pa-tients. Higher tidal volumes were recorded and we observed improvement in oxygen-ation indexes.Conclusion. Continuously inhaled dry salt micro particles, administered complemen-tary to classic BPD management, could improve respiratory and overall morbid-ity and mortality in infants with any form of BPD. Further study of these possible effects is needed, as there is no data pub-lished on this matter so far.

Novel processes and related technologies for micro metal forming

Processes with high energy assistance, such as ultrasonic vibration or local heating, and automatic assembly system in a progressive die were developed for micro metal forming in order to improve process accuracy of micro product due to some size effects in this study. Furthermore, application of textured diamond like carbon (DLC) coating on die surface was attempted to improve the tribological performance for dry micro forming operations.

An experimental and analytical study based on fractal theory of satin fabrics in unsaturated permeability

Prediction of relative permeability is important to avoid dry spots or micro voids in the liquid composite molding process. Most of previous studies focused on plain and twill, but few are about stain and none of them provide explicit equation to calculate accurate values of unsaturated permeability. The main purpose of this work is to first propose a new model which is proposed mainly based on fractal theory and has no empirical constant in the expression, to calculate the permeability of satin fabric. And then we employ a new experimental method to calculate the unsaturated permeability. Finally, a contrast experiment of 5-harness fabric and 8-harness fabric is designed at different injection pressures, and the accurate values of permeability are obtained. The results show that unsaturated and saturated permeabilities are in the same order of magnitude; furthermore, unsaturated permeability is 77% of saturated permeability in 5-harness fabric and 73% in 8-harness fabric.

Comparison of Conventional and Dry Electrical Discharge Machining

For manufacturing of micro holes ElectricalDischarge Machining (EDM) can be used, which is well-established due toits thermal working principle that allows almost force free machining independent of the material’s mechanical properties. The importance of this production technology is increasing, especially for the machining of ceramic materials, which are required in many applications within the field of microtechnology. However, the production of precise micro holes with complex geometries and high aspect ratios is associated with a many challenges. Hightool electrode wear, low material removal rate and small gap widths are observed in the process. This paper presents an optimized dry EDM technology for the manufacturing of micro holes in Si3N4-TiNceramic. The experiments were carried out with different energy influencing process parameters for the spark discharge and flushing pressure, which were systematically evaluated by methods of statistical Design of Experiments. Subsequently dry EDM and conventional EDM micro drilling processes were compared and the differences between both processes were evaluated. The influences of liquid and gaseous dielectric are analyzed in terms of process stability and axis movements.

The effect of grinding aids on dry micro fine grinding of feldspar

The aim of this study was to investigate dry micro-fine grinding of sodium feldspar (albite) with and without grinding aids using a vertical stirred ball mill. The effect of amine based various grinding aids (BMA 1923, BMA 1517, KATPLAST 54 and GRACE XS 304) and dosages (500, 1000 and 2000g/t) were investigated and test results were evaluated based on the product size (d80) and specific energy consumption. Tests revealed that the grinding energy required to reach target grinding size (d80=10 micron) was reduced up to 60% using grinding aids. BMA 1923 was determined to be the most effective grinding aid in terms of target d80 except that lower sizes could be reached with BMA 1517 at the same dosage and similar energy consumptions.

J2240102 弾性表面波を用いた粉体フィーダーの提案([J224-01]『マイクロ・ナノ機械の信頼性』のための材料創製・測定・解析技術 ナノ構造加工・プロセス)

In order to operate dry micro powder, we propose a powder feeder driven by surface acoustic wave (SAW). The powder feeder consists of one interdigital transducer (IDT) and two triangular guide walls. The IDT has 20 electrode pairs, a pitch size of 400 μm, and an aperture width of 5 mm, while the guide wall, located at an inclination angle of 5° against the central axis of the IDT, has a length of 35 mm and a minimum 300-μm interval between walls. The IDT and the guide walls are made of a 1-μm Al layer and were fabricated on a piezoelectric wafer (127.8-degree y-rotated x-propagating LiNbO_3) by one photolithography process. To investigate characteristics of the powder feeder, we carried out a transport experiment by using copper powder whose particle size was about 10 μm. As a result, when a signal of 31.6-MHz radio frequency was applied to the IDT, the powder was gradually collected during transport to the opposite side of the IDT until the powder particles arrived at the substrate edge one after the other and fell down through the narrow part between the guide walls. This result demonstrates that, by arranging the guide walls, the powder can be accurately poured down a target point.

Application of Dry Nano Powder Inverse Imprint Technology in Transferring and Replication of Micro Patterns

Abstract This research aims to develop a new dry nano powder inverse imprint technology, and probe into transferring and replication of micro patterns. First, a polydimethylsiloxane (PDMS) mould surface, with micro patterns of grating structures, undergo activation treatment with oxygen plasma in order to improve mould surface energy, and thus, spin coat photoresist onto the surface more easily. Then, the surface is heated to restore its hydrophobicity, and by means of nano powder, micro patterns are transfer printed onto the polymethylmethacrylate (PMMA). Research results show that dry nano powder soft coat transferring and forming technology can accurately reproduce the required patterns. In the experiment, gas assisted nano powder imprint technology is used to apply even pressure, coupled with even temperature rise for solidification, then, patterns can be effectively transfer printed and completely formed. Further, these patterns are in perfect contact with the PMMA surface, thus, greatly increasing the valid imprint area and enhancing transferring reproductiveness. The technology integrates technologies, such as, soft lithography, solidifying photoresist, and gas assisted pressure application, and is utilized to transfer print micro patterns in a grating structure, and thus, complete the transferring process of dry micro structure patterns.

Energy Distribution into Electrodes in Wet and Dry Micro EDM

Energy Distribution into Electrodes in Wet and Dry Micro EDM

Floor cleaning: effect on bacteria and organic materials in hospital rooms

Routine surface cleaning is recommended to control the spread of pathogens in hospital environments. In Norway, ordinary cleaning of patient rooms is traditionally performed with soap and water. In this study, four floor-mopping methods--dry, spray, moist and wet mopping--were compared by two systems using adenosine triphosphate (ATP) bioluminescence (Hygiena and Biotrace). These systems assess residual organic soil on surfaces. The floor-mopping methods were also assessed by microbiological samples from the floor and air, before and after cleaning. All methods reduced organic material on the floors but wet and moist mopping seemed to be the most effective (P < 0.001, P < 0.011, respectively, ATP Hygiena). The two ATP methods were easy to use, although each had their own reading scales. Cleaning reduced organic material to 5-36% of the level present before cleaning, depending upon mopping method. All four mopping methods reduced bacteria on the floor from about 60-100 to 30-60 colony-forming units (cfu)/20cm2 floor. Wet, moist and dry mopping seemed to be more effective in reducing bacteria on the floor, than the spray mopping (P=0.007, P=0.002 and P=0.011, respectively). The burden of bacteria in air increased for all methods just after mopping. The overall best cleaning methods seemed to be moist and wet mopping.

Nano-lamination in amorphous carbon for tailored coating in micro-dry stamping of AISI-304 stainless steel sheets

Nano-lamination is a new way to make full use of multi-layered structure for coating instead of the mono-layered coating system. Different from the conventional nano-lamination approach, where two different kinds of material system are deposited in layers, the amorphous carbon layer, a-C:H, is alternatively deposited with graphite-like cluster layer, resulting in an amorphous carbon base nano-laminated coating. In this nano-lamination, the pulse bias voltage and the pulse duration time are programmed to control the bi-layer thickness and number of laminates. Furthermore, the mechanical properties are also controllable by varying the bi-layer thickness and sub-layer ratio. In this paper, the effect of number of layers and bi-layer thickness on the mechanical properties is investigated by the nano-indentation technique. Higher hardness and Young's modulus is attained with reduction of bi-layer thickness. The scratching test of this nano-laminated coating is made to demonstrate that it has sufficient scratch load above 100 N. Furthermore, a dry micro stamping test is performed to prove that this nano-laminated coating has sufficient wear-toughness enough to make dry stamping in 10,000 times in practice even if it has nearly the same Young's modulus and hardness as the mono-layered coating. No delamination or break-away occurs on the ironed surface of coated tools while severe delamination is observed in the conventional mono-layered coating.

Shock wave driven microparticles for pharmaceutical applications

Ablation created by a Q-switched Nd:Yttrium Aluminum Garnet (Nd:YAG) laser beam focusing on a thin aluminum foil surface spontaneously generates a shock wave that propagates through the foil and deforms it at a high speed. This high-speed foil deformation can project dry micro- particles deposited on the anterior surface of the foil at high speeds such that the particles have sufficient momentum to penetrate soft targets. We used this method of particle acceleration to develop a drug delivery device to deliver DNA/drug coated microparticles into soft human-body targets for pharmaceutical applications. The device physics has been studied by observing the process of particle acceleration using a high-speed video camera in a shadowgraph system. Though the initial rate of foil deformation is over 5 km/s, the observed particle velocities are in the range of 900–400 m/s over a distance of 1.5–10 mm from the launch pad. The device has been tested by delivering microparticles into liver tissues of experimental rats and artificial soft human-body targets, modeled using gelatin. The penetration depths observed in the experimental targets are quite encouraging to develop a future clinical therapeutic device for treatments such as gene therapy, treatment of cancer and tumor cells, epidermal and mucosal immunizations etc.