Compressed Air Jet Research Articles

Erosion characteristics of Teflon under different operating conditions

Abstract The present study investigated the solid particle erosion characteristics of Teflon under different impingement angles (15–90°), impact velocities (30–50 m/s), erodent sizes (300–600 μm) and stand-off distances (15–25 mm) at ambient temperature. The Teflon showed ductile erosion behavior exhibited a peak erosion rate at a 30° impact angle. The design of experiments approach utilizing Taguchi’s orthogonal arrays was applied to test the specimens on a compressed air jet type erosion test rig. Erosion efficiency (η) values were 0.29–16.7%, which indicates micro-plugging, plastic deformation and micro-cutting action as dominating erosion mechanisms. The experimental results are closer to the theoretical model. An optimal parameter combination was determined, which leads to minimization of erosion rate. Analysis of variance (ANOVA) was performed on the measured data and signal-to-noise (S/N) ratios. A mathematical correlation, consistent with the experimental observations, is proposed as a predictive equation for estimation of erosion rate of tested material. The morphology of erodent surfaces was examined by using scanning electron microscopy (SEM). Possible erosion mechanisms are discussed.

Prediction of automated sorter performance utilising a Monte Carlo simulation of feed characteristics

To evaluate the performance of an automated sorter typically requires testing of the material to be separated on a full-scale device. In many cases limitations on the quantity of material available for testing, and the costs of the test programme, may limit the range of operating conditions examined. In this paper we propose a method for prediction of automated sorter performance, based on material and machine characteristics, which can be used to evaluate how changes to these characteristics affect performance.The distribution of particles at the point of identification is a key parameter in determining sorter efficiency. A Monte Carlo simulation was used to predict the position of particles on a feed conveyor used to deliver particles to the identification zone. The results produced show that this technique can be used to simulate the particle distribution achieved by an operating automated sorter (TiTech Combisense).Sorter efficiency depends on firstly accurate identification of the target product (typically deflected) and secondly the precision of selective deflection, using compressed air jets or mechanical actuators. A reduction of deflection efficiency is generally caused by the co-deflection of “non-target” particles resulting from their close proximity to particles being deflected. In order to fine tune the sorter model data from automated sorting experiments were analysed to provide information on deflection efficiency over a wide range of operating conditions. The sorter model developed for the −10+6mm size fraction was shown to provide a realistic prediction for coarser (−15+10mm) particles.The sorter model was used to demonstrate that sorter performance could be significantly improved by improved particle feed distribution. When a high separation efficiency is required for a sorting application a 3 stage process was predicted to have a higher separation efficiency than a single stage process using the same number of sorters.

Effective Injection of Ceramics Nanoparticle Pastes into Plasma Spray for Speedy Layer Formation

Thermal nanoparticle spraying was developed to create fine ceramics layers on free surfaces. Resin slurry containing ceramics nanoparticles were atomized by a compressed air jet in a chamber, and the resulting micro mists of composited droplets were effectively injected from a tubular nozzle into the plasma flare. Alumina particles with average diameters of 200 nm were dispersed into the acrylic liquid resin at 40% volume ratio. The microsized mist droplets with average diameters of 20 μm were first formed using the compressed air jet under pressure of 2 atm, and then introduced into the arc plasma with an argon gas spray of 50 slpm in flow rate. The alumina layer of 300 μm thickness was formed successfully on the SUS-304 substrate of 50×50×5 mm in size, which was placed at a distance of 100 mm from the plasma gun, and a higher speed coating at the deposition rate of 50-100 μm/s was achieved. Crystal phases of the coated layer were analyzed by X-ray diffraction. The cross sectional microstructures were observed with optical and scanning electron microscopy. Porosities of the coated layers were estimated through dielectric constant measurements using terahertz wave spectroscopy.

Synthesis of MWCNT nanofluid and evaluation of its potential besides soluble oil as micro cooling-lubrication medium in SQL grinding

Grinding, being a high specific energy involving process, essentially requires a high-performance cutting fluid when small quantity lubrication (SQL) is employed. In SQL, a small volume of metal working fluid is broken into micro-droplets by a compressed air jet so that the aerosol jet cools and lubricates machining zone more efficiently than flood cooling. In the present work, a new generation grinding fluid was indigenously synthesized by dispersing multi-walled carbon nanotube (MWCNT) in deionized water for SQL grinding of steel by an alumina wheel, and its capability was evaluated in depth in comparison with the commercially used soluble oil. It was observed that a maximum of 1 vol% MWCNT could be dispersed without any settling tendency over 48 h, which subsequently rendered the highest thermal conductivity to the nanofluid sample. It was approximately 35 % higher than that of soluble oil. In a simulative ball (Al2O3) on disc (hardened AISI 52100 steel) test, it was further found that this nanofluid sample was 30 % more lubricious than its counterpart. The higher heat dissipation ability and better lubricity finally resulted in remarkably superior performance of MWCNT nanofluid to that of soluble oil. In comparison with the later MWCNT nanofluid, in particular, at 3 bar of atomizing air pressure and 350 ml/h flow rate, could offer substantially better G ratio, significantly reduce tangential grinding force and produce comparable surface finish. Additionally, presence of more number of long and sheared chips and less spherical chips in the collected sample was a clear indicator of reduction in grinding temperature when soluble oil was replaced by MWCNT in SQL mode.

The Rationalization of Parameters of the Sucion Intake Device for Packed Bulk Construcion Materials

Pneumatic transport is one of the most progressive means of mechanization and automation of loose goods transportation. It is used in aluminium, chemical, food, textile, construction and other industries. However, wide use of pneumatic transport is limited by the incomplete information on this subject. In this article provides a description of the design of useful models of the suction intake device пневмотранспортной installation. A useful model was developed with the participation of the author of the staff of the Department of transport and technological machines architectural-building University. The author has developed stages of the suction intake unit and carried out theoretical and experimental research on each step to achieve the most effective operation of the device. In view of the fact that for the main parameters of the suction intake devices of the theory of destroying the fabric of a flooded the air flow is not developed to a sufficient degree, the author has studied the process of propagation and interaction of flooded jet with the surface. The article systematized and presents the results of experimental research on the interaction of flooded jets of air sealing with building materials of different kinds. The author determined the optimal parameters of the process of packed loosening material jets of compressed air at the fence material suction fence device.

Performance improvement of minimum quantity lubrication (MQL) technique in surface grinding by modeling and optimization

Abstract Although cutting fluids have many technological advantages in grinding operation, they have serious ecological and economic problems. On the other hand, in dry grinding, there exist challenges of probable thermal damages on the workpiece surface. One efficient alternative is minimum quantity lubrication (MQL) technique. MQL technique uses a spray of small oil droplets in a compressed air jet. The lubricant is sprayed directly into the cutting zone. Therefore, it provides efficient lubrication and improves cutting performance without using huge flow of fluids. In this research, the effect of mechanical properties of workpiece (especially hardness) on performance of MQL in grinding is investigated. Two soft steels (CK45 and S305) and two hard steels (HSS and 100Cr6) were ground with an aluminum oxide grinding wheel as case studies. A comparative study of three cooling conditions including: dry, conventional fluid cooling and MQL have been carried out. Output parameters were grinding forces, friction coefficient, surface roughness, surface morphology and form of the chips. The results show that MQL can considerably decreases grinding forces and friction coefficient in soft and hard steels. Furthermore, the surface finish and quality are significantly better when MQL technique is applied in grinding of hard steels. But in case of soft steels, surface finish is the worst in comparison to other grinding environments. So, it is anticipated that MQL may not be suitable for soft steels limiting its usability range towards harder steels. Hence, to improve the performance of grinding of soft steels using MQL technique, modeling and optimization of surface roughness have been conducted. The second order surface roughness estimation model based on RSM (response surface method) has been developed. Three process parameters including depth of cut, cutting speed and feed rate have been considered for the model development. The model has been tested and validated through ANOVA (analysis of variance). Finally, the GA (genetic algorithm) gives minimum value of surface roughness and the corresponding optimal machining parameters was in close agreement with experimental test.

Coupled fluid and solid evolution in analogue volcanic vents

AbstractVolcanic eruptions emit rock particulates and gases at high speed and pressure, which change the shape of the surrounding rock. Simplified analytical solutions, field studies, and numerical models suggest that this process plays an important role in the behavior and hazards associated with explosive volcanic eruptions. Here we present results from a newly developed laboratory‐scale apparatus designed to study this coupled process. The experiments used compressed air jets expanding into the laboratory through fabricated rock analogue material, which evolves through time during the experiment. The compressed air was injected at approximately 2.5 times atmospheric pressure. We fabricated rock analogues from sand and steel powder samples with a three‐dimensional printing process. We studied the fluid development using phase‐locked particle image velocimetry, while simultaneously observing the solid development via a video camera. We found that the fluid response was much more rapid than that of the solid, permitting a quasi‐steady approximation. In most cases, the solid vent flared out rapidly, increasing its diameter by 20 to 100%. After the initial expansion, the vent and flow field achieved a near‐steady condition for a long duration. The new expanded vent shapes permitted lower vent exit pressures and larger jet radii. In one experiment, after an initial vent shape development and establishment of steady flow behavior, rock failure occurred a second time, resulting in a new exit diameter and new steady state. This second failure was not precipitated by changes in the nozzle flow condition, and it radically changed the downstream flow dynamics. This experiment suggests that the brittle nature of volcanic host rock enables sudden vent expansion in the middle of an eruption without requiring a change in the conduit flow.

Improvised arrangement of aerosol delivery to the ventilator dependent patient.

Sir, The patients supported by invasive mechanical ventilation (IMV) often require aerosol therapy for bronchodilators and inhaled corticosteroids. Mucolytics, antibiotics and other medications can also be given by this method.[1] Aerosol therapy is indicated in these patients for management of asthma, bronchospasm, increased airway resistance, intrinsic positive end-expiratory pressure, difficult to wean, and ventilator dependent patients. Aerosol therapy helps in reducing work of breathing by decreasing pulmonary dynamic hyperinflation and resistance of the respiratory system.[2] Effective delivery of aerosol to the lungs depends on formulation of drug, aerosol generator, and technique of administration. Various devices are used to generate aerosol, but pressurized metered-dose inhaler (pMDI) and nebulizers are the most commonly used in patients supported by IMV. The commonly used nebulizers are the jet and the ultrasonic devices. Vibrating mesh nebulizers and intratracheal nebulizing catheters are newer aerosol generating devices. These devices are connected to the inspiratory limb of the ventilator circuit by specific adaptors attached to the artificial airway. Several ventilator parameters also affect the effective delivery of aerosol to the patient. pMDI require a specific adaptor, a spacer and synchronization with ventilator for effective delivery of aerosol. If properly administered pMDI and nebulizers are equally effective in delivery of aerosol therapy to the mechanically ventilated patients although using nebulizers is the common practice. Jet nebulizers use a jet of compressed air or oxygen, while ultrasonic nebulizers use piezo-electric crystals vibrations to produce aerosol. New vibrating mesh nebulizers use a vibrating mesh or plate with multiple apertures to generate aerosol. Jet nebulizers are cost-effective and easy to use and adding a reservoir between jet nebulizer and endotracheal tube increases aerosol delivery. Some new generation ventilators have an in-built mechanism for supporting the jet or ultrasonic nebulizers. These ventilators synchronize inspiratory flow and volume to activate the jet nebulizer intermittently during inspiration.[3] Over a period of time, these compatible jet nebulizers tend to be damaged or lost. Many ventilators are not compatible with jet nebulizers or newer aerosol therapy devices. In these situations, often a jet nebulizer operated by compressed oxygen from wall system or cylinder, is attached to the inspiratory limb of breathing circuit. A minimum flow of 6-8 L is required to generate the aerosol. The volume added by this method can affect ventilator parameters and can be very harmful, especially to the pediatric patients who have small lung volumes. Self-inflating manual resuscitator is a breathing system that uses nonrebreathing unidirectional valves. A pressure limiting device is present near inspiratory valve to prevent barotrauma in all infant/child and some adult manual resuscitators. There is a connection port to attach a reservoir bag at the bag inlet.[4] In this improvized arrangement, a T-adaptor with jet nebulizer assembly is attached to the above mentioned connection port [Figure 1]. A one-way valve [Direction, Figure 1] is attached to the free end of the T-adaptor to prevent aerosol loss and direct airflow to the bag inlet when it is re-expanding. Presence of resuscitation bag next to the jet nebulizer and addition of 3-4 mL of normal saline to the drug can help in effective delivery of aerosol. The tidal and minute volumes can be controlled manually to deliver aerosol safely to the ventilator dependent patients where compatible aerosol device is not available. Figure 1 Improvized arrangement

Contactless object manipulation using multiple air jets on planar surface (Experimental case studies for small control range with continuous air jets)

We propose a technology for manipulating the position and attitude of an object on a planar surface in a contactless manner. This technology involves multiple ejectors that stream jets of compressed air onto an object from various directions. By regulating air jet directions and volumes, the object can be actively "force closured" and its position and attitude can be manipulated freely. As the first step of this research, we discuss the fundamental ideas and the technological challenges as a manipulation method. Next we provide a preliminary investigation with one degree-of-freedom experimental system. Based on this, we examine two DOF system with three air jets and finally three DOF system with four air jets.

압축공기 분사시스템을 이용한 유류오염 해안의 효율적 정화 및 이에 따른 미생물군집분석

본 연구의 목표는 압축공기분사시스템을 이용하여 원유로 유출이 된 해안을 정화함에 있어서 그 정화효율성과 정화 전후의 총석유탄화수소(total petroleum hydrocarbon; TPH) 농도 및 미생물군집변화를 관찰함으로써 그 최적 정화과정을 이해하기 위한 기초자료를 얻고자 하는 것이다. 압축공기제트시스템을 2-5회 연속적용 시 오염지의 TPH가 약 66%까지 저감이 된 반면에 대조구인 해수를 펌핑한 경우에는 40% 정도의 저감효과가 관찰이 되었다. 압축공기의 분사 후 PCR-DGGE에 의한 미생물군집분석 결과에서는 유류분해미생물의 군집은 확인이 되지 않았다. 이는 정화에 의한 낮은 TPH 농도(약 100 mg/kg 수준, 탄소원), 처리환경에 내재적인 제한적인 질소 및 인의 농도에 기이한 것으로 판단된다. 따라서 잔여분의 유류는 에어제트시스템을 적용시 제한적 영양염류(질소 및 인 등)를 적절한 방식과 농도로 투여할 경우 거의 완전하게 제거가 가능할 것으로 사료된다. 향후 본 기술은 고농도의 유류 및 유기물로 오염된 다양한 수질환경 및 토양환경의 효율적이고 환경친화적인 정화에 활용이 될 것으로 기대된다. The objectives of this study were to investigate effectiveness of the Compressed Air Jet (CAJ) System for cleaning up shorelines contaminated with crude oils and to examine effects of the system on total petroleum hydrocarbon (TPH) removal and microbial community changes before and after remediation of the oil-contaminated shorelines. These data will lead to better understanding of optimized remediation process. About 66% of TPH reduction was observed when the contaminated site was treated with the CAJ System 2, 3, 4, and 5 times. This treatment system was more efficient than the seawater pumping system under similar treatment conditions (by 40%). By the way, little oil degrader communities were observed despite a potential function of the air jet system to stimulate aerobic oil degraders. The apparent low population density of the oil degraders might be as a result of low concentration of TPH as a carbon source and limiting nutrients such as nitrogen and phosphorus. It was proposed that the CAJ System would contribute significantly to removal of residual oils on the shorelines in combination with addition of these limiting nutrients.

Utilization of teflon and aluminum oxide for wheel cleaning in Minimum Quantity Lubrication (MQL) grinding

Researches concerning cooling-lubrication optimization in grinding have been conducted to contribute to a more sustainable process. An alternative to flood coolant is minimum quantity lubrication (MQL), which spray oil droplets in a compressed air jet. However, problems related to wheel cleaning were reported, due to wheel loading by a mixture of chips and oil, resulting in worsening of surface quality. This work aims to evaluate the viability of Teflon and aluminum oxide for wheel cleaning, compared to MQL without cleaning and MQL with cleaning by compressed air, through the following output variables: surface roughness, roundness, wheel wear, grinding power and acoustic emission. Vickers microhardness measurements and optical microscopy were also carried out. The results showed that both materials were efficient in cleaning the wheel, compared to MQL without cleaning, but not as satisfactory as compressed air. Much work is to be done in order to select the right material for wheel cleaning.

Fluoride Release and Recharge Ability of a Novel Fluoride Release Composite Resin

Objective: To evaluate the fluoride release rates and fluoride recharge capability of a experimental resin composite, a compomer, a giomer and a resin-modified glass ionomer cement. Methods: Ten disc specimens of each material were prepare and polished with abrasive paper, followed by clearing with oil-free compressed air jet. The specimens were placed in a plastic vessel containing 5ml deionized water immediately after fabrication. Each specimen was removed and put to a new a vessel containing deionized water each day, and the sample solution was test for fluoride concentration each day using a compound fluoride ion selective electrode and a conductivity meter. All specimens were removed from container after 28 days and were recharged by immersing in a fluoride foam solution for four minutes. Then fluoride release from these recharged samples was measured daily for 7 days. Recharge was repeated three times. Result: Fuji II LC demonstrated the highest fluoride release ( p <0.01), followed by experimental resin and Compoglass. Both Beautufil and Charisma presented the lowest fluoride release ( p <0.01) during the first two weeks. All materials except Charisma demonstrated a sharp decline of fluoride release, followed by a comparatively stable stage of fluoride release for about twenty days. All materials presented fluoride release increase substantially one day after recharge but declines rapidly almost to the baseline level after 2 days except for Fuji II LC that showed a continual fluoride release for 5 days. Conclusion: The experimental composite resin has a capability of fluoride release and recharge that are comparable to compomers.

Development of Thermal Spraying and Coating Techniques by Using Thixotropic Slurries Including Metals and Ceramics Particles

Thermal nanoparticles coating and microlines patterning were newly developed as novel technologies to fabricate fine ceramics layers and geometrical intermetallics patterns for mechanical properties modulations of practical alloys substrates. Nanometer sized alumina particles were dispersed into acrylic liquid resins, and the obtained slurries were sputtered by using compressed air jet. The slurry mists could blow into the arc plasma with argon gas spraying. On stainless steels substrates, the fine surface layers with high wear resistance were formed. In cross sectional microstructures of the coated layers, micromater sized cracks or pores were not observed. Subsequently, pure aluminum particles were dispersed into photo solidified acrylic resins, and the slurry was spread on the stainless steel substrates by using a mechanical knife blade. On the substrates, microline patterns with self similar fractal structures were drawn and fixed by using scanning of an ultra violet laser beam. The patterned pure metal particles were heated by the argon arc plasma spray assisting, and the intermetallics or alloys phases with high hardness were created through reaction diffusions. Microstructures in the coated layers and the patterned lines were observed by using a scanning electron microscopy.

Development and testing of a laser-based decontamination system

Decontamination of radioactive concrete surfaces may be necessary during operation or decommissioning of nuclear power plants. Usually only the upper layers of the concrete structure are contaminated and are removed using labor-intensive mechanical milling processes. Production of a large amount of dust, which can lead to secondary contamination, is inherent to these processes. Improvements in high-energy laser technology have now made it possible for laser radiation to be used in decontamination technologies for the removal of concrete layers. A decontamination unit comprising a diode laser with a beam power of 10kW in continuous wave (CW) mode in combination with an autonomous manipulator was developed for use in nuclear plants. The laser beam melts the concrete surface to a depth of approximately 5mm. Compressed air jets then detach the molten layer from the concrete surface and convey it to a suction system, with which it is transported to a collection container. Most of the radionuclides are trapped in the solidifying melt particles, which form an extremely stable effluent well suited to long-term storage. A relatively small amount of dust is generated in the process. Because there is no backlash during energy transfer, the laser device carrier can be designed to be lightweight and flexible. A specially developed manipulator that can move freely along walls and ceilings by means of suction plates is used for the carrier unit. This results in short setup times for preparing for use of the device and minimal personnel exposure to the radiation. Experiments were conducted on a concrete wall to demonstrate the functionality of the overall system in realistic conditions. An optimal ablation rate of 2.16m²/h at an ablation depth of 1–5mm was achieved. Today’s commercially available diode lasers with powers higher than 50kW enable ablation rates of >10m²/h to be achieved and hence make these laser-based systems competitive alternatives to mechanical systems.

Obtaining Slots and Channels by using a 1070 nm Wavelength Laser

Slots and channels are sometimes necessary in machine building; the surfaces of the slots and channels could be obtained by means of a laser beam machining equipment. Essentially, the material removal from the workpiece needs the development of thermal phenomena of melting and vaporizing and of dynamic phenomena, respectively, by which the melted and vaporized material is moved from the machining zone. The paper includes the results of the researches concerning the possibilities to use 1070nm wavelength laser equipment whose output power is of 300W, in order to obtain slots and channels in metallic test pieces. The sizes of the parameters able to characterize the machined surface are influenced by the machining conditions. The theoretical analysis of the machining process highlighted the necessity of sending a compressed air jet along the laser beam axis and of an adequate selection of the machining parameters. Experimental researches were developed by changing the speed of the relative motion between the laser spot and the test piece. Empirical relations were established by mathematical processing of the experimental results. The empirical relations highlight the influence exerted by speed between the test piece and the laser beam on the depth of the channels thus generated.

Influence of Periodic-Blowing Actuators on the Wake and the Total Drag of Generic 3D Car Models

Within the scope of the Collaborative Research Centre SFB 557 of Complex Turbulent Shear Flows at TU Berlin this project deals with the reduction of the total drag of generic three-dimensional car models (Ahmed body) by means of Active Flow Control (AFC). The highly complex wake region behind these models consists of steady longitudinal vortices occuring at the outer slant edges depending on the slant angle and unsteady lateral vortex structures occurring at the upper and lower edge of the base between the longitudinal structures. During the experiments these vortex structures were influenced by different actuation concepts using steady- and periodic-blowing compressed-air jets. Avariation of the forcing intensity and frequency (Strouhal number) showed a strong influence of these parameters on the effectiveness of the actuation. The isolated use of the different actuation concepts leads to a drag reduction of up to 5.6% (steady blowing) or 5.1% respectively (periodic-blowing slot). The combinati...

압축공기의 흡입과 분사를 위한 멀티 에어건의 설계 개발

이 논문의 목적은 작업장에서 사용하기 위한 에어건의 개발에 관련된 것이다. 에어건은 공작기계를 사용하는 산업현장에서 공작물 칩과 절삭유의 제거를 위한 도구이다. 그리고 그것은 일반적으로 압축공기를 분사하는 용도로 사용된다. 작업자는 에어의 흡입과 분사를 위해 각각의 에어건을 준비하여야 한다. 따라서 우리는 새로운 에어건을 개발하였다. 이 논문에서 우리는 에어건의 설계와 분석을 위한 연구를 한다. 에어건은 몸체, 파이프, 개폐 유닛, 전환 유닛, 에어 튜브 그리고 조립을 위한 요소들로 구성된다. 개발된 에어건은 그 효율을 확인하기 위해 실험된다. The purpose of this paper is concerned with a development of air gun for use at work. A air gun is the tool to remove of cutting fluid and workpiece chip in industrial field used machine tool. And it generally is used to shoot a jet of compressed air. Worker must prepare respectively air gun for suction and shooting a jet of compressed air. Therefore we has developed new air gun. In this paper we research for design and analysis of it. The air gun is composed of body, pipe, opening and shutting unit, turning unit, air tube and elements for fabrication. The developed air gun is experimented to confirm the efficiency.

Modeling and analyzing the effects of air-cooled turning on the machinability of Ti–6Al–4V titanium alloy using the cold air gun coolant system

This study provides the mathematical models for modeling and analyzing the effects of air-cooling on the machinability of Ti–6Al–4V titanium alloy in the hard turning process. A cold air gun coolant system was used in the experiments and produced a jet of compressed cold air for cooling the cutting process. The air-cooling process seems to be a good environment friendly option for the hard turning. In this experimental investigation, the cutting speed, feed rate and cutting depth were chosen as the numerical factor; the cooling method was regarded as the categorical factor. An experimental plan of a four-factor (three numerical plus one categorical) D-optimal design based on the response surface methodology (RSM) was employed to carry out the experimental study. The mathematical models based on the RSM were proposed for modeling and analyzing the cutting temperature and surface roughness in the hard turning process under the dry cutting process and air-cooling process. Tool wear and chip formation during the cutting process were also studied. The compressed cooling air in the gas form presents better penetration of the lubricant to the cutting zone than any conventional coolants in the cutting process do. Results show that the air-cooling significantly provides lower cutting temperature, reduces the tool wear, and produces the best machined surface. The machinability performance of hard turning Ti–6Al–4V titanium alloy on the application of air-cooling is better than the application of dry cutting process. This air-cooling cutting process easily produces the wrinkled and breaking chips. Consequently, the air-cooled cutting process offers the attractive alternative of the dry cutting in the hard turning process.

Prediction of Surface Roughness in Compressed Air Jet Assisted High Speed End Milling of Silicon Using Diamond Coated Tools

The majority of semiconductor devices are made up of silicon wafers. Manufacturing of high-quality silicon wafers includes numerous machining processes, including end milling. In order to end mill silicon to a nano-meteric surface finish, it is crucial to determine the effect of machining parameters, which influence the machining transition from brittle to ductile mode. Thus, this paper presents a novel experimental technique to study the effects of machining parameters in high speed end milling of silicon. The application of compressed air, in order to blow away the chips formed, is also investigated. The machining parameters’ ranges which facilitate the transition from brittle to ductile mode cutting as well as enable the attainment of high quality surface finish and integrity are identified. Mathematical model of the response parameter, the average surface roughness (Ra) is subsequently developed using RSM in terms of the machining parameters. The model was determined, by Analysis of Variance (ANOVA), to have a confidence level of 95%. The experimental results show that the developed mathematical model can effectively describe the performance indicators within the controlled limits of the factors that are being considered.

Improving minimum quantity lubrication in CBN grinding using compressed air wheel cleaning

The application of minimum quantity lubrication (MQL) in grinding has emerged as an alternative for reducing the abundant flow of cutting fluids, thus achieving cleaner production. Although considered an innovative technique in grinding operations, its widespread application is hindered due primarily to the high heat generation and wheel pore clogging caused by machined chips, harming the final product quality and increasing tool wear on the machine. This study sought to improve MQL use in grinding. In addition to the conventional MQL injected at the wheel/workpiece interface, a compressed air jet was used to clean the mixture of MQL oil and machined chips from clogged wheel pores. Experiments were conducted using external cylindrical plunge grinding on AISI 4340 quenched and tempered steel, and a vitrified cubic boron nitrite (CBN) wheel. The cooling-lubrication methods employed were the conventional flood coolant application, MQL (without cleaning), and MQL with a cleaning jet directed at the wheel surface at different angles of incidence. The main goal of these experiments was to verify the viability of replacing the traditional abundant flow of cutting fluid with MQL and wheel cleaning. The analyses were conducted by measuring the following output variables of the process: workpiece surface roughness and roundness errors, diametrical wheel wear, acoustic emission generated by the process, and metallographic images of the ground surface and subsurface. Results show the positive effects of implementing the cleaning jet technique as a technological improvement of minimum quantity lubrication in grinding in order to reduce the usage of cutting fluids. The MQL technique with cleaning compressed air jet, for a specific angle of incidence (30°), proved to be extremely efficient in the improvement of the surface quality and accurate workpiece shape; it also reduced wheel wear when compared to the other cooling-lubrication methods that were tested (without a cleaning jet).