The Experts below are selected from a list of 3219 Experts worldwide ranked by ideXlab platform
M Papini - One of the best experts on this subject based on the ideXlab platform.
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aerodynamic focusing of an Abrasive air Jet and its effect on machining resolution
International Journal of Machine Tools & Manufacture, 2019Co-Authors: Joshua Palumbo, Jan K. Spelt, M PapiniAbstract:Abstract To decrease the size of the eroded footprint resulting from Abrasive air Jet machining, the aerodynamic focusing of an Abrasive particle Jet was investigated. Using a slot nozzle Abrasive Jet, the best focusing employed a pair of bounding air Jets tilted 60 ° to the Abrasive Jet, at an impingement height of approximately 10% of the standoff distance from the workpiece. An optimum bounding Jet pressure existed to achieve the maximum focusing, resulting in a machined channel width reduction of up to 16% with a corresponding depth increase of 84% compared to no bounding Jets. A novel apparatus was constructed to generate an annular bounding Jet impinging a central Abrasive Jet formed from a round nozzle. However, aerodynamic focusing, in this case, could not be achieved due to the large stagnation zone that formed near the annular Jet impingement. Computational fluid dynamics simulations were used to understand the mechanics of particle focusing.
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Abrasive Jet turning of glass and pmma rods and the micro machining of helical channels
Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology, 2018Co-Authors: Athena Nouhi, Jan K. Spelt, M PapiniAbstract:Abstract This paper investigates the use of air-driven Abrasive Jets as a lathe and as a means of machining helical patterns into rotating rods. The first part of the paper presents a model for the prediction of material removal during the machining of rotating and translating ductile (PMMA) and brittle (glass) rods using Abrasive Jet micromachining (AJM). The model predictions were in good agreement with the experimental measurements, showing that, for a given particle speed, the volumetric removal was only a function of the Abrasive dose received by the surface, and was unaffected by the rod diameter, its rotational speed, and the axial feed speed. The second part of the paper presents a new experimental procedure for machining helical channels in glass and PMMA rods using a cylindrical steel spring as a mask. Such helical channels may have applications in microfluidic devices where they can be used to aid liquid mixing and the separation of particles from a flow. The use of spring masks at various pitches and the control of the exposure time of the Jet to the workpiece made it possible to fabricate helical channels with a wide range of aspect ratios, from 0.09 to 1.2. High curvature, which is favorable in the microfluidic separation of particles, was achieved by machining rods of small diameter. In addition to microfluidic applications, the models and techniques can potentially be used to machine threads in glass and other difficult to machine materials.
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a rotating mask system for sculpting of three dimensional features using Abrasive Jet micro machining
Journal of Materials Processing Technology, 2017Co-Authors: M Sookhak R Lari, Ahad Ghazavi, M PapiniAbstract:Abstract Channels with non-conventional shaped cross sections have applications especially in microfluidics, where flow and heat transfer characteristics may depend on shape. Most microfabrication technologies capable of sculpting desired micro-channel shapes are limited in the range of shapes they can produce. Abrasive Jet micromachining (AJM) uses a Jet of impacting Abrasive particles to mechanically etch the target surface. Its directional etch capability makes it well suited for the sculpting of a wide variety of micro-features with three-dimensional (3D) topographies. Elastomeric masks have in the past been used to define complex patterns in AJM applications. Traditionally, such masks have been applied directly to the target, but this only allows the AJM of shallow features without any control over their cross-sectional shape. This paper presents a new technique that allows the instantaneous AJM erosive footprint size and shape to be controlled using a novel rotating mask apparatus (RMA). Models for predicting the required rotating mask pattern required to create a desired footprint are also presented. The models were experimentally verified for symmetric and asymmetric W-shaped, trapezoidal and wedge shaped footprints. The benefits of the RMA include: (i) the ability to generate virtually any footprint, including those that mimic moving a source (e.g. nozzle) or multiple sources of various sizes instantly from one location to another; (ii) improved mask longevity; and (iii) use of traverses in a straight line, rather adjacent traverses, in order to sculpt desired 3D feature shapes.
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prediction of the erosive footprint in the Abrasive Jet micro machining of flat and curved glass
Tribology International, 2017Co-Authors: Kamran Kowsari, Athena Nouhi, Jan K. Spelt, M Papini, V HadaviAbstract:Abstract A computational fluid dynamics (CFD) procedure is presented for the prediction of the erosive footprint size in Abrasive Jet micro-machining (AJM). The CFD-obtained footprints were in good agreement with those measured experimentally. The footprint was found to be due to both primary particle impacts in the conical plume emanating from the nozzle, and secondary particle impacts driven by the flow. The footprint depended on target curvature because the spread in lateral particle rebounds differed, depending on the target radius. It thus follows that footprints obtained from shallow channels machined on flat targets cannot be used to predict channel shape on curved surfaces. Since the footprint must consider secondary impacts, this has important implications for surface profile modeling of curved surfaces.
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dust reduction in Abrasive Jet micro machining using liquid films
Powder Technology, 2016Co-Authors: Reza Haj Mohammad Jafar, Jan K. Spelt, M Papini, V HadaviAbstract:Abstract Abrasive Jet micro-machining (AJM) uses a high-velocity particle Jet to erode features in target substrates for a variety of applications, including micro-electro-mechanical and micro-fluidic device fabrication. AJM can result in a dusty environment due primarily to airborne, rebounding Abrasive particles that eventually settle. This paper proposes a novel concept of covering the target with a layer of liquid in order to improve the process cleanliness. Films of water, glycerin, and a polymer solution were used to investigate the effect of liquid viscosity and film thickness on the percentage of captured particles, and also on the depth, width, erosion rate, roughness, and waviness of Abrasive Jet micro-machined channels. The glycerin film captured up to 61% of the rebounding particles during the machining of micro-channels. The channel depth, width, erosion rate, and roughness decreased, and the channel centreline waviness increased. Films of the long-chain polymer solution and of pure water absorbed up to 42% and 36%, respectively, of the rebounding particles, while not significantly changing the channel depth, width, roughness, and waviness. For all liquids, the percentage of trapped particles increased with increasing film thickness. The results showed that AJM with the target covered by a thin liquid film is a viable way of increasing process cleanliness by decreasing the amount of airborne particulates.
Jan K. Spelt - One of the best experts on this subject based on the ideXlab platform.
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aerodynamic focusing of an Abrasive air Jet and its effect on machining resolution
International Journal of Machine Tools & Manufacture, 2019Co-Authors: Joshua Palumbo, Jan K. Spelt, M PapiniAbstract:Abstract To decrease the size of the eroded footprint resulting from Abrasive air Jet machining, the aerodynamic focusing of an Abrasive particle Jet was investigated. Using a slot nozzle Abrasive Jet, the best focusing employed a pair of bounding air Jets tilted 60 ° to the Abrasive Jet, at an impingement height of approximately 10% of the standoff distance from the workpiece. An optimum bounding Jet pressure existed to achieve the maximum focusing, resulting in a machined channel width reduction of up to 16% with a corresponding depth increase of 84% compared to no bounding Jets. A novel apparatus was constructed to generate an annular bounding Jet impinging a central Abrasive Jet formed from a round nozzle. However, aerodynamic focusing, in this case, could not be achieved due to the large stagnation zone that formed near the annular Jet impingement. Computational fluid dynamics simulations were used to understand the mechanics of particle focusing.
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Abrasive Jet turning of glass and pmma rods and the micro machining of helical channels
Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology, 2018Co-Authors: Athena Nouhi, Jan K. Spelt, M PapiniAbstract:Abstract This paper investigates the use of air-driven Abrasive Jets as a lathe and as a means of machining helical patterns into rotating rods. The first part of the paper presents a model for the prediction of material removal during the machining of rotating and translating ductile (PMMA) and brittle (glass) rods using Abrasive Jet micromachining (AJM). The model predictions were in good agreement with the experimental measurements, showing that, for a given particle speed, the volumetric removal was only a function of the Abrasive dose received by the surface, and was unaffected by the rod diameter, its rotational speed, and the axial feed speed. The second part of the paper presents a new experimental procedure for machining helical channels in glass and PMMA rods using a cylindrical steel spring as a mask. Such helical channels may have applications in microfluidic devices where they can be used to aid liquid mixing and the separation of particles from a flow. The use of spring masks at various pitches and the control of the exposure time of the Jet to the workpiece made it possible to fabricate helical channels with a wide range of aspect ratios, from 0.09 to 1.2. High curvature, which is favorable in the microfluidic separation of particles, was achieved by machining rods of small diameter. In addition to microfluidic applications, the models and techniques can potentially be used to machine threads in glass and other difficult to machine materials.
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prediction of the erosive footprint in the Abrasive Jet micro machining of flat and curved glass
Tribology International, 2017Co-Authors: Kamran Kowsari, Athena Nouhi, Jan K. Spelt, M Papini, V HadaviAbstract:Abstract A computational fluid dynamics (CFD) procedure is presented for the prediction of the erosive footprint size in Abrasive Jet micro-machining (AJM). The CFD-obtained footprints were in good agreement with those measured experimentally. The footprint was found to be due to both primary particle impacts in the conical plume emanating from the nozzle, and secondary particle impacts driven by the flow. The footprint depended on target curvature because the spread in lateral particle rebounds differed, depending on the target radius. It thus follows that footprints obtained from shallow channels machined on flat targets cannot be used to predict channel shape on curved surfaces. Since the footprint must consider secondary impacts, this has important implications for surface profile modeling of curved surfaces.
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dust reduction in Abrasive Jet micro machining using liquid films
Powder Technology, 2016Co-Authors: Reza Haj Mohammad Jafar, Jan K. Spelt, M Papini, V HadaviAbstract:Abstract Abrasive Jet micro-machining (AJM) uses a high-velocity particle Jet to erode features in target substrates for a variety of applications, including micro-electro-mechanical and micro-fluidic device fabrication. AJM can result in a dusty environment due primarily to airborne, rebounding Abrasive particles that eventually settle. This paper proposes a novel concept of covering the target with a layer of liquid in order to improve the process cleanliness. Films of water, glycerin, and a polymer solution were used to investigate the effect of liquid viscosity and film thickness on the percentage of captured particles, and also on the depth, width, erosion rate, roughness, and waviness of Abrasive Jet micro-machined channels. The glycerin film captured up to 61% of the rebounding particles during the machining of micro-channels. The channel depth, width, erosion rate, and roughness decreased, and the channel centreline waviness increased. Films of the long-chain polymer solution and of pure water absorbed up to 42% and 36%, respectively, of the rebounding particles, while not significantly changing the channel depth, width, roughness, and waviness. For all liquids, the percentage of trapped particles increased with increasing film thickness. The results showed that AJM with the target covered by a thin liquid film is a viable way of increasing process cleanliness by decreasing the amount of airborne particulates.
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implementation of a shadow mask for direct writing in Abrasive Jet micro machining
Journal of Materials Processing Technology, 2015Co-Authors: Athena Nouhi, Jan K. Spelt, M Sookhak R Lari, M PapiniAbstract:Abstract Abrasive Jet micromachining uses a Jet of high-speed particles to erode a wide variety of materials. Since the air driven Jet is highly divergent, the edges of the desired features are usually defined using a mask which is attached to the surface of the target material. This paper presents an alternate technique using shadow masks that can be moved over the surface, thus allowing direct writing of features on the surface. This eliminates the additional cost and time of fabricating and attaching traditional masks. The technique was used to machine straight channels in borosilicate glass, and their quality was compared to those machined using traditional clamped masks. The channels machined using the shadow mask were found to be approximately 10% wider than those machined using clamped masks up to an aspect ratio of approximately 0.5. Under these conditions, the shadow mask channels were bounded on the edges by lightly-eroded, frosted regions approximately 60 μm wide. The effects of nozzle standoff, shadow mask standoff, particle size and mask thickness on the frosted regions and the channel width were studied. To create a direct-writing device, a crossed arrangement of two mutually perpendicular sets of shadow masks was used to generate arbitrarily curved paths. These crossed shadow masks resulted in less frosting than did the parallel masks.
Vincenzo Tagliaferri - One of the best experts on this subject based on the ideXlab platform.
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fluidized bed assisted Abrasive Jet machining fb ajm precision internal finishing of inconel 718 components
Journal of Manufacturing Science and Engineering-transactions of The Asme, 2007Co-Authors: Massimiliano Barletta, Daniele Ceccarelli, S. Guarino, Vincenzo TagliaferriAbstract:The relatively new technique of fluidized bed assisted Abrasive Jet machining (FB-AJM) is applied to finishing the inner surfaces of tubular Inconel 718 components. The effects. of Abrasive size, Jet pressure, and machining cycle were evaluated, and the behavior of Abrasive cutting edges acting against the surface during the process to remove material is accounted for. The finished surface was found to be highly dependent on Jet pressure because it affects the Abrasive contact against the surface as well as the finishing force acting on the Abrasive, on the Abrasive grain size, which controls the depth of cut, and on machining cycle, which controls the interaction time between the Abrasives and the surface being finished. By altering these conditions, this process achieves surface roughness (R-a) as fine as 0.1 mu m and imparts minimal additional residual stress on the surface. This study also reveals the mechanisms that determine the smoothing of the inner surface of Inconel 718 tubes and improve the form accuracy, i.e., the internal roundness of the Inconel 718 tube.
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progress in fluidized bed assisted Abrasive Jet machining fb ajm internal polishing of aluminium tubes
International Journal of Machine Tools & Manufacture, 2007Co-Authors: Massimiliano Barletta, G Rubino, S. Guarino, Vincenzo TagliaferriAbstract:Abstract This paper deals with the internal finishing of tubular components made from a high strength aluminium alloy (AA 6082 T6) using a fluidized bed assisted Abrasive Jet machining (FB-AJM) system. Firstly, a Taguchi's experimental plan was used to investigate the influence of Abrasive Jet speed, machining cycle, and Abrasive mesh size on surface roughness and material removal trends. Secondly, the leading finishing mechanisms were studied using combined 3d profilometer-SEM analysis to monitor the evolution of the surface morphology of machined workpieces. Finally, the circumferential uniformity and precision machining of the inner surface of workpieces were tested by evaluating the values of the more significant roughness parameters in different circumferential locations. Consistent trends of surface roughness vs. operational parameters were measured, and significant material removal was found to affect the workpieces during machining. As a result, FB-AJM was found to preferentially machine the asperities and irregularities of the surface, thereby altering the overall surface morphology producing more regular and smoother finishing. Moreover, the good circumferential uniformity and machining accuracy FB-AJM guarantees even on ductile aluminium alloy workpieces ensure that this technology can be applied to a diverse set of industrial components.
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development of an Abrasive Jet machining system assisted by two fluidized beds for internal polishing of circular tubes
International Journal of Machine Tools & Manufacture, 2006Co-Authors: Massimiliano Barletta, Vincenzo TagliaferriAbstract:Abstract This paper deals with the definition of a relatively novel machining technology to finish the internal part of narrow and long tubular parts made from high resistance stainless steel. A hybrid technology, namely, fluidized bed assisted Abrasive Jet machining (FB-AJM), was developed and a thorough experimental investigation was concurrently performed. First, a systematic approach, based upon design of experiments, was used to examine the influence of leading operative variables on process. Surface roughness and material removal trends consistent with theoretical expectations were found. Subsequently, the machining mechanisms were analyzed in terms of the evolution of roughness and waviness profile. FB-AJM was found to be a not pressure-copying machining technology. Lastly, the uniformity and the precision of machining all around the internal circumferences of the workpieces were checked out to assure the applicability of FB-AJM to process an ever-growing variety of complex shaped components.
Massimiliano Barletta - One of the best experts on this subject based on the ideXlab platform.
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fluidized bed assisted Abrasive Jet machining fb ajm precision internal finishing of inconel 718 components
Journal of Manufacturing Science and Engineering-transactions of The Asme, 2007Co-Authors: Massimiliano Barletta, Daniele Ceccarelli, S. Guarino, Vincenzo TagliaferriAbstract:The relatively new technique of fluidized bed assisted Abrasive Jet machining (FB-AJM) is applied to finishing the inner surfaces of tubular Inconel 718 components. The effects. of Abrasive size, Jet pressure, and machining cycle were evaluated, and the behavior of Abrasive cutting edges acting against the surface during the process to remove material is accounted for. The finished surface was found to be highly dependent on Jet pressure because it affects the Abrasive contact against the surface as well as the finishing force acting on the Abrasive, on the Abrasive grain size, which controls the depth of cut, and on machining cycle, which controls the interaction time between the Abrasives and the surface being finished. By altering these conditions, this process achieves surface roughness (R-a) as fine as 0.1 mu m and imparts minimal additional residual stress on the surface. This study also reveals the mechanisms that determine the smoothing of the inner surface of Inconel 718 tubes and improve the form accuracy, i.e., the internal roundness of the Inconel 718 tube.
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progress in fluidized bed assisted Abrasive Jet machining fb ajm internal polishing of aluminium tubes
International Journal of Machine Tools & Manufacture, 2007Co-Authors: Massimiliano Barletta, G Rubino, S. Guarino, Vincenzo TagliaferriAbstract:Abstract This paper deals with the internal finishing of tubular components made from a high strength aluminium alloy (AA 6082 T6) using a fluidized bed assisted Abrasive Jet machining (FB-AJM) system. Firstly, a Taguchi's experimental plan was used to investigate the influence of Abrasive Jet speed, machining cycle, and Abrasive mesh size on surface roughness and material removal trends. Secondly, the leading finishing mechanisms were studied using combined 3d profilometer-SEM analysis to monitor the evolution of the surface morphology of machined workpieces. Finally, the circumferential uniformity and precision machining of the inner surface of workpieces were tested by evaluating the values of the more significant roughness parameters in different circumferential locations. Consistent trends of surface roughness vs. operational parameters were measured, and significant material removal was found to affect the workpieces during machining. As a result, FB-AJM was found to preferentially machine the asperities and irregularities of the surface, thereby altering the overall surface morphology producing more regular and smoother finishing. Moreover, the good circumferential uniformity and machining accuracy FB-AJM guarantees even on ductile aluminium alloy workpieces ensure that this technology can be applied to a diverse set of industrial components.
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development of an Abrasive Jet machining system assisted by two fluidized beds for internal polishing of circular tubes
International Journal of Machine Tools & Manufacture, 2006Co-Authors: Massimiliano Barletta, Vincenzo TagliaferriAbstract:Abstract This paper deals with the definition of a relatively novel machining technology to finish the internal part of narrow and long tubular parts made from high resistance stainless steel. A hybrid technology, namely, fluidized bed assisted Abrasive Jet machining (FB-AJM), was developed and a thorough experimental investigation was concurrently performed. First, a systematic approach, based upon design of experiments, was used to examine the influence of leading operative variables on process. Surface roughness and material removal trends consistent with theoretical expectations were found. Subsequently, the machining mechanisms were analyzed in terms of the evolution of roughness and waviness profile. FB-AJM was found to be a not pressure-copying machining technology. Lastly, the uniformity and the precision of machining all around the internal circumferences of the workpieces were checked out to assure the applicability of FB-AJM to process an ever-growing variety of complex shaped components.
Fengzhou Fang - One of the best experts on this subject based on the ideXlab platform.
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theoretical study on particle velocity in micro Abrasive Jet machining
Powder Technology, 2019Co-Authors: Ruslan Melentiev, Fengzhou FangAbstract:Abstract Micro-Abrasive Jet machining (AJM) is an advanced subtractive machining technology with ample opportunities to form regular micro-patterns on freeform surfaces. AJM removes material mainly through erosion and abrasion, which transform kinetic energy to fracture and deform substrates. The kinetic energy of a solid particle is tightly connected to its velocity, which is the most significant source of error in precise prediction of a machined feature. The present study involves both theoretical analysis and two-dimensional axisymmetric numerical simulation of particle velocity fields at the lower end of the micro-scale. The developed model represents the finest particles in a cylindrical nozzle down to an inner diameter of 100 μm. The computed results agree well with the experimental data. It is shown that, due to viscous friction, such nozzles are significantly less efficient in terms of particle saturation with kinetic energy. The study highlights the effects of nozzle diameter and length, air pressure, particle size and density on particle velocity development through the Jet field. Finally, practical recommendations and multiple regression models of maximum particle velocity, location from the nozzle exit and simplex velocity profile approximation are offered for management of particle kinetic energy.
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recent advances and challenges of Abrasive Jet machining
Cirp Journal of Manufacturing Science and Technology, 2018Co-Authors: Ruslan Melentiev, Fengzhou FangAbstract:Abstract Abrasive Jet machining (AJM) is a manufacturing technology based on erosion localization and intensification. AJM has a progressively important influence on the machining technology market. Over the past 20 years, there has been an exponential growth in the number of papers that discuss AJM. Various innovations and process developments such as intermittent, submerged, thermally assisted and other Jet conditions were proposed. This paper examines AJM’s technological advantages and the variety of machining operations in different industries where AJM is utilized. Particular attention is devoted to the micro-texturing capabilities of powder blasting and its application in tribology. New evidence of ductile and brittle material removal mechanisms are reviewed together with recently discovered elastic removal mode. The effects of hydraulic, Abrasive and machining parameters on particles kinetic energy, machined surface roughness and footprint size are described in detail. Nozzle wear has a strong dependence on nozzle materials, its geometry, particles size, hardness, and flow rate. The trend of AJM development is a shift from macro to micro scale. Improvements in micro-machining resolution, process controlling and erosion prediction are current challenges facing AJM.
