The Experts below are selected from a list of 15186 Experts worldwide ranked by ideXlab platform
Jan K. Spelt - One of the best experts on this subject based on the ideXlab platform.
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prediction of the erosive footprint in the abrasive jet Micro Machining of flat and curved glass
Tribology International, 2017Co-Authors: Kavin 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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Selective removal of metallic layers from sintered ceramic and metallic plates using abrasive slurry-jet Micro-Machining
Journal of Manufacturing Processes, 2017Co-Authors: Kavin Kowsari, Marta Papini, Jan K. SpeltAbstract:Abrasive slurry-jet Micro-Machining (ASJM) is a low-cost and relatively quick alternative for the selective removal of metallic layers compared to conventional processes such as chemical-mechanical planarization (CMP). The present study used a computational fluid dynamics (CFD)-aided methodology with over-lapping ASJM channel Machining to predict the thickness of copper and nickel-phosphorous layers that could be removed without eroding the underlying ceramic or metallic substrate. High-viscosity soybean oil was used instead of water to eliminate undesirable erosion caused by the secondary slurry flow adjacent to the primary footprint, thereby providing better control of the areas being eroded. Experiments and CFD models showed that the much larger boundary layer thickness of soybean oil reduced the particle velocities near the surface and modified particle trajectories so that erosion was minimized beyond the primary jet footprint where the flow moved mostly parallel to the target surface. CFD models were used to explain measured variations in the specific erosion rates found in single-pass channels of varying depths, brought about by the geometry of the Machining front. It was found that the greater ability of viscous soybean oil to deflect the particles prior to impact caused the Machining of relatively deep channels to be uneconomical, while the opposite trend was found using water. The generalized functions for the dependence of erosion on particle impact velocity and angle were measured experimentally for electrodeposited copper and nickel-phosphorous, and then used as inputs in CFD models to obtain erosion patterns. These were then calibrated and used in an existing superposition model for the prediction of the profile of channels machined using ASJM. In summary, the present work demonstrated that ASJM can be used to selectively remove metal layers deposited on both ceramic and metal substrates by controlling the process conditions.
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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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calibrated cfd erosion modeling of abrasive slurry jet Micro Machining of channels in ductile materials
Journal of Manufacturing Processes, 2016Co-Authors: H Nouraei, Kavin Kowsari, Jan K. Spelt, M Papini, B SamarehAbstract:Abstract Abrasive slurry jet Micro-Machining (ASJM) uses a relatively high-speed jet of fine abrasive slurry to precisely machine controlled-depth Micro-features such as channels. Existing surface evolution models, developed for air-driven erosion processes, cannot account for the effect of slurry flow on the channel sidewall erosion that leads to the progressive channel widening observed in the ASJM of ductile materials. This paper presents a novel numerical–empirical model to predict the profiles of Micro-channels in ductile materials (i.e. polymethylmethacrylate (PMMA), 6061-T6 aluminum alloy, 316L stainless steel and Ti–6Al–4V titanium alloy) using ASJM. The specific erosion rates of these materials were measured as a function of jet angle using a 10 μm nominal diameter aluminum oxide slurry. The erosion rate-impact angle relations were corrected using computational fluid dynamic (CFD) models to account for the local impact angles and velocities of the particles. The erosion rate-impact angle relations were then used in three-dimensional CFD models to obtain the particle trajectories, impact angles, and velocities on a shallow eroded profile, and thus predict the erosion for deeper profiles. The model was verified by comparison with experiments which showed the previously-observed widening of the machined channels as the depth increased due to secondary erosion by particles impacting the channel sidewalls. The widening effect was found to be substantial in the PMMA but less important in Ti–6Al–4V titanium alloy due to its greater erosion resistance. The numerical–empirical approach could accurately estimate the widening and predicted the channel cross-sections up to an aspect ratio of approximately 1 with a maximum error of less than 5%.
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operating parameters to minimize feature size in abrasive slurry jet Micro Machining
Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology, 2016Co-Authors: H Nouraei, Kavin Kowsari, Jan K. Spelt, M PapiniAbstract:Abstract In low-pressure abrasive slurry jet Micro-Machining (ASJM), an aqueous slurry of abrasive particles is used to erode features with relatively high resolution in a variety of brittle and ductile materials. The effects of ASJM operating parameters on the minimum size of Micro-channels machined in borosilicate glass and polymethylmethacrylate (PMMA) were investigated experimentally and with CFD models. The operating parameters were found to have very different effects in these two materials due to fundamental differences in the erosion mechanisms. It was also found that, although the ASJM operating parameters could be adjusted to control the trajectory of particles and thereby reduce the size of the erosive jet footprint, this did not necessarily result in narrower channels, because of the oblique secondary impact of abrasive particles on the channel sidewalls adjacent to the immediate footprint. For both glass and PMMA, the channel width increased with depth, but the channel widening by secondary oblique impacts was more substantial in PMMA due to its ductile erosive behavior. Increasing the particle kinetic energy widened the channels machined in both glass and PMMA for a given depth. Narrower channels could be machined for a given depth by: (i) increasing the slurry temperature, (ii) reducing the jet impingement angle in both glass and PMMA, (iii) Machining at a slower scan speeds in PMMA, but not in glass, (iv) using smaller orifices and particles, and (v) coating the target with a sacrificial surface layer.
M Papini - One of the best experts on this subject based on the ideXlab platform.
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fabrication of high aspect ratio free standing structures using abrasive water jet Micro Machining
Journal of Materials Processing Technology, 2020Co-Authors: Ehsan Azarsa, Lorenzo Cinco, M PapiniAbstract:Abstract The abrasive water jet Micro-Machining of high aspect ratio free-standing structures such as fins used in heat sinks was investigated. The aim was to fabricate the maximum number of fins per unit length with the highest aspect ratio into Al6061-T6, in order to maximize heat transfer potential. Adjacent straight channels at various offsets were machined using a Micro-nozzle, thus leaving the free-standing structures in between. The effect of varying nozzle traverse speed, number of passes, water jet pressure, channel offset, and abrasive mass flow rate on the quality of the resulting free-standing structures was studied. Under some conditions, an undesirable ‘leveling’ phenomenon was found to occur, i.e. the tops of the free-standing structures eroded due to particle impacts at the periphery of the jet, and secondary slurry flow from within the channels between the structures. In general, conditions that led to a higher erosion rate (higher water jet pressures, lower nozzle traverse speeds, and higher abrasive mass flow rates) were found to minimize the leveling at a given offset, because the channels between the structures rapidly became deep, and secondary slurry flow was directed along the channel, rather than up the sidewalls. A threshold minimum offset to avoid this phenomenon was also determined. Contrary to previously reported results, it was found that the jet had ample energy to erode the target material even at effective stand-off distances (distance between nozzle and channel bottom) greater than 10 mm, provided that sufficiently large abrasive particles are used. With these factors in mind, it was demonstrated that high-quality free-standing structures with aspect ratios of more than 40 could be fabricated.
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masked Micro channel Machining in aluminum alloy and borosilicate glass using abrasive water jet Micro Machining
Journal of Manufacturing Processes, 2018Co-Authors: Naser Haghbin, Farbod Ahmadzadeh, M PapiniAbstract:Abstract Abrasive water jets (AWJs) have recently been used to mill unmasked features as narrow as 600 μm. This paper investigated the use of metal masks in order to decrease this minimum possible feature width in Al6061-T6 and borosilicate glass. Although there was under-etching on the channel sidewalls below the mask edges, it was nevertheless found that masked channels could be machined that were between 2–3 times narrower with 11% lower centerline roughness and 44% lower waviness than those created without masks. It was also found that increases in mask thickness led to increases in the channel centerline depth and width, and decreases in the centerline roughness and waviness. Increases in the abrasive mass flow rate increased the channel width, but decreased the depth. Finally, the normalized instantaneous centerline erosion rates in the masked channels decreased faster with depth than in the unmasked cases. Reasons for these trends were discussed in terms of changes in abrasive slurry flow and in the size of the stagnation zone within the channels brought about by the masks. Overall, the study demonstrates that masked AWJ Micro-Machining of features as narrow as ∼150 μm wide is possible, thus demonstrating the feasibility of the technique for the manufacture of Microfluidic and other components.
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prediction of the erosive footprint in the abrasive jet Micro Machining of flat and curved glass
Tribology International, 2017Co-Authors: Kavin 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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calibrated cfd erosion modeling of abrasive slurry jet Micro Machining of channels in ductile materials
Journal of Manufacturing Processes, 2016Co-Authors: H Nouraei, Kavin Kowsari, Jan K. Spelt, M Papini, B SamarehAbstract:Abstract Abrasive slurry jet Micro-Machining (ASJM) uses a relatively high-speed jet of fine abrasive slurry to precisely machine controlled-depth Micro-features such as channels. Existing surface evolution models, developed for air-driven erosion processes, cannot account for the effect of slurry flow on the channel sidewall erosion that leads to the progressive channel widening observed in the ASJM of ductile materials. This paper presents a novel numerical–empirical model to predict the profiles of Micro-channels in ductile materials (i.e. polymethylmethacrylate (PMMA), 6061-T6 aluminum alloy, 316L stainless steel and Ti–6Al–4V titanium alloy) using ASJM. The specific erosion rates of these materials were measured as a function of jet angle using a 10 μm nominal diameter aluminum oxide slurry. The erosion rate-impact angle relations were corrected using computational fluid dynamic (CFD) models to account for the local impact angles and velocities of the particles. The erosion rate-impact angle relations were then used in three-dimensional CFD models to obtain the particle trajectories, impact angles, and velocities on a shallow eroded profile, and thus predict the erosion for deeper profiles. The model was verified by comparison with experiments which showed the previously-observed widening of the machined channels as the depth increased due to secondary erosion by particles impacting the channel sidewalls. The widening effect was found to be substantial in the PMMA but less important in Ti–6Al–4V titanium alloy due to its greater erosion resistance. The numerical–empirical approach could accurately estimate the widening and predicted the channel cross-sections up to an aspect ratio of approximately 1 with a maximum error of less than 5%.
Duncan Paul Hand - One of the best experts on this subject based on the ideXlab platform.
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high energy green nanosecond and picosecond pulse delivery through a negative curvature fiber for precision Micro Machining
Optics Express, 2015Co-Authors: Piotr Jaworski, Fei Yu, J C Knight, Jonathan D Shephard, Richard Carter, Duncan Paul HandAbstract:In this paper we present an anti-resonant guiding, low-loss Negative Curvature Fiber (NCF) for the efficient delivery of high energy short (ns) and ultrashort (ps) pulsed laser light in the green spectral region. The fabricated NCF has an attenuation of 0.15 dB/m and 0.18 dB/m at 532 nm and 515 nm respectively, and provided robust transmission of nanosecond and picosecond pulses with energies of 0.57 mJ (10.4 kW peak power) and 30 µJ (5 MW peak power) respectively. It provides single-mode, stable (low bend-sensitivity) output and maintains spectral and temporal properties of the source laser beam. The practical application of fiber-delivered pulses has been demonstrated in precision Micro-Machining and marking of metals and glass.
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high peak power nanosecond and picosecond pulse delivery through a hollow core negative curvature fiber in the green spectral region for Micro Machining
Advanced Photonics (2014) paper SoM3B.5, 2014Co-Authors: Piotr Jaworski, Fei Yu, W J Wadsworth, J C Knight, Jonathan D Shephard, Richard Carter, T A Birks, Duncan Paul HandAbstract:We report efficient delivery of nanosecond and picosecond laser pulses in the green spectral region with peak powers of 6.9kW and 3MW respectively through a hollow-core Negative Curvature Fiber and demonstration of fiber-based precision Micro-Machining.
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picosecond and nanosecond pulse delivery through a hollow core negative curvature fiber for Micro Machining applications
Optics Express, 2013Co-Authors: Piotr Jaworski, Fei Yu, Robert R J Maier, W J Wadsworth, J C Knight, Jonathan D Shephard, Duncan Paul HandAbstract:We present high average power picosecond and nanosecond pulse delivery at 1030 nm and 1064 nm wavelengths respectively through a novel hollow-core Negative Curvature Fiber (NCF) for high-precision Micro-Machining applications. Picosecond pulses with an average power above 36 W and energies of 92 µJ, corresponding to a peak power density of 1.5 TWcm−2 have been transmitted through the fiber without introducing any damage to the input and output fiber end-faces. High-energy nanosecond pulses (>1 mJ), which are ideal for Micro-Machining have been successfully delivered through the NCF with a coupling efficiency of 92%. Picosecond and nanosecond pulse delivery have been demonstrated in fiber-based laser Micro-Machining of fused silica, aluminum and titanium.
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a hollow core negative curvature fibre for efficient delivery of nir picosecond and femtosecond pulses for precision Micro Machining
Workshop on Specialty Optical Fibers and their Applications (2013) paper F3.3, 2013Co-Authors: Piotr Jaworski, Robert R J Maier, W J Wadsworth, J C Knight, Jonathan D Shephard, David Guillaume Maclachlan, Robert R Thomson, Duncan Paul HandAbstract:We have delivered picosecond and femtosecond pulses with peak powers of 15.3 MW and 0.95 MW respectively through a hollow-core Negative Curvature Fibre and thereby demonstrated the suitability of fibre-delivered beam in precision Micro-Machining applications.
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delivery of high power nanosecond and picosecond pulses through a hollow core negative curvature fibre for Micro Machining applications
International Quantum Electronics Conference, 2013Co-Authors: Piotr Jaworski, Robert R J Maier, W J Wadsworth, Jonathan D Shephard, T A Birks, J C Knighf, Duncan Paul HandAbstract:This paper reports the investigation of a novel type of hollow core Microstructured fibre, the Negative Curvature Fibre (NCF), showing that it can deliver significantly larger pulse energies and shorter (ps) pulses (in comparison with other Microstructured fibre designs) at 1064nm and 1030nm wavelengths, and demonstrate its application to Micro-Machining. This fibre was fabricated by the commonly used stack and draw technique. Eight circular capillaries were used to fabricate a preform, which was drawn down to produce a final fibre with a hollow core of 38.3μm diameter .
Piotr Jaworski - One of the best experts on this subject based on the ideXlab platform.
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high energy green nanosecond and picosecond pulse delivery through a negative curvature fiber for precision Micro Machining
Optics Express, 2015Co-Authors: Piotr Jaworski, Fei Yu, J C Knight, Jonathan D Shephard, Richard Carter, Duncan Paul HandAbstract:In this paper we present an anti-resonant guiding, low-loss Negative Curvature Fiber (NCF) for the efficient delivery of high energy short (ns) and ultrashort (ps) pulsed laser light in the green spectral region. The fabricated NCF has an attenuation of 0.15 dB/m and 0.18 dB/m at 532 nm and 515 nm respectively, and provided robust transmission of nanosecond and picosecond pulses with energies of 0.57 mJ (10.4 kW peak power) and 30 µJ (5 MW peak power) respectively. It provides single-mode, stable (low bend-sensitivity) output and maintains spectral and temporal properties of the source laser beam. The practical application of fiber-delivered pulses has been demonstrated in precision Micro-Machining and marking of metals and glass.
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high peak power nanosecond and picosecond pulse delivery through a hollow core negative curvature fiber in the green spectral region for Micro Machining
Advanced Photonics (2014) paper SoM3B.5, 2014Co-Authors: Piotr Jaworski, Fei Yu, W J Wadsworth, J C Knight, Jonathan D Shephard, Richard Carter, T A Birks, Duncan Paul HandAbstract:We report efficient delivery of nanosecond and picosecond laser pulses in the green spectral region with peak powers of 6.9kW and 3MW respectively through a hollow-core Negative Curvature Fiber and demonstration of fiber-based precision Micro-Machining.
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picosecond and nanosecond pulse delivery through a hollow core negative curvature fiber for Micro Machining applications
Optics Express, 2013Co-Authors: Piotr Jaworski, Fei Yu, Robert R J Maier, W J Wadsworth, J C Knight, Jonathan D Shephard, Duncan Paul HandAbstract:We present high average power picosecond and nanosecond pulse delivery at 1030 nm and 1064 nm wavelengths respectively through a novel hollow-core Negative Curvature Fiber (NCF) for high-precision Micro-Machining applications. Picosecond pulses with an average power above 36 W and energies of 92 µJ, corresponding to a peak power density of 1.5 TWcm−2 have been transmitted through the fiber without introducing any damage to the input and output fiber end-faces. High-energy nanosecond pulses (>1 mJ), which are ideal for Micro-Machining have been successfully delivered through the NCF with a coupling efficiency of 92%. Picosecond and nanosecond pulse delivery have been demonstrated in fiber-based laser Micro-Machining of fused silica, aluminum and titanium.
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a hollow core negative curvature fibre for efficient delivery of nir picosecond and femtosecond pulses for precision Micro Machining
Workshop on Specialty Optical Fibers and their Applications (2013) paper F3.3, 2013Co-Authors: Piotr Jaworski, Robert R J Maier, W J Wadsworth, J C Knight, Jonathan D Shephard, David Guillaume Maclachlan, Robert R Thomson, Duncan Paul HandAbstract:We have delivered picosecond and femtosecond pulses with peak powers of 15.3 MW and 0.95 MW respectively through a hollow-core Negative Curvature Fibre and thereby demonstrated the suitability of fibre-delivered beam in precision Micro-Machining applications.
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delivery of high power nanosecond and picosecond pulses through a hollow core negative curvature fibre for Micro Machining applications
International Quantum Electronics Conference, 2013Co-Authors: Piotr Jaworski, Robert R J Maier, W J Wadsworth, Jonathan D Shephard, T A Birks, J C Knighf, Duncan Paul HandAbstract:This paper reports the investigation of a novel type of hollow core Microstructured fibre, the Negative Curvature Fibre (NCF), showing that it can deliver significantly larger pulse energies and shorter (ps) pulses (in comparison with other Microstructured fibre designs) at 1064nm and 1030nm wavelengths, and demonstrate its application to Micro-Machining. This fibre was fabricated by the commonly used stack and draw technique. Eight circular capillaries were used to fabricate a preform, which was drawn down to produce a final fibre with a hollow core of 38.3μm diameter .
H Nouraei - One of the best experts on this subject based on the ideXlab platform.
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calibrated cfd erosion modeling of abrasive slurry jet Micro Machining of channels in ductile materials
Journal of Manufacturing Processes, 2016Co-Authors: H Nouraei, Kavin Kowsari, Jan K. Spelt, M Papini, B SamarehAbstract:Abstract Abrasive slurry jet Micro-Machining (ASJM) uses a relatively high-speed jet of fine abrasive slurry to precisely machine controlled-depth Micro-features such as channels. Existing surface evolution models, developed for air-driven erosion processes, cannot account for the effect of slurry flow on the channel sidewall erosion that leads to the progressive channel widening observed in the ASJM of ductile materials. This paper presents a novel numerical–empirical model to predict the profiles of Micro-channels in ductile materials (i.e. polymethylmethacrylate (PMMA), 6061-T6 aluminum alloy, 316L stainless steel and Ti–6Al–4V titanium alloy) using ASJM. The specific erosion rates of these materials were measured as a function of jet angle using a 10 μm nominal diameter aluminum oxide slurry. The erosion rate-impact angle relations were corrected using computational fluid dynamic (CFD) models to account for the local impact angles and velocities of the particles. The erosion rate-impact angle relations were then used in three-dimensional CFD models to obtain the particle trajectories, impact angles, and velocities on a shallow eroded profile, and thus predict the erosion for deeper profiles. The model was verified by comparison with experiments which showed the previously-observed widening of the machined channels as the depth increased due to secondary erosion by particles impacting the channel sidewalls. The widening effect was found to be substantial in the PMMA but less important in Ti–6Al–4V titanium alloy due to its greater erosion resistance. The numerical–empirical approach could accurately estimate the widening and predicted the channel cross-sections up to an aspect ratio of approximately 1 with a maximum error of less than 5%.
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operating parameters to minimize feature size in abrasive slurry jet Micro Machining
Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology, 2016Co-Authors: H Nouraei, Kavin Kowsari, Jan K. Spelt, M PapiniAbstract:Abstract In low-pressure abrasive slurry jet Micro-Machining (ASJM), an aqueous slurry of abrasive particles is used to erode features with relatively high resolution in a variety of brittle and ductile materials. The effects of ASJM operating parameters on the minimum size of Micro-channels machined in borosilicate glass and polymethylmethacrylate (PMMA) were investigated experimentally and with CFD models. The operating parameters were found to have very different effects in these two materials due to fundamental differences in the erosion mechanisms. It was also found that, although the ASJM operating parameters could be adjusted to control the trajectory of particles and thereby reduce the size of the erosive jet footprint, this did not necessarily result in narrower channels, because of the oblique secondary impact of abrasive particles on the channel sidewalls adjacent to the immediate footprint. For both glass and PMMA, the channel width increased with depth, but the channel widening by secondary oblique impacts was more substantial in PMMA due to its ductile erosive behavior. Increasing the particle kinetic energy widened the channels machined in both glass and PMMA for a given depth. Narrower channels could be machined for a given depth by: (i) increasing the slurry temperature, (ii) reducing the jet impingement angle in both glass and PMMA, (iii) Machining at a slower scan speeds in PMMA, but not in glass, (iv) using smaller orifices and particles, and (v) coating the target with a sacrificial surface layer.
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abrasive enhanced electrochemical slurry jet Micro Machining comparative experiments and synergistic effects
Journal of Materials Processing Technology, 2014Co-Authors: H Nouraei, Jan K. SpeltAbstract:Abstract Abrasive enhanced electrochemical slurry-jet Machining (ESJM) is presented as a new approach to the Micro-Machining of metals using a combination of abrasive slurry-jet Machining (ASJM) and electrochemical jet Machining (ECJM). A novel ESJM prototype was developed to generate a charged slurry jet consisting of a mixture of Al2O3 abrasive particles and an electrolytic solution of NaCl and NaNO3. A DC potential of 30 V was applied between the nozzle and specimen. A series of Micro-channels were machined in Stellite 12 using ASJM, ECJM and ESJM processes to investigate the relative effects of erosion and anodic dissolution on the material removal rate and surface finish in the combined process of ESJM. The results illustrated that the ESJM process results in significantly greater target mass loss rate than the separate erosion and corrosion processes. The magnitude of the synergistic effect on the rate of mass loss was found to vary from positive to negative as the erosion component increased with increasing particle kinetic energy (jet pressure) and particle concentration. The roughness of the channels machined using ESJM was between that obtained with ASJM and ECJM. The roughness decreased as the erosion component of the total mass loss increased.
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abrasive slurry jet Micro Machining of holes in brittle and ductile materials
Journal of Materials Processing Technology, 2014Co-Authors: Kavin Kowsari, H Nouraei, Jan K. Spelt, M Papini, D F JamesAbstract:Abstract This paper investigated the effects of elasticity and viscosity, induced by a dilute high-molecular-weight polymer solution, on the shape, depth, and diameter of Micro-holes drilled in borosilicate glass and in plates of 6061-T6 aluminum alloy, 110 copper, and 316 stainless steel using low-pressure abrasive slurry jet Micro-Machining (ASJM). Holes were machined using aqueous jets with 1 wt% 10 μm Al 2 O 3 particles. The 180 μm sapphire orifice produced a 140 μm diameter jet at pressures of 4 and 7 MPa. When the jet contained 50 wppm of dissolved 8 million molecular weight polyethylene oxide (PEO), the blind holes in glass were approximately 20% narrower and 30% shallower than holes drilled without the polymer, using the same abrasive concentration and pressure. The addition of PEO led to hole cross-sectional profiles that had a sharper edge at the glass surface and were more V-shaped compared with the U-shape of the holes produced without PEO. Hole symmetry in glass was maintained over depths ranging from about 80–900 μm by ensuring that the jets were aligned perpendicularly to within 0.2°. The changes in shape and size were brought about by normal stresses generated by the polymer. Jets containing this dissolved polymer were observed to oscillate laterally and non-periodically, with an amplitude reaching a value of 20 μm. For the first time, symmetric ASJM through-holes were drilled in a 3-mm-thick borosilicate glass plate without chipping around the exit edge. The depth of symmetric blind holes in metals was restricted to approximately 150 μm for jets with and without PEO. At greater depths, the holes became highly asymmetric, eroding in a specific direction to create a sub-surface slot. The asymmetry appeared to be caused by the extreme sensitivity of ductile materials to jet alignment. This sensitivity also caused the holes in metals to be less circular when PEO was included, apparently caused by the random jet oscillations induced by the polymer. Under identical conditions, hole depths increased in the order: borosilicate glass > 6061-T6 aluminum > 110 copper > 316 stainless steel. The edges of the holes in glass could be made sharper by Machining through a sacrificial layer of glass or epoxy.
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surface evolution models for abrasive slurry jet Micro Machining of channels and holes in glass
Wear, 2014Co-Authors: H Nouraei, Kavin Kowsari, Marcello Papini, Jan K. SpeltAbstract:Abstract Abrasive slurry jet Micro-Machining (ASJM) uses a jet of abrasive slurry to erode features with relatively high resolution without the need for a patterned mask. The present study investigated the ability of a surface evolution model to predict the profiles of Micro-channels and holes machined in borosilicate glass with a newly developed ASJM system. The system could produce Micro-channels with depth and width variations along their length of less than 3%, and a channel-to-channel repeatability within 5%. The fundamental erosion rate of the borosilicate glass was measured as a function of impact angle using a slurry of water mixed with a low concentration of 10 and 25 µm nominal diameter aluminum oxide particles. This erosion rate-impact angle relationship was used in an existing model developed previously for the abrasive air jet Micro-Machining of brittle materials. The results demonstrated that, despite the differences in abrasive flow patterns between air and slurry based systems, the surface evolution model accurately predicted the profiles of Micro-channels with a maximum error of 7% for aspect ratios (depth/width) of up to 5. The predicted profiles of holes were also in reasonable agreement with a maximum error of 14% for aspect ratios close to 1.