Nozzle Stand-off Distance Research Articles

Numerical simulation of the first layer printing in electric field-assisted fused filament fabrication for robust unconventionally oriented additive manufacturing

Fused filament fabrication (FFF) stands as a prominent thermoplastic additive manufacturing technique that has a wide range of potential applications. However, the conventional FFF process encounters limitations in unconventional environments, particularly in environments devoid of gravity, such as in extraterrestrial environments or in limited manufacturing conditions where maintaining consistent nozzle standoff distance becomes a challenging task. Fluctuations in nozzle standoff distance lead to inadequate material adhesion and dimensional errors, which results in a high failure rate and prolonged completion time. Thus, the conventional FFF process requires continuous monitoring or human intervention to ensure successful operation. To overcome the shortcomings of the traditional FFF process, an electric field-assisted FFF (E-FFF) process can be utilized to reduce the need for constant supervision and enable reliable production of parts. The E-FFF process integrates a high-voltage power supply unit with a standard FFF printer, generating an electrostatic force between the nozzle and the build plate. The generated electrostatic force can effectively attract the extruded molten polymer toward the build plate, even at a larger z-height of up to 1200 μm in unconventional build platform orientations such as vertical or reverse printing orientation. In this paper, finite element analysis is used to simulate the FFF and E-FFF process. The simulation focuses on the adhesion between extruded material and build plate with extended nozzle standoff distances and predicts the minimum voltage required to achieve a good material adhesion in unconventional orientations for the E-FFF process. The simulation model demonstrated its efficacy by estimating the minimum required voltage levels necessary for successful printing within the E-FFF process across a range of nozzle standoff distances in unconventional orientations.

DEPENDENCE OF MICROHARDNESS OF ASD-1 COATINGS ON COLD SPRAYING PROCESS PARAMETERS

Purpose. To investigate the effect of the main parameters of the cold spraying process, particularly the temperature and pressure of the gas at the nozzle inlet and stand-off distance, on the microhardness of the ASD-1 aluminum coating. Research methods. The planning and conducting of experimental research were carried out using the design of experiment methodology and regression analysis. The analysis of the obtained results of the experiments was carried out in the software package for statistical data Stat-Ease 360. The research of the microhardness of the sprayed coatings was carried out following GOST 9450-76 “Measurements microhardness by diamond instruments indentation@ using a LECO AMH5 micro-Vickers hardness tester on the prepared cross-section of samples with coatings. Results. Three-dimensional (response surfaces) and contour graphs of the dependence of the microhardness of coatings deposited by the cold spraying method from ASD-1 powder on the main process parameters - the temperature and pressure of the gas at the nozzle inlet and stand-off distance in a wide range of values - were constructed. According to the results, it was established that the gas temperature and the spraying distance have the most significant influence on the microhardness of the coatings. The relationship between the investigated parameters of spraying with the temperature and velocity characteristics of the powder particles and their effect on the microhardness is described. Scientific novelty. The complex effect of the main parameters of the cold spraying process, particularly the temperature and gas pressure at the nozzle inlet and the stand-off distance, on the microhardness of ASD-1 aluminum coatings in a wide range of values, was investigated. Practical value. The obtained dependences of coating microhardness on process parameters can be used in developing scientifically-based recommendations and technological processes of deposition of protective and restorative coatings by cold spraying, particularly on parts of aircraft engines.

Optimization of cold spray process parameters to maximize adhesion and deposition efficiency of Ni+Al2O3 coatings

The paper considers the conducted study of the complex effect of low-pressure cold spraying parameters, namely the nozzle inlet temperature, stand-off distance, and powder feed rate on the adhesion and deposition efficiency of coatings from a Ni+Al2O3 powder on VT3-1 titanium alloy substrate. Based on predetermined information, the main levels and intervals of factor variation were selected. The dependence of the adhesion and deposition efficiency on the selected variables was approximated by a second-order polynomial. In accordance with the developed matrix of the experiment (central compositional design), a coating of the studied powder was deposited. The average value of these parameters was determined using standard methods for studying the adhesion strength (ASTM C603) and the deposition efficiency for thermal spray coatings. Based on the results of experimental data, regression equations were obtained for adhesion and deposition efficiency. For the purpose of checking the adequacy of the model, an analysis of variance was performed. It was confirmed that the obtained empirical dependences can be used to predict the adhesion and deposition efficiency of cold spraying of coatings from a Ni+Al2O3 powder on VT3-1 titanium alloy in the specified ranges of values of spraying parameters. Multi-factor optimization of the spraying parameters in order to obtain maximum values of adhesion strength and deposition efficiency was performed using the response surface methodology in the Stat-Ease 360 software. Three-dimensional and contour graphs of the dependence of the adhesion and deposition efficiency on the studied parameters were developed from the obtained empirical models. The optimal combination of parameters of low-pressure cold spraying, which ensures the maximum adhesion (34.78 MPa) and deposition efficiency (29.46%) of the Ni+Al2O3 coating mixture, is the nozzle inlet temperature—537 °C, stand-off distance—11 mm, and powder feed rate—0.6 g s−1.

Experimental and numerical simulations to examine the mechanism of nozzle geometry affecting cavitation water jets

The geometry of the cavitation nozzle is the major determinant of the cavitation process and cleaning effect. To better service the cleaning industry, it is necessary to understand the process by which nozzle geometry impacts cavitation. This research uses experimental flow visualization and large eddy simulation (LES) to study the cavitation effects of three different nozzle configurations (Cylindrical, organ-pipe and converging–diverging nozzles). The shedding frequency of the cavitation cloud was determined through power spectrum analysis (PSD). The collapse range of the cavitation cloud produced was measured using the frame difference technique (FDM). A cleaning experiment was carried out to remove the tube scale with the aim of assessing the performance of the nozzle. The findings indicate that under the impact of the re-entrant jet, the cavitation cloud was distorted and fractured, and large shear stresses were produced at the fracture sites. The cylindrical nozzle creates a flow field with more vapour, velocity, and Reynolds stress than the other two nozzles. The findings from the cleaning experiments indicate that the utilization of appropriate nozzle geometry and an optimal standoff distance can significantly enhance the efficiency of tube descaling. This paper can help choose the right nozzle geometry and standoff distance for the cavitation water jet cleaning process, offer crucial technical support for the efficient cleaning within tubes.

Optimization of silica sand abrasive parameters on machining of glass plate in AJM using Taguchi method

Fine abrasive blasting of glass materials is widely used in the micro-electromechanical systems and biomedical industries. Creating high-quality holes in these materials requires precise control of the input parameters. In this study, experimental and optimization study was performed to assess the impact of various parameters during abrasive jet machining (AJM) on material removal rate (MRR), where SiC is used as the abrasive particle. Experiments were performed in line with the Taguchi experimental design where L9 orthogonal array was selected to understand the influence of nozzle diameter, standoff distance (SOD), and work piece (glass) thickness on MRR. It was observed that the material removal rate was proportional to the abrasive particles’ kinetic energy. Among the considered parameters viz. nozzle diameter, standoff distance, and work piece thickness, nozzle diameter exerted most significant effect on MRR followed by SOD and work piece thickness. Highest MRR, 0.0143 g/sec, was observed at SOD of 2.05 mm, nozzle diameter of 3 mm and work piece thickness of 4 mm. The researchers can follow the same methodology and determine the efficiency of industrial wastes possessing high hardness as abrasive particles, thereby, contributing additionally towards ecology protection.

Electric field-assisted fused filament fabrication process for robust additive manufacturing in unconventional orientations

Fused filament fabrication (FFF) is one of the most widely used thermoplastic additive manufacturing techniques that have great potential for numerous applications. However, for more advanced additive manufacturing with unusual environments, such as in-space manufacturing, conventional FFF is limited by the lack of gravity and inconsistent nozzle standoff distance. Varying nozzle standoff distances in the FFF process typically result in problems with the adhesion of extruded material as well as dimensional and geometrical errors in the extruded material, which leads to a long setup time and a high failure rate. Conventional FFF typically needs continuous monitoring or human intervention to ensure successful printing. This paper innovated an electric field-assisted FFF (E-FFF) process for robust fabricating parts in unconventional printing orientations while eliminating the need for constant supervision and human intervention to maintain and adjust the z-height calibration. The E-FFF system integrates a high-voltage power supply with a conventional FFF printer to produce an electrostatic force between the nozzle and the build plate. The generated electrostatic force is capable of attracting the extruded molten polymer material towards the build plate even at larger z-heights of up to 1200 μm under unconventional printing orientations. The effectiveness of the E-FFF process was demonstrated by comparing the E-FFF and conventional FFF processes. The results affirm the assistance of gravitational force on conventional FFF processes in the normal printing orientation. The novel E-FFF process with robust printing capabilities in the vertical and reverse orientations enables much larger nozzle standoff distances than that of the conventional FFF process, which exhibits great potential to be used in the micro/zero-gravity environment in the future. A two-dimensional finite element simulation model is used to understand the effects of applied voltage on the E-FFF process and calculate the electric field intensity. The simulation results showed that the electric field intensity of E = 1.27 × 106 V/m is sufficient for successful printing in all demonstrated printing orientations.

Mechanical optimisation of Ni coatings produced by low-pressure cold spray

ABSTRACT Nickel-based coatings are widely used as thermal barriers in several sectors thanks to their remarkable corrosion and wear resistance and outstanding stability at high temperatures. Recently, Ni coatings, produced with thermal spraying and vacuum techniques, have been investigated for solar power energy applications. In the present manuscript, low-pressure cold spray (LPCS) was used to deposit pure Nickel onto a steel substrate. The influence of gas temperature, nozzle stand-off distance, and advancing speed on morphological and mechanical properties were studied. The optimal deposition conditions were derived by ANOVA analysis. The hardness and the adhesion strength were approximately 160 HV and 26 MPa, respectively. The highest thickness obtained under the optimised deposition with a single pass was around 900 µm.

Water vapor cutting fluid assisted productive machining of Inconel 718

ABSTRACT High-speed turning of Inconel 718 has been assessed with coated carbide tooling incorporating the minutely explored eco-friendly cutting fluid as water vapour. Effect of total seven parameters, viz. nozzle diameter, stand-off distance, pressure, flowrate, cutting speed, feedrate and depth of cut, has been explored for the resulting machined surface quality in terms of surface roughness and surface alterations; additionally introspection of chip reduction ratio has been done to evaluate cooling/lubrication mechanics of water vapour at tool-work interface. The parameters of stand-off distance, cutting speed, feedrate and depth of cut were dominantly affecting the surface roughness with their contributions being 9.70%, 22.70%, 20.85% and 34.47% respectively. By increasing nozzle diameter, stand-off distance and pressure, around 13.28%, 16.47% and 8.82% reduction in surface roughness is possible respectively on account of enhancement of cooling and lubrication effect; however conversely increasing the cutting speed brought around 40% increment in surface roughness.

Mechanical properties, durability performance and interlayer adhesion of 3DPC mixtures: A state‐of‐the‐art review

AbstractIn this study, the strength and durability performance of 3D printing concrete mixtures (3DPC) were examined in terms of the materials used in their production and printing process parameters (interlayer interval time, printing speed, and nozzle shape). Due to the anisotropic nature of 3DPC, it was understood that the compressive strength depends on the loading direction. It was emphasized that it is necessary to control the shrinkage behavior of 3DPC mixtures due to the lack of formwork and the high dosage of binders. It was reported that the interlayer adhesion of 3DPC is highly dependent on the interlayer interval time and printing speed parameters. It was understood that nozzle shape and standoff distance affect the mechanical properties and surface roughness of 3DPC specimens, and this effect is more pronounced in mixtures with high static yield stress values.

Influence of spraying parameters on microstructure of oxygen-rich TiO2 coatings deposited using suspension low-pressure cold spray

The low process temperature and short nozzle standoff distance has caused mainly the cold spraying of powder to be developed so far. In the presented work, we low-pressure cold sprayed suspensions. Titanium dioxide suspension was self-synthesized using a sol-gel approach and modified with hydrogen peroxide. Obtained oxygen-rich groups are thermally-sensitive but make TiO2 an active photocatalyst in VIS light. The research aimed to establish process parameters retaining oxygen-rich TiO2 in the coating and simultaneously producing a coating of a high surface specific area. The chemical structure and morphology were controlled through the following deposition parameters: scanning step, standoff distance, traverse speed, and working gas temperature. The coatings were characterized using scanning electron microscopy, optical microscopy, and Raman spectroscopy. Finally, the scheme of deposition was proposed for a better understanding of suspension spraying of modified TiO2.

Estimation and analysis of surface heat flux during gas quenching through IHC method

Gas Quenching is a process of quenching steel components with a gas quenchant. This process, due to its several advantages is being extensively used now a days. This work studies the effect of the variation of gas jet pressure and the standoff distance (SOD), which is the distance between the quench probe and the tip of the nozzle on the quenching heat transfer during gas quenching. A gas quenching chamber of octagonal cross-section of side 100 mm was used for quenching experiments, in which an array of nozzles was fixed. The cylindrical workpieces of 20 mm diameter and 50 mm length were machined from stainless steel 304L and K-type thermocouples were fixed at the selected locations inside the workpiece to read the temperature during quenching. Compressed air as the quenchant at different pressures of 4 bar, 6 bar and 8 bar and different SOD of 9 cm, 10 cm and 11 cm were used to study the effect of these two parameters on the quenching heat transfer rates. Surface heat flux computations were made using Inverse Heat Conduction (IHC) method using the measured time–temperature data as input. It was found out that as the pressure increased, the cooling rate and the peak surface heat flux increased and as the nozzle standoff distance was increased, the cooling rate and the peak surface heat flux dropped. The effect of increasing the nozzle SOD by 1 cm was more than the reduction of gas jet pressure by 2 bar.

A novel and prediction approach of sheep wool reinforced polyester composites: Surface qualities and hybrid modeling

AbstractThis research aims to describe the hybrid algorithm's effectiveness in predicting and optimizing the abrasive water jet machining (AWJM) parameter on flexible sheep wool reinforced polyester composites. Selected five parameters are transverse speed (TS), water jet pressure (WJP), nozzle stand‐off distance (NSoD), reinforcement weight percentage (wt%) and abrasive size (AS). In contrast, Surface Roughness (Ra) and Kerf Angle (Ka) are output performances. Multi objective optimization by ratio analysis (MOORA) is a tool is used for selecting and optimizing control variables. The most influential control variables are AS, WJP, TS, wt%, and NSoD, according to MOORA–Entropy feature selection results. The support vector machine algorithm (SVM) represents the AWJM process, and the model's performance is compared to SVM hybrid models. The differential evolutionary (DE) algorithm and the Entropy idea create a hybrid model. An SVM model is compared with the Hybrid SVM—Entropy model; hybrid improves prediction performance by 21.6%. When the MOORA—SVM—Entropy hybrid model is compared to the SVM model, it is revealed that the MOORA—SVM—Entropy hybrid model's prediction performance improves by 38.7%. According to the MOORA—Entropy approach, the optimal control variables are A2, B1, C1, D3, and E1.

Effect of ceramic particle reinforcement type and process parameters on abrasive water jet processing of aluminum metal matrix composites fabricated by stir casting and hot rolling

In the present study, three AA6061 composites reinforced with 8% SiC, B4C, and Al2O3 were produced using the stir casting method. The composite specimens were molded in the thickness of 20 mm, and then the thicknesses of the samples were reduced to 7 mm by employing a hot rolling process at 450 °C. The effect of abrasive water jet cutting parameters such as nozzle speed (NS) and stand-off distance (SOD) on the kerf taper angle (KTA) and surface roughness (SR) were studied. The experiments were conducted based on the Taguchi L9 orthogonal array and the experimental results were analyzed by using the analysis of variance (ANOVA). The test results revealed that the most effective cutting variable on the KTA and SR was the type of reinforcement ceramic particle. The lowest KTA and the best SR values were recorded in the cutting of the Al2O3-reinforced composite specimen. The influence of the ceramic particle reinforcements on the SR and KTA was 60.6% and 65.1%, respectively. The effect ratio of the SOD, the second most effective process variable, to the SR is 28.1%, while the effect ratio to the KTA is 22.0%. Predictive models were developed for the KTA ( R2 = 93.29%) and SR ( R2 = 91.84) by the regression analysis. A close correlation with the ratio of 95.43% was achieved between the KTA and SR.

Microstructural characterization, driving mechanisms, and improvement strategies for interlayer bond strength of additive-manufactured cementitious composites: A review

3D printed cementitious composites (3DPCC) are one of the contemporary digitization and fabrication techniques being adopted by the construction industry. Improving interlayer bond strength (IBS) is one of the most significant barriers to commercializing 3DPCC. This article focuses on the characterization of interlayer bond mechanism via microstructural characterization techniques such as scanning electron microscopy, computed tomography imaging, and mercury intrusion porosimetry. Moreover, different driving mechanisms that result in poor IBS of 3DPCC are critically analyzed, including thixotropic behavior, surface moisture content, mix design, surface roughness, time gap, nozzle standoff distance, and curing regime. Finally, this article thoroughly reviews mitigation strategies (such as mechanical interlocking and chemical bonding agent) to determine the best appropriate strategy for enhancing the IBS of 3DPCC. The results reveal that the poor IBS of 3DPCC is due to the formation of voids between the layers, which is caused primarily by a loss of surface moisture content and thixotropic behavior. However, because of its complex dependence on various parameters, the precise cause of weak interfacial properties is still unknown. With the use of a chemical bonding agent and mechanical interlocking mechanisms, the IBS of 3DPCC can be increased by 20–30% and 50–60%, respectively. The long-term performance of mitigation strategies, on the other hand, has not been thoroughly investigated. This article will help researchers understand the mechanism underlying 3DPCC's poor interfacial properties and develop new or improved enhancement strategies to promote 3DPCC preparation in the construction industry.

Influence of printing parameters on 3D printing engineered cementitious composites (3DP-ECC)

3D printing of engineered cementitious composites (3DP-ECC) serves as an effective means to enable digital and automated construction while removing the dependence of steel reinforcement typical in normal concrete construction. As generally recognized, process control in 3DP is as crucial as material constituents to the performance of the printed structure. Printing parameters pose direct influence on the micro-structure of material, which further impacts the macro-scale properties of printed ECC. In this paper, the effects of different nozzle standoff distances and nozzle travelling speeds are investigated. It is found that lowering the nozzle standoff distance within a certain range increases the in-plane tensile strength and strain capacity of 3DP-ECC by 39% and 30%, respectively. The tensile performance is also enhanced by a moderate printing speed. In addition, a 141% increase in interfacial fiber bridging force is found with elevated nozzle standoff distance. Furthermore, the micro-structure observed via μ-CT correlates well with the printing parameters, micro-structure and macro-scale properties of 3DP-ECC.

3D printability of ternary Portland cement mixes containing fly ash and limestone

This paper reports the influence of limestone, by partial replacement of fly ash, on the fresh properties, printability, and interlayer bond strength of 3D printed high volume fly ash mortar. Limestone powders at replacement levels between 0 and 15% (mass basis) were used to proportion ternary binder formulations. The incorporation of limestone alters fresh properties like slump, slump flow, yield stress. It was observed from the results of 3D printing test that ternary mixes with limestone demonstrates higher buildability. Based on the material relative deformation at different times and concurrent printing, the effect of mix designwas linked to the printing performance. The results of interlayer bond strength revealed that bond strength decreases with increase in limestone dosage. It was observed that the bond strength for the high buildable mix in the bottom layers was lower followed by middle and top layers. This is due to an overestimation of bond strength caused by X-directional porosity (i.e. printing direction) resulting from increased nozzle standoff distance induced by bottom layer suppression.

A new calculation formula to describe the dynamic pressure of water jet peening with elliptical nozzle for high-efficiency treatment

Water jet peening is a good potential method to control welding residual stresses. The water jet with elliptical nozzle can improve the treatment efficiency due to its large treatment area. In this article, the water jet velocity and dynamic pressure for different elliptical nozzle dimensions and standoff distances are discussed by numerical simulation. The results show that when the axial distance is 10 mm, the effective impact diameter of the elliptical nozzle a/b=8–12 is about 2 times or more than that of the circular nozzle. The length of the jet core of the elliptical nozzle is only related to the outlet structure and is independent of the inlet pressure. The correlation between the dimensionless core length of the elliptical water jet and its long and short axes is derived. When the ratio of the major axis to the minor axis is between 7 and 13, the core length of the elliptical water jet is 7–7.5 times that of its minor axis. Combining the suitable treatment area and dynamic pressure, the elliptical nozzle with an axis ratio of 8 is recommended to control the welding residual stress. Finally, a new formula for calculating dynamic pressure distribution is proposed for the elliptical nozzle water jet at different stages.

Design of novel nozzles for higher interlayer strength of 3D printed cement paste

In this study, novel nozzles for cement paste 3D printing are designed and optimized for higher interlayer strength via experiment and volume-of-fluid (VOF) based simulation, in terms of various outlet shapes and two nozzle components namely the interface shaper and the side trowel. These nozzles are evaluated experimentally and theoretically based on their performances in the specimen interlayer strength, interfacial shear stress, and cross-sectional geometry. It is concluded that the “Cir3” and the “Kidney” outlet shapes achieve the best performance with the paste water-cement (w/c) ratio ranging from 0.21 to 0.23, subject to the nozzle stand-off distance of 12 mm and printing speed of 60 mm/s. In addition, the interface shaper and the side trowel are able to further enhance the interlayer strength significantly by up to 2 times, through optimization of the interfacial geometry and minimization of the interlayer notch of 3D printed cement paste. It is also confirmed that the optimal nozzle varies with the w/c ratio of cement paste due to different notch depths that are generated, such that nozzle optimization is required along with material development for cement paste 3D printing.

Vibration-Assisted Axial Nozzle Jet Flow Wire Electrochemical Machining for Micromachining

Abstract Wire electrochemical machining (WECM) has the capability to produce metal microcomponents with high aspect ratios. However, because interelectrode gap mass transportation of electrolyte is not homogeneous due to inappropriate and insufficient flushing, novel vibration-assisted axial nozzle jet flow WECM is introduced, and a unique experimental setup and tool are created. A comparison of the axial flow system, axial flow with PZT vibration with this newly developed flushing strategy was made. The effect of the most influencing parameters, i.e., pulse voltage, wire feed rate, and duty ratio, on the machining results of each flushing strategy being analyzed. The improvement of 36% slit width reduction and 75% increase in machining accuracy compared to axial flow WECM and 23% slit width reduction and 40% increase in machining accuracy compared to axial flow with PZT vibration WECM was observed using this novel technique with microslits machined on 100 μm thick stainless steel SS304. The effect of nozzle diameter and workpiece nozzle stand-off distances on slit width machining results has been investigated. The average slit width is 115 μm at 0.4 mm nozzle diameter, and it rises to 143 μm at 1 mm nozzle diameter. The average slit width is 110 μm at a 5 mm workpiece nozzle stand-off distance, and it rises to 145 μm at a 20 mm workpiece nozzle stand-off distance. This research report also discusses microslit machining of NiTinol shape memory alloy for improving WECM performance.

Analysis of various laser cutting parameters on material removal rate for machining of aluminium 5052 using one-factor approach

In this research work, the effect of laser cutting parameters on material removal rate of aluminium 5052 is presented. The material removal rate has been analysed using various investigating techniques such as precise measuring scale and optical microscope. The various cutting parameters considered such as cutting speed, laser output power, nozzle stand-off distance and nozzle diameter. The cut quality further investigated for kerf width deviation and surface roughness using one factor approach. Using microstructural analysis, it was analysed that cutting rate and laser power as most significant parameters.