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This paper aims to analyze experimentally and numerically the effect of the nozzle temperature and feed rates on the dimensions of the fused deposition modeling (FDM) polymer parts.

In total, 30 strips per sample were printed with the same width as the nozzle diameter. The strips were printed with one vertical movement of the nozzle head. The width of the strips was measured with a caliper at five locations. A linear regression model was created based on the experimental data to understand the correlation between the strip width deviation and the parameters of interest. Numerical simulations were performed to predict the swell of the polymer exiting the nozzle using finite element method combined with level set method. The experimental results were then used to validate the models.

The average accuracy of polylactic acid (PLA) samples was better than that of acrylonitrile butadiene styrene (ABS) samples. The average strip width had a tendency to increase with increasing temperature for PLA samples, whereas ABS samples showed mixed behavior. The strip width decreased with increasing feed rate for most cases. The measurement positions had a major effect on strip width when compared to nozzle temperature and feed rate. The numerical model predictions were in good agreement with the experimental data. A few discrepancies were observed at high feed rates and nozzle temperatures.

This study will contribute to gaps in knowledge regarding the effect of processing conditions on dimensional accuracy of FDM-printed parts. The developed numerical model can be efficiently used to predict the dimensional accuracy of FDM-printed parts.

The purpose of this paper is to study the combined effects of inlet airflow temperature and the expansion angle of the upper expansion surface (upper expansion angle) on the performance of the scramjet nozzle.

The Spalart-Allmaras turbulence two-dimensional model of the nozzle is established for the study. The influence of inlet airflow temperature on the performance of the nozzle is analyzed by detecting the change of the wall pressure of the nozzle. The three angles are chosen for the upper expansion angle (β_b) in the model: 8°, 12° and 16°. The temperature of inlet airflow is 600–1,800 K.

The study results show that when the β_b is 8° and 16°, the wall pressure of the nozzle has a complicated and large fluctuation with the inlet airflow temperature, while the wall pressure has little change as β_b is 12°; the thrust coefficient, pitching moment coefficient and lift coefficient of the nozzle fluctuate greatly with the increase of the inlet airflow temperature when β_b is 8° and 16°, while the thrust coefficient, pitching moment coefficient and lift coefficient have little fluctuation as β_b is 12°.

The study of the combined effects of the inlet airflow temperature and upper expansion angle on the performance of the scramjet nozzle can provide guidance for the design of scramjet nozzles.

Most rapid prototyping (RP) relies on energy fields to handle materials, among which electricity has been much more utilized, resulting in distinctive responsiveness of non-linear, overshoot, variable inertia, etc. The purpose of this paper is to eliminate the drawbacks of array nozzle clogging, stringing, melt sagging, particularly in multi-material RP, by focusing on the electrothermal response so as to adaptively distribute thermal more accurate, rapid and balanced.

This paper presents an electrothermal response optimization method of nozzle structure for multi-material RP based on fuzzy adaptive control (FAC). The structural, physical and control model are successively logically built. The fractional order electrothermal model is identified by Riemann Liouville fractional differential equation, using the bisection method to approximate the physical model via least square method to minimize residual sum of squares. The FAC is thereafter implemented by defining fuzzy proportion integration differentiation control rules and fuzzy membership functions for fuzzy inference and defuzzification.

The transient thermodynamic and structural statics, as well as flow field analysis, are conducted. The response time, mean temperature difference and thermal deformation can be found using thermal-solid coupling finite element analysis. In physical experimental research, temperature change, together with material extrusion loading, were measured. Both numerical and physical studies have revealed findings that the electrothermal responsiveness varies with the three-dimensional structure, materials and energy sources, which can be optimized by FAC.

The proposed FAC provides an optimization method for extrusion-based multi-material RP between the balance of thermal response and energy efficiency through fulfilling potential of the hardware configuration. The originality may be widely adopted alongside increasing requirements on high quality and high efficiency RP.

A main cause of defects within material extrusion (MatEx) additive manufacturing is the nonisothermal condition in the hot end, which causes inconsistent extrusion and polymer welding. This paper aims to validate a custom hot end design intended to heat the thermoplastic to form a melt prior to the nozzle and to reduce variability in melt temperature. A full 3D temperature verification methodology for hot ends is also presented.

Infrared (IR) thermography of steady-state extrusion for varying volumetric flow rates, hot end temperature setpoints and nozzle orifice diameters provides data for model validation. A finite-element model is used to predict the temperature of the extrudate. Model tuning demonstrates the effects of different model assumptions on the simulated melt temperature.

The experimental results show that the measured temperature and variance are functions of volumetric flow rate, temperature setpoint and the nozzle orifice diameter. Convection to the surrounding air is a primary heat transfer mechanism. The custom hot end brings the melt to its setpoint temperature prior to entering the nozzle.

This work provides a full set of steady-state IR thermography data for various parameter settings. It also provides insight into the performance of a custom hot end designed to improve the robustness of melting in MatEx. Finally, it proposes a strategy for modeling such systems that incorporates the metal components and the air around the system.

Temperature is a critical factor in the fused filament fabrication (FFF) process, which affects the flow behavior and adhesion of the melted filament and the mechanical properties of the final object. Therefore, modeling and predicting temperature in FFF is crucial for achieving high-quality prints, repeatability, process control and failure prediction. This study aims to investigate the melt deposition and temperature profile in FFF both numerically and experimentally using different Acrylonitrile Butadiene Styrene single-strand specimens. The process parameters, including layer thickness, nozzle temperature and build platform temperature, were varied.

COMSOL Multiphysics software was used to perform numerical simulations of fluid flow and heat transfer for the printed strands. The polymer melt/air interface was tracked using the coupling of continuity equation, equation of motion and the level set equation, and the heat transfer equation was used to simulate the temperature distribution in the deposited strand.

The numerical results show that increasing the nozzle temperature or layer thickness leads to an increase in temperature at points close to the nozzle, but the bed temperature is the main determinant of the overall layer temperature in low-thickness strands. The experimental temperature profile of the deposited strand was measured using an infrared (IR) thermal imager to validate the numerical results. The comparison between simulation and observed temperature at different points showed that the numerical model accurately predicts heat transfer in the three-dimensional (3D) printing of a single-strand under different conditions. Finally, a parametric analysis was performed to investigate the effect of selected parameters on the thermal history of the printed strand.

The numerical results show that increasing the nozzle temperature or layer thickness leads to an increase in temperature at points close to the nozzle, but the bed temperature is the main determinant of the overall layer temperature in low-thickness strands. The experimental temperature profile of the deposited strand was measured using an IR thermal imager to validate the numerical results. The comparison between simulation and observed temperature at different points showed that the numerical model accurately predicts heat transfer in the 3D printing of a single-strand under different conditions. Finally, a parametric analysis was performed to investigate the effect of selected parameters on the thermal history of the printed strand.

This work aims to develop a new kind of semicrystalline polymer filament and optimize its printing parameters in the fused deposition modeling process. The purpose of this work also includes producing FDM parts with good ductility.

A new kind of semicrystalline filaments composed of long-chain polyamide (PA)1012 was prepared by controlling screw speed and pulling speed carefully. The optimal printing parameters for PA1012 filaments were explored through investigating dimensional accuracy and bonding strength of FDM parts. Furthermore, the mechanical properties of PA1012 specimens were also evaluated by varying nozzle temperatures and raster angles.

It is found that PA1012 filaments can accommodate for FDM process under suitable printing parameters. The print quality and mechanical properties of FDM parts highly depend on nozzle temperature and bed temperature. Even though higher temperatures facilitate stronger interlayer bonding, FDM parts with excellent tensile strength were obtained at a moderate nozzle temperature. Moreover, a bed temperature well above the glass transition temperature of PA1012 can eliminate shrinkage and distortion of FDM parts. As expected, FDM parts prepared with PA1012 filaments exhibit good ductility.

Results in this work demonstrate that the PA1012 filament allows the production of FDM parts with desired mechanical performance. This indicates the potential for overcoming the dependence on amorphous thermoplastics as a feedstock in the FDM technique. This work also provides insight into the effect of materials properties on the mechanical performance of FDM-printed parts.

To study the flow character in a micro nozzle.

The flow in the micro nozzle is simulated using the Direct Simulation Monte‐Carlo (DSMC) method. Considering characteristics of high‐temperature gas flow, the Cercignani‐Lampis‐Lord (CLL) gas‐surface interaction model is adopted in the simulation of high‐temperature gas flow in the Laval nozzle at different inlet pressures and temperatures.

The results showed that as the temperatures of inlet flow increased, the thrust efficiency will increased accordingly, however, the influence of inlet pressure variety on the nozzle performance is insignificant.

A useful reference to the design and performance improvement of micro thruster and MEMS power system.

This paper aims to provide an overview of the recent findings of the mechanical properties of parts manufactured by fused deposition modeling (FDM). FDM has become a widely used technique for the manufacturing of thermoplastic parts. The mechanical performance of these parts under service conditions is difficult to predict due to the large number of process parameters involved. The review summarizes the current knowledge about the process-property relationships for FDM-based three-dimensional printing.

The review first discusses the effect of material selection, including pure thermoplastics and polymer-matrix composites. Second, process parameters such as nozzle temperature, raster orientation and infill ratio are discussed. Mechanisms that these parameters affect the specimen morphology are explained, and the effect of each parameter on the strength of printed parts are systematically presented.

Mechanical properties of FDM-produced parts strongly depend on process parameters and are usually lower than injection-molded counterparts. There is a need to understand the effect of each parameter and any synergistic effects involved better.

Through the optimization of process parameters, FDM has the potential to produce parts with strength values matching those produced by conventional methods. Further work in the field will make the FDM process more suitable for the manufacturing of load-bearing components.

This paper presents a critical assessment of the current knowledge about the mechanical properties of FDM-produced parts and suggests future research directions.

This paper aimed to propose a novel fused-coating-based additive manufacturing (FCAM); the study of key process parameters and mechanical tests are performed to determine the proper parameters when building metal components.

Sn63Pb37 alloy is deposited in an induction heating furnace with a fused-coating nozzle to build metal parts on a copper-clad substrate. The process parameters including nozzle pressure, nozzle and substrate temperature and nozzle gap between substrate are analyzed and found to have great influence on parts quality. The mechanical property tests between the fused-coating and casting parts are performed in horizontal and vertical directions. Also, the optical microscopy images are used to ascertain under which conditions good bonding can be achieved.

A FCAM method is proposed, and the exploration study about the manufacturing process is carried out. The critical parameters are analyzed, and microscopy images prove the suitable temperature range that requires to fabricate metal parts. The mechanical tests confirm that tensile strength of printing parts is improved by 20.4 and 11.9 per cent in horizontal and vertical direction than casting parts. The experimental results indicate that there is a close relationship between process parameters and mechanical properties.

This paper proves that FCAM provides an alternative way to quickly make functional metal parts with good quality and flexibility compared with other additive manufacturing methods. Moreover, good mechanical property is achieved than conventional casting parts.

The purpose of this paper is to analyze the effect of printing parameters on the mechanical properties of standard dog bone specimens manufactured by fused deposition modeling.

Polylactic acid (PLA) specimens were printed and tested according to the ASTM standard. The effect of five important printing parameters, layer height, raster angle, printing speed, nozzle temperature and nozzle diameter, was examined on ultimate tensile strength (UTS), elongation and apparent density. Five levels were attended for each parameter, and a high number of required experiments were reduced by applying the L₂₅ Taguchi design of the experiment.

The effect of each parameter on outputs and optimal values for maximum tensile strength were determined. The most influential parameter is the raster angle of 64.96%. Nozzle temperature has a low effect of 1.76%, but nozzle diameter contribution is 9.77%. The experiment results are validated by analysis of variance analysis, and the optimal predicted level for parameters is 90° raster angle, 0.2 mm layer height, 100 mm/s printing speed, 200°C nozzle temperature and 0.8 mm nozzle diameter. The maximum UTS observed is 48.70 MPa for 0.8 mm nozzle diameter, whereas the minimum is 18.49 for 0.2 mm nozzle diameter.

This paper is a very extensive experimental research report on the effect of the parameters for the tensile property of 3D printed PLA specimens by the Taguchi method. The documented results can be further developed for an optimization model to obtain a desired mechanical property with less variation and uncertainty in a product.