Due to the availability of materials and low cost for production, fused deposition modeling is becoming the most widely used additive manufacturing (AM) technology. However, the reasonable choice of process parameters for FDM is a significant task that directly affects the performance of the printed part. Therefore, it is necessary to investigate the influences of various process parameters on the quality characteristics of the components. The objectives of this study are to thoroughly review the current state of research that characterizes, estimates the effects of process parameters on mechanical properties, and summarizes the conclusions of existing works. In addition, some general issues of the presented research are summarized, and the need for future development is also emphasized. Finally, the research proposes several areas that deserve further study in this field.

In the present study, a comparison of two widely used optimization approaches for fused deposition modeling (FDM), that is, Taguchi method in contrast with response surface method (RSM), was investigated. Four operating parameters, namely extrusion temperature, layer thickness, raster width, print speed, and their interaction terms, were identified as control variables with three levels, while tensile strength and compressive strength were selected responses. L27 orthogonal array and face-centered central composite design (FCCCD) were used for the experimental approach for Taguchi and RSM, respectively. The signal-to-noise (S/N) ratio and analysis of variance (ANOVA) were employed to find the optimal FDM parameter combination as well as the main factor that affect the performance of the PLA samples. Based on experimental results, it was observed that conclusions about significant ranking of parameters on FDM process from these two methods were different. However, both the Taguchi method and RSM succeed in predicting better results compared with the original groups. In addition, the optimum combinations for tensile strength and compressive strength obtained from the RSM were 2.11% and 8.15% higher than Taguchi method, respectively.

The objective of the present work is to evaluate the influence of material color on mechanical properties of fused deposition modeling (FDM) parts. The performance of the products is evaluated by testing eight different colors of acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) material in terms of tensile strength, compressive strength, and flexural strength. The analysis of data shows a significant difference in mechanical characteristics of prints depending on filament color. For different colors, these three strengths almost follow the same rising and falling tendency. In order to explore the relationship between mechanical strengths and filament colors, the color-mixing theory and the least-squares method are adopted to fit the best ratio coefficients of different color combinations. Results are presented showing that the strength value (e.g., tensile) of the mixed color can be evaluated through that of primary colors by fitting the other strength (e.g., compressive or flexural). It is shown that the predicted value is always no more than 7% error compared with the actual strength, in spite of two-color or three-color mixtures. An additional confirmation test with seven colored PLA filaments from different suppliers was conducted to focus on the extensibility. The outcomes show the maximum fitting errors of strengths for mixed colors in all cases are within 5%, proving the effectiveness and applicability of this predicted approach. This study can bring a detailed analysis that enables better estimation of the function of material color and contributes to improving the property of FDM printed products for consumers by choosing the suitable filament color.

The aim of this article is to provide an effective method to generate the ground structure in truss topology optimization. The core of this method is to place nodal points for the ground structure at the intersection of the first and third principal stress trajectories, which are obtained by solving the equivalent static problem in the design domain with a homogeneous isotropic material property. It is applicable to generate the ground structure for arbitrary regular and irregular geometric design domains. The proposed method is tested on some benchmark examples in truss topology optimization. The optimization model is a standard linear programming problem based on plastic design and solved by the interior point algorithm. Compared with other methods, the proposed method may use a well-defined ground structure with fewer nodes and bars, resulting in faster solution convergence, which shows it to be efficient.

Taking the PLA molded by FDM as the research object, the influence of various process parameters on mechanical properties is investigated through comparative experiments, which provides reference and help for the promotion and application of FDM molding technology. During the molding process, the PLA material undergoes the process of melting to solidification, thus the performance of the molded part is worse than the original due to thermal shrinkage and other reasons. To improve the quality and mechanical properties of the molded parts, the experiment is designed using an orthogonal test method in parallel with nine different sets of process parameters (layer thickness, build direction, filling speed, and infill density, etc.). Ultimately, the mechanical properties of PLA are tested and the results are analyzed respectively to determine the main factors affecting the mechanical properties and their optimal level combination. Among them, fill rate is the crucial factor in compressive property, while build direction has a significant effect on surface roughness, tensile property and bending property.

Photomultiplication-type ultraviolet (UV)/visible photodetectors (PDs) are demonstrated in an electrodeposited Cu₂O/C₆₀ hybrid structure. These simple organic/inorganic hybrid PDs exhibit external quantum efficiencies (EQEs) of 1.1 × 10⁴% under illumination of 365 nm UV light at −3 V, indicating a large gain of photocurrent for these devices. Such an EQE is one of the highest values among the reported organic/inorganic hybrid PDs at the same voltage. Cu₂O and C₆₀ are found to play different roles in realizing the photomultiplication. Copper vacancies are proposed as the defects in the electrodeposited Cu₂O layers, which can trap photogenerated holes. Such trapped holes will trigger the injection of multiple electrons and hence result in the photocurrent gain of the devices while C₆₀ primarily acts as a light absorption media to provide free holes.