Abstract
Additive manufacturing is a recent trend in production processes owing to its many benefits. It can be defined as the process of producing parts through the deposition of material in a layer-by-layer fashion. It has been a topic of intense study and review by many researchers. Adding three-dimensional (3D) printed objects on existing surfaces enables creation of multi-material objects with tailored mechanical properties. Currently, 3D printing has extended from polymers to composites. Carbon fiber composites are one of the latest among them. Nowadays, for further enhancement of the 3D printed specimen properties pre-treatments and post-treatment are carried out. Moreover, there are special types of 3D printing technologies such as selective inhibition sintering (SIS), and layered manufacturing will facilitate localized 3D printing and reverse engineering in the 3D printing technology. Many algorithms and methods are also developed for the best fulfillment of these techniques. Here in this issue “Special Collection on Recent Trends in Design and Additive Manufacturing,” eight articles are collected presenting the current trends in the additive manufacturing technology.
The review article titled “Additive manufacturing: Challenges, trends, and applications” performed a comprehensive review on additive manufacturing. The authors discussed the evolution of additive manufacturing as a prominent technology and its various phases. Most importantly, part orientation, build time estimation, and cost computation were covered here. Moreover, the authors tried to identify the problems associated with different additive manufacturing techniques and comparative analysis with other methods, such as subtractive manufacturing. The review will help readers understand the different aspects of additive manufacturing and explore new avenues for future research.
In the article titled “Molding process and properties of continuous carbon fiber three-dimensional printing,” the authors introduced a novel molding process of 3D printing for continuous carbon fiber composites. The article includes the construction of printing material, the design of printer nozzle, and the modification of printing process. For the sake of ensuring the continuity of composited material during the processing, a cutting algorithm for jumping point is proposed to improve the printing path during process. On this basis, the experiment of continuous carbon fiber composite is performed and the mechanical properties of the printed test samples are analyzed. The results were analyzed and compared with the pure material.
The article titled “Influence of fabric pre-treatment on adhesion of three-dimensional printed material on textile substrates” studies the possible pre-treatment methods for 3D printing on a cotton fabric. The authors have shown that pre-treatments make the textile surface more hydrophobic or more hydrophilic resulting in significant modifications of the adhesion forces. In addition, the infill orientation was found to have significant effect. Meanwhile, surface roughness was found to be changing depending on the infill angle. However, no significant differences of the tensile strength or the elongation at break were measured.
In the article titled “Prediction and analysis of surface roughness in selective inhibition sintered high-density polyethylene parts: A parametric approach using response surface methodology–gray relational analysis,” the authors fabricated high-density polyethylene (HDPE) specimens through SIS process. They have investigated the key contributing parameters such as layer thickness, heater energy, heater federate, and printer feedrate on the surface quality characteristics (Ra, Rz, and Rq) of HDPE. The SIS system is custom built, and experiments are conducted based on four-factor, three-level Box–Behnken design. The empirical models have been developed for predicting the influence of selected parameters on surface quality. The optimal process parameters were obtained using gray relational multi-criteria decision-making approach. They found that surface quality of sintered components is influenced significantly with heater energy and heater feedrate, followed by layer thickness using response surface analysis. Confirmation experiments based on optimal process variables were conducted to validate the developed gray relational analysis strategy.
The article titled “Layered manufacturing for medical imaging data” discusses a modeling procedure to efficiently create geometrical representations of objects from computerized tomography scan and magnetic resonance imaging data sets. Even though there are many different models for the same, they either require extra efforts to resolve ambiguity problems and to fix broken surfaces or they cannot generate legitimate models for layered manufacturing. In this proposed procedure, in the first step, it extracts the iso-surface of the target object from the input data set. Then it converts the iso-surface into a 3D image and filters this 3D image using morphological operators to remove dangling parts and noises. Finally, a boundary representation is built from the distance field to model the target object. Compared with conventional modeling techniques, the proposed method possesses the following advantages: (1) it reduces human efforts involved in the geometrical modeling process; (2) it can construct both solid and hollow models for the target object, and wall thickness of the hollow models is adjustable; (3) the resultant boundary representation guarantees to form a watertight solid geometry, which is printable using 3D printers; and (4) the proposed procedure allows users to tune the precision of the geometrical model to compromise with the available computational resources.
The article titled “Toward the integration of lattice structure-based topology optimization and additive manufacturing for the design of turbomachinery components” discusses the extraordinary potential of topology optimization method (especially when coupled with additive manufacturing and lattice structures) of the rotating machines. Here, the authors discuss about the applicability of topology optimization, additive manufacturing, and lattice structures to the fields of turbomachinery and rotor-dynamics. The techniques are applied to a turbine disk to optimize its performance in terms of resonance and mass reduction. The obtained results allow improving existing turbomachinery components’ performance when compared with traditional one.
The article titled “Analysis on selective laser melting of WC-reinforced H13 steel composite powder by finite element method” developed a 3D finite element model for the selective laser melting process to analyze the melting behavior of WC-reinforced H13 steel composite powder. In this model, convection and radiation on the external surface during laser irradiation were considered, and moving Gaussian heat flux was assumed in the thermal model. The molten pool geometry based on the simulated temperature distributions was investigated for various parameters. The input values were experimentally determined at given mixing ratios of WC and H13 steel. The simulation results showed that the relative fractions of WC and H13 steel powder significantly affect molten pool geometry. In terms of point-of-process parameters, the distribution factor, packing efficiency, and absorption coefficient are the main parameters that control molten pool geometry.
In the article titled “Rail wear inspection based on computer-aided design model and point cloud data,” the authors developed a structured light rail wear inspection system to obtain continuous 3D data. Furthermore, the data processing method for aligning the point cloud from structured light scanning to the nominal computer-aided design model of the rail is investigated. For further data registration, the point cloud of the computer-aided design model is generated, and the normal vectors of these points are calculated. The vertical and lateral wear amounts are obtained on the cross section by slicing the aligned 3D point clouds data. Finally, the proposed system and method are validated by comparing the vertical wear amounts with the two-dimensional laser scanning and contact measurement results.