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The purpose of this paper is provide a broad view for the standardization efforts of color quality evaluation of color 3D printing techniques. Further, this review paper demonstrates the processes and color properties of most color 3D printing techniques with specific devices and applications to extend the range of possible memberships of standardization group.

Six color 3D printing techniques including plastic-based, paper-based, powder-based, organism-based, food-based and metal-based color 3D printing have been introduced and illustrated with colorization principles and forming features in detail. Moreover, for printed 3D color objects, literature about color measurement, color specification and color reproduction are described and analyzed, respectively.

Four color 3D printing techniques including plastic-based, paper-based, powder-based and food-based color 3D printing show great affinity toward standardization of color quality evaluation, while their colorization principles indicate that it is difficult with a single standard frame. It is possible to develop a completed color quality evaluation standard for color 3D printing based on approaches in color 2D printing when color measurement method and devices are standardized together.

The paper provides an important guide focusing on the efforts to standardize the colorization processes and color quality evaluation of the color 3D printing techniques.

This paper aims to summarize the up-to-date research performed on combinations of various biofibers and resin systems used in different three-dimensional (3D) printing technologies, including powder-based, material extrusion, solid-sheet and liquid-based systems. Detailed information about each process, including materials used and process design, are described, with the resultant products’ mechanical properties compared with those of 3D-printed parts produced from pure resin or different material combinations. In most processes introduced in this paper, biofibers are beneficial in improving the mechanical properties of 3D-printed parts and the biodegradability of the parts made using these green materials is also greatly improved. However, research on 3D printing of biofiber-reinforced composites is still far from complete, and there are still many further studies and research areas that could be explored in the future.

The paper starts with an overview of the current scenario of the composite manufacturing industry and then the problems of advanced composite materials are pointed out, followed by an introduction of biocomposites. The main body of the paper covers literature reviews of recently emerged 3D printing technologies that were applied to biofiber-reinforced composite materials. This part is classified into subsections based on the form of the starting materials used in the 3D printing process. A comprehensive conclusion is drawn at the end of the paper summarizing the findings by the authors.

Most of the biofiber-reinforced 3D-printed products exhibited improved mechanical properties than products printed using pure resin, indicating that biofibers are good replacements for synthetic ones. However, synthetic fibers are far from being completely replaced by biofibers due to several of their disadvantages including higher moisture absorbance, lower thermal stability and mechanical properties. Many studies are being performed to solve these problems, yet there are still some 3D printing technologies in which research concerning biofiber-reinforced composite parts is quite limited. This paper unveils potential research directions that would further develop 3D printing in a sustainable manner.

This paper is a summary of attempts to use biofibers as reinforcements together with different resin systems as the starting material for 3D printing processes, and most of the currently available 3D printing techniques are included herein. All of these attempts are solutions to some principal problems with current 3D printing processes such as the limit in the variety of materials and the poor mechanical performance of 3D printed parts. Various types of biofibers are involved in these studies. This paper unveils potential research directions that would further widen the use of biofibers in 3D printing in a sustainable manner.

The purpose of this paper is to study a feasible visualization of large-size three-dimension (3D) color models which are beyond the maximum print size of newest paper-based 3D printer used 3D cutting-bonding frame (3D-CBF) and evaluate the effects of cutting angle and layout method on printing time of designed models.

Sixteen models, including cuboid model, cylinder model, hole model and sphere model with different shape features, were divided into two symmetric parts and printed by the Mcor IRIS HD 3D printer. Before printing, two sub-parts were rearranged in one of three layout methods. Nine scaled sizes of original models were printed to find the quantitative relationship between printing time and scale values in each type. For the 0.3 times of original models, six cutting angles were evaluated in detail.

The correlation function about colorization time and printed pages was proposed. Based on 3D-CBF, the correlation between printing time and scale size is statistically defined. Optimization parameters of designed parts visualization about cutting angel and layout method were found, even if their statistical results were difficult to model their effects on printing time of specimens.

The research is comparative and limited to the special models and used procedures.

The paper provides a feasible visualization and printing speed optimization methods for the further industrialization of 3D paper-based printing technology in cultural creative field.

This paper aims to present the results that can be achieved using continuous three-dimensional (3D) printing technology.

In the first section, conventional additive manufacturing and continuous 3D-printing are described and compared against each other. Essential is the new approach to coat the particulate material and to print it on a tilted surface. For this special setup, theoretical considerations for sources of distortions are given. These considerations define the design of the test parts. For the evaluation of a tilted setup a prototype using large dimensions is shown. Of special interest is the exact transportation using a large mass of particulate material.

The 3D-printing principle is suitable for tilted surfaces, making production without any downtime possible. The parts produced using the prototype continuous 3D-printer have sufficient accuracy for foundry use, although various considerations and the setup show that angular deflections can be caused by inaccuracies in the feeding system.

The parts’ accuracy is additionally affected by the thickness of unbound particle material under the building area. The amount of unbound particle material is of a constructive nature. Thus, the setup is limiting the investigations. Using the current material system, the printing should take place as near to the conveyor belt as possible.

This paper outlines which kind of parts can be manufactured using continuous 3D-printing.

This article shows a first evaluation of parts printed using continuous 3D-printing. It gives a perspective on future designs from rapid prototyping machines based on these principles and shows the possible benefits. The change over from rapid prototyping to rapid manufacturing will be strongly accelerated by said machine design.

The purpose of this work is to introduce a novel approach of using additive manufacturing (AM) to produce dense complex ceramic and metallic parts. Powder 3D printing has been gaining popularity due to its ease of use and versatility. However, powder-based methods such as Selective Laser Melting (SLM) and Sintering (SLS), utilizes high power lasers which generate thermal shock conditions in metals and are not ideal for ceramics due to their high melting temperature. Indirect additive manufacturing methods have been explored to address the above issues but have proven to be wasteful and time-consuming.

In this work, a novel approach of producing high density net-shaped prototypes using subtractive sintering (SS) and solvent jetting is developed. AM combined with SS (AM-SS) is a process that includes five simple steps. AM-SS can produce repeatable and reliable results as has been shown in this work.

As a proof-of-concept, a zirconia dental crown with a high density of 97% is fabricated using this approach. Microstructure and properties of the fabricated components are analyzed.

A major advantage of this method is the ability to efficiently fabricate high density parts using either metal powder and more importantly, ceramic powder which is traditionally difficult to densify using AM. Additionally, any powder particle size (including nano) and shape can be used which is not the case for traditional powder-based 3D printing.

This study aims to examine on-site particle concentration levels due to emissions from a wide spectrum of additive manufacturing techniques, including polymer-based material extrusion, metal and polymer-based powder bed fusion, directed energy deposition and ink-based material jetting.

Particle concentrations in the operating environments of users were measured using a combination of particle sizers including the TSI 3910 Nano SMPS (10–420 nm) and the TSI 3330 optical particle sizer (0.3–10 µm). Also, fumes from a MEX printer during printing were directly captured using laser imaging method.

The number and mass concentration of submicron particles emitted from a desktop open-type MEX printer for acrylonitrile-butadiene-styrene and polyvinyl alcohol approached and significantly exceeded the nanoparticle reference limits, respectively. Through laser imaging, fumes were observed to originate from the printer nozzle and from newly deposited layers of the desktop MEX printer. On the other hand, caution should be taken in the pre-processing of metal and polymer powder. Specifically, one to ten micrometers of particles were observed during the sieving, loading and cleaning of powder, with transient mass concentrations ranging between 150 and 9,000 µg/m³ that significantly exceeded the threshold level suggested for indoor air quality.

Preliminary investigation into possible exposures to particle emissions from different 3D printing processes was done, which is useful for the sustainable development of the 3D printing industry. In addition, automatic processes that enable “closed powder cycle” or “powder free handling” should be adopted to prevent users from unnecessary particle exposure.

The material-jetting-type (MJ) 3-D printing technology has advantages in resolution and color printing. During the printing process, a leveling technique is needed to precisely control the thickness and flatness of each layer. Roller-type leveling mechanism has been adopted in commercial MJ 3-D printers, but it is lack of research on roller leveling process parameters and establishing experimental procedures. Therefore, in this study, a roller-type leveling mechanism for a MJ color 3 D printer was developed, and experimental approaches were utilized to determine process parameters.

The roller-type leveling mechanism was chosen to provide functions of flattening and removal of excess material. The parameters studied were roller speed and rotational direction. Surface roughness, Ra, of printed single-layered specimens was measured at 15 locations for plane roughness and along five lines for line roughness to evaluate the leveling results. Adopting suitable parameters, color samples with and without leveling were printed for comparison and verification.

According to plane roughness results, forward rotation achieved better leveling. Plane roughness was the major criteria to determine roller speed with the assistance of standard deviation of line roughness. The best parameters of the self-developed MJ color 3-D printer were found to be rolling forward at 1,100 rpm. In addition, printed color samples showed great improvement in surface roughness with leveling and no obvious color mixing after leveling.

Leveling is important to achieve desired layer thickness, smooth surface and good color quality in color 3-D printing. For MJ 3-D printing, only patents were revealed regarding roller design, but paper publications have not been presented. This research practically proposed to use experimental approach to understand the effects of roller operating parameters and to find the suitable ones based on surface roughness results.

This research established the experimental procedures and also suggested guidelines of experimentally obtaining suitable roller leveling process parameters. Developers can refer to this study results to design and adjust leveling mechanism in a new MJ 3-D printer.

The experimental approach can be applied to similar MJ 3-D printing systems if different materials are introduced or the platform speed is changed. The observed trends suggested several guidelines to plan limited experiments only to obtain suitable roller process parameters.

The purpose of this paper is to describe, review, classify and analyze the current challenges in three-dimensional printing processes for combined electrochemical and microfluidic fabrication areas, which include printing devices and sensors in specified areas.

A systematic review of the literature focusing on existing challenges is carried out. Focused toward sensors and devices in electrochemical and microfluidic areas, the challenges are oriented for a discussion exploring the suitability of printing varied geometries in an accurate manner. Classifications on challenges are based on four key categories such as process, material, size and application as the printer designs are mostly based on these parameters.

A key three-dimensional printing process methodologies have their unique advantages compared to conventional printing methods, still having the challenges to be addressed, in terms of parameters such as cost, performance, speed, quality, accuracy and resolution. Three-dimensional printing is yet to be applied for consumer usable products, which will boost the manufacturing sector. To be specific, the resolution of printing in desktop printers needs improvement. Printing scientific products are halted with prototyping stages. Challenges in three-dimensional printing sensors and devices have to be addressed by forming integrated processes.

The research is underway to define an integrated process-based on three-dimensional Printing. The detailed technical details are not shared for scientific output. The literature is focused to define the challenges.

The research can provide ideas to business on innovative designs. Research studies have scope for improvement ideas.

Review is focused on to have an integrated three-dimensional printer combining processes. This is a cost-oriented approach saving much of space reducing complexity.

To date, no other publication reviews the varied three-dimensional printing challenges by classifying according to process, material, size and application aspects. Study on resolution based data is performed and analyzed for improvements. Addressing the challenges will be the solution to identify an integrated process methodology with a cost-effective approach for printing macro/micro/nano objects and devices.

A solid freeform fabrication (SFF) technique is described where powder is deposited layer‐by‐layer using electrophotographic printing. In the electrophotography process, powder is picked up and deposited using an electrostatically charged surface. A test bed was designed and constructed to study the application of electrophotography to SFF. It can precisely deposit powder in the desired shape on each layer. A polymer toner powder was used to build small components by thermally fusing each layer of printed powder using a hot compaction plate. The feasibility of 3D printing using this approach was also studied by printing a binder powder using electrophotography on to a part powder bed.

This paper aims to investigate the mechanical behavior of three-dimensional (3D) calcium sulfate porous structures created by a powder-based 3D printer. The effects of the binder-jetting and powder-spreading orientations on the microstructure of the specimens are studied. A micromechanical finite element model is also examined to predict the properties of the porous structures under the load.

The authors printed cylindrical porous and solid samples based on a predefined designed model to study the mechanical behavior of the prototypes. They investigated the effect of three main build bed orientations (x, y and z) on the mechanical behavior of solid and porous specimens fabricated in each direction then evaluated the micromechanical finite-element model for each direction. The strut fractures were analyzed by scanning electron microscopy, micro-computed tomography and the von Mises stress distribution.

Results showed that the orientation of powder spreading and binder jetting substantially influenced the mechanical behavior of the 3D-printed prototypes. The samples that were fabricated parallel to the applied load had higher compressive strength compared with those printed perpendicular to the load. The results of the finite element analysis agreed with the results of the experimental mechanical testing.

The mechanical behavior was studied for the material and the 3D-printing machine used in this research. If one were to use another material formulation or machine, the printing parameters would have to be set accordingly.

This work aimed to re-tune the control factors of an existing rapid prototyping process for the given machine. The authors achieved these goals without major changes in the already developed hardware and software architecture.

The results can be used as guidelines to set the printing parameters and a model to predict the mechanical properties of 3D-printed objects for the development of patient- and site-specific scaffolds.