The use of parallel mechanisms in the structure of 3D printers are developing. Parallel mechanisms have excellent capabilities in terms of accuracy, stiffness and high load-bearing capacity. This article studies a 3D printer with four degrees of freedom that has three degrees of linear freedom and one degree of rotational freedom. The advantages of this printer are greater than conventional Cartesian printers, including higher print speed and stiffness, and there are also higher degrees of freedom for manoeuvrability. In this paper, the Newton-Euler analytical method is used to analyse the inverse dynamics and identify the driving forces required by the 3D nozzle motion. By coding the inverse dynamic equations in the MATLAB software environment, the driving forces diagrams are extracted based on the printer's nozzle motion. To validate the inverse dynamics relationships, simulations with the Simmechanic model of MATLAB software have been performed. Through changing the speed of movement of the printer nozzle and also change of the velocity and acceleration of drives, the forces required for the drive also change. The effect of changes in print speed of a specific geometry on the driving forces is also studied. As well as, choosing the optimum print speed with regard to the motor driver power and the dynamics of the forces applied to the drivers and the less print time are the most important factors that are discussed in this article.

Background: This study describes the possibility of implemen ng threedimensional prin ng technology to create a precise construc on of a planned bolus, based on computed tomography informa on stored in the Digital Imaging and Communica ons in Medicine (DICOM) format file. Materials and Methods: To create the bolus with a 3D printer, we converted data in the DICOM format to the stereolithography (STL) format. In addi on, we produced a paraffin bolus that, tradi onally, is manually placed directly on the pa ent. CT scans were acquired for both boluses, and the images were superimposed onto the pa ent CT scans that were used to design the bolus. The superimposi on of images was performed to compare the fit of the bolus printed on a 3D printer to that of the paraffin bolus made in the tradi onal way. In addi on, for both models, the dose distribu on was simulated. To quan fy the level of matching ML, special formula was used. The ML parameter had a value between 0 and 100%, where 100% indicated a perfect fit between the model and the 3D printed bolus. Results: We verified that 100% of the volume of the 3D printed bolus was located within the contour of the designed model. The ML of the bolus was 94%. For the classical paraffin bolus the ML was only 28%. Conclusion: A bolus printed on a threedimensional printer can faithfully reproduce the structure specified in the project plan. Compared to the classical paraffin bolus, the three-dimensional printed bolus more closely matched the planned model and possessed greater material uniformity.

The microstructure and properties of solid oxide fuel cell (SOFC) connected to the fabrication process are discussed in this paper. In this research, we investigate the relationship between electrochemical performance in solid oxide fuel cells and the evolution of the morphology of its electrodes. This work fabricated a planar multilayer anode-supported, anode functional layer (AFL), electrolyte, and cathode solid oxide fuel cell through slurry-based 3D printing. After drying and sintering, scanning electron microscope (SEM) images a multilayer porous structure with large pores up to several microns and smaller pores of 100 nm, and the constituent particles' microstructure for anode-cathode layers were observed. The electrolyte layer structure was dense and without pores. In the study of electrochemical properties, the maximum power density at the output voltage of 0. 5 V was achieved at 0. 84 W/cm2 at an open-circuit voltage (OCV) of 1. 06 V at 800 °, C with H2 gas as fuel. The impedance curve values under open-circuit voltage were 0. 23 V and 1. 25 V at high and low frequencies, respectively.

Presently, Three-dimensional printer technology, an exceptionally light curing-based process, has developed intensively. Depending on the light source, many commercial three-dimensional printers are available at low to high prices. Blue light, ultraviolet, and laser are the most common light sources suitable for light projection-based technology. However, improving the interaction between the light source and the material processed is still challenging. The study aimed to find the optimum parameters of distance the moving ultraviolet light to the material and print speed based on curing depth. In this study, a commercial ultraviolet light source was carried out using Cure Beam Ultraviolet Light with a wavelength of 405 nm, which was exposed in a dark environment and at room temperature. The material was Eco UV Resin Anycubic, one of the photoliquid types. MiView camera was used to obtain the depth of the curing during the light exposure using a commercial three-dimensional printer. The response surface method optimized the printing parameter with 13 sets of specimens. The specimens were printed in the form of a line shape. Characterization and mechanical properties were investigated using a scanning electron microscope and Shore D Durometer. The results show that the optimum setup printing parameters were 10 mm and 1 mm/s for distance and print speed, respectively. Furthermore, the optimum parameter setting of curing depth was 8.029 mm. The surface shows the smooth (curing area) and wavy area. The hardness numbers of the optimum parameter were 61.3 HD  (top) and 58.5 HD (bottom).

Cellular structures are broadly used because of their exclusive properties in tissue engineering. This research proposes a new method, both in design and manufacturing, to engineer their mechanical properties considering gradient material and geometrical features and evaluate the possibility of using created structures as bone implants. Schwarz-primitive surface has been utilized to design cellular structures with different porosities and unit cell sizes. A total of 18 cellular structures were designed and fabricated using the SLS 3D printer with a new unconventional approach in adjusting the settings of the machine, and their mechanical properties were extracted. The structures' internal properties were evaluated using the FESEM. Comparing the mechanical compressive test results showed that adjustments in material and geometry improved mechanical properties (such as the compressive moduli, compressive strength, and yield strength). For instance, in 3 mm samples, the elastic modulus in material gradient and geometrical gradient structures is 20% and 73 % higher than the minimum values of the uniform structure. FESEM imaging revealed that adjusting the absorbed energy by powders (controlled by laser characteristics) leads to the formation of natural voids with diameters in the range of 6 to 144 μ m for the gradient structures. Evaluation of the designed structures showed that 6 of them (4 uniform porosity and 2 geometrically gradient) have mechanical behavior of the desired tissue. The research outcomes can assist in optimizing manufactured parts by SLS 3D printers with internal and external controlled properties to obtain more desirable mechanical characteristics, especially for tissue engineering applications.