Polylactic acid (PLA) is produced from renewable materials, has a low melting temperature and has a low carbon footprint. These advantages have led to the extensive use of polylactic acid in additive manufacturing, particularly by fused filament fabrication (FFF). PLA parts that are 3D printed for industrial applications require stable mechanical properties and predictability regarding their dependence on the process parameters. Therefore, the development of the FFF process has been continuously accompanied by the development of software packages that generate CNC codes for the printers. A large number of user-controllable process parameters have been introduced in these software packages. In this respect, a lot of articles in the specialized literature address the issue of the influence of the process parameters on the mechanical properties of 3D-printed specimens. A systematic review of the research targeting the influence of process parameters on the mechanical properties of PLA specimens additively manufactured by fused filament fabrication was carried out by the authors of this paper. Six process parameters (layer thickness, printing speed, printing temperature, build plate temperature, build orientation and raster angle) were followed. The mechanical behavior was evaluated by tensile, compressive and bending properties.

The printing variable least addressed in previous research aiming to reveal the effect of the FFF process parameters on the printed PLA part’s quality and properties is the filament color. Moreover, the color of the PLA, as well as its manufacturer, are rarely mentioned when the experimental conditions for the printing of the samples are described, although current existing data reveal that their influence on the final characteristics of the print should not be neglected. In order to point out the importance of this influential parameter, a natural and a black-colored PLA filament, produced by the same manufacturer, were selected. The dimensional accuracy, tensile strength, and friction properties of the samples were analyzed and compared for printing temperatures ranging from 200 °C up to 240 °C. The experimental results clearly showed different characteristics depending on the polymer color of samples printed under the same conditions. Therefore, the optimization of the FFF process parameters for the 3D-printing of PLA should always start with the proper selection of the type of the PLA material, regarding both its color and the fabricant.

Initially developed as a rapid prototyping tool for project visualization and validation, the recent development of additive manufacturing (AM) technologies has led to the transition from rapid prototyping to rapid manufacturing. As a consequence, increased attention has to be paid to the mechanical, chemical and physical properties of the printed materials. In mechanical engineering, the widespread use of AM technologies requires the optimization of process parameters and material properties in order to obtain components with high, repeatable and time-stable mechanical properties. One of the main problems in this regard is the anisotropic behavior of components made by additive manufacturing, determined by the type of material, the 3D printing technology, the process parameters and the position of the components in the printing space. In this paper the influence of the printing orientation angle on the tensile behavior of specimens made by material jetting is investigated. The aim was to determine if the positioning of components at different angles relative to the X-axis of the printer (and implicitly in relation to the multijet printing head) contributes to anisotropic behavior. The material used was a photopolymer with a mechanical strength between 40 MPa and 55 MPa, according to the producer. Four sets of tensile test specimens were manufactured, using flat build orientation and positioned on the printing table at angles of 0˚, 30˚, 60˚ and 90˚ to the X-axis of the printer. Comparative analysis of the mechanical behavior was carried out by tensile tests and microscopic investigations of the tensile test specimens fracture surfaces.

The paper presents a fatigue analysis of low level links of a parallel topology robot guiding device mechanism. This mechanism has a FP3+3·RRS+MP3structure. The 3D model of the guiding device is presented. In a SolidWorks Motion study, motion laws for motors are defined and a force is applied on the mobile platform MP3. The loads on low level links are imported in SolidWorks Simulation module. Then, von Mises stresses are determined by finite element method and, based on these results, fatigue analysis is performed. Two variants of low level links are analized: first, with no fillet between the base cylinder and the body and second, with fillet.

Gears are frequently used in mechanical systems for power transmission, speed variation and for changing their operating sense. Mathematical modeling of gear transmissions offers a better understanding of their dynamic behavior. A significant amount of literature and studies are available in this field. Because the gears are critical components of any rotating machine, they have received considerable attention regarding their mathematical modeling, being published a lot of papers concerning this problem. The purpose of this paper is to present a mathematical model for studying the dynamic behavior of a single stage helical gearbox. Based on the proposed mathematical model and using specialized software, a numerical simulation of the gearbox dynamics will be performed. Simulation results will be compared with data obtained experimentally-obtained data.

The paper presents the finite element analysis of the outer bearing bush of a Kaplan turbine. In order to obtain von Mises stress plot, the forces are applied on the links of the 3D model of the runner blade operating mechanism, the motion is simulated, the meshing of bush model is done and the stress calculus is performed. For modeling and simulation, SolidWorks 2010 software was used.

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