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The assessment of the ability of polymeric materials to transmit heat is of interest both from the point of view of ensuring maximum thermal transfer and thermal insulation. A simple equipment was designed and materialized for studying thermal transfer in polylactic acid rods made by 3D printing. The results of some experimental tests carried out using the equipment were mathematically processed, determining empirical mathematical models of the second-degree polygon type and a power-type function. The analysis of the empirical mathematical models and the graphic representations made on their basis revealed a decrease in temperature with the increase of the distance from the heated end of the cylindrical rod type test sample and the increase in temperature along the rod until the state of thermal equilibrium is reached.

There are situations where parts manufactured by 3D printing processes must have a high abrasion resistance. To conduct experimental research on this subject, relatively simple test equipment for abrasive wear of pin-on-disk type was designed and materialized. The test pieces from the research material were pressed with known forces on the surface of a rotating abrasive paper disk. The test pieces were made of polyethylene terephthalate PET and polyethylene terephthalate carbon fiber reinforced PET CF15. As output parameters, the speed of decreasing the mass and the length of the test piece were used, respectively, for predetermined test durations. An experimental Taguchi L8 program was used, with 7 independent variables at two levels of variation. The experimental results were mathematically processed determined empirical mathematical models of the power function type. It was found that the strongest influence on the values of the output parameters was exerted by the average travel speed and by the granulation of the particles incorporated in the abrasive paper disk.

The extension of 3D printing processes for parts made of polymeric materials highlighted the possibility of manufacturing threaded surfaces through such processes. In principle, the operation of a threaded joint involves tensile forces in the threaded rod. The dimensional characteristics of the threaded surface and some input factors in the 3D printing process can influence the tensile strength of threaded rods made of polymeric materials. An experimental research aimed at the tensile behavior of a threaded joint was designed, using a plastic screw and a special steel nut. A factorial experiment was designed and implemented to identify an empirical mathematical model capable of highlighting the influence of the dimensional characteristics of the threaded surface and some of the input factors in the 3D printing process on tensile strength. The test samples from polymeric materials were manufactured by 3D printing, then subjected to tensile tests. The mathematical processing of the experimental results allowed the determination of a mathematical model that allows the inclusion of the ordering of the factors taken into account in terms of the intensity of the influence that these factors exert on the tensile strength of the threaded rods. It was found that the diameter of the threaded rod exerts the strongest influence on the tensile strength of the threaded rod obtained by 3D printing, increasing the diameter of the threaded rod causing an increase in the maximum deformation of the rod. Increasing the thread pitch leads to a decrease in the maximum deformation of the threaded rod.

The strength of a joint between the ends of one or more strips can be improved by making the contours of the joint into the shape of either the Greek letter omega or of a dovetail. From the point of view of industrial practice, it is of interest to study the behavior of these joints under stretching demands. The emergence and development of additive manufacturing processes for parts made of polymeric materials has led to the idea of conducting experimental tests to highlight the behavior of omega and dovetail-type joints during the tensile test. For the tensile testing of some test samples in which omega and dovetail joints were used, a Taguchi array of type L18 was employed, with eight independent variables, one variable with a two-level variation, and seven variables with variations on three levels. As independent variables, the type of joint, the couple of polymer materials used to make the two components of the joint, some characteristic dimensions of the joint contours, and some input factors in the 3D printing process were established. The values of average force and average displacement at the peak were considered output parameters. The experimental results were mathematically processed, determining empirical mathematical models of the second-degree polynomial type. These models highlight the influence exerted by the considered input factors on the values of the output parameters.

The form of the outer and inner surfaces of hollow spherical parts determines the developments of some particular categories of efforts during the compression tests. The overall purpose of the research presented in this paper was to study the behaviour of the hollow spherical parts under axial compression. The PLA hollow spherical parts were obtained by 3D printing and using distinct values for certain process input factors. The finite element method was used to theoretically investigate the behaviour of the parts and it highlighted the total plastic deformation of the test pieces. To experimentally verify the theoretical considerations, an L9 Taguchi orthogonal design was performed. The empirical mathematical model thus determined highlighted the stronger influence exerted by the printing plate temperature, printing speed, and part wall thickness.

The thermal properties of parts obtained by 3D printing from polymeric materials may be interesting in certain practical situations. One of these thermal properties is the ability of a material to expand as the temperature rises or shrink when the temperature drops. A test experiment device was designed based on the thermal expansion or negative thermal expansion of spiral test samples, made by 3D printing of polymeric materials to investigate the behavior of some polymeric materials in terms of thermal expansion or contraction. A spiral test sample was placed on an aluminum alloy plate in a spiral groove. A finite element modeling highlighted the possibility that areas of the plate and the spiral test sample have different temperatures, which means thermal expansions or contractions have different values in the spiral areas. A global experimental evaluation of four spiral test samples was made by 3D printing four distinct polymeric materials: styrene-butadiene acrylonitrile, polyethylene terephthalate, thermoplastic polyurethane, and polylactic acid, has been proposed. The mathematical processing of the experimental results using specialized software led to establishing empirical mathematical models valid for heating the test samples from −9 °C to 13 °C and cooling the test samples in temperature ranges between 70 °C and 30 °C, respectively. It was found that the negative thermal expansion has the highest values in the case of polyethylene terephthalate and the lowest in the case of thermoplastic polyurethane.

Background and Objectives: Acrylic resins remain the materials of choice for removable prosthesis due to their indisputable qualities. The continuous evolution in the field of dental materials offers practitioners today a multitude of therapeutic options. With the development of digital technologies, including both subtractive and additive methods, workflow has been considerably reduced and the precision of prosthetic devices has increased. The superiority of prostheses made by digital methods compared to conventional prostheses is much debated in the literature. Our study’s objective was to compare the mechanical and surface properties of three types of resins used in conventional, subtractive, and additive technologies and to determine the optimal material and the most appropriate technology to obtain removable dentures with the highest mechanical longevity over time. Materials and Methods: For the mechanical tests, 90 samples were fabricated using the conventional method (heat curing), CAD/CAM milling, and 3D printing technology. The samples were analyzed for hardness, roughness, and tensile tests, and the data were statistically compared using Stata 16.1 software (StataCorp, College Station, TX, USA). A finite element method was used to show the behavior of the experimental samples in terms of the crack shape and its direction of propagation. For this assessment the materials had to be designed inside simulation software that has similar mechanical properties to those used for obtaining specimens for tensile tests. Results: The results of this study suggested that CAD/CAM milled samples showed superior surface characteristics and mechanical properties, comparable with conventional heat-cured resin samples. The propagation direction predicted by the finite element analysis (FEA) software was similar to that observed in a real-life specimen subjected to a tensile test. Conclusions: Removable dentures made from heat-cured resins remain a clinically acceptable option due to their surface quality, mechanical properties, and affordability. Three-dimensional printing technology can be successfully used as a provisional or emergency therapeutic solution. CAD/CAM milled resins exhibit the best mechanical properties with great surface finishes compared to the other two processing methods.

A better understanding of heat transfer through materials used for 3D-printed parts could lead to an extension and an optimization of their use. A topic of interest could be analyzing temperature variation in these materials during cooling processes. Experimental research and equipment were designed to obtain additional information on the surface temperature decrease when the opposite wall surface is exposed to a freezing temperature. Experimental tests were performed on samples made of polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS). An experimental Taguchi L8 program was used, with seven independent variables at two levels of variation. The experimental data analysis with specialized software based on the least-squares method identified a mathematical model of first-degree polynomial type. The coefficients for each input factor involved provide information on the magnitude and trend of the considered output parameter when the input factors’ values change. It was found that the thickness of the 3D printing layer, the thickness of the test sample, and the 3D printing speed are the main factors that affect the temperature decrease rate.

During the electrical discharge machining process, the electrical discharges are developing between the close asperities that exist on the tool electrode and workpiece surfaces, along a trajectory of minimum electrical resistance. As a consequence of the electrical discharges, small quantities of the electrode’s materials are melted or even vaporized and afterward removed from the machining gap. Various factors exert influence on the material removal from the peaks of asperities placed on the electrode’s surfaces. An experimental method of the simulation of the material removing process was designed and applied. Single electrical discharges characterized by distinct energies were generated between the conical peaks of the previously prepared test pieces made of some electroconductive materials and the flat surface of the copper electrodes. The quantities of the material removed from the conical peaks of the test piece materials under the action of electrical discharges were measured and used to determine empirical mathematical models. These models highlight the influence exerted by some factors specific to the electrical discharges (cone angle, the voltage between electrodes, the capacitance of the capacitors included in the discharge electric circuit) on the material removal from the conical peaks of the test pieces.

The vibroburnishing is a process of surface plastic deforming applied to parts made of metallic materials to diminish the surface roughness, to increase the microhardness of the superficial layer, to generate internal stresses more convenient in certain service conditions of the parts. Practically, the ball vibrorolling process appeared as a result of including a vibratory motion. A ball is used as a deformation tool, as in the case of the more known process of burnishing. The analysis of the vibrorolling process showed that the simplest and the most accessible way of changing the process results could be based by considering the workpiece peripheral rotation speed and the longitudinal feed, respectively. An experimental research was proposed and performed to establish some empirical mathematical models that highlight the influence exerted by the workpiece peripheral rotation speed and by the longitudinal feed on the values of theRasurface roughness parameter and on the thickness of the hardened surface layer at the ball vibrorolling of the external cylindrical surfaces. The investigation considered also the influence of the distance from the test sample surface on the variation of the Vickers microhardness in the test sample superficial layer.

A characteristic of the evolution of manufacturing processes in recent years is the expansion of technologies based on additive manufacturing, especially in the case of parts made of plastic materials. One of the accessible processes for making plastic parts is fused filament fabrication. In many situations, when using fused filament fabrication, it is necessary to obtain surfaces characterized by certain values of roughness parameters. Several factors can influence surface roughness. Some of these factors consider the materialization conditions of the 3D printing process. Starting from the hypothesis that the cooling conditions and the surface position can influence the roughness parameters values, experimental tests were carried out by modifying the values of the two factors. The experimental results were mathematically processed, and power function type mathematical models were determined for the roughness parameters Rz, Rt, Rp, Ra, Rq, Rc. These models provide information on the direction of action, the intensity of the influence exerted by the cooling conditions, and the angle of inclination of the test sample surface on the values of the mentioned roughness parameters.

One of the machining methods able to ensure a high material removal rate in the case of obtaining threaded surfaces is the whirling machining. In order to obtain a high accuracy of the machined surface and low values of the surface irregularities, an adequate selection of the machining parameters is necessary. A geometrical analysis of generating the surfaces in case of applying the whirl threading was developed. Geometrical and kinematical conditions were considered and software was used in order to modelling the process and to highlight the influence exerted by some process input factors on the machining errors and height of the surface irregularities.

3D printing is one of the big top up-to-date technologies. Our aim is to show that up to a point 3D prints can successfully replace traditionally manufactured assemblies in the case of educational projects or lab experiments. We have considered a 3D printed simple-frame robotic arm upon which we have performed FEA analyses. They have shown promising results against its steel-based peer up to certain loads under the same working conditions in terms of safety factor and safety margin.

The ball vibroburnishing is a processing method based on the plastic deformation of the workpiece surface layer, as a result of a vibration movement achieved by the ball pressed with a known force on the workpiece surface. The surface obtained by ball vibroburnishing includes grooves with different directions and partially overlapped. To know better the influence exerted by the ball vibroburnishing conditions on the main dimensional characteristics of the grooves, an experimental research was designed and materialized. As the process input factors, the diameter of the ball, the force, and the workpiece rotation speed were used. The depth and width of the groves generated by the moving balls on the workpiece surface layer were measured. By mathematical processing of the experimental results, empirical mathematical models were determined. These models highlight the intensity of the influence exerted by the ball vibroburnishing process input factors on the main dimensions of the grooves.

The elaboration of a modern manufacturing technology needs a certain quantum of information concerning the part to be obtained. When it is necessary to elaborate the technology for an existing object, such an information could be ensured by using the principles specific to the reverse engineering. Essentially, in the case of this method, the analysis of the surfaces and of other characteristics of the part must offer enough information for the elaboration of the part manufacturing technology. On the other hand, it is known that the laser marking is a processing method able to ensure the transfer of various inscriptions or drawings on a part. Sometimes, the laser marking could be based on the analysis of an existing object, whose image could be used to generate the same object or an improved object. There are many groups of factors able to affect the results of applying the laser marking process. A theoretical analysis was proposed to show that the heights of triangles obtained by means of a CNC marking equipment depend on the width of the line generated by the laser spot on the workpiece surface. An experimental research was thought and materialized to highlight the influence exerted by the line with and the angle of lines intersections on the accuracy of the marking process. By mathematical processing of the experimental results, empirical mathematical models were determined. The power type model and the graphical representation elaborated on the base of this model offered an image concerning the influences exerted by the considered input factors on the marking process accuracy.The elaboration of a modern manufacturing technology needs a certain quantum of information concerning the part to be obtained. When it is necessary to elaborate the technology for an existing object, such an information could be ensured by using the principles specific to the reverse engineering. Essentially, in the case of this method, the analysis of the surfaces and of other characteristics of the part must offer enough information for the elaboration of the part manufacturing technology. On the other hand, it is known that the laser marking is a processing method able to ensure the transfer of various inscriptions or drawings on a part. Sometimes, the laser marking could be based on the analysis of an existing object, whose image could be used to generate the same object or an improved object. There are many groups of factors able to affect the results of applying the laser marking process. A theoretical analysis was proposed to show that the heights of triangles obtained by means of a CNC marking eq...

Electronic learning, distant learning, collaborative work, mobile learning and internet based learning concepts are ever more present in superior learning systems. At this date for study or for finding different information we may access different search engines (like Google) where we can consult information based websites, blogs or online tutorials. Elearning systems can be grouped in online systems that have no direct interaction between the students and the professor, face to face systems that use both electronic resources and student-professor interaction, selflearning systems based on blogs, tutorials, teaching programs or web based systems. We can safely assume that e-learning is rapidly growing and that many universities have online free platforms developed for aiding students. The technological leap of current industries poses new challenges for the traditional educational systems. Efforts are known and acknowledged for changing and enhancing the existent educational systems and the orientation towards online learning processes.

There is an entire array of options when you are planning a CAM machining strategy. Knowing your equipment possibilities and adjusting your software options to them has become mandatory in terms of cost and time efficiency. This paper aims to present the main options for most common software solutions used today in modern mechanical engineering which can be applied to the existing hardware manufacturing equipment found in enterprises or educational centers.

In the present study the authors propose an experimental framework in order to perform FEA analyses upon a 3D model of a connecting rod. The study presents some of the technical issues that have been overcome by choosing the right software tools and the differences in terms of results that they may produce, it shows the setup used in the analyses including its constraints and loads, the proposed algorithm that imposed the number of analyses as well as their type, and the way the analyses were conducted in order for the results to validate or invalidate a optimized model. Because the connecting rod's 3D model presents a high level of complexity in terms of the number of free forms surfaces contained within the geometry, the authors propose a procedure by which they divide the geometry in areas of interest and in doing so can determine the most critical and the most affected areas under a given load for each FEA analysis. This procedure allows a virtual perspective of the modality through which the considered part gets affected and behaves under a given load in terms of distribution of stress and deformation, results that are consistent with its overall behavior.

In the technical literature there are some studies which use measured signals in order to compensate the errors caused by vibrations [1, 2], by the cutting force [3], by the deflections of the technological system [4], and others. Also, the technical literature presents some studies [6, which give few measurement techniques in order to measure the error which appears into the turning process and also, some methods to compensate or eliminate the consequences produced by those errors. In such conditions, this study propose to establish a possible methodology that can make the measurement of the radial deviation which corresponds to a work piece obtained into a turning process. The novelty of this study comes from the method of measurement used and from the measurement stand which provide the values of the radial deflection for the processed work piece, during the process. The experimental procedure assumes the existence of an experimental stand which allows to measure the distance between a sensor and the considered work piece. In such conditions, the mathematical algorithms used will transform the received electrical signal into a physical displacement. The obtained results suggest that the signal provided by the experimental stand and which it is used for measure the distance between a sensor and the considered work piece, allows to establish, with accuracy, the values for the radial deviations of the work piece. Also, this fact can offer a graphical representation of the shape which corresponds to the real profile of the processed work piece.

The study aims to propose an alternative method of segmentation of digitized data. It begins by layering the item's surface. It analyzes the nodes inside a point cloud to detect any consistent shape change. If one detected, then it holds it and looks for the next one which may describe a possible shape change. The points between those two are classified and marked as part of the shape change curvature line. The method remembers the marked points and holds them as central nodes which will later form reference regions. It uses normal vectors behavior methods to detect shape changes along X and Y axis. As any other direction would not be detectable by the bi-dimensional approach it then introduces a morphological parameter capable on its own to fully describe the curvature variation of a given item's surface by means of Gauss's curvature. To evaluate curvature variation, the method proposes that the central node's curvature should be compared with every found limit points. Because of the noise present in any points cloud it establishes a threshold value beyond which points may describe accurately any shape change. This procedure takes place for all analyzed reference regions and collects only those who have a greater value than the threshold one. This considerations may be extrapolated to other types of geometries as well, as it is the case with cylinders or cones.

The vibro-burnishing is a process by means a ball or a roller or other tool active surface is pressed and moved, inclusively by applying a vibratory motion, along the surface to be finished, generating a specific microrelief. A device for vibro-burnishing adapted on a universal lathe was analyzed by means of some principles corresponding to the Axiomatic Design theory. The analysis was developed by adopting some simplifying assumptions and it proved an adequate design, by considering some functional requirements and design parameters specific to the device.

The phonic pollution is a problem of interest in the mechanical workshops. Various solutions could be applied in order to diminish the intensity level of the sound generated by various noise sources. The research presented in this paper aimed to highlight some aspects concerning the measuring of the sound intensity level in a mechanical workshop and some possibilities of decreasing the sound intensity level by using fences made of distinct materials. The sound intensity level corresponding to the use of a universal lathe was experimentally measured by means of an adequate apparatus. The results of experimental research were mathematically processed and some empirical mathematical models were determined. The analysis of the experimental results and empirical mathematical models highlighted the influence exerted by some factors on the sound intensity level and some possibilities of diminishing the phonic pollution by using various phonic fences.

Stamping of the bearing cages ensures a high enough productivity and consistency with the requirements of a large series manufacture. The roughness of stamped surfaces is one of the parameters for assessing the quality of the cages, which in its turn determines the behaviour in service of the bearings. A large number of input factors corresponding to the stamping process exert influence on roughness parameters. An experimental research has been conceived and developed to assess the influence exerted by the thickness of the blank and the clearance between the active elements of the die on the value of the surface roughness parameter Ra. The mathematical processing of experimental results allowed the identification of empirical mathematical models and graphical representations were designed to offer additional information concerning the influence of the two input factors in the stamping process on a quality parameter of the bearing cage.

E-learning methods apply to most modern and various domains but also represent a great tool for the mechanical educational system where there are a lot of sustained efforts for its implementation. Using, administrating and maintaining an e-learning system for a certain field of study requires knowledge related to computation system's utilization but also the understanding the working mechanisms behind it that allows the system to be fully customized in order to be perfect fitted to the user's needs and requirements. A Moodle based test is evaluated from several points of views such as coherence clarity, concise content, information synthesis capacity and the presentation mode which makes the difference between clear or fuzzy graphical representations or terms. The authors appreciate that the ability of managing information in real time by the professor is a decisive decision in order to successfully implement an e-learning web platform. Updating information and structuring trainee's activities from thoroughgoing study up to their individual proposals for conceived applications leads to a better understanding and practical knowledge of theory.

The advantage of the technological assisted design consists in easy modification of the machining technologies for obtaining machine alternation, tool changing, working parameters variation or the modification of loads to which the tools are subjected. By determining tool movement inside machining and by using tool related moving speeds needed for both positioning and manufacturing we are able to compute the required machining time for each component of the machining operation in progress. The present study describes a cost optimization model for machining operations which uses the following components: machine and its operator related cost, set-up and adjustment, unproductive costs (idle state), direct and indirect costs. By using manufacturing technologies assisted design procedures we may obtain various variants for the technological model by modifying the machining strategy, tooling, working regimes or the machine-tool that are used. Simulating those variants allows us to compare and establish the optimal manufacturing variant as well as the most productive one.