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Energy metrics in 3D-printing technologies are of major importance for sustainable manufacturing. The printing parameters (PP) affect the energy consumption remarkably and define the overall Energy Printing Consumption (EPC), the Specific Printing Energy (SPE), and Specific Printing Power (SPP). This study investigates the impact of six PPs: the infill raster density (ID), raster deposition angle (RDA), nozzle temperature (NT), fused filament printing speed (PS), layer deposition thickness (LT), and bed temperature (BT), on the above three energy indexes, i.e. the EPC, SPE, and SPP. The experimental course follows the Taguchi L25 orthogonal array (OA) with six repetitions. The experimental data were dissolved and studied utilizing descriptive statistical tools, i.e. main effect plots (MEP plots), ANOVA, and response surface methodology (RSM). Six evaluation experiments validated the extracted quadratic regression models (QRM). The above statistical models thoroughly describe the effects of six intended fused filament fabrication (FFF) printing parameters on the energy metrics (EPC, SPE, and SPP). Additionally, the physical mechanism is explained in depth by applying mechanical strength evaluation tests for all ranges of parameters' values. This study proposes a methodology for efficient and sustainable FFF. [ABSTRACT FROM AUTHOR]

Polylactic acid (PLA) material in filament form can be 3D printed and form complex physical models by using a low-cost material extrusion mechanism in a process that is broadly known as fused filament fabrication (FFF). Even though the PLA-FFF process has been extensively studied in the literature, its parts' mechanical response varies significantly, and it has not been studied in association with six control parameters at the same time, i.e. the infill density (ID), raster deposition angle (RDA), nozzle temperature (NT), printing speed (PS), layer thickness (LT), and bed temperature (BT). The simultaneous influence of the variable parameters on the mechanical properties is a challenging assignment and aspires to rank the six parameters' importance, model the process, and finally validate the models by using independent experiments. One-hundred twenty-five experiments run following the Taguchi L25 orthogonal array repeated five times for the study purpose. After an extensive literature survey and preliminary experiments, the parameter selection and discrete values were selected. The experimental results were analyzed using statistical tools and critically compared with that of the literature. The RDA, NT, PS, and ID significantly impact the mechanical response of the 3D printed PLA parts. [ABSTRACT FROM AUTHOR]

Fused Filament Fabrication (FFF) process employs thermoplastic materials in filaments form to build functional components by selectively placing extruded material progressively in thin sheets. Thermoplastic Polyurethane (TPU) is a high potential material for elastic and wearable electronics or medical applications due to its lower stiffness than PLA and ABS materials. This research investigates the effects of two independent 3D printing parameters, Layer Height (LH) and Nozzle Temperature (NT), on the Mechanical Response (MR) of FFF 3D printed TPU parts. Tensile, flexural and impact tests were conducted. The values studied herein are the Ultimate Tensile Strength (T-σb), the Tensile Modulus of Elasticity (T-E), the Flexural Stress at Break (F-σb), the Flexural Modulus of Elasticity (F-E) and the Impact Strength (IS). Pure TPU pellets were used to produce the filament. Then, specimens were 3D printed with three different LT and NT levels and nine experiments were conducted, according to the full combinatorial design. Experiments were repeated three times each (3×9 = 27). The results were analyzed and modeled using descriptive tools, main effect plots, ANOVA, and interactions charts. It was found that the LH and NT are affecting all the MR values. The 0.2 mm LH and 215oC NT optimized the MR values. [ABSTRACT FROM AUTHOR]

This study investigates the influence of the stand-off distance (SoD), laser speed (LS) and laser power (LP) on kerf geometry (upper width Wu, down width Wd and kerf angle KA) and mean surface roughness (Ra) during CO2 laser cutting of 3D-Printed Polyethylene-Terephthalate-Glycol (PET-G) thin plates. A full factorial design is implemented, having two levels for SoD and three levels for LS and four levels for LP, resulting in twenty-four (24) cuts. The specimens were manufactured with the Fused Filament Fabrication (FFF) process and had a thickness of 4 mm. First, the Wu, Wd, and KA parameters were measured. Then, the specimens were cut into 24 smaller parts, and the Ra of the processed surfaces was measured. After analyzing the results using descriptive statistical analysis and contour plots corresponding to the two objectives of KA and Ra, a feed-forward and backpropagation neural network (FFBP-NN) was applied. After a series of subsequent training, it was found that the 3-10-2 NN architecture was quite efficient in explaining the variation in terms of the responses, thus having merit in practical applications related to laser cutting. The LC surfaces showed much better Ra (7.2-12 μm) than those in the literature for FFF parts surfaces without post-processing (10.3-30 μm). [ABSTRACT FROM AUTHOR]

Gear hobbing is a highly utilized flexible manufacturing process for massive production of external gears. However, the complex geometry of cutting hobs is responsible for the almost exclusive utilization of high-speed steel (HSS) as cutting tool material. The limited cutting performance of HSS, even coated HSS, restricts the application of high cutting speeds and restricts the full exploitation of modern CNC hobbing machine tools. The application of cemented carbide tools was considered as a potential alternative to modern production requirements. In former investigations an experimental variation of gear hobbing, the so-called fly bobbing was applied, in order to specify the cutting performance of cemented carbide tools in gear production. These thorough experiments indicated that cracks, which were not expected, might occur in specific cutting cases, leading to the early failure of the entire cutting tool. In order to interpret computationally the reasons for these failures, an FEM simulation of the cutting process was developed, supported by advanced software tools able to determine the chip formation and the cutting forces during gear hobbing. The computational results explain sufficiently the failure mechanisms and they are quite in line with the experimental findings. The first part of this paper applies the verified parametric FEM model for various cutting cases, indicating the most risky cutting teeth with respect to their fatigue danger. In a step forward, the second part of the paper illustrates the effect of various technological and geometric parameters to the expected tool life. Therefore, the optimization of the cutting process is enabled, through the proper selection of cutting parameters, which can eliminate the failure danger of cemented carbide cutting tools, thus achieving satisfactory cost effectiveness.

Gear Hobbing is a complex gear manufacturing method, possessing great industrial significance. The convoluted geometry of the cutting tools brings on modeling problems and is the main reason for the almost exclusive application of HSS as cutting material. However, despite its complicated kinematics, gear hobbing is sufficiently described by well-established software tools, which were presented in the first part of the present paper. Experimental investigations exhibited the cutting performance of cemented carbide cutting teeth, which were expected to be potential alternatives for massive hob production. In these cutting experiments, hardmetal tools exhibited in several cases early and unexpected brittle failures, which were interpreted by the FRSFEM model in the first part of the paper. This analysis indicated that the occurring dynamic stresses are the reason for the observed fatigue failures on the cemented carbide tools. The occurring stresses are highly dependent on the selection of cutting parameters and on the tool geometry. Therefore, the proper selection of the cutting data may prevent the early tool failures, as the dominant parameters for tool wear, allowing it to be worn out by the conventional abrasive mechanisms. Thus, the doubtless dominance of cemented carbide over the HSS tools, may be rendered. The present work illustrates a parametric analysis, which describes quantitatively the effect of various cutting and technological parameters on the stress level occurring in gear hobbing, with cemented carbide cutting teeth. Hereby, the optimization of the tool life is enabled, allowing the maximum exploitation of modern gear bobbing machine tools. Optimized gear bobbing with cemented carbide tools may be used, in order to introduce higher cutting speeds in massive gear production.

Gear hobbing is an efficient method to manufacture high quality and performance toothed wheels, although it is associated with complicated process kinematics, chip formation and tool wear mechanisms. The variant cutting contribution of each hob tooth to the gear gaps formation might lead to an uneven wear distribution on the successive cutting teeth and to an overall poor tool utilization. To study quantitatively the tool wear progress in gear hobbing, experimental-analytical methods have been established. Gear hobbing experiments and sophisticated numerical models are used to simulate the cutting process and to correlate the undeformed chip geometry and other process parameters to the expected tool wear. Herewith the wear development on the individual hob teeth can be predicted and the cutting process optimized, among others, through appropriate tool tangential shifts, in order to obtain a uniform wear distribution on the hob teeth. To determine the constants of the equations used in the tool wear calculations, fly hobbing experiments were conducted. Hereby, it was necessary to modify the fly hobbing kinematics, applying instead of a continuous tangential feed, a continuous axial one. The experimental data with uncoated and coated high speed steel (HSS) tools were evaluated, and correlated to analytical ones, elaborated with the aid of the numerical simulation of gear hobbing. By means of the procedures described in this paper, tool wear prediction as well as the optimization of various magnitudes, as the hob tangential shift parameters can be carried out. [DOI: 10.1115/1.1430236]

The rotational speed requirements of high speed spindles led to the development of angular contact hybrid bearings with ceramic balls and PVD coated steel races. The present paper describes the determination and verification of critical coating fatigue stresses as well as their application in coating fatigue calculations of hybrid bearing steel races. The fatigue limits of low temperature deposited PVD coatings were determined by the application of the impact test and its FEM simulation and validated through their successful application to the prediction of coating life in rolling contact fatigue tests of coated specimens. Furthermore, a computer program that performs the quasi-static simulation of bearing operation yields the necessary kinematic and dynamic parameters for a FEM simulation of the stress field occurring in coated rings. For the investigated bearings, an adequate fatigue performance of their coated races was computationally exhibited. The PVD coated hybrid bearings illustrated the predicted behavior in long duration tests, conducted in full scale test rigs.

In this work the tensile strength of parts build with the fused deposition modelling process is studied. ABS and ABS plus parts were built with different building parameters and tested according to the ISO 527 standard on a tensile test machine. It was found that the building direction does not significantly affect the tensile strength of the parts, although the parts were anisotropic. Parts build with larger layer thickness showed lower tensile strength. The average deviation between nominal and experimental tensile strength was about 5% for ABS and about 40% for ABS plus. ABS plus specimens had on average 15% higher strength than ABS. The fracture surface of selected specimens was examined under a SEM, to determine failure mode of the filament strands. [ABSTRACT FROM AUTHOR]

Friction Stir Welding (FSW) is a solid-state process which is extensively used to join aluminum sheet structures in a wide variety of industries, including aerospace, automotive, railway, and maritime. This research is focused on the influence of the tool rotational speed on the mechanical properties of friction stir welded 2 mm thick AA1050 aluminum alloys butt joints. Tool rotational speeds from 500rpm to 2000 rpm with a 250rpm step and 1.7mm and 1.8mm plunge depth values were used. Experiments were conducted in a vertical Haas VF2 3 axis CNC milling machine center. Three joint specimens were tested for each case. The tensile properties of the friction stir welded AA1050 aluminum alloys were investigated in the direction perpendicular to the friction stir welding joint. Tensile experiments were conducted using a Schenk Trebel Co. tensile test machine and the Ultimate Tensile Strength, the Young's Modulus and strain were calculated. Results were compared with reference material values. In all cases the calculated values were significantly lower than the equivalent reference material values which is expected due to the fact that the area of the welding joint was lower than the specimen cross sectional area, for the welding conditions employed. [ABSTRACT FROM AUTHOR]