articles+ search results

NUMERICAL control of machine tools, RAPID prototyping, CONTINUITY, GEOMETRIC modeling, THREE-dimensional modeling, MACHINING, and METAL cutting

Efficient and productive manufacturing of freeform shapes requires a suitable three-dimensional CAD model at the entrance to the CAM system. The paper deals with the impact of NURBS or B-spline CAD model geometric continuity on the accuracy and productivity of 5-axis ball-end milling of freeform surfaces. The relationship between a different order of CAD model geometric continuity and the quality of the toolpath generated in CAM system is analysed and demonstrated on an example of a Blisk blade profile. In order to reveal the effect of CAD geometry on the quality of the machined surface, linear interpolation of cutter location points, i.e. piecewise linear discrete toolpath, is considered. Also, no further smoothing of the toolpath is applied. The distance of the cutter location points is commonly used as the indicator of toolpath quality. In addition, the discrete curvature of a linear discrete toolpath is introduced here, and its dependence on the curvature and continuity of the underlying CAD model is demonstrated. In this paper, it is shown that increasing the order of CAD model geometric continuity significantly eliminates sharp changes in the distance of cutter location points, and smoothes the discrete curvature of the toolpath. Finally, it is experimentally verified that increasing the continuity of the CAD model from G0 to G3, while maintaining the same cutting conditions, leads to an increase in workpiece accuracy and a reduction in machining time, without the need to smooth the toolpath generated in the CAM system. [ABSTRACT FROM AUTHOR]

ONTOLOGIES (Information retrieval), FLEXIBLE manufacturing systems, PRODUCT life cycle, INTERNET, and MANUFACTURING processes

The new generation of smart manufacturing technology enables upgrading within the manufacturing industry, as well as increase the complexity of manufacturing systems. The integration of information and ontology across the full life cycle of a product involves multi-scientific and multi-disciplinary dimensions. It requires a deep integration of industry chain enterprises in the process of domain ontology sharing and digital asset collaboration to achieve an efficient "new demand → existing ontology → innovation → new product → new ontology" agile manufacturing paradigm transfer. A digital-twin and ontology collaboration framework based on the industrial internet identification and resolution system (I3R system) is presented in this paper. Taking flexible manufacturing system (FMS) as an example, the four core key technologies required in this framework are described in detail: (1) a generic digital-twin modeling approach for the full life cycle of FMS; (2) ontology for the full life cycle of FMS; (3) digital-twin data collection technology for human-cyber-physical system (HCPS) in smart manufacturing; (4) distributed collaboration framework based on I3R. To illustrate in detail how the proposed methods and techniques can be applied in reality, we show different application scenarios based on the proposed methods and techniques in the various stages of the full FMS life cycle. Meanwhile, the implementation method of the I3R system-based digital-twin collaborative prototyping platform for industry chain cooperative enterprises is discussed, as well as the idea of its derived top-level application. [ABSTRACT FROM AUTHOR]

RAPID prototyping, MACHINING, SURFACE roughness, IMPELLERS, MACHINERY, DEEP drawing (Metalwork), and SHEET metal work

In the deformation machining (DM) approach, the machining and incremental forming operations are combined to utilize the strengths of the two processes to produce monolithic components with thin structures using a single setup. DM offers a high degree of flexibility to manufacture monolithic components in comparison to conventional techniques. Some freeform monolithic products are difficult to machine with the 3-axis machining approach due to restricted entry of the tool in certain portions of the geometry. This paper presents a novel double-sided deformation machining (DSDM) technique to manufacture freeform double-sided monolithic components. As a test case, a double-sided monolithic impeller-shaped structure with freeform blades is manufactured with the proposed technique. For this, first, a blank is machined to create the required structure and blades of desired thickness. These machined structures are used as preforms for the incremental forming (bending) of the blades to the final shape. As the existing commercial toolpath development packages are not compatible with the DM process, a novel feature-based double-sided combined machining-forming toolpath is developed for the DSDM operation. Here, the blades are deformed separately and sequentially. This avoids the collision issue and achieves a faster forming operation. To evaluate the quality of the monolithic components developed, a few response parameters, like the process forces, the geometrical accuracy in terms of springback, and the surface roughness, are reported. [ABSTRACT FROM AUTHOR]

ONTOLOGIES (Information retrieval), FLEXIBLE manufacturing systems, PRODUCT life cycle, INTERNET, and MANUFACTURING processes

The new generation of smart manufacturing technology enables upgrading within the manufacturing industry, as well as increase the complexity of manufacturing systems. The integration of information and ontology across the full life cycle of a product involves multi-scientific and multi-disciplinary dimensions. It requires a deep integration of industry chain enterprises in the process of domain ontology sharing and digital asset collaboration to achieve an efficient "new demand → existing ontology → innovation → new product → new ontology" agile manufacturing paradigm transfer. A digital-twin and ontology collaboration framework based on the industrial internet identification and resolution system (I3R system) is presented in this paper. Taking flexible manufacturing system (FMS) as an example, the four core key technologies required in this framework are described in detail: (1) a generic digital-twin modeling approach for the full life cycle of FMS; (2) ontology for the full life cycle of FMS; (3) digital-twin data collection technology for human-cyber-physical system (HCPS) in smart manufacturing; (4) distributed collaboration framework based on I3R. To illustrate in detail how the proposed methods and techniques can be applied in reality, we show different application scenarios based on the proposed methods and techniques in the various stages of the full FMS life cycle. Meanwhile, the implementation method of the I3R system-based digital-twin collaborative prototyping platform for industry chain cooperative enterprises is discussed, as well as the idea of its derived top-level application. [ABSTRACT FROM AUTHOR]

CLASS A metals, SURFACE finishing, RAPID prototyping, SURFACE texture, ENVIRONMENTAL risk, METAL powders, and POWDERS

Additive manufacturing (AM) has transformed the way of manufacturing metallic parts due to its ability of rapid prototyping, customization, reduced waste, and cost-effectiveness for small-batch manufacturing, and it has been increasingly replacing milling and molding processes. Directed energy deposition and powder-based fusion AM are the major classes of metal AM technologies, which are already well-established to print high-volume and small complex parts, respectively. However, the increasing demand for the fabrication of small devices, due to the miniaturization trend that is occurring in several industries fields, requires the development of specialized metal AM systems with the ability to increase the resolution of the printed parts. Thus, micro-metal additive manufacturing (MMAM) systems are now being developed using a scaling-down approach of the currently well-established metal AM technologies. In this review, a state-of-art analysis of the existing body of knowledge including the existing MMAM technologies, process parameters, and main results associated with MMAM was compiled and critically discussed. A surface texture index is defined, and a comparison of the trade-off between surface finishing and the building rate was performed considering the metal AM processes and the already developed scaled-down technologies. Additionally, other important aspects of the process (e.g., cost-related, health, environmental risks) are discussed. [ABSTRACT FROM AUTHOR]

KETONES, POLYETHER ether ketone, RAPID prototyping, YOUNG'S modulus, DIFFERENTIAL scanning calorimetry, and POLYLACTIC acid

Fused filament fabrication (FFF) is an additive manufacturing (AM) technology which is rapidly progressing from production of prototypes to manufacture of customized end use parts for the automotive, biomedical, and aerospace industries. The properties of manufactured parts have been proven to be dependent on not only the material's inherent properties but importantly the FFF process parameters. Commodity thermoplastics such as acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) have been on the forefront of FFF research since its development. However, as FFF technology progresses from rapid prototyping to rapid manufacturing, understanding the behaviour of high-performance engineering thermoplastics in this process is imperative. While previous studies have investigated the effects of FFF process parameters on polyether ether ketone (PEEK) and polyetherimide (PEI), more limited research has been performed on polyether ketone ketone (PEKK) despite its widespread applications in the biomedical and aerospace industries. This study investigated the effects of process parameters including build orientation, infill pattern, number of contours and raster angle on the tensile properties of PEKK. Tensile test results showed significant variations in Young's modulus and elongation at break. Statistical analysis was performed which determined the optimum process parameters to maximize tensile properties and revealed that build orientation was the most significant parameter, followed by number of contours. Fractography showed differences in failure mode and ductility among the sample groups. Analysis using differential scanning calorimetry (DSC) showed that the difference in percentage crystallinity among sample groups was not significant and thus the varied tensile properties was improbable to be due to differences in crystallinity developed within the specimens. Further analysis revealed that a variation in FFF process parameters can cause differences in percentage, size and location of porosity which in turn affects mechanical properties. [ABSTRACT FROM AUTHOR]

FUSED deposition modeling, THREE-dimensional printing, COORDINATE measuring machines, RAPID prototyping, and ENGINEERING design

Despite the large diffusion of additive manufacturing, and markedly fused filament fabrication, some quality aspects of the 3D printed parts have not been dealt with sufficiently. This applies particularly to geometric accuracy and the influence process parameters have on it. The paper describes an experiment in which 27 copies of a part were manufactured by means of a desktop fused filament fabrication device while manipulating layer thickness, printing speed, and number of contours. The effect of such process parameters on five typologies of geometric deviations and the duration of the printing process was assessed. While all the process parameters showed effects on both the printing time and some geometric deviations, the number of contours resulted as the most critical factor. The paper includes a proposal to optimize geometric accuracy and the rapidity of the process, which foresees the maximization of the number of contours, the minimization of the layer thickness, and the use of an intermediate value for printing speed. [ABSTRACT FROM AUTHOR]

FABRICATION (Manufacturing) and POLYMERS

As a promising technology capable of transforming the conventional manufacturing techniques, the use of additive manufacturing (AM) has span beyond the prototyping it was initially known for, and its use is currently revolutionising the future of the manufacturing and research world. A review of some of the advances made in the additive manufacturing of polymers and their composites is presented in this paper. Some of the advantages and disadvantages of the different AM techniques used in polymer composites (PC) fabrications are presented, and the different areas of applications of the AM fabricated PC are highlighted. Also highlighted are some of the potentials and challenges associated with the fabrication of components using 4D printing. Finally, the paper presents the prospects and the endless opportunities that abound with the AM of polymeric materials. [ABSTRACT FROM AUTHOR]

METAL stamping, SHEET metal, FIBER-reinforced plastics, STRAIN rate, RAPID tooling, and THREE-dimensional printing

3D printed polymer composite materials offer a cost-effective and rapid tooling option for prototyping, and low-cost, low-volume sheet metal forming applications. Due to the high anisotropy in mechanical properties of 3D printed composites, accurate characterization and finite element modeling of the material become paramount for successful design and application of these forming tools. This paper presents experimental characterization of 3D printed fiber–reinforced polymer composite material at various strain rates. A homogenized material model with orthotropic elasticity and the Hill 1948 anisotropic yield criterion were then calibrated based on these experimental data. Finite element simulations of the stamping of high-strength steel sheets using composite tooling were performed, and tool deformation was predicted and compared with experimental measurements. FE simulation results were in good agreement with stamping experiments performed with polymer tooling. It was found that the anisotropy and strain rate sensitivity of 3D printed polymer composites play a significant role in their performance as tooling materials. [ABSTRACT FROM AUTHOR]

FREE surfaces, SIMPLE machines, RAPID prototyping, SPLINES, PROBLEM solving, DATA structures, and SPLINE theory

Ultra-precision turning technology (UPT) plays a critical role in optical freeform surface manufacturing. There are researches focusing on solving problems of UPT tool path generation of freeform surfaces, but most of them are regardless of surface boundary contours. It is not convenient to generate path to machine complex structural parts with more surfaces simultaneously if boundary contours are ignored. To further improve UPT machining capacity, in our study, how to solve the UPT path generation problem about freeform surface with free boundary contours, which is called double free face (DFF), is focused. The Archimedean spiral is generated and discrete to driving point sequence, which is similar to the previous studies. Innovative contents are described as below. First, data structure of DFF topology is proposed, which contains expressions of the surfaces and boundary contours. And then, the surface projection and boundary wire projection algorithms are designed to calculate the projected tool location point. When the projected point is a tangential contact to the surface, this point is cutting point, and when the tool is projected to the contour wire or not projected to any geometry element, the point is not cutting point. How to judge whether the projected point is inside the face or outside is introduced. Third, the transition path is calculated by interpolating the two adjacent cutting paths using iterative cubic spline interpolation method to ensure enough movement smoothness. Finally, tool paths of case DFFs are generated and machined to verify the effectiveness of this proposed UPT path generation strategy. [ABSTRACT FROM AUTHOR]