The manufacturing of complex parts can be easily achieved by additive manufacturing (AM), which has attracted a significant attention from both academia and industry. Regardless of the shape of the ...model, the 3-axis AM techniques slice the model into a series of sections along the Z-axis and then use a fixed direction filling algorithm to plan the interiors of the sections. This approach greatly simplifies the planning of manufacturing processes. However, this directional construction method can lead to a series of problems, such as staircase effect, supporting effect, anisotropic mechanical property, and sizing limitation. In order to address these issues, both academia and industry have investigated multi-axis AM technology. Multi-axis AM dynamically constructs parts through redundant degrees of freedom, thus overcoming the problems of 3-axis AM process. This paper analyses the limitations of 3-axis AM process, summarizes the potential of multi-axis AM technology and describes methods for implementing multi-axis AM. The paper concludes with a discussion of the new opportunities and current challenges of multi-axis AM technology.
A revised version of Table 2 of Nanao et al. J. Synchrotron Rad. (2022). 29, 581–590 is provided.
Corrections to Table 2 of Nanao et al. J. Synchrotron Rad. (2022). 29, 581–590 are reported.
The anisotropy of mechanical strength on a 3D printed model can be controlled in a multi-axis 3D printing system as materials can be accumulated along dynamically varied directions. In this paper, we ...present a new computational framework to generate specially designed layers and toolpaths of multi-axis 3D printing for strengthening a model by aligning filaments along the directions with large stresses. The major challenge comes from how to effectively decompose a solid into a sequence of strength-aware and collision-free working surfaces. We formulate it as a problem to compute an optimized governing field together with a selected orientation of fabrication setup. Iso-surfaces of the governing field are extracted as working surface layers for filament alignment. Supporting structures in curved layers are constructed by extrapolating the governing field to enable the fabrication of overhangs. Compared with planar-layer based Fused Deposition Modeling (FDM) technology, models fabricated by our method can withstand up to 6.35× loads in experimental tests.
This paper presents a new method to fabricate 3D models on a robotic printing system equipped with multi-axis motion. Materials are accumulated inside the volume along curved tool-paths so that the ...need of supporting structures can be tremendously reduced - if not completely abandoned - on all models. Our strategy to tackle the challenge of tool-path planning for multi-axis 3D printing is to perform two successive decompositions, first volume-to-surfaces and then surfaces-to-curves. The volume-to-surfaces decomposition is achieved by optimizing a scalar field within the volume that represents the fabrication sequence. The field is constrained such that its iso-values represent curved layers that are supported from below, and present a convex surface affording for collision-free navigation of the printer head. After extracting all curved layers, the surfaces-to-curves decomposition covers them with tool-paths while taking into account constraints from the robotic printing system. Our method successfully generates tool-paths for 3D printing models with large overhangs and high-genus topology. We fabricated several challenging cases on our robotic platform to verify and demonstrate its capabilities.
The maintenance works (e.g. inspection, repair) of aero-engines while still attached on the airframes requires a desirable approach since this can significantly shorten both the time and cost of such ...interventions as the aerospace industry commonly operates based on the generic concept “power by the hour”. However, navigating and performing a multi-axis movement of an end-effector in a very constrained environment such as gas turbine engines is a challenging task. This paper reports on the development of a highly flexible slender (i.e. low diameter-to-length ratios) continuum robot of 25 degrees of freedom capable to uncoil from a drum to provide the feeding motion needed to navigate into crammed environments and then perform, with its last 6 DoF, complex trajectories with a camera equipped machining end-effector for allowing in-situ interventions at a low-pressure compressor of a gas turbine engine. This continuum robot is a compact system and presents a set of innovative mechatronics solutions such as: (i) twin commanding cables to minimise the number of actuators; (ii) twin compliant joints to enable large bending angles (±90°) arranged on a tapered structure (start from 40mm to 13mm at its end); (iii) feeding motion provided by a rotating drum for coiling/uncoiling the continuum robot; (iv) machining end-effector equipped with vision system. To be able to achieve the in-situ maintenance tasks, a set of innovative control algorithms to enable the navigation and end-effector path generation have been developed and implemented. Finally, the continuum robot has been tested both for navigation and movement of the end-effector against a specified target within a gas turbine engine mock-up proving that: (i) max. deviations in navigation from the desired path (1000mm length with bends between 45° and 90°) are ±10mm; (ii) max. errors in positioning the end-effector against a target situated at the end of navigation path is 1mm. Thus, this paper presents a compact continuum robot that could be considered as a step forward in providing aero-engine manufacturers with a solution to perform complex tasks in an invasive manner.
•A novel slender continuum robot is introduced for in-situ repair/inspection of jet engines.•A new kinematic model is introduced for the new tapered design.•Modes of control for the continuum robot were developed, including tip-following, feeding-in/out, Machining commands.•Navigation and inspection/machining tests in engine model were introduced.
The current global energy crisis necessitates a shift to renewable energy sources to mitigate climate change impacts. Wave energy emerges as a promising renewable resource to fulfill increasing ...energy demands. This energy can be extracted using wave energy converters (WECs), with multi-axis WECs (MA-WECs) being more effective than single-axis versions due to their capacity to harness energy from waves in various directions. The challenge lies in determining the ideal geometric design for MA-WECs, that can be tackled through multi-objective optimization (MOO) techniques. This research focuses on evaluating different MOO algorithms for the optimal geometric design of MA-WECs. To assess the structural response of different geometries and sizes, the study utilized the NEMOH boundary element method solver, aiming to maximize power output, lower the levelized cost of energy (LCOE), and optimize the geometry configuration. Findings indicate that the choice of optimization algorithm considerably influences the MA-WEC's optimal design, enhancing power efficiency, reducing device volume, and cutting costs more effectively than the initial design.
•Performance evaluation of multi-objective evolutionary algorithms for WEC geometry.•Enhanced design solutions for multi-axis WECs using evolutionary algorithms.•Multiple geometries for multi-axis WECs are presented to find optimal geometry.•Optimal geometries found while minimizing the LCOE simultaneously.
This paper presents a multi-axis low-cost soft magnetic tactile sensor with a high force range for force feedback in robotic surgical systems. The proposed sensor is designed to fully decouple the ...output response for normal, shear and angular forces. The proposed sensor is fabricated using rapid prototyping techniques and utilizes Neodymium magnets embedded in an elastomer over Hall sensors such that their displacement produces a voltage change that can be used to calculate the applied force. The initial spacing between the magnets and the Hall sensors is optimized to achieve a large displacement range using finite element method (FEM) simulations. The experimental characterization of the proposed sensor is performed for applied force in normal, shear and 45° angular direction. The force sensitivity of the proposed sensor in normal, shear and angular directions is 16 mV/N, 30 mV/N and 81 mV/N, respectively, with minimum mechanical crosstalk. The force range for the normal, shear and angular direction is obtained as 0-20 N, 0-3.5 N and 0-1.5 N, respectively. The proposed sensor shows a perfectly linear behavior and a low hysteresis error of 8.3%, making it suitable for tactile sensing and biomedical applications. The effect of the material properties of the elastomer on force ranges and sensitivity values of the proposed sensor is also discussed.
Small‐radius curved bridges are mostly used for overpass ramps, that are spatially irregular and usually have very complex seismic behavior. It is not easy to reproduce such behavior because of the ...need for large‐scale shaking tables. The hybrid test is one of the most effective approaches for solving this problem by considering the structural elements of interest as physically tested substructure while the rest is numerically simulated. In this paper, a hybrid test system was first developed based on the OpenFresco framework, where one of the piers was considered as the tested substructure, and the rest was simulated by OpenSees. A novel spatial loading device (SLD), configured as the Stewart pattern, was then developed to achieve the boundary conditions between substructures. The control schemes to perform the force‐displacement mixed control, conduct the geometric transformation while considering the load point offset, and achieve an external displacement control were proposed and validated through several rounds of hybrid testing. The experimental results indicate that the experimental system including loading control subsystem and hybrid control subsystem can realize the loading command accurately.
The production of high-precision parts and assemblies for aerospace applications requires not only mechanical but also physical and chemical methods of machining the workpieces to achieve required ...tight tolerances. Aerospace parts are often produced out of hard materials such as titanium or nickel alloys as well as soft materials such as aluminium alloys. In this paper, the improvement of the manufacturing process of thin-walled reflector for the narrow directional onboard antenna is investigated by applying multi-axis electroerosion machining. Due to advances in the technology of assembling waveguides, channels and flanges, it became necessary to change the material of the parabolic antenna reflector, which has excellent solderability, however, is poorly suited to stamping. Since stamping is no longer able to ensure precision in manufacturing, the edge of the reflector is machined using electrical discharge machining (EDM) which performance has low dependence on the material hardness. The mirror material is an aluminium-mangenese alloy of high corrosion resistance, high plasticity (relative elongation at break is 18%), high resistance to puncture loads and low weight. Cutting forces arising during the turning process can cause bending of the antenna mirror surface. The imperfection of the mirror creates uncorrelated areas which are parasitic radiating surfaces. These parasitic radiating surfaces reduce the efficiency of the antenna. A novel machining strategy using a wire EDM machine with an additional inbuilt two axes rotary table is used to replace mechanical cutting, as this machining no longer meets the high requirements for surface quality paired with geometrical tolerances. Measured Ra values of the machined edge machined by wire EDM are lower than 1.6 µm and the geometrical accuracy of the produced part is significantly improved, the standard deviations from the roundness of produced reflector surface are below 30 µm.
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