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.
•Robot assisted additive manufacturing is an emerging disruptive technology.•Multiple robots can be used to produce multi-material large objects.•Robotic-systems can be used to develop hybrid systems ...where additive and subtractive process are combined.
The additive manufacturing and the robotic applications are tremendously increasing in the manufacturing field. This review paper discusses the concept of robotic-assisted additive manufacturing. The leading additive manufacturing methods that can be used with a robotic system are presented and discussed in detail. The information flow required to produce an object from a CAD model through a robotic-assisted system, different from the traditional information flow in a conventional additive manufacturing approach is also detailed. Examples of the use of robotic-assisted additive manufacturing systems are presented.
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.
•The geometric errors to the machining with non-rotary cutters are compensated.•The cutter rotation angle is considered for the machining with non-rotary cutters.•The geometric errors are modeled by ...considering the cutter rotation angle.•The cutting point is chosen as the reference point in the compensation algorithm.
As one of the main error sources, the geometric errors are compensated in this work for the accurate worm grinding of spur face gears. The previous methods of the geometric error compensation are usually applied to the machining with rotary cutters, of which the error of cutter rotation angle is not compensated since it does not affect the machining result. These methods are inappropriate to the worm grinding of face gears, because the worm is a non-rotary cutter and the machining result is sensitive to the error of cutter rotation angle. In this work, an innovative geometric error compensation method is proposed to the machining with non-rotary cutters based on two main points. First, the cutter rotation angle is considered to both the modeling and compensation of the geometric errors. Second, the instantaneous ideal contact point, which is calculated according to the generation process of the worm grinding of face gears, is chosen as the reference point to the compensation algorithm rather than the cutter tip point used in the previous method. The proposed method is validated by the example with both the theoretical calculation and practical machining.
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ID23‐2 is a fixed‐energy (14.2 keV) microfocus beamline at the European Synchrotron Radiation Facility (ESRF) dedicated to macromolecular crystallography. The optics and sample environment have ...recently been redesigned and rebuilt to take full advantage of the upgrade of the ESRF to the fourth generation Extremely Brilliant Source (ESRF‐EBS). The upgraded beamline now makes use of two sets of compound refractive lenses and multilayer mirrors to obtain a highly intense (>1013 photons s−1) focused microbeam (minimum size 1.5 µm × 3 µm full width at half‐maximum). The sample environment now includes a FLEX‐HCD sample changer/storage system, as well as a state‐of‐the‐art MD3Up high‐precision multi‐axis diffractometer. Automatic data reduction and analysis are also provided for more advanced protocols such as synchrotron serial crystallographic experiments.
ID23‐2 is a microfocus synchrotron beamline dedicated to macromolcular crystallography at the ESRF‐EBS.
The Parallel Robotics Inspired Goniometer (PRIGo) is a novel compact and high‐precision goniometer providing an alternative to (mini‐)kappa, traditional three‐circle goniometers and Eulerian cradles ...used for sample reorientation in macromolecular crystallography. Based on a combination of serial and parallel kinematics, PRIGo emulates an arc. It is mounted on an air‐bearing stage for rotation around ω and consists of four linear positioners working synchronously to achieve x, y, z translations and χ rotation (0–90°), followed by a ϕ stage (0–360°) for rotation around the sample holder axis. Owing to the use of piezo linear positioners and active correction, PRIGo features spheres of confusion of <1 µm, <7 µm and <10 µm for ω, χ and ϕ, respectively, and is therefore very well suited for micro‐crystallography. PRIGo enables optimal strategies for both native and experimental phasing crystallographic data collection. Herein, PRIGo hardware and software, its calibration, as well as applications in macromolecular crystallography are described.
This article introduces a novel highly integrated direct drive rotation wire frame mechanism for multi-axis micro wire electrical discharge machine tool. The design allows the micro electrode wire ...center to rotate along the motor's output shaft by ±90°, enabling machining over a complete circular area. This enhances the rotation precision and reduces the displacement of each axis, ensuring that the length of the electrode wire remains unchanged during the rotation process and thereby maintaining a stable friction force with the V-grooves. Building upon the direct drive rotation wire frame, a six-axis micro-wire electrode discharge machining machine has been developed, facilitating multi-axis coordinated processing. This study establishes the forward and inverse kinematic models using homogeneous transformation matrices to describe each axis's motion of the machine tool. A closed-form solution for the inverse kinematic model has been derived and effectively utilized for machining path planning for the electrode wire. To comprehensively characterize the machine tool's performances, a method that combines coordinate transformation, analytical geometry, and the Monte Carlo approach has been employed to determine the actual working space and the dexterity of the machine tool. Finally, a preliminary experiment with the six-axis micro wire electrical discharge machine tool demonstrates the effectiveness of the proposed direct drive rotation wire frame, verifying the inverse kinematic closed-form solutions, the practical workspace of the machine tool, and the effectiveness of dexterity and geometric error modeling.
•Direct drive rotation wire frame enables wire rotates ±90° in WEDM with lower inertia and higher dexterity.•Comprehensively analyzing kinematics, dexterity and geometric error of novel 6-axis WEDM machine tool.•Comparison of designing freeform surface and machined surface verify feasibility of machine tool.
Additive manufacturing has been employed in numerous areas owing to its advantages of fabricating complex geometries and creating less material waste. Nevertheless, parts manufactured by additive ...manufacturing processes tend to have poor surface quality and low dimensional accuracy. To overcome the limitations of additive manufacturing technologies, the favorable capabilities of subtractive manufacturing, i.e., high surface quality, can be integrated to form a hybrid process. A novel 6-axis hybrid additive-subtractive manufacturing process is proposed and developed in this paper. The hybrid process is realized using a six degrees of freedom (DOF) robot arm, equipped with multiple changeable heads and an integrated manufacturing platform. Based on the obtained results from different case studies, the hybrid additive-subtractive process has shown to have potentials in reducing production time, fabricating parts with better surface quality by removing the staircase error, manufacturing high quality freeform surfaces through the dynamic adjustment of tool axis direction, and eliminating the need for support structure because of the 6-DOF flexibility.
Thanks to recent improvements, computational methods are able to produce high-quality hexahedral meshes, whose hexahedrons are arranged along the principal curvature directions of the input surfaces. ...Curvature-aware print-paths following these curvature directions have been recently proposed by Gunpinar and enable reduction in stair-stepping effect in the printed parts. However, crosswise contacts can exist between the print-paths (i.e., print-paths are quasi-perpendicular to each other), which is undesirable as failures may occur particularly at those contact regions. Therefore, the present work aims at generation of curvature-aware print-paths without crosswise contacts between them. To solve this problem, we inspire from fluid flow and imitate (laminar) streamlines for an inlet and an outlet of a duct for designing print-paths. A hexahedral mesh is decomposed into blocks (cuboid-like sub-volumes), each of which is covered with fluid flow-inspired print-paths. A multi-axis (collision-free) additive manufacturing (AM) planning technique is also proposed. As a proof of concept, fluid flow-inspired curvature-aware print-paths are validated using a multi-axis AM simulator and machine.
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•A fluid-flow inspired print-path planning technique from hexahedral meshes.•Continuous print-paths and preventing problems of cross-wise contacts.•Curvature-aware print-paths to cover features of a part in a conformal manner.•Support of multi-axis additive manufacturing.•Adjustment of print-path orientations according to specific guidelines.
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