1,721,038 research outputs found
Additive manufacturing as an essential element in the teaching of robotics
Full text linkThis paper aims to describe how additive manufacturing can be useful in enhancing a robotic course, allowing students to focus on all aspects of the multidisciplinary components of this subject. A three-year experience of the course of "robotic system design" is presented to support the validity of the use of this technology in teaching. This course is specifically aimed at Master of Science (MSc) Mechanical Engineering students and therefore requires one to view the subject in all its aspects including those which are not conventionally taken into consideration such as mechanical design, prototyping and the final realization
A preliminary 6 Dofs robot based setup for fused deposition modeling
No full textThis paper is aimed at describing a preliminary setup based on a robotic arm with 6 degrees of freedom that could be exploited to build 3D printed objects that better suit their specification. Standard Fused Deposition Modeling (FDM) 3D printers obtain the final object by superimposing a layer on top of another, along a unique direction. A robot arm has been used to experiment with deposition on differently oriented planes in order to build features that can act as reinforcement, customize existing builds, reconstruct damaged parts and remove the necessity for wasteful extrusions to generate supports. The initial steps from the design of the system to the preliminary experimental results will be addressed
Development of an automatic robotic procedure for machining of skull prosthesis
No full textThe project presented in this paper develops within the field of automation in the medical-surgical sector. It aims at automating the process for the realization of prosthetic devices for the skull in cranioplasty, following a craniotomy intervention for brain tumor removal. The paper puts emphasis on the possibility to create the prosthetic device in run-time during the surgery, in order to ease the work that surgeons have to do during the operation. Generally, a skull prosthesis is realized before the day of the intervention, based on the plan of the medical operation, on the results of computed tomography, and through image processing software. However, after the surgery is performed, a non-negligible geometrical uncertainty can be found between the part of the skull actually removed and the cut planned during the preliminary analysis, so that the realized prosthesis (or even the skull, at worse) may need to be retouched. This paper demonstrates the possibility to introduce a fully automated process in a hospital environment, to manufacture in runtime the prosthetic operculum, relying on the actual geometry of the incision of the skull detected during the intervention. By processing a 3D scan of the skull after the craniectomy, a digital model of the prosthesis can be created and then used as an input to generate the code to be run by a robotic system in charge of the workpiece machining. Focusing on this second step, i.e., the manufacturing process, the work describes the way the dimensions of the raw material block are automatically selected, and the way robot trajectories for milling operation are automatically generated. Experimental validation demonstrates the possibility to complete the prosthesis within the surgery time, thus increasing the accuracy of the produced prosthesis and consequently reducing the time needed to complete the operation
A power recirculating test rig for ball screws: A new perspective for endurance tests
Full text linkBall screw mechanisms are commonly designed and adopted to work for a high number of cycles, so that one of their most relevant characteristics is mechanical endurance. State-of-art experimental setups designed to characterize these mechanisms under operational load conditions require a layout able to withstand high loads and a relevant power to actuate the ball screw, therefore, being rather complex and expensive. To overcome these issues, this paper proposes an innovative test bench exploiting the recirculating power principle, designed for testing a ball screw under operational loads. It enables (at the same time) a reduction of loads on the test rig frame and a reduction of the mechanical power required to actuate the screw. The concept and the design of the proposed test bench are presented, as well as a simplified model to calculate the motor torque and the forces transmitted at the supports. An experimental setup is then realized and tested under actual loads for endurance tests. The results show that the use of the recirculating principle is promising to realize a test rig for endurance tests on a ball screw, thanks to the effectiveness of the solution and the simplicity of the realization of the system even under heavy loads. Among all the measuring instruments adopted (accelerometers, strain gauges, thermocouples and laser sensors for distance measurement on the test bench), the adoption of accelerometers on the nuts seems to be the most promising for condition monitoring, allowing to detect an incipient fault before a macroscopic failure of the ball screw system occurs
Violin training with a magnetostrictive actuator
No full textProfessional players claim that stringed musical instruments exhibit better acoustic behaviour if they are frequently played. Although in literature there is no clear relationship between these phenomena, this work aims to develop a device capable of “making a violin sound” autonomously, so that it can always be kept in optimal conditions. The paper shows the design aspects of the magnetostrictive actuator, its operating principle, the prototype development and the experimental characterization. The prototype is then mounted on a new violin, simulating its continuous use for a week. During the test the acoustic measurements showed a large change in the acoustic response of the instrument, thus demonstrating the effectiveness of the magnetostrictive actuator in the training of a stringed instrument
Robotic FDM for free-form fabrication: evaluating adaptive non-planar slicing with different contour methods
No full textPurpose: This study aims to investigate and compare three nonplanar (NP) slicing algorithms. The algorithms aim to control the layer thickness variation (LTV), which is a common issue in supportless fabrication of free-form parts. The comparison underlines the differences between theoretical and real scenarios, resulting in guidelines for toolpath generation of complex objects. Design/methodology/approach: The algorithm comparison uses a representative complex geometry, i.e. the quarter of torus. It presents an increasing overhang and constant curvature. It is represented using a parametric definition in the first two algorithms and by triangular meshes as the real scenario. The algorithms work on the contouring stage, whereas a B-spline approach is used to build the inner side of layers. Constant layer thickness (LT) is imposed, and an adaptive approach is adopted to avoid over-extrusion. Three algorithms are validated with a robotized fused deposition modeling system. LTs are measured on cross-sectioned samples and compared with the theoretical cases. Findings: The results show that two algorithms can provide an LTV of about 0% on the contour. Nevertheless, the theoretical results on the inner side are divergent from the previous evidence, moving on to higher LTV (approximately 90%). The need for an adaptive approach is demonstrated, resulting in an LTV reduction (approximately 30%). Printed parts present the same trends of theoretical results confirming the algorithms’ capabilities. Originality/value: The work shows, for the first time, a comparison between NP slicing techniques. The LTV problem in hollow and filled components is analyzed through theoretical and experimental evidence. The results are promising for supportless fabrication of free-form parts
Test of a Numerical Model for a Haptic Pedal Brake System under Different Operating Conditions
No full textThe present study focuses on the analysis of the haptic brake pedal developed hydraulic brake system numerical model behavior varying its operative parameters: nominal conditions, increase of air content in brake fluid and brake pads wear are simulated and compared. To carry out the analysis, an experimental setup based on EtherCAT® network and admittance control loop has been implemented, together with a refinement of the numerical model in order to test plausible passenger car and race car systems. The results show about twice brake pedal angle travel for passenger car layout with respect to the race counterpart. Moreover, the different tested conditions physics captured by the numerical model is reflected in the correspondent pedal angle travels and in the haptic feedback to the user
Defect detection on RTM composite parts via robotic contact measurement system
No full textIn this work a new approach to detect and to evaluate defects typical of carbon fiber parts manufactured via resin transfer molding (RTM) is presented. The approach is based on a robotic contact measurement system, as an alternative or combined solution to vision methods. The research is meant to provide more accurate local geometry information to the global information acquired using vision systems. The system consists of a collaborative robot equipped with a force-torque sensor that scans the surface of the workpiece with a defined motion strategy. To evaluate the system, tests were conducted on a 3D printed part presenting a feature representative of the defects found on carbon fiber components. The results are compared with the CAD model and data acquired using a structured light scanner, showing that robotic contact measurement can be a viable method to enhance the reconstruction of a part with a higher accuracy. The system is then applied and validated on a real part made with RTM
Non-planar slicing for filled free-form geometries in robot-based FDM
No full textMulti-axis techniques in Additive Manufacturing (AM) unlock promising features such as supportless fabrication, reduced material consumption, improved surface quality and mechanical properties. Among those techniques, non-planar (NP) slicing promises to be the most suitable approach to fabricate 3D-components with significant curvature such as free-form geometries. Those are characterized by a layer thickness variation (LTV) along the curvature, which should be minimized. Industrial 6-axis robots are mandatory to achieve such performances. NP slicing generalization is challenging. On one side, there is a need to define a suitable contouring method compatible with the different geometrical features present in objects. On the other side, the generalized slicing method must be able to reconstruct the inner side not provided by superficial information provided by triangular mesh. In this work, a new algorithm to generate filled NP layer has been proposed using a contouring method that reduces the LTV. The bidirectional rectilinear infill strategy has been adapted for NP layers providing a more feasible toolpath to Fused Deposition Modeling (FDM) and such Direct processes where curved paths are detrimental. The proposed strategy has been validated by fabricating a tubular geometry with a robotized FDM system. Tubular geometry provides a sub-optimal solution of LTV known analytically for the contour. The infill algorithm has been tested with a complex surface applying the NP torus on a waved shape. Previous studies consider only contour providing an LTV ranging in +0% ÷ -46%. This study considers only the inner side. The analytical LTV resulted in a range of +0% ÷ -60%. The cross sections of the components were analyzed and compared with the analytical results. Although the proposed infill strategy does not maintain completely the contour layer thickness in the infill side, it shows to be able to cover more complex NP layers without saddle points
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