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Control of the mean process force direction by adaption of the radial tool immersion.
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The static and dynamic mechanical properties of standard industrial robots differ strongly from common CNC-machines. For robot-based machining operations, these properties have to be considered. In this paper, a method for the optimal placement of the workpiece within the workspace, the design of the machining process and the compensation of toolpa...
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... to loads in x 0 -direction, static forces in y 0 -direction induce deflections, which are approximately five times larger. By selecting the radial immersion of the tool in dependence on the feed direction, the mean force direction is adapted to account for the anisotropic stiffness of the robotic system (see Figure 6): feed direction mean force immersion removed material toolpath The spindle speed n and axial depth of cut a p are selected based on directional stability lobes for the given cutting conditions (see [2]). The computation of the directional stability lobes is based on measured direct TCP frequency response functions (FRFs) (see [19, pp.258-276]). ...
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This review paper focus on the application of various machining techniques based on the phenomena of CNC operations, the study of different machining operations cannot be over emphasized due to its importance in the area of manufacturing and production companies. Therefore, this paper has study various application of this CNC machining techniques s...
Citations
... With reference to the work related to the introduction of industrial robots to machining operations, many research works have been created [25][26][27][28][29][30][31][32]. These studies indicates to many advantages of introducing robotization in the form of increased repeatability and contributing to the reduction of product manufacturing costs. ...
The article concerns the possibility of carrying out an optimization process of the extending the life of a brush tool which is use
during the process of removing burrs and rounding edges. The work focused on the influence of selected parameters on the wear time of
tools. A number of tests were carried out to optimize the selection of parameters in terms of tool life, while maintaining the proper quality of
the manufactured products, which translates into their reliability. As part of the work carried out, an optimal set of parameters was prepared
to extend the tool's operational time. These parameters are the rotational speed of 1400 rpm and the external diameter of the tool of 200
mm. Thanks to the use of new parameters of the brushing process, the tool's operational time was extended by about 67%.The work carried out, after verification as part of large-scale production, led to a reduction in the consumption of tools, which had a positive impact on
the improvement of the company's financial result (reduction of cost per part) and also contributed to the reduction of the carbon footprint.
The work indicates further areas for development.
... The results show that when positioning EC is done with the help of the BP neural network, the accuracy of compensation is better than when using the error model. Lastly, the traditional BP neural network has a slow convergence rate, so an algorithm that combines the PSO algorithm and the BP neural network is proposed to optimise the BP neural network so that the KUKA robot's positioning EC effect is better [118]. As science and technology have gotten better, mechanical processing technology has come a long way, and the types of industrial products are starting to change. ...
Aircraft assembly technology encompasses the intricate processes of designing, fabricating, and assembling various components into a final aircraft product. Central to this technology are advanced techniques like automated drilling and riveting systems, and specialized aircraft tooling designs which ensure precision, accuracy, and cost-effectiveness. This research explores critical innovations aimed at enhancing assembly accuracy, efficiency, and quality while reducing time and cost. A focal point is the flexible tooling design for automatic drilling and riveting of an aircraft wing spar. By incorporating a pre-assembly tooling design on a movable frame, this approach eliminates secondary positioning errors, optimizes frame size through a weight reduction algorithm, and ensures the requisite stiffness during assembly operations. The study also examines the impact of floor strength and thermal expansion on assembly accuracy. Using DELMIA-V5 software, the research creates a "Standard Hands-on Data Guide" to streamline tooling construction in offline mode, detailing a sequential component installation process on the jig and subsequent automatic drilling and riveting at the ADR station. Furthermore, the study develops an accuracy compensation method in the kinematic geometry of industrial robots, improving the Absolute Positioning Accuracy (APA) by over 75% and reducing the mean positional error by 85.40%. This method employs spatial grid discretization to accurately map and compensate for positioning errors, significantly enhancing the precision of the automated drilling process. The flexible tooling design and the accuracy compensation method collectively advance the speed and accuracy of aircraft assembly, ensuring high standards of safety and reliability. This research holds practical implications for the aircraft manufacturing industry, promoting improved assembly practices and the integration of sophisticated digital tools and simulations to achieve superior outcomes.
... Such applications are driven by a demand for low-volume, highly flexible production with high dimensional tolerance. It is thus unsurprising that a majority of research in this area explores increasing the process capability of industrial robotics through dimensional compensation for the passive compliance of the tool-robot system [10]- [12] and compensation for chatter instability [13]. Few works, such as [14] consider handling uncertainty in robotic milling applications. ...
... Such modelling approaches have been proposed in a robotic context in [22]. In [12], this is applied directly to an industrial robot to guide the optimal workpiece placement for dimensional compensation of a milling task. Similarly, [23] employs a novel voxel-based simulation approach for dimensional compensation. ...
... and it is clear that the latter 3 terms add energy to the system that violates (12). In general, a loss of passivity affects the stability of the interaction between the robot and environment, and convergence to zero tracking error is no longer guaranteed in free space [32]. ...
This paper addresses the problem of robotic cutting during disassembly of products for materials separation and recycling. Waste handling applications differ from milling in manufacturing processes, as they engender considerable variety and uncertainty in the parameters (e.g. hardness) of materials which the robot must cut. To address this challenge, we propose a learning-based approach incorporating elements of interaction control, in which the robot can adapt key parameters, such as feed rate, depth of cut, and mechanical compliance during task execution. We show how a mathematical model of cutting mechanics, embedded in a simulation environment, can be used to rapidly train the system without needing large amounts of data from physical cutting trials. The simulation approach was validated on a real robot setup based on four case study materials with varying structural and mechanical properties. We demonstrate the proposed method minimises process force and path deviations to a level similar to offline optimal planning methods, while the average time to complete a cutting task is within 25% of the optimum, at the expense of reduced volume of material removed per pass. A key advantage of our approach over similar works is that no prior knowledge about the material is required.
... Further work has been carried out to limit the memory requirement issues with the frame-slice voxel representation by inserting vertices on the voxels' edges, allowing a larger resolution without deteriorating the efficiency and accuracy [7]. Such approaches are met in dynamic simulations of machining robots for trajectory compensation [8]. ...
... Among the existing discrete methods, the voxel and dexel ones are the best candidates for machining simulations [8,10]. In this work, the dexel approach is preferred for its lower memory consumption than voxel/octree approach and for its straightforward interaction between a triangle-mesh swept surface and the workpiece. ...
In the Industry 4.0 era, the modelling of machining operations happens to be a crucial aspect of production sector. With adequate models, predicting the appearance of chatter and selecting optimised operational parameters is possible. For the dynamics simulation of machine tools or robots performing 5-axis operations, modelling approaches are continuously in improvement. A robust method is proposed for the cutter-workpiece engagement (CWE) computation at each step of a dynamic simulation, by determining the machining forces as well as the resulting machined surface. The CWE is estimated based on the interference between the workpiece, modelled with tri-dexel approach, and the tool, considered as a triangle-mesh surface of the swept volume. The relative closest triangle algorithm is used for a robust intersection management, suited for 5-axis trajectories. A hybrid dexel-based-analytic method is presented for accurate estimation of the uncut chip thickness. Furthermore, an approach is proposed for a simulation-based evaluation of the part resulting from dynamic simulations by comparing dexel networks with each other. It allows to assess the impact of operational parameters on parts at the simulation level. The CWE determination method proposed is validated with experimental data from force measurements and benchmark tests of different scales from macro- to micro-milling.
... Further work has been carried out to limit the memory requirement issues with the Frame-Slice Voxel representation by inserting vertices on the voxels edges, allowing a larger resolution without deteriorating the efficiency and accuracy [7]. Such approaches are met in dynamic simulations of machining robots for trajectory compensation [8]. ...
... A synthesis of the modelling approaches performances is proposed in Table 1 where the efficiency stands for the computing speed and memory requirements, accuracy is the ability to approach exact solutions and robustness is the image of the range of use. Among the existing discrete methods, the voxel and dexel ones are the best candidates for machining simulations [8,10]. In this work, the dexel approach is preferred for its lower memory consumption than voxel/octree approach and for its straightforward interaction between a triangle mesh swept surface and the workpiece. ...
In the context of Industry 4.0, the modelling of machining operations happens to be a crucial aspect of production sector. With adequate models, it is possible to predict the appearance of chatter and select optimised operational parameters. For the dynamics simulation of machine tools or robots performing 5-axis operations, modelling approaches are continuously in improvement. A robust method is proposed for the computation of the cutter-workpiece engagement (CWE) at each step of a dynamic simulation for the determination of the machining forces and the resulting machined surface. The CWE is estimated based on the interference between the workpiece, modelled with tri-dexel approach, and the tool, considered as a triangle-mesh swept volume. The relative-closest triangle algorithm is used for a robust intersection management with 5-axis trajectories. A hybrid dexel-based-analytic method is presented for accurate estimation of the uncut chip thickness. Furthermore, an approach is proposed for a simulation-based evaluation of the part resulting from dynamic simulations by comparing dexel networks with each other, allowing to assess the impact of operational parameters on the parts. The proposition is validated through experimental and virtual data with forces measurements as well as benchmark tests.
... The specific static and dynamic characteristics of robotic arms require dedicated planing of machining operations to improve accuracy by using a multi-axis compensation mechanism [14] and position control depending on force [15], kinematic analysis of the arm [16,17], or the effective stiffness of the arm [18]. Alternatively, a dedicated design of robotic arm for machining can improve the stiffness and dynamic properties, as well as the costs [19], and specific robotic designs [20,21] have been analysed to better understand their dynamic responses. ...
Structural potting is used to prepare honeycomb panels to fix metallic elements, typical in aircraft doors. In this paper, a full procedure for structural potting using robotic arms is presented for the first time. Automating this procedure requires the integration of, first, machining operations to remove the skin layers and prepare the potting points and, then, resin injection into the honeycomb cells. The paper describes the design, prototyping, and testing of specific end-effectors. Different end-effectors were explored to ensure efficient injection. The results obtained with the prototypes show that the potting quality is adequate to accomplish the required process checks for industrial manufacturing. The injection process time can be reduced by a factor greater than 3.5, together with the extra assets associated with the automation of complex tasks. Therefore, structural potting automation is demonstrated to be feasible with the end-effectors proposed for milling and injection, which are ready for use with conventional robotic arms in manufacturing lines.
... recently novel concepts for the combination of material removal simulation and dynamic machine tool simulation have shown significant improvements for the compensation of deflections and process stability prediction [31]. In particular, a compensation of tool centre point deflections caused by process forces allows to increase the quality of produced parts, and therefore enable the utilization of low stiffness robotic milling systems for the machining under high process force loads. ...
... By spatial compression mechanisms, the memory consumption and computation efficiency of the naive dense voxel representation can be improved [7]. Octree data structures and the model presented in [31] are examples for the compression of homogeneous sub-volumes. Under the assumption of a perfect surface voxelization with implicit voxel position encoding and neglecting the memory consumption of the spatially compressed inner volume and necessary data structures, the voxel representation memory consumption would be proportional to the surface area of the solid. ...
... Under the assumption of a perfect surface voxelization with implicit voxel position encoding and neglecting the memory consumption of the spatially compressed inner volume and necessary data structures, the voxel representation memory consumption would be proportional to the surface area of the solid. While these assumptions cannot be realized in actual implementations, the model presented in [31] comes close, by increasing the subdivision rate in the spatial voxel structure and balancing the memory consumption of tree structure and actual voxel data. ...
The simulation of subtractive manufacturing processes has a long history in engineering. Corresponding predictions are utilized for planning, validation and optimization, e.g., of CNC-machining processes. With the up-rise of flexible robotic machining and the advancements of computational and algorithmic capability, the simulation of the coupled machine-process behaviour for complex machining processes and large workpieces is within reach. These simulations require fast material removal predictions and analysis with high spatial resolution for multi-axis operations. Within this contribution, we propose to leverage voxel-based concepts introduced in the computer graphics industry to accelerate material removal simulations. Corresponding schemes are well suited for massive parallelization. By leveraging the computational power offered by modern graphics hardware, the computational performance of high spatial accuracy volumetric voxel-based algorithms is further improved. They now allow for very fast and accurate volume removal simulation and analysis of machining processes. Within this paper, a detailed description of the data structures and algorithms is provided along a detailed benchmark for common machining operations.
... Virtual simulation methods can be divided into three types according to the relationship between force and deformation: static stiffness method, quasi-static stiffness method and dynamic coupling method. Static stiffness method 33,129,[146][147][148] is based on robot stiffness model to predict static deformation, and the prediction accuracy depends on the accuracy of the stiffness parameters. Because the dynamic characteristics of the robot are not considered, it is suitable for machining deformation simulation with the spindle speed higher than the robot nature frequency. ...
Due to the advantages of large workspace, low cost and the integrated vision/force sensing, robotic milling has become an important way for machining of complex parts. In recent years, many scholars have studied the problems existing in the applications of robotic milling, and lots of results have been made in the dynamics, pose planning, deformation control etc., which provides theoretical guidance for high precision and high efficiency of robotic milling. From the perspective of complex parts robotic milling, this paper focuses on machining process planning and control techniques including the analysis of the robot-workspace, robot trajectory planning, vibration monitoring and control, deformation monitoring and compensation. As well as the principles of these technologies such as robot stiffness characteristics, dynamic characteristics, chatter mechanisms, and deformation mechanisms. The methods and characteristics related to the theory and technology of robotic milling of complex parts are summarized systematically. The latest research progress and achievements in the relevant fields are reviewed. It is hoped that the challenges, strategies and development related to robotic milling could be clarified through the carding work in this paper, so as to promote the application of related theories and technologies in high efficiency and precision intelligent milling with robot for complex parts.
... In each case, an equivalent stiffness value is computed (with for example the Conservative Congruence Transformation [8]) and used to calculate the corresponding static deflection of the tool center point [1]. This deflection is used to shift the initial trajectory, also called the mirroring method [9]. ...
... • Model predictive compensation solutions offered by the recent advancements in controls 9 , we could show that the error for aluminium parts could be reduced from around 1.0mm to 0.1mm using standard robots without any mechanical modifications [25]. ...
Digital Twins are one of the hottest digital trends. In this contribution we review the concept of Digital Twins and the chances for novel industrial applications. Mathematics are a key enabler and the impact will be highlighted along four specific examples addressing Digital Product Twins democratizing Design, Digital Production Twins enabling robots to mill, Digital Production Twins driving industrialization of additive manufacturing, and Digital Performance Twins boosting operations. We conclude the article with an outlook on the next wave of Digital Twins, Executable Digital Twins, and will review the associated challenges and opportunities for mathematics.
