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In the computer numerical control (CNC) machining for free form surfaces, the time-optimized and smooth feedrate profile plays an essential role in the high-speed and high-precision machining. For the traditional feedrate scheduling method (e.g., the "bang-bang" control method), there may be many fluctuations in the planned feedrate profile, especially in region of large curvature, which results in poor quality of machining surface. To address this issue, a novel concept called sliding arc tube (SAT) is proposed in this paper, from which the trajectory is partitioned as feedrate restricted intervals (FRIs) determining the target feedrate and the positions of tool acceleration and deceleration on the tool path. The SAT is built based on the local geometric information of tool paths. As the SAT is constructed in the tube-shaping process and then sliding on the tool path and finally blocked by it, the breaking point for generating the FRI is found on the trajectory curve. For the proposed FRI identification method, it is computational efficient and it can be implemented in the real-time manner in the CNC controller. Results from both simulation and real machining experiments validate that, with the proposed SAT, the FRIs can be precisely and efficiently identified for the given trajectory curve, the frequent acceleration and deceleration of machine tool is alleviated, and the machining quality can be improved in this way. [ABSTRACT FROM AUTHOR]

The present paper aims to describe the development of a FEM model for the simulation of a die-sinking micro-EDM process. A commercial FEM code specific for the simulation of thermo-mechanical forming processes was used. The developed model was based on the capacity of the code to simulate the removal process or the separation of the material through the mesh element deletion. The electrical discharges were simulated through a proper heat flux and the material melting temperature was set as a trigger for the element deletion. The heat flux was related to the EDM process parameters by means of mathematical models selected from the literature. In the first part of the present work, a model based on a single discharge analysis was developed; then, the model was extended to a sink EDM process characterised by repeated discharges. The model was validated in terms of machining time, top diameter and MRR by the execution of experimental tests. [ABSTRACT FROM AUTHOR]

5-axis hybrid additive-subtractive manufacturing is a new and promising technology for many industrial applications. Because of its complexity, the machining simulation is very important to verify the effectiveness of tool path. However, most simulation methods are proposed for subtractive manufacturing and additive manufacturing separately. This paper presents a novel geometric simulation technique for the 5-axis hybrid additive-subtractive manufacturing, which is based on Laser Engineered Net Shaping (LENS) and milling. In the proposed method, 5-axis additive swept volume elements are represented with Tri-dexel models and then converted into triangular meshes for visualization. Workpiece after additive manufacturing can be then used as a workblank for subtractive manufacturing simulation. Finally, a geometric simulation module is developed based on SIEMENS NX software to demonstrate the feasibility of the proposed simulation method. [ABSTRACT FROM AUTHOR]

As corner smoothing algorithm is crucial to high-speed CNC machining, a new error constraint optimization method for corner smoothing algorithm is proposed in this paper. Traditional corner smoothing algorithms are all based on a toolpath to generate motion trajectory, and the same allowable error is used for all smoothed corners. However, in using this method, the contour error of workpiece will be invalidated because of the cutting tool radius in real cutting processing, thereby resulting in over-cutting or inefficiency. In this study, the tool offset and corner smoothing algorithm are combined in order to optimize the error constraint. Besides, a cutting process geometry model was established to analyze the error relationship. On the basis of this model, the smoothing error constraints of each corner can be solved according to the allowable contour error of the workpiece. Finally, motion trajectory is planned through a multi-constraint planning strategy, which can balance the contour error in workpiece at each corner and can guarantee the cutting accuracy, compared with the traditional corner smoothing algorithm. Moreover, a test workpiece is designed to verify the correctness of the proposed algorithm through simulation and actual experiments. The experimental outcome proves that the proposed method improves the workpiece cutting accuracy in high-speed CNC machine tool. [ABSTRACT FROM AUTHOR]

From Germany's Industry 4.0 mission to Made in China 2025 and Make in India mission to British Factory of the Future in 2050, digital manufacturing (DM) is promoting in the world's major industrial countries as a technology foundation of the future manufacturing. At the same time, in the different segments of the DM realm, different forms of information technologies (IT) are flourishing such as the following: computer-aided manufacturing, robotics control in manufacturing, and process simulation. This paper is aimed to review the latest initiatives ofDMin the leading universities and major industrial countries. Along with, a critical literature review of various initiatives in the area of DM-assisted hybrid additive manufacturing (DM-HAM) has also been carried out. DM-HAM seems to be very promising for next generation multi-operational manufacturing as it is time saving and economical. The highlights of this review will provide a guide for the upcoming research activities in the area of DM-HAM. [ABSTRACT FROM AUTHOR]

The classical conjugation and envelope method is very accurate and effective for forward and inverse calculations of grinding helical surfaces. However, this method involves complicated mathematics and requires that the profiles be continuous. It can also result in undercutting or interference to the desired surface profiles. In this paper, a new approach is proposed to simulate the grinding process of helical surfaces on cutting tools. The paper begins with the reconstruction of cutter helicoids from sampled points. Using the recovered helical parameters from the sample points, the cross-sectional profile of the cutter surface is derived using a polynomial curve. A numerical method for calculating the profile of the grinding wheel required for the cutter surface profile is then provided. Finally, an optimization method is presented for solving the problem of inverse calculation to determine the helical surface profile for a given grinding wheel profile and setting parameters. The feasibility of the approach is tested by simulation results, which shows that the proposed approach can eliminate undesired tool-work interferences and undercutting. [ABSTRACT FROM AUTHOR]

This paper highlights the issues of multi-stage process planning within facilities of definite processing capabilities, under the consideration of multiple choices of process routings. The process alternative based on operation concentration, accomplished by integrating burnishing into machining operations, is compared to a process with operation differentiation, assuming part finishing in separate grinding operations. A modelling approach to manufacturing knowledge representation, an average linkage clustering procedure of defined machine capability patterns and a set of validation criteria are proposed to enable the cellular decomposition of the facilities and optimum part flow allocation. Simulation investigations of alternative process flows have been performed using stochastic type models and data sets derived from industrial practice. The investigations show the distinct prevalence of the design solutions with operation concentration in terms of assumed performance measures. The results of this work indicate the practical usability of the developed modelling framework applied to exploring the total operational issues of cellular flexible manufacturing systems (FMSs). [ABSTRACT FROM AUTHOR]

Rough machining is a major stage of production in face-gear precision manufacturing, and flexible, universal, and efficient rough machining is conducive to the reduction of manufacturing cost and time. Therefore, in this paper, the planing method for spur face-gear processing with a 4-axis CNC planer is proposed, together with a detailed study on the principle of meshing between the shaper and the face-gear, equations of the shaper tooth surface and the face-gear tooth surface, and the application of the planer tool to copy the shaper. Then, on this basis, equations of profiling curves as well as equations of the swing angle range and the radical feed range of the planer tool are derived. Finally, the method of planing the spur face-gear through multi-group envelopes is proposed with the NC processing code written according to the above principle, and the feasibility of the planing method for the spur face-gear and the correctness of the NC code are proved by the results of the simulation processing test based on the Vericut software. [ABSTRACT FROM AUTHOR]

Nowadays, high-speed machining is usually used for production of hardened material parts with complex shapes such as dies and molds. In such parts, tool paths generated for bottom machining feature with the conventional parallel plane strategy induced many feed rate reductions, especially when boundaries of the feature have a lot of curvatures and are not parallel. Several machining experiments on hardened material lead to the conclusion that a tool path implying stable cutting conditions might guarantee a better part surface integrity. To ensure this stability, the shape machined must be decomposed when conventional strategies are not suitable. In this paper, an experimental approach based on high-speed performance simulation is conducted on a master bottom machining feature in order to highlight the influence of the curvatures towards a suitable decomposition of machining area. The decomposition is achieved through the construction of intermediate curves between the closed boundaries of the feature. These intermediate curves are used as guidance curve for the tool paths generation with an alternative machining strategy called 'guidance curve strategy'. For the construction of intermediate curves, key parameters reflecting the influence of their proximity with each closed boundary and the influence of the curvatures of this latter are introduced. Based on the results, a method for defining guidance curves in four steps is proposed. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a novel mobile parallel robot, which is able to carry welding and machining processes from inside the international thermonuclear experimental reactor (ITER) vacuum vessel (VV). The kinematics design of the robot has been optimized for ITER access. To improve the accuracy of the parallel robot, the errors caused by the stiffness and manufacture process have to be compensated or limited to a minimum value. In this paper kinematics errors and stiffness modeling are given. The simulation results are presented. [Copyright &y& Elsevier]

Reparameterization-based toolpath generation methods are usually adopted for machining triangular meshes, trimmed surfaces and compound surfaces. The quality of the reparameterization has an important effect on that of the surface. In this paper, a combined reparameterization procedure is introduced to generate an optimal mapping between the designed surface and a specified planar circular region with relatively less distortion both in length and in angle. Then, for five-axis sculptured surface machining the mathematical model of spiral guide path with maximum path interval is constructed in the circular region. Cutter contact paths are obtained by inversely mapping the guide path onto the designed surface. Under constraints of gouging and collision, continuous and optimal cutter orientations are subsequently calculated. Finally, the results of simulation and experiment of the machining process are given to illustrate the feasibility and applicability of the proposed method. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a systematic scheme for developing feasible tool-paths for machining a sculptured surface on a multi-axis NC machine. In our previous paper (in CAD journal), a simplified problem of CT-dependent partitioning of a sculptured surface is solved with application of the focal surfaces. The derived solution to the problem is convenient for particular cases when the angle of the surfaces and local relative orientation is identical to zero (). In general case of sculptured surface machining on multi-axis NC machine, the identity often doesn’t observe. Here this problem is enhanced up to cases when the actual value of the angle could be of arbitrary value. The reported approach is based on application of the characteristic surfaces of novel kind. The characteristic surfaces of the newly discovered kind are referred to as the characteristic -surfaces. The reported solution to the problem is based on implementation of the DG/K-method of surface generation. The methodology presented here is a general one. It combines the activities of exploration of topology of a given sculptured surface, of the generating surfaces of the cutting tool, of the cutting tool configuration and of the cutting tool motion that it performs in the machining operation relative to the work, thus making the production process flexible, automatic and controllable. The approach is the CAD/CAM orientated one. The effectiveness of the proposed approach is verified from numerical simulation. Perfect correlation of the reported results with those previously published by the author, as well as by other researchers, is observed. [Copyright &y& Elsevier]

Recently, CNC machining simulations require exponentially increasing computational time and memories of the computers, which have become a significant challenge for both computer hardware and software. This paper presents a novel geometric model for CNC machining simulations, which is called Level of details based on G-Code, or G-LODs for short. The G-LODs uses a type of progressive mesh to construct the surface simulation grid ( SSG). The SSG can be adopted to simulate the CNC machining processes at proper level of details. So theoretically simulations based on the G-LODs will not excessively occupy the computational and storage resources of computers. Based on the SSG, the G-buffer method is used to construct the solid model of the parts. The methodology of how to construct the G-LODs is established. In conclusion, several simulation examples based the G-LODs are presented. [ABSTRACT FROM AUTHOR]

Abstract: A Finite Element Data Exchange System (FEDES) is developed to transfer and map finite element analysis (FEA) data between different FE solvers and meshes. Six commercial FE codes (ABAQUS, ANSYS, DEFORM, MSC.MARC, MORFEO and VULCAN) are incorporated in FEDES. Four mapping techniques are developed and embedded in FEDES which allow the data mapping between meshes with different element types and densities. The algorithms of the mapping techniques are described and compared for 2D and 3D models. The design and capabilities of FEDES are also described. Results from the data transfer and mapping between different FE simulations are presented and discussed. Two manufacturing chains are simulated using FEDES in this paper. The first manufacturing chain is simulated on a parallelepiped geometry including casting, forging and heat treatment processes. The second manufacturing chain is simulated on an aero-engine vane component including metal deposition, welding, heat treatment, machining and shot-peening processes. The development of FEDES demonstrates an integrated simulation platform for modelling manufacturing chains of processes using different FE solvers and meshes. [Copyright &y& Elsevier]

Abstract: Machining tasks are performed on machine tools with enormous amount of energy consumption in manufacturing system. Understanding and characterizing task-oriented energy consumption is significantly essential to explore the potential on energy-saving in production management. To achieve it, this paper proposes a modeling method of task-oriented energy consumption for machining manufacturing system. The energy consumption characteristics driven by task flow in machining manufacturing system are analyzed, which describes that energy consumption dynamically depends on the flexibility and variability of task flow in production processes. Based on the task-oriented energy consumption characteristics, an event graph methodology has been exploited to model the energy consumption driven by tasks in production processes of machining manufacturing system. The proposed modeling method is solved in Simulink simulation environment, and applied to select the flexible processes of tasks for optimizing energy consumption. The results show a valuable insight of energy consumption in machining manufacturing system so as to make robust decisions on the potential for improving energy efficiency. [Copyright &y& Elsevier]

Abstract: The phenomenological models for material flow stress and fracture typically used in the finite element simulations of hard machining processes do not adequately represent the constitutive behavior of the workpiece that is usually heat treated to hardness levels ranging from 50 to 62HRC. Thus, new flow stress models which include also the hardness effect should be developed and used accordingly in computer simulation of hard machining. This paper describes the development of a hardness-based flow stress and fracture models for machining AISI H13 tool steel, which can be applied for a wide range of work material hardness. These models were implemented in a non-isothermal viscoplastic numerical model to simulate the influence of work material hardness on the chip formation process. Predicted results are validated by comparing them with experimental results from literature. They are found to predict well the cutting forces as well as the change in chip morphology from continuous to segmented chip as the hardness values change. [Copyright &y& Elsevier]

Abstract: Flow stress identification of work-piece materials for its use in machining operation simulation models has been long treated. The interest in defining the flow stress in an easy and fast way without using complicated dynamic characterization tests leads to analyse the inverse identification of flow stress employing cutting operations. This paper presents a revision of different aspects concerning the inverse algorithms applied to the primary shear zone (PSZ). It also presents a new approach for studying material''s behaviour on the secondary shear zone (SSZ) where experimentally measured temperatures have been included in the inverse algorithm. Two steels, 42CrMo4 and 20NiCrMo5 are employed and finite element method (FEM) simulations are carried out in order to evaluate the usefulness of the calculated flow stress laws and proposed algorithm. [Copyright &y& Elsevier]

Digitization modeling and CNC machining method of cone-generated double-enveloping worm drive are proposed in this study. The modeling coordinate frame is developed, and coordinate transformation matrices are also built for different coordinate systems. Next, the common normal vectors and relative velocity vectors of the conical cutter and worm and worm and worm wheel are derived by using differential geometry, kinematic analysis, and coordinate transformation method; then, the mathematical models of the worm drive are established applying spatial meshing principle. In addition, the solving algorithms for the complex multivariate nonlinear constrained mathematical models of the worm drive are developed according to the worm drive’s surface-generating characteristic; then, the meshing point cloud that represents the tooth profile of the worm drive are calculated based on the developed algorithms; finally, the digital CAD models of the worm drive could be constructed on the basis of the point cloud in the modeling software system. The CNC machining code is generated based on the accurate digital CAD models, and the surfaces of the worm drive could be machined in the CNC machining center. The modeling and machining experiment results demonstrate the validity and accuracy of the proposed modeling and CNC machining method for cone-generated double-enveloping worm drive. [ABSTRACT FROM AUTHOR]

Our two major concerns, which should be taken into consideration as soon as we start the selecting the machining parameters, are the minimization of the machining time and the maintaining of the high-speed machining machine in good state. The manufacturing strategy is one of the parameters which practically influences the time of the different geometrical forms manufacturing, as well as the machine itself. In this article, we propose an optimization methodology of the machining strategy for pockets of complex forms. For doing this, we have developed analytic models expressing the feed rate of the cutting tools trajectory. Then, we have elaborated an optimization method based on the analysis of the different critical parameters so as to distinguish the most suitable strategies to calculate the cutting time and define the machine dynamics. To validate our results, we have compared them to the experimental ones and also to those found in literature. [ABSTRACT FROM AUTHOR]

This work is motivated by a practical need for operation scheduling for an automobile manufacturing industry involved with machining of different types of vibration dampers. This work aims to minimize the makespan time for relatively different types of vibration dampers with nonuniform flow pattern through a two-parallel inseparable hybrid flow shop. A mathematical model has been developed for simulation of the hybrid flow line performance. The simulation provides data relating to completion time, queue status, and machine utilization of various schedules. After analysis and evaluation of different possible schedules, simultaneous processing of two types of dampers is suggested. The model was evaluated for nonuniform flow pattern for any number of types of dampers for different sets, and a parallel solution based on completion time is suggested. [ABSTRACT FROM AUTHOR]