144 research outputs found

    Correlation between machining direction, cutter geometry and step-over distance in 3-axis milling: Application to milling by zones.

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    Computer-Aided Manufacturing (CAM) occupies an increasingly important role in engineering with all it has to offer in terms of new possibilities and improving designer/manufacturer productivity. The present study addresses machining of free-form surfaces on a 3-axis NC machine tool. There have recently been a large number of studies devoted to planning tool paths on free-form surfaces with various strategies being adopted. These strategies are intended to increase efficiency by reducing the overall length of machining. Often, the choice of the cutter is arbitrary and the work focuses on planning. In order to boost productivity, the present work offers assistance in choosing the cutting tool, the machining direction and cutting by surface zones, adopting a milling strategy by parallel planes. To do so, a comparison is made between milling using a spherical end milling cutter and a torus end milling cutter with the same outer radius. This comparison relates to the radius of curvature of the trace left by the cutter at the point of contact between the tool and the workpiece in relation to the direction of feed motion

    Five-axis Flank Milling and Modeling the Spiral Bevel Gear with a Ruled Tooth Surface Design

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    Spiral bevel gears usually are cut by the machine tools which are specifically made for manufacturing spiral bevel gear. For some practical applications, such as repair, prototype, and small batch, there are only several spiral bevel gears need to be machined. It seems not wise to buy a gear manufacturing machine tool for cutting those several gears. Consequently, some other manufacturing methods are introduced to cope with this situation. Recent advances in computer numerical control (CNC) milling machine tools make it possible to manufacture good quality spiral bevel gears. Moreover, CNC milling machine tools are usually cheaper than the specific gear manufacturing machine tools. Even more, they are not only cut gears but also other parts. Therefore, computer numerical control (CNC) milling is introduced in industry to cut spiral bevel gears. End milling and flank milling are two modes of CNC milling. Compared to end milling, flank milling has been highlighted in quality enhancement, manufacturing time and cost reduction. Theoretically, the result of flank milling a developable ruled surface does not contain geometric deviations. Hence, flank milling has been widely used to machine the parts with ruled surface or the surface close to ruled surface, such as turbines and blades. Due to the fact that the tooth surfaces of spiral bevel gears are close to ruled surface (the tooth surface of Format-cut spiral bevel is part of a cone), flank milling can also be used to cut spiral bevel gears. However, there is no literature about flank milling spiral bevel gears. Moreover, the current existing tooth surface models (except the tooth surface of Format-cut spiral bevel gear) are implicit, which makes further calculation inefficient and difficult. To address these two problems, a new ruled tooth surface design is proposed to spiral bevel gears design. Subsequently, the design model is used to be machined with five-axis flank milling by introducing a new tool path planning approach. To obtain the simulate machined tooth surface, a new geometric envelope approach is proposed to calculate the cutter envelope surface as a closed-form representation. Then the result of geometric deviations, which are obtained by comparing the design tooth surface and the simulate machined tooth surface, shows the flank milling is appropriate to cut spiral bevel gears. Furthermore, the conventional face-milled model is also used as the design model for flank milling, and another result of geometric deviations is obtained. Subsequently, both results are compared, and the comparison shows that the proposed design reduces the geometric deviations effectively. Moreover, the closed-form simulate machined tooth surface can only be obtained by using the proposed design

    Software Simulation of Numerically Controlled Machining

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    The field of numerically controlled (NC) machining has long been interested with predicting and measuring the errors in machining. Creating a simulation of NC machining is one way of achieving this. This thesis presents one such implementation of an NC simulation. It also runs a number of numerical and physical tests to verify the simulation?s correctness. The numerical tests show that the simulator work correctly as well as providing guide lines for appropriate simulation parameters. The physical tests show that the results of the simulation match the results of real NC machines. It is hoped that this thesis can provide a guide for the creation of machining simulators and their verification

    Surface Design for Flank Milling

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    In this dissertation, a numerical method to design a curved surface for accurately flank milling with a general tool of revolution is presented. Instead of using the ruled surface as the design surface, the flank millable surface can better match the machined surface generated by flank milling techniques, and provide an effective tool to the designer to control the properties and the specifications of the design surface. A method using the least squares surface fitting to design the flank millable surface is first discussed. Grazing points on the envelope of the moving tool modeled by the grazing surface are used as the sample points and a NURBS surface is used to approximate the given grazing surface. The deviation between the grazing surface and the NURBS surface can be controlled by increasing the number of the control points. The computation process for this method is costly in time and effort. In engineering design, there is a need for fast and effortless methods to simplify the flank millable surface design procedure. A technique to approximate the grazing curve with NURBS at each tool position is developed. Based on the characteristics of the grazing surface and the geometries of the cutting tool, these NURBS representations at a few different tool positions, namely at the start, interior and end, are lofted to generate a NURBS surface. This NURBS surface represents the grazing surface and is treated as the design surface. Simulation results show that this design surface can accurately match the machined surface. The accuracy of the surface can be controlled by adding control points to the control net of the NURBS surface. A machining test on a 5-axis machine was done to verify the proposed flank millable surface design method. The machined surface was checked on a CMM and the obtained results were compared with the designed flank millable surface. The comparison results show that the machined surface closely matches the design surface. The proposed flank millable surface design method can be accurately used in the surface design

    A new geometric-and-physics model of milling and an effective approach to medial axis transforms of free-form pockets for high performance machining

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    Mechanical part quality and productivity depend on many parameters in CNC milling processes, such as workpiece material, cutters, tool paths, feed rate, and spindle speed, etc. To pursue high performance machining, the cutting parameter optimization is in high demand in industry, though it is quite challenge. This innovative research successfully addresses some essential problems in optimizing the cutting parameters by developing a new geometric-and-physics integrated model of milling and proposing an effective approach to the medial axis transforms of free-form pockets. In this research, an original geometric model of 21/2- and 3-axis CNC milling is developed and integrated with a well-established mechanistic model. A main research contribution is that this integrated model can predict complex milling processes in higher fidelity with instantaneous material remove rates, cutting forces and spindle powers, compared to prior machining models. In the geometric model, an in-process workpiece model is introduced by using a group of discrete Z-layers and applying the B-Rep scheme to represent the workpiece shape on each layer, in order to accurately represent instantaneous cutter-and-workpiece engagement in 2Yz- and 3-axis milling. Hence, the un-deformed chip geometry can be found even for complex part milling, which is then fed to the mechanistic model to predict instantaneous cutting forces. By using this integrated model, cutting parameters can be optimized for profiling, pocketing, and surface milling to ensure steady cut and the maximum material removal rates. This model has been verified by experiments, and will be implemented into a software tool for Bombardier Aerospace. Another important research in this work is to propose aggressive roughing of free-form pockets for ultimately high cutting efficiency. For this purpose, an accurate, efficient approach to the medial axis transforms of free-form pockets and an optimal approach to multiple cutters selection and their path generation are proposed. The main contributions of this research include (1) a new mathematical model of medial axis point, (2) an innovative global optimization solver, the hybrid global optimization method, (3) an optimization model of selecting multiple cutters for the maximum material removal rate. This research can substantially promote aggressive roughing in the machining industry to increase cutting efficiency of free-form pockets. The technique has been validated using considerable number of cutting tests and can be directly implemented into commercial CAD/CAM softwar

    A Practical and Optimal Approach to CNC Programming for Five-Axis Grinding of the End-Mill Flutes

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    For a solid carbide tapered end-mill, every flute includes a flute surface and a rake face along a helical side cutting edge, and the end-mill core is at the center and is tangent to all the flutes. The flutes significantly affect the tools cutting performance and life, and the core radius mainly affects the tools rigidity. Mainly, two methods are adopted in industry to grind the flutes; these are: the direct method and the inverse method. In the direct method, a flute is ground using a standard grinding-wheel moving in multi-axis machining to generate the rake face and the flute surface. However, the flute is the natural outcome of the grinding process without any control. On the other side, the inverse method employs the concept of inverse engineering to build a grinding-wheel that accurately grinds the end-mill flutes. This yields a free-form grinding-wheel profile that is used on a 2-axis grinding machine; however, the flute shapes are only exact on one section of the end-mill; when the grinding-wheel moves along the side cutting edge to smaller sections; the deviation of the generated flute from the designed one will be increased. Thus, neither can this method grind the rake face with the prescribed normal rake angle, nor generate the side cutting edge in good agreement with its design. Moreover, the grinding-wheel profile is very difficult and expensive to make. To address these problems, a practical and optimal approach for five-axis grinding of prescribed end-mill flutes is proposed by; first, establishing a 5-axis flute grinding theory describing the wheels locations and orientations during grinding the rake faces with constant normal rake angles; Second, introducing a simple grinding-wheel consisting of lines and circular arcs; and finally, applying an optimization algorithm to optimize the grinding-wheel shape and path. Overall, this approach significantly advances the CNC programming technique for the 5-axis flute grinding, and can substantially increase the quality of the solid carbide end-mills and lays a good foundation for the CAD/CAE/CAM of end-mills. The advantages of this approach over the other approaches are verified using computer simulation

    Modeling and simulation of surface generation in manufacturing

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    The paper describes the state-of-the-art in modeling and simulation of surface texture and topography generation at micro and nano dimensional scales. Three main classes of manufacturing processes used for the generation of engineering surfaces are considered: material removal processes, material conservative processes, and material additive processes. Types of modeling techniques for the simulation of surface generation are reviewed and discussed including analytical models, numerical multi-physics models, and data-driven methods. After presenting the application of those modeling techniques for the prediction of characteristics and geometry of surfaces generated by different manufacturing processes, their performance, implementation, and accuracy are discussed. Finally, a roadmap for the realization of a complete surface generation digital twin in manufacturing is outlined

    Optimization of Operation Sequencing in CAPP Using Hybrid Genetic Algorithm and Simulated Annealing Approach

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    In any CAPP system, one of the most important process planning functions is selection of the operations and corresponding machines in order to generate the optimal operation sequence. In this paper, the hybrid GA-SA algorithm is used to solve this combinatorial optimization NP (Non-deterministic Polynomial) problem. The network representation is adopted to describe operation and sequencing flexibility in process planning and the mathematical model for process planning is described with the objective of minimizing the production time. Experimental results show effectiveness of the hybrid algorithm that, in comparison with the GA and SA standalone algorithms, gives optimal operation sequence with lesser computational time and lesser number of iterations

    Optimization of Operation Sequencing in CAPP Using Hybrid Genetic Algorithm and Simulated Annealing Approach

    Get PDF
    In any CAPP system, one of the most important process planning functions is selection of the operations and corresponding machines in order to generate the optimal operation sequence. In this paper, the hybrid GA-SA algorithm is used to solve this combinatorial optimization NP (Non-deterministic Polynomial) problem. The network representation is adopted to describe operation and sequencing flexibility in process planning and the mathematical model for process planning is described with the objective of minimizing the production time. Experimental results show effectiveness of the hybrid algorithm that, in comparison with the GA and SA standalone algorithms, gives optimal operation sequence with lesser computational time and lesser number of iterations

    Autonomous Navigation of Automated Guided Vehicle Using Monocular Camera

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    This paper presents a hybrid control algorithm for Automated Guided Vehicle (AGV) consisting of two independent control loops: Position Based Control (PBC) for global navigation within manufacturing environment and Image Based Visual Servoing (IBVS) for fine motions needed for accurate steering towards loading/unloading point. The proposed hybrid control separates the initial transportation task into global navigation towards the goal point, and fine motion from the goal point to the loading/unloading point. In this manner, the need for artificial landmarks or accurate map of the environment is bypassed. Initial experimental results show the usefulness of the proposed approach.COBISS.SR-ID 27383808
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