37 research outputs found

    On initialization of milling paths for 5-axis flank CNC machining of free-form surfaces with general milling tools

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    We propose a path-planning algorithm for 5-axis flank CNC machining with general tools of varying curvature. Our approach generalizes the initialization strategy introduced for conical tools [Bo et al., 2017] to arbitrary milling tools. Given a free-form (NURBS) surface and a rotational milling tool, we look for its motion in 3D to approximate the input reference surface within a given tolerance. We show that for a general shape of the milling tool, there exist locally and generically four 3D directions in which the point-surface distance follows the shape of the tool up to second order. These directions form a 3D multi-valued vector field and its integration gives rise to a set of integral curves. Among these integral curves, we seek straight line segments that correspond to good initial positions of the axes of the milling tool. We validate our method against synthetic examples with known exact solutions and, on industrial datasets, we detect approximate solutions that meet fine machining tolerances. We also demonstrate applicability of our method for efficient flank milling of convex regions that is not possible using traditional conical tools.RYC-2017-2264

    Highly-accurate 5-axis flank CNC machining with conical tools

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    A new method for 55-axis flank computer numerically controlled (CNC) machining using a predefined set of tappered ball-end-mill tools (aka conical) cutters is proposed. The space of lines that admit tangential motion of an associated truncated cone along a general, doubly curved, free-form surface is explored. These lines serve as discrete positions of conical axes in 3D space. Spline surface fitting is used to generate a ruled surface that represents a single continuous sweep of a rigid conical milling tool. An optimization based approach is then applied to globally minimize the error between the design surface and the conical envelope. Our computer simulation are validated with physical experiments on two benchmark industrial datasets, reducing significantly the execution times while preserving or even reducing the milling error when compared to the state-of-the-art industrial software

    PENGARUH INKLINASI PAHAT TERHADAP MORFOLOGI CHIP PADA PEMESINAN MILLING CNC 5 AXIS

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    Penelitian ini bertujuan untuk mengetahui pengaruh inklinasi pahat terhadap morfologi chip dan gaya potong yang dihasilkan pada proses pemesinan miling pada material alumunium AISI 7072, dengan menggunakan pahat flat-end mill dan memvariasikan sudut inklinasi. Parameter yang menjadi variasi pada penelitian ini adalah sudut inklinasi benda kerja yaitu 5°, 10°, 15°, 20°, 25° dan 30°. Salah satu dampak negatif dari gaya potong yang besar adalah berupa rendahnya lifetime atau umur pahat sehingga menyebabkan pahat mudah mengalami kerusakan. Untuk menghindari hal ini, pengamatan dilakukan dengan menggunakan metode eksperimental, setiap chip yang diperoleh pada proses pemesinan dianalisa sehingga mendapat hubungan dengan besar gaya potong. Pengambilan data gaya potong dilakukan pada awal pemakanan. Data yang diperoleh kemudian dibandingkan dengan prediksi gaya potong lalu diambil nilai gaya tertinggi setiap sumbu dari berbagai variasi sudut inklinasi. Sample chip yang diperoleh dari proses pemesinan dengan berbagai variasi sudut inklinasi lalu diamati dan diukur dengan menggunakan mikroskop serta dibandingkan dengan perhitungan prediksi morfologi chip. Hasil analisis dari berbagai proses pemesinan dengan memvariasikan sudut inklinasi menunjukan bahwa, semakin bertambahnya sudut inklinasi maka semakin meningkat pula gaya potong yang dihasilkan. Peningkatan gaya potong dapat dilihat dari panjang chip dan lebar chip bertambah sedangkan ketebalan chip berkurang seiring dengan dengan meningkatnya sudut inklinasi benda kerja dari 5° sampai dengan 30°. ***** This study aims to determine effect of tool inclination on chip morphology and cutting forces produced in the milling machining process on alumunium AISI 7072 material, using flat-end mill tool and varying the inclination angle of the tool. The parameter that varies this study is the inclination angle of workpiece which is 5°, 10°, 15°, 20°, 25° dan 30°. One of the negative impacts of large cutting forces is a low tool life that causes the tool to easily experience damage. To avoid this, observations were made using an experimental method, each chip obtained in the machining process is analyzed so as to obtain a a relationship with the cutting forces Cutting force data was collected at the beginning of the machining process. The data obtained is then compared with the prediction cutting force, and the highest force value for each axis of the various inclination angle variations is taken. Sample chip obtained from the machining process with various inclination angles variations were then observed and measured using a microscope and compared with chip morphology predictions calculations. The result of analysis of the various machining processes by varying the inclination angle showed that, as the inclination angel increases, The cutting force produced also increases. The increasse in cutting force can be seen from the chip length and chip widht increasing while chip thickness decreasing along with the increasing the inclination angle of the workpiece from 5° to 30°

    Characterizing envelopes of moving rotational cones and applications in CNC machining

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    Motivated by applications in CNC machining, we provide a characterization of surfaces which are enveloped by a one-parametric family of congruent rotational cones. As limit cases, we also address ruled surfaces and their offsets. The characterizations are higher order nonlinear PDEs generalizing the ones by Gauss and Monge for developable surfaces and ruled surfaces, respectively. The derivation includes results on local approximations of a surface by cones of revolution, which are expressed by contact order in the space of planes. To this purpose, the isotropic model of Laguerre geometry is used as there rotational cones correspond to curves (isotropic circles) and higher order contact is computed with respect to the image of the input surface in the isotropic model. Therefore, one studies curve-surface contact that is conceptually simpler than the surface-surface case. We show that, in a generic case, there exist at most six positions of a fixed rotational cone that have third order contact with the input surface. These results are themselves of interest in geometric computing, for example in cutter selection and positioning for flank CNC machining.RYC-2017-2264

    Automated Process Planning for Five-Axis Point Milling of Sculptured Surfaces

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    Ph.DDOCTOR OF PHILOSOPH

    A CAD/CAM concept for High Speed Cutting compatible rough machining in die, mould and pattern manufacturing

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    Die, mould and pattern manufacturing plays a central role in the production of capital and consumer goods. Ever-shorter product life cycles and the expanding diversity of features require continued cuts in production lead times. Recently, these developments in the market, accompanied by a simultaneous demand for improved quality at a lower cost, are becoming clearly noticeable. Along with the streamlining of organizational structures and advanced technological developments, it is above all the introduction of CAD/CAM software that offers great potential for reducing lead times for components with free surfaces. The role of milling in the integrated process chain of die, mould and pattern manufacturing is steadily gaining importance. This is due to the ongoing further development of milling-machine technology, the cutting tools and their coatings, and of the CAD /CAM systems themselves. Generally speaking, the milling process is divided into the operations of roughing and finishing. For rough milling, efficient machining means high stock-removal rates together with close contour approximation and low tool wear. Rough milling is normally carried out layer by layer, i.e. in a 2.SD machining operation with constant depth per cut because the rate of material removal and process reliability are usually highest when this method is used. High-speed cutting (HSC), which has been the subject of extensive university research for far more than ten years, has meanwhile become established as a finishing process in many companies. However, the application of HSC demands the observance of geometric and, above all, technological constraints. A considerable degree of optimization can be achieved when these constraints are applied to rough milling. In the integrated process chain, the CAD/CAM system performs the task of calculating NC programs based on CAD data which meet the requirements posed by rough and finish machining operations. While general interest was focused on the development of CAM strategies for HSC finish machining, advanced development of technology-oriented CAM modules for upstream roughing operations was neglected. The paper at hand deals with the development of a CAM module for rough-machining complex components in die, mould and pattern manufacturing. It provides an insight into the process-technological demands made on HSC operations and their application in rough machining, from which guidelines and requirements on technologically oriented NC functions for CAM software were derived. These encompass both the complete development of an interactive, dialogue-based user guidance function and the algorithmic conversion of the calculation routines. The concept at hand was almost entirely implemented and integrated in the CAD/CAM system developed by Tebis AG, Germany, which was conceived especially for die, mould and pattern manufacturing and is scheduled for introduction to the free market starting in April 2001

    Rationalization with ruled surfaces in architecture

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    A virus-evolutionary, multi-objective intelligent tool path optimisation methodology for sculptured surface CNC machining

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    Today’s production environment faces multiple challenges involving fast adaptation to modern technologies, flexibility in accommodating them to current industrial practices and cost reduction through automating repetitive tasks. At the same time the requirements for manufacturing functional, aesthetic and versatile products, turn these challenges to clear and present industrial problems that need to be solved by delivering at least semi-optimal results. Even though sculptured surfaces can meet such requirements when it comes to product design, a critical problem exists in terms of their machining operations owing to their arbitrary nature and complex geometrical features as opposed to prismatic surfaces. Current approaches for generating tool paths in computer-aided manufacturing (CAM) systems are still based on human intervention as well as trial-and-error experiments. These approaches neither can provide optimal tool paths nor can they establish a generic approach for an advantageous and profitable sculptured surface machining (SSM). Major goal of this PhD thesis is the development of an intelligent, automated and generic methodology for generating optimal 5-axis CNC tool paths to machine complex sculptured surfaces. The methodology considers the tool path parameters “cutting tool”, “stepover”, “lead angle”, “tilt angle” and “maximum discretisation step” as the independent variables for optimisation whilst the mean machining error, its mean distribution on the sculptured surface and the minimum number of tool positions are the crucial optimisation criteria formulating the generalized multi-objective sculptured surface CNC machining optimisation problem. The methodology is a two-fold programming framework comprising a virus-evolutionary genetic algorithm as the methodology’s intelligent part for performing the multi-objective optimisation and an automation function for driving the algorithm through its argument-passing elements directly related to CAM software, i.e., tool path computation utilities, objects for programmatically retrieving tool path parameters’ inputs, etc. These two modules (the intelligent algorithm and the automation function) interact and exchange information as needed towards the achievement of creating globally optimal tool paths for any sculptured surface. The methodology has been validated through simulation experiments and actual machining operations conducted to benchmark sculptured surfaces and corresponding results have been compared to those available from already existing tool path generation/optimisation approaches in the literature. The results have proven the methodology’s practical merits as well as its effectiveness for maintaining quality and productivity in sculptured surface 5-axis CNC machining

    Friction Force Microscopy of Deep Drawing Made Surfaces

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    Aim of this paper is to contribute to micro-tribology understanding and friction in micro-scale interpretation in case of metal beverage production, particularly the deep drawing process of cans. In order to bridging the gap between engineering and trial-and-error principles, an experimental AFM-based micro-tribological approach is adopted. For that purpose, the can’s surfaces are imaged with atomic force microscopy (AFM) and the frictional force signal is measured with frictional force microscopy (FFM). In both techniques, the sample surface is scanned with a stylus attached to a cantilever. Vertical motion of the cantilever is recorded in AFM and horizontal motion is recorded in FFM. The presented work evaluates friction over a micro-scale on various samples gathered from cylindrical, bottom and round parts of cans, made of same the material but with different deep drawing process parameters. The main idea is to link the experimental observation with the manufacturing process. Results presented here can advance the knowledge in order to comprehend the tribological phenomena at the contact scales, too small for conventional tribology
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