Abstract: The aim of this study is to develop a reliable monitoring system for cutting tools in end milling. In this research, cutting force sensor and a vision system are used to monitor milling operations. The fundamental challenge to research is to develop a single-sensor monitoring system, reliable as a commercially available system, but much cheaper than the multi-sensor approaches. The cutting forces are measured with piezoelectric table dynamometer. Optical visual system is used to observe the actual tool conditions after the machining tests. The force sensor signals are then sent to the neuro-fuzzy algorithm, which is trained to determine the tool condition and the amount of tool wear. A neuro-fuzzy algorithm is investigated, to identify the parameters of membership functions, the set of rules and the output weights. The trained adaptive neuro-inference system is also used to discriminate different malfunction states from measured signals. By developed tool condition monitoring system, the machining process can be on-line monitored and stopped for tool change based on a pre-set tool-wear limit. The developed system is used to monitor milling operations and provide warnings to operator, to minimize tool breakage. The effectiveness of tool condition monitoring in ball end milling is investigated through several cutting experiments.

Key words: monitoring, wear, tool condition, single sensor, visual system, ANFIS.

pp. 69-74

INNOVATIVE ASSEMBLY TECHNOLOGY AND ASSISTANCE SYSTEMS FOR LARGE COMPONENTS IN AIRCRAFT ASSEMBLY

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Rainer MÜLLER, Matthias VETTE, Ortwin MAILAHN, Andreas GINSCHEL, Jan BALL

¹⁾ Prof. Dr.-Ing., chief executive officer, assembly technology, ZeMA, Saarbrücken, Germany

²⁾ Dipl.-Wirt.-Ing. (FH), M.Eng , chief engineer, assembly technology, ZeMA, Saarbrücken, Germany

³⁾ Dipl.-Ing., research assistant, assembly technology, ZeMA, Saarbrücken, Germany

⁴⁾ M.Sc., research assistant, assembly technology, ZeMA, Saarbrücken, Germany

^5*) B.Eng., research assistant, assembly technology, ZeMA, Saarbrücken, Germany

Abstract: The global competition challenges aircraft manufactures in high wage countries. The assembly of large components is distinguished by fixed position assembly. Due to a high variant and changing tasks an automation is not economically compared to small and average components. Worker perform a lot of process steps manually and several production resources are necessary. Nowadays, fixed appliances are used in the positioning of fuselages to assemble an aircraft section with the help of component jigs in assigned areas, which picture and support the geometry of components. To comply the required tolerances the appliances have to feature high rigidity and accuracy in shape, which is achieved only by heavy and expensive appliances. Aircraft manufacturer require a huge amount of different resources and personnel, so there are high costs. The aircraft manufacturers deal with a varying number of items, growing product variants and an increase of requirements for their products. To meet the varying demand and increasing product variants more flexible product systems are required. Due to these high costs the demand for automated reconfigurable assembly systems, which offer a high flexibility and lower manufacturing costs, has grown. The research project “IProGro” deals with this challenge and develops innovative production systems for large parts. On one hand the flexibility is reached by a reconfigurable fixture for the parts on the other hand it is achieved by assistance systems, which guide staff during assembly processes.

Key words: Large components, aircraft, reconfigurable assembly system, laser projection, Assistance System, mechatronic modularization.

pp. 75-80

PREDICTION OF CUTTING PARAMETERS BY MILLING FUNCTIONALLY GRADED MATERIAL USING NEURAL NETWORK

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Tomaz IRGOLIC, Uros ZUPERL, Franc CUS

¹⁾ B.Sc., researcher, University of Maribor, Faculty of mechanical engineering, Maribor, Slovenia

²⁾ Assist. Prof., University of Maribor, Faculty of mechanical engineering, Maribor, Slovenia

³⁾ Full. Prof., University of Maribor, Faculty of mechanical engineering, Maribor, Slovenia

Abstract: Paper shows the general characteristics of graded materials, their previous industrial use and potential use of graded materials in the future. In any case, today the use of graded materials is increasing and moving from the laboratory environment into everyday use. However, the subsequent processing of the graded material remains the big unknown, and represents a major challenge for researchers and industry around the world. It could be said that the study of machinability of these materials is in its infancy and in this area are many unanswered questions. Machinability problem of graded materials was undertaken at the Faculty of Mechanical Engineering in Maribor. After a radical study of the literature and potential machining processes of graded materials, we started with the implementation of cutting processes on the workpiece. This professional paper presents the first results of the analysis, which will be used for further research and machinability study of graded materials. Also prediction of cutting forces with neural network by milling functionally graded material was made. In paper first predicted cutting forces by milling graded material are presented.

Key words: functionally graded material, LENS, cutting parameters, artificial neural network.

pp. 81-86

Graphical Method in CATIA Environment for Profiling Rotating Cutters

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Gabriel FRUMUŞANU, Silviu BERBINSCHI, Nicolae OANCEA

¹⁾ Prof., Manufacturing Engineering Department, “Dunărea de Jos” University, Galaţi, Romania

²⁾ PhD, Mechanical Engineering Department, “Dunărea de Jos” University, Galaţi, Romania

³⁾Prof., Manufacturing Engineering Department, “Dunărea de Jos” University, Galaţi, Romania

Abstract:In this paper, we present a graphical method, developed in CATIA environment, based on the method of substituting circles family and dedicated to profiling rotating cutters. Hereby, the family of substituting circles associated with the worked piece (the profile to be generated) is determined at the same time to the curve transposed, in the rolling motion, to the tool centrod. After finding the position of the contact points between the generated profile and the family circles, we can determine, in the transposed family, the locus of the points from the reciprocal enwrapping profile – the rotating cutter profile. The paper also includes a method application for generating the helical surface of a ball screw, and a comparison between the profiling results when using the graphical method, versus an analytical method. The results prove the coincidence between the two profiles determined as above, on one hand, and both rapidity and precision of the graphical method, on the other hand.

Key words: graphical method, CATIA, reciprocal enwrapped surfaces, rotating cutter, ball screw.

pp. 87-92

COMPUTER AIDED ENGINEERING OF INDUSTRIAL ROBOTS

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Cristina PUPĂZĂ, George CONSTANTIN, Ștefan NEGRILĂ

¹⁾ Assoc. Prof., PhD, Machines and Manufacturing Systems Department, University “Politehnica” of Bucharest, Romania

²⁾ Prof., PhD, Machines and Manufacturing Systems Department, University “Politehnica” of Bucharest, Romania

³⁾ MSC-Eng., Assystem Romania S.R.L., Bucharest, Romania

Abstract: : The paper presents a comprehensive CAE perspective on industrial robots. It is a synthesis of a recent research and provides an overview on the most efficient types of modeling, simulation and optimization techniques that can be accessed for industrial robots. The paper also contains a state of art review in the domain. The CAE study was performed on a simplified model of an industrial robot. Results of the static, modal analysis and an extended kinematic study are presented and coupled with FEM optimization procedures. All the results are analyzed in respect with the influence of the static and dynamic behavior on the positioning accuracy of the robot. The model preparation stages are detailed, the simulation procedures are presented and the results are explained. Using a limited number of simulations, the CAE optimization allowed the exploration of an extended design space, taking into account a large number of variants and identifying the best design through-out a ranking and sorting scheme. Because the simulations and the optimization procedures supposed a reduced, but still important number of FEM solutions, a special attention has been paid to the model preparation stages. Further research is in progress on a more detailed model and information regarding the stiffness of the joints will be also considered.

Key words: robot, FEM, static, dynamic, kinematics, simulation, optimization, coupled procedures.

pp. 93-98

SOME CHARACTERISTICS OF ELECTRON BEAM MELTING PROCESS

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Adriana MUNTEANU, Laurenţiu SLĂTINEANU, Margareta COTEAŢĂ

¹⁾ Lecturer, PhD, Department of Machine Tools, “Gheorghe Asachi” Technical University of Iaşi, Romania

²⁾ Professor, PhD, Department of Machine Manufacturing Technology, “Gheorghe Asachi” Technical University of Iaşi, Romania

³⁾ Lecturer, PhD, Department of Machine Manufacturing Technology, “Gheorghe Asachi” Technical University of Iaşi, Romania

Abstract:The electron beam melting is a process applied in case of some electron beam machining methods. Essentially, the electron beam machining is based on the effects generated in the workpiece surface layers as a consequence of the penetration in this layer of electrons included in a high energy electron beam. For this reason, it is important to better know the characteristics of the melting processes developed in the workpiece material under the action of high energy electron beam. The method of systemic analysis was applied in order to highlight the factors able to exert influence on the output parameters specific to the electron beam melting process. A complete factorial experiment was thought and developed; by mathematical processing of experimental results, empirical models being determined. The analysis of empirical mathematical models and some graphical representations elaborated on the base of these empirical models allowed formulating some remarks concerning the variation of the weld depth and width at the variation of electron beam current intensity and speed of relative motion between electron beam and test piece.

Key words: electron beam melting, systemic analysis, beam current intensity, relative motion speed, empirical models.

pp. 99-104

USING A CNC MILLING MACHINE FOR INCREMENTAL FORMING

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Melania TERA, Radu BREAZ, Octavian BOLOGA, Gabriel RACZ

¹⁾ Assist. Prof., PhD, Industrial Machines and Equipments Department, Faculty of Engineering, "Lucian Blaga" University of Sibiu, Romania

²⁾ Prof., PhD, Industrial Machines and Equipments Department, Faculty of Engineering, "Lucian Blaga" University of Sibiu, Romania

³⁾ Prof., PhD, Industrial Machines and Equipments Department, Faculty of Engineering, "Lucian Blaga" University of Sibiu, Romania

⁴⁾ Prof., PhD, Industrial Machines and Equipments Department, Faculty of Engineering, "Lucian Blaga" University of Sibiu, Romania

Abstract: The Asymmetric single point incremental forming (ASPIF) is a manufacturing technology with a high degree of novelty which has been widely recognized as a solution with great potential in manufacturing small batches or even single sheet metal parts. Machines for this specifically process are hardly are almost inexistent for that reason some solutions would be using CNC machines or industrial robots. The technological equipment used for the incremental forming is the CNC cutting milling machine-tools. The control system of the CNC equipment is tuned according the accuracy domain of the milling process, which lies within micrometers range. The control parameters are chosen in order to minimize the positioning errors and to deal with predictable and constant forces. This research presents an approach of re-tuning the control system of the CNC equipment for the requirements of the ASPIF process, a smaller accuracy, lying within millimeters range and unpredictable forces. In the last stage of the paper there was realized a comparative study of the parts' roughness function of the employed incremental forming process.

Key words: CNC milling machine, control parameters, incremental forming, roughness, simulation.

pp. 105-114

OPTIMAL SERVOMOTOR SELECTION ALGORITHM FOR INDUSTRIAL ROBOTS

AND MACHINE TOOLS NC AXIS

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Adrian NICOLESCU, Cezara AVRAM, Mario IVAN

¹⁾ PhD, Eng., Prof., Department of Machines and Manufacturing Systems, University "Politehnica" of Bucharest, Romania

²⁾ Eng., Assistant Prof., Department of Machines and Manufacturing Systems, University "Politehnica" of Bucharest, Romania

³⁾ Eng., Lector, Department of Machines and Manufacturing Systems, University "Politehnica" of Bucharest, Romania

Abstract: This paper presents a complete calculus algorithm for selecting the optimal servomotors of the kinematic chains included in the numerically controlled axes (NCA) of machine tools (NCMT) and industrial robots (IR). The algorithm can be applied for both type controlled axes, i.e. industrial robots, and machine tools, as well as either rotation axis or translation axis, regardless of their mechanical structure. The presented calculus algorithm includes six major steps: defining the working cycle motion diagram for the operated mechanical system and complementary input data; identifying the static and dynamic forces applied to the driven system during operation and the specific mechanical structure on NCA (i.e. specific transfer ratio of each included mechanism); preliminary selection of the driving servomotor by checking the kinematic criterion; determining of the total resistant equivalent load applied on the driven element; secondary selection of the driving servomotor by checking the static and dynamic criterion; and tertiary selection of the driving servomotor by checking the performance parameters related to full kinematic chain driving (acceleration time, braking time, servomotor's thermal behavior). The motor finally chosen represents the optimum solution for driving the NCA in terms of satisfying all imposed criteria (kinematic criterion, static criterion, dynamic criterion) and complying as well the necessary performance requirements for NCA's electro-mechanic driving system.

Key words: optimal selection, algorithm, servomotor, industrial robot, machine tools, NC axis.

pp. 115-120

FINITE ELEMENT MODELLNG OF POLYMER COMPOSITES PROCESSING

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Victor POPOVICI, Marinela MARINESCU, Larisa BUTU, Claudia BORDA, Delicia ARSENE

¹⁾ Assoc. Prof., PhD, Materials Technology and Welding Department, Bucharest, Romania

²⁾ Lecturer. PhD, Materials Technology and Welding, Bucharest Department,, Romania

³⁾ Lecturer. PhD, Materials Technology and Welding, Bucharest Department,, Romania

⁴⁾ Lecturer. PhD, Materials Technology and Welding, Bucharest Department,, Romania

⁵⁾ Lecturer. PhD, Materials Technology and Welding, Bucharest Department,, Romania

Abstract: This article presents finite element analysis of resin-hardener system’s behaviour during composites processing. One of the main studied problems was variation of shearing force produced in the system by moving a vibrating probe between composite’s layers. The fluid viscosity is defined like resistance to flowing. As follows, time variation of shearing force determined as a result of composites modeling with finite elements, describes composite system variation of viscosity depending on time. The results expected response the state of loading of the structure which has been modelling so the real conditions of its. They can provide information for a range of sizes of the same structure, as well as a range of values of the forces taken.

Key words: finite element, modelling, polymer composite, shearing force, cross linking.

Electronic mail: orgcom@icmas.eu