© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

DYNAMIC LIFE CYCLE PERFORMANCE SIMULATION OF PRODUCTION SYSTEMS

Jorg NIEMANN¹, Engelbert WESTKAMPER^1
1IFF Institute of Industrial Manufacturing and Management, Universitat Stuttgart, Fraunhofer IPA, Nobelstrasse 12, 70569 Stuttgart, Germany

Abstract

The paper presents a framework for controlling the life cycle of so called "integrated manufacturing systems". In the process, the economic efficiency of continuous improvement measures taken during its further life are evaluated in a simulation and monitored using real production data. To do so the paper identifies relevant data sources and describes the integration into a simulation model. To improve the performance of the manufacturing system the model describes general starting points. Before implementation the changes will be simulated and evaluated. After implementation the data from reality will be compared with the forecast to improve the model.

Author Keywords :

production planning, life cycle, simulation

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

OPTIMIZATION OF PROCESS PARAMETERS WITH GENTELLIGENTR COMPONENTS

Berend DENKENA¹, Alessandro BATTINO¹, Christian LIEDTKE^1
1Institute of Production Engineering and Machine Tools (IFW), University of Hannover, Schoenebecker Allee 2, 30823 Garbsen, Germany

Abstract

The ability to learn from experience and to flexibly adapt to changes in the environment are fundamental characteristics of modern production companies. Manufacturing systems are required to be flexible and fault tolerant and will in future contain learning, collaborative and intelligent entities that can dynamically adjust themselves so as to achieve global system objectives. The development of such entities, called "gentelligent^R components" is one focus of current research activities at the Hannover Center for Production Technology (PZH). The capacities of gentelligent^R components to gather information and to act autonomously offer new potentials for increasing efficiency in production. Regarding the precision of machining processes, online distributed monitoring and local elaboration of information provide the means to intervene on process parameters so as to adapt to conditions changed after completion of planning activities. In this paper, a concept for the partial integration of process planning and production control is presented, which allows exploiting the potentials of gentelligent^R components in order to flexibly react to disturbances in production. Moreover, a fuzzy-expert infrastructure is described, which is adapted to process monitoring data so as to determine correction measures.

Author Keywords :

manufacturing process optimization, process planning, process monitoring

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

MICROELECTRONIC DEVICE QUALITY IMPROVEMENT USING TAGUCHI METHOD

Tatjana SIBALIJA¹, Vidosav MAJSTOROVICH^1
1Mechanical Engineering Faculty, Laboratory for Production Metrology and TQM, Kraljice Marije 16, 11120 Belgrade 35 PF 34, Serbia

Abstract

This paper is based on Taguchi Design of Experiment model, as a specific quality engineering technique for minimization of process variation, within Taguchi TQM model. Since thermosonic wire bonding is essential process in microelectronic device assembly, the aim of this project is to redesign thermosonic copper wire bonding process, in order to achieve product - microelectronic device quality improvement, simultaneously achieving process cost reduction. After defining the specifications for quality characteristics, selection of microelectronic components, machine, tool and initial process parameters values, process design is preformed using Taguchi orthogonal design technique. Analysis of experimental results provides selection and verification of the adopted process parameters values, thereby leading to product quality characteristics improvement.

Author Keywords :

taguchi model, design of experiment, microelectronic device assembly, thermosonic copper wire bonding.

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

QUALITY CONTROL OF FREE FORM SURFACES

Jozef PETERKA¹, Alexander JANAC¹, Ladislav MOROVIC¹, Peter POKORNY^1
1Slovak University of Technology Bratislava, Slovakia, Faculty of Materials Science and Technology Trnava, Department of Machining and Assembly

Abstract

The paper brings the new known about the quality control by copy milling. We will present our 3D optical digitizing system for the free form surfaces scanning and the measuring. In this paper we will show some examples of scanning and measuring of real dies and models.

Author Keywords :

reverse engineering, quality control optical measuring system

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

A HAPTIC INTERFACE FOR FIVE-AXIS NC-PROGRAMMING: CONCEPT, IMPLEMENTATION AND EVALUATION

Berend DENKENA¹, Rene APITZ¹, Pawel KOWALSKI^1
1Institute of Production Engineering and Machine Tools (IFW), University of Hannover, Schonebecker Allee 2, 30823 Garbsen, Germany, info@ifw.uni-hannover.de

Abstract

This paper features an approach for five-axis NC-programming that is based on Virtual Reality (VR) methods. It capitalises on a haptic input device with five degrees of freedom. The force feedback provided may include factors like workspace limitations or collisions. The presented approach follows a paradigm that is different from conventional approaches as well as from previous VR-based concepts: It focuses on providing support for complex subtasks of the NC programming process, and aims at deriving this support from technological and kinematical boundary conditions. Its key issue is to develop algorithms to utilise manual input from a VR-based simulation system for creating tool sub paths for milling operations with up to five degrees of freedom. The approach is not meant to substitute conventional strategies thoroughly: Its main advantage is relief in tool positioning and error correction. The paper describes the system's concept and implementation as well as its evaluation, which was performed comparing it to a commercial CAM platform.

Author Keywords :

NC-programming, CAM, haptics

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

FROM CONDITION MONITORING TO WEAR PROGNOSIS AND PREDICTIVE MAINTENANCE

Berend DENKENA¹, Gunter RADONS¹, Peter BLUMEL^2
1Institute of Production Engineering and Machine Tools (IFW), University of Hannover, Schoenebecker Allee 2, 30823 Garbsen, Germany. E-mail: {denkena|bluemel}@ifw.uni-hannover.de
²Institute of Physics (IP), University of Chemnitz, Reichenhainer Straße 70, 09126 Chemnitz, Germany. E-mail: radons@physik.tu-chemnitz.de

Abstract

The increasing requirements of the industrialised countries for availability of their production facilities, accompanied by the reduction of maintenance budgets, require a maintenance that flexibly and accurately adapts the real states and needs of the facilities. Condition monitoring has been found a promising approach to initiate maintenance measures based on the actual state of a component. However, most of the condition monitoring-systems do their analysis only based on process states and disregard history data. In the approach presented in this paper, maintenance activities are planned by a long-term analysis of process data. Furthermore, an approach for disturbance prediction based on a nonlinear discrete event simulation is presented. Finally, an implementation at a car factory in Germany is exemplarily described and an outlook on disturbance prediction is given.

Author Keywords :

availability ,maintenance, condition monitoring

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

ESTIMATION OF SIMULATION ERRORS DUE TO INACCURATE EVALUATION OF MATERIAL PROPERTIES IN METAL FORMING

Danuta SZELIGA¹, Stanisław WĘGLARCZYK¹, Maciej PIETRZYK^1
1Akademia Gorniczo-Hutnicza, Mickiewicza 30, 30-059 Krakow, Poland

Abstract

Determination of the error of the finite element simulations of metal forming processes, which is caused by inac?curacies of the rheological law, is the general objective of the paper. Evaluation of various plastometric tests is the particular aim of the first part of the research. Sources of errors in the tests are analysed and the influence of the assumed friction coefficient on the flow stress calculated by the inverse method is assessed. Sensitivity pa?rameter, defined as partial derivative of the flow stress with respect to the friction coefficient, is calculated. Fur?ther research focus on evaluation of capabilities of mathematical models, which are used as constitutive laws in the FE codes. Analysis of capabilities of various functions to describe properly flow stress was performed and er?rors due to approximation of the experimental data were determined. The last part of the research focus on evaluation of the error of the FE simulations caused by an inaccurate determination of the flow stress. Sensitivity analysis was performed for the industrial forging process. Closed die forging, in which free flow of material is allowed at certain stage of deformation, was selected for the analysis. Sensitivity of the load and filling of the groove with respect to material parameters was determined. In consequence, evaluation of simulation errors due to inaccurate determination of material properties was performed.

Author Keywords :

finite element method, metal forming,simulation errors, sensitivity analysis

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

AUTOMATIC HP ADAPTIVITY TO IMPROVE ACCURACY OF MODELING OF HEAT TRANSPORT AND LINEAR ELASTICITY PROBLEMS IN ENGINEERING

Maciej PASZYNSKI¹, Magdalena KOPERNIK¹, Łukasz MADEJ¹, Maciej PIETRZYK^1
1Department of Computer Methods in Metallurgy, AGH University of Science and Technology, Krakow, Poland

Abstract

Typical engineering problem, i.e. heat transport modelled by Laplace equation or deformation of the body modelled by linear elasticity, involves solution of the Partial Differential Equation (PDE). Modelling requires supplying physical quantities on the Finite Element (FE) mesh describing geometry of modelled domain. In many cases the object under consideration consists of different materials, described by various material constants. In such a case, singularities at interfaces of different materials appear leading to large errors of the numerical solution in those areas. For elliptic problems, the error propagates into entire domain. The finite element mesh must be refined to minimize the error of the solution. However, it is very hard to design finite element mesh resolving those singularities by hand. Hp adaptive code, which constructs in a fully automatic mode a sequence of finite element meshes delivering exponential convergence of the error of the FE solution, is presented in this paper. Several examples involving heat transport and linear elasticity problems are shown and significant improvement of accuracy of the solution is proved.

Author Keywords :

finite element method, hp adaptivity, heat transport, linear elasticity

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

TAKING MANUFACTURING DISPERSIONS INTO ACCOUNT FOR ASSEMBLY: MODELLING AND SIMULATION

Frederic GERMAIN¹, Max GIORDANO¹, Pierre Antoine ADRAGNA^1
1Laboratoire de Mecanique Appliquee - Universite de Savoie - France

Abstract

The model of clearance and deviation domains, based on the concept of small displacement torsors, allows three-dimensional worst-case tolerance analysis and synthesis. This kind of tolerancing guarantees the complete interchangeability between the different parts composing a mechanism that, in a general way, is over constrained since it does not take into account manufacturing characteristics. During the assembly of mechanisms, the probability that the defects of all the parts of the assembly are in one of the most unfavourable configurations is very little. It then would be interesting to have a statistical approach that takes into account manufacturing dispersions. One can then increase the tolerances while controlling the risk of non-quality. With this intention, two approaches are possible: the simulations of Monte Carlo, and analytical calculation. We propose, basing ourselves on the theory of the domains developed by our team, to apply these two methods. The first consists in simulating, for each assembly, on the one hand the dimensional variations to define a random resulting clearance domain, and on the other hand the geometrical variations to define a random resulting deviation torsor. The second consists in calculating numerically the multiple integral of the probability densities of the random variables intervening in the assembly loop, and whose bounds are defined by random variables. The modelling of manufacturing dispersions allows, according to these two approaches, a numerical simulation of the assemblies. They present each advantages and disadvantages in terms of precision and computing time.

Author Keywords :

statistical tolerancing, Monte Carloclearance domain, deviation torsor

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

INERTIAL TOLERANCING : THE SORTING PROBLEM

Maurice PILLET¹, Pierre Antoine ADRAGNA², Frédéric GERMAIN^2
1Laboratoire LISTIC - Université de Savoie - ESIA - IUT Annecy - B.P. 806 - 74016 Annecy Cedex maurice.pillet@univ-savoie.fr
²Laboratoire LISTIC - Université de Savoie - ESIA - IUT Annecy - B.P. 806 - 74016 Annecy Cedex pierre-antoine.adragna@univ-savoie.fr; frederic.germain@univ-savoie.fr

Abstract

Inertial tolerancing presents a new way to define the conformity of a characteristic without defining the specification interval as it is traditionally the case. Conformity is defined by "inertia" (Taguchi loss function [5]) around the target. The principle of inertial tolerancing consists of tolerancing the mean square deviation from the target. The tolerances are not represented by the traditional [Min Max] interval. We have shown [1] [3] that this tolerancing method offers numerous advantages in term of Quality/Cost ratio, but it raises severe problems when batches are not acceptable. In these cases with traditional tolerancing, the products are sorted in order to eliminate each part outside tolerance. In inertial tolerancing, the problem consist in eliminating products the most far from the target to obtain an inertia corresponding to the specifications. The sorting limits depend on three elements: standard deviation, deviation from the target and distribution law. In this paper, the proposed method differentiates two situations. In the first one the distribution law is considered as a uniform law [a b] not centred on the target. In the second one we consider a normal law with a standard deviation σ en a deviation from the target δ Analytical solution is given for the first situation. In the second situation, analytical solution is impossible and we propose a very quick algorithm allowing resolving this problem. An Excel solution is presented. The proposed solution can be used in the case of traditional tolerancing when the conformity is decided on the capability index C_pm [2].

Author Keywords :

statistical tolerancing, inertial tolerancing, acceptance sampling, (mechanical assembly)

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

A CAD TOOL TO TOLERANCE EVALUATION BASED ON PROCESS MANUFACTURING INFORMATION

Abdelmjid SAKA¹, Abdelaziz SAKA¹, Michel CARRARD^2
1Ecole Superieure de Technologie de Fee (Morocco), e-mail : abdelmjid.saka@laposte.net
²Institut Superieure de Technologie de Cachan (France), e-mail : michel.carrard@iut-cachan.u-psud.fr

Abstract

The development and application of a CAD based computer aided tolerancing model for the machining process (a typical type of manufacturing process) is chosen as the research topic of this paper. The proposed methodology integrates the CAD tools and methods (digitalization, transformation) with the CAT methods (Monte Carlo simulation) to calculate the final tolerance of a machining process. This study will present a more comprehensive model dealing with Dimensioning and Tolerancing. The methods presented in this study can be used in the design phase for machining.

Author Keywords :

tolerance evaluation, process manufacturing CAD, CAT , Monte Carlo simulation

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

EFFICIENCY OF WIRE ELECTRICAL DISCHARGE MACHINING OF WC-CO CEMENTED CARBIDES

Stanisław ZABORSKI¹, Dariusz POROS^1
1 Institute of Production Engineering and Automation, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, tel./fax: +48 71 3202703, POLAND

Abstract

Traditional methods of machining of cemented carbides are problematic as well technologically as economically.Such materials characterize good wear, corrosion resistance properties but are doubtful in conventional machining. Owing to their outstanding combination of hardness, strength and wear resistance, advanced ceramics are widely used as structural components and wear-resistant parts (including tools and dies). Wire-electro discharge machining (WEDM) is an important non-traditional machining process, widely used for machining a variety of difficult-to-machine materials including cemented carbides with intricate shapes. It is observed that parameters such as time between two pulses and pulse duration have more influence on the surface characteristics. Material ratio, roughness of surface, efficiency of cutting and wire wear ratio of machined cemented carbides are studied in this paper

Author Keywords :

cemented carbides, WEDM, surface layer

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

PHYSICAL MODELING APPLICATION FOR ANALYSIS OF METAL FORMING PROCESSES

Zbigniew GRONOSTAJSKI¹, Marek HAWRYLUK¹, Pawel KARBOWSKI¹, Pawel BANDOLA^1
1Wroclaw University of Technology, Institute of Engineering and Automation

Abstract

Physical modeling is one of the most prevalent methods for analysis of metal forming processes. It can be the alternative or the supplement for mathematical modeling by the finite element method which is also recently very popular. This method makes possibility to define the schedule of deformations and the strains, to estimate the force parameters of given process and also to locate of dead zones as well as the mistakes of flowing. In the work the main idea of physical modeling and the most interesting examples of physical modeling method application into analysis of metal forming processes are presented. The most important similarity conditions between physical model and real process, like materials similarity in the range of plastic and elastic deformation, geometrical, frictional and thermal similarities are described. A new approach to the plastic similarity condition used for physical modeling of metal forming processes is proposed in the paper. It assumes quantitative estimation of the flow stress curves.

Author Keywords :

physical modelling, similarity condition, model materials

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

ANALYSIS OF SHAPE DEVIATIONS OF MEASURED GEOMETRIES WITH A MODAL BASIS

Pierre Antoine ADRAGNA²,Serge SAMPER², Maurice PILLET¹, Hugues FAVRELIERE^2
1Laboratoire LISTIC - Université de Savoie - ESIA - IUT Annecy - B.P. 806 - 74016 Annecy Cedex maurice.pillet@univ-savoie.fr
²Laboratoire LISTIC - Université de Savoie - ESIA - IUT Annecy - B.P. 806 - 74016 Annecy Cedex pierre-antoine.adragna@univ-savoie.fr; serge.samper@univ-savoie.fr; hugues.favreliere@univ-savoie.fr

Abstract

In mechanical assembly, dimensions are functional, but often the shape is also very important in the product function. The qualification of the form defect is necessary for the optimization of this functional condition. Geometrical tolerancing defined by the norm does not allow defining the shape of the surface in the interior of this space. To answer to these specific needs, a research axis consists of the link between the measured defect and the origin of this defect thanks to the creation of a basis of typical defects. The method we propose is a decomposition based on eigen modes of vibration of the ideal designed surface. This method inherits of the modal shape and finite elements analysis properties: - Versatility: any kind of geometry can be analysed - Deviation unification: size, position, form and roughness can be analysed by the same method - Form growing complexity: from large wavelength defect to small undulations. The measured feature gives a set of points that have to be filtered in order to distinguish those defects. The decomposition of the actual geometry in a set of modal natural shapes sorts defects from the lowest to the highest level of complexity. Although tolerancing of geometrical forms is applied either to surfaces or to outlines of parts, we are interested in this paper to form defects of surfaces, but the presented method allows describing distributor spool

Author Keywords :

statistical tolerancing, inertial tolerancing, acceptance sampling, (mechanical assembly)

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

CAM SYSTEM APPLICATION FOR SHAPE CUTTING PROGRAMMING ON WIRE SAW TYPE PS2Tsk

Bożena CIAŁKOWSKA¹, Zbigniew RODZIEWICZ¹, Jerzy SOBIECH^1
1Institute of Production Engineering and Automation, Wroclaw University of Technology

Abstract

Possibilities of CAM system application for programming requirements when we cut different shapes in hard to machining materials using diamond wire and saw PS2Tsk. The main goal will present as well as short characteristic of investigation stand and results analysis.

Author Keywords :

shape cutting, abrasive wire programming

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

MECHATRONIC COMPONENTS FOR MACHINE TOOLS

Reimund NEUGEBAUER¹, Markus WABNER², Steffen IHLENFELDT¹, Volker WITTSTOCK^1
1Fraunhofer Institute for Macine Tools and Forming Technology IWU, Chemnitz
²Institute of Machine Tools and Manufacturing Processes, Technical University of Chemnitz

Abstract

Highly concentrated functionalities which may be realised by combining classical production engineering equipment with information technology capabilities determine the trends achieved in manufacturing technology. The consequent implementation of this development idea finally leads to mechatronic solutions with local or decentralised intelligence. In the paper, motivations, approaches and solutions for improvement of the machine tool behaviour by Mechatronic components are presented.

Author Keywords :

machine tool, mechatronic component, mechatronics, adaptronics

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

DEVELOPMENT OF AN ON-LINE TEST FOR THE ACCURACY EVALUATION OF A CRADLE MILLING MACHINE

Andrea DEL TAGLIA¹, Gianni CAMPATELLI^1
1University of Firenze - Department of Industrial Technologies and Mechanical Engineering

Abstract

The high accuracy required by most of the today's manufacturing processes could be attained by means of two strategies: improving the intrinsic machine tool accuracy (design strategy) or through the periodic adjustment of the machine accuracy (control strategy). This second strategy is used mostly for specially designed machine tools while the first strategy is used for more common design solutions. Usually special machine tools are used for mass production of specific components and are dedicated to such production for most of their working life. In this work we have developed a performance test strategy for a special "cradle" milling machine, used for the mass production of automotive homokinetics joints. The general idea of this work is to develop a new test strategy that allows an easy test of the machine accuracy without turning off the machine tool (gaining so production time), evaluating the axes that need a set up through the measurement of a special workpiece (performance test piece). The advantage is mainly due to the fact that it's no more necessary to turn off the machine and lose production time and so the performance test could be repeated more frequently, granting so a better overall product quality.

Author Keywords :

performance test, cradle milling machine on line test

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

THE ACCURACY OF THE SHIFT AND TURNING MOTION FOR A MANIPULATOR ARM

Jirí VONDRICH¹, Filip SIBRAVA^1
1Department of Mechanics and Materials Science, Faculty of Electrical Engineering, Czech Technical University in Prague, Technická 2, 166 27 Praha 6, Czech Republic, vondrich@fel.cvut.

Abstract

The purpose of article is to determine the accuracy of the shift and turning motion for a manipulator arm. The control of the manipulator arm is demonstrated, which uses a numerical fuzzy-algorithm written in Matlab or Simulink. The system consisted of the arm subsystem and two subsystems, which simulated direct-current motors. The motors are described by mathematical equations in Matlab. The model of manipulator arm is described by two non-linear differential equations of the second-degree Motion equations were deduced by Langrangian equations of the second order. The introduced regulator is optimal for the desired shift of the manipulator arm and for the desired angle of the manipulator arm. The designed controller has two inputs and two outputs. One output was dedicated to an angle regulation and the second one was dedicated to an arm shifting. Both inputs (and outputs) have the same number of fuzzy sets. For more suitable regulation quality, of it is important to repeat cycle simulation - correction of rules and sets more than once. For a more complicated system, it is easier to uses a fuzzy regulator, which uses training through neural net. The optimal course of the shift and turning for the manipulator arm is in the starting and stationary state.

Author Keywords :

fuzzy control, Matlab, Simulink, manipulator

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

ESTIMATION OF THE INFLUENCE OF MACHINING ERRORS ON BALL SCREWS RIGIDITY

Jerzy Z. SOBOLEWSKI¹, Jaroslaw MALKINSKI^2
1Institute of Machine Design Fundamentals, Warsaw University of Technology, jso@simr.pw.edu.pl
²Institute of Machine Design Fundamentals, Warsaw University of Technology, jarmal@simr.pw.edu.pl

Abstract

The paper presents problems of calculation of ball screws rigidity. Rigidity is the main criterion for application of ball screws in NC machine tools feed systems. One of rigidity components is the balls/balltrack area rigidity, dependent on Hertz' deflections. However, due to machining errors, the ball screws functional properties (especially rigidity) are considerably lower than the theoretical ones. On the basis of a mathematical model developed by the authors, a computer simulation of the influence of machining errors on contact deflections was carried out. It affirmed that the rigidity of balls/balltrack area depends not only on accuracy grade but also on geometrical parameters of the thread. Measurements of ball screws rigidity were executed and the results were compared with the results of computer simulation. This effected a verification of computational model and a determination of the confidence level of calculations. A coefficient known as the geometry correction factor was introduced in order to estimate the influence of machining errors on lowering the level of rigidity. This coefficient was compared to the correction factor of accuracy applied in ISO norms for estimating ball screws rigidity. These operations make it possible to predict the properties of ball screws, and aim at selecting the design parameters in early stages of a technical project.

Author Keywords :

ball screws, rigidity machining errors identification

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

A COMPARATIVE STIFNESS ANALYSIS OF A RECONFIGURABLE PARALLEL MACHINE WITH THREE OR FOUR DEGREES OF MOBILITY

Rani RIZK¹, Jean Christophe FAUROUX¹, Mircea MUNTEANU², Grigore GOGU^1
1Mechanical Engineering Research Group (LaMI), IFMA&UBP, Campus des Cézeaux, BP265, 63175 France, mail: rrizk/fauroux/gogu@ifma.fr
²TRANSILVANIA University of Brasov, Strength of Materials and Vibration Dept, Brasov Romania, mail: mmm@deltanet.ro

Abstract

Stiffness performance is a very important aspect to be considered in the design of parallel machines. This article presents a comparative stiffness analysis based on numerical simulation for a reconfigurable parallel machine to 3 or 4 degrees of mobility (D.O.M.). The two configurations have decoupled motions and are isotropic in translation. This paper focuses on stiffness analysis of the both configurations. Stiffness matrix establishes the relation between elastic displacements (translation and rotation) of the moving-platform and loading (forces and torques) at a characteristic point. Numerical simulation gives stiffness maps in different positions of the workspace and allows us to set up critical stiffness positions. In a second stage the flexibility matrix is partitioned into four sub-matrices relating translations-forces, angles-forces, translations-torques, angles-torques. Their eigenvalues and eigenvectors are calculated. The eigenvalues give the extremal stiffness. The eigenvectors give the principal axes where a load gives a pure elastic displacement in the same direction. Finally, a stiffness comparison is performed between the two configurations. Conclusions are set up on stiffness and accuracy as well.

Author Keywords :

parallel machine, numerical simulations, stiffness, accuracy

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

PROCESS MONITORING USING INTEGRATED FORCE SENSORS

Garret O'DONNELL¹, Gerald BYRNE², Kevin KELLY¹, Andreas KIRCHHEIM^3
1Department of Mechanical and Manufacturing Engineering, Trinity College Dublin, Ireland
²School of Electrical, Electronic and Mechanical Engineering, University College Dublin, Ireland
³Kistler Instrumente AG, Winterthur, Switzerland

Abstract

Two piezo electric force sensors rings were developed and integrated into a direct driven motor spindle for in-process monitoring of machining operations. One of the force sensor rings was located behind the front thrust bearing in the motor spindle measuring the force component in the feed direction. The second sensor ring was installed in the spindle suspension measuring three components of force. Experimental results are presented which demonstrate the performance of the integrated force sensor during drilling operations. Performance comparisons are made between the integrated force sensors and traditional monitoring sensors such as motor power and acoustic emission (AE). The non cutting influences such as thermal expansion, spindle dynamics and axes inertia present in the sensor signals are identified.

Author Keywords :

process monitoring force sensors machining

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

REAL-TIME COMPENSATION SYSTEM FOR THERMAL ERRORS OF THE PC-NC MACHINE TOOLS AND ITS APPLICATIONS

JaeJong LEE¹, DaeBong CHOI¹ , HyunTaik CHOI^1
1Korea Institute of Machinery and Materials, jjlee@kimm.re.kr

Abstract

One of the major limitations of productivity and quality in metal cutting is the machining accuracy of machine tools. The machining accuracy is affected by geometric errors, thermally-induced errors, and the deterioration of the machine tools. Geometric and thermal errors of machine tools should be measured and compensated to manufacture high quality products. In metal cutting, the machining accuracy is more affected by thermal errors than geometric errors. Especially, because the thermal errors of the CNC machining tools different from with respect to the moving positions, the thermal error should be compensated with respect to the X, Y, and Z positions as soon as possible. In this paper, the thermal error compensation system and its application is studied for the CNC and the PC-NC machine tools. In metal cutting, the machining accuracy of machine tools is more affected by thermal errors than geometric errors (about 40~70% of the occurring errors in machine tools result from thermal errors). Thermal errors caused by spindle heads are greater than those of the machine tool axes. In order to compensate the thermal errors by real-time, one-board type compensation device for the CNC and PC-NC machine tools is proposed.

Author Keywords :

compensation device, on-the-machine measurement,spherical ball artifact, neural network,volumetric thermal error

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

THERMAL DISPLACEMENT REDUCTION FOR THE HIGH SPEED SPINDLE BY THE INTERNAL SHAFT COOLING

DaeBong CHOI¹, SooTae KIM², DongSu JEONG², Jae Jong Lee¹, YongKee KIM^3
1Machine Tools Group, Korea Institute of machinery and Materials, Korea
²Dept. of Mechanical Engineering, Changwon National University, Korea
³KOSPIN Co., Ltd, Korea

Abstract

Use of the high frequency motor spindles is increasing for the high speed grinding machine and milling machine recently. The important problem in the high speed motor spindles is to reduce and minimize the thermal displacement by the cooling for motor, bearings and spindle shaft. The temperature distribution and thermal displacement of motor spindle according to the spindle speed, the bearing preload and the flow rates of external and internal cooling for motor and shaft are measured and simulated by using the three dimensional model through the finite element method. This study will find out more effective cooling condition and bearing preload on the developed motor spindle with the internal shaft cooling system to minimize the thermal errors.

Author Keywords :

high speed motor spindle, thermal displacement, bearing preload, shaft cooling, temperature distribution hollow cooling

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

TOOL CONDITION MONITORING USING MACHINE VISION AND PROTOCOLS FOR SENSOR SAMPLING

Manbir SODHI¹, Martin NOEL¹, Bernard LAMOND^2
1Univ. of Rhode Island, RI 02879, USA - currently at NATO Undersea Research Center, La Spezia, Italy.
²Université Laval, Quebec City, Quebec, Canada.

Abstract

Gains in computing power and advances in sensor technology have enabled real-time condition based monitoring for a broad range of applications, including tool condition monitoring for metal cutting operations. As the extent of automation in manufacturing increases, especially with the widespread use of flexible machines, the role of condition monitoring is increasingly more important for the attainment of higher productivity rates. In this paper we present details of a machine vision based tool monitoring system implemented on a CNC lathe. We then assess the utility of the information gathered using such systems in improving the performance of flexible machines, which have tool magazines and can be programmed to change tools automatically, with respect to cutting tool consumption and machining time requirements. Four sensor sampling protocols are analyzed: Fixed life, Continuous sampling, Intermittent sampling and End-of-life signaling. In the Fixed life case the tool life is considered to be known and tooling decisions are made based on this deterministic information. In the continuous sampling case, information about the tool condition is updated continuously. In intermittent sampling tool condition status is available after discrete time intervals, and in end-of-life signaling the tool status is detected only when catastrophic failure conditions are imminent. A discussion of the sampling protocols is presented and their implications for tool condition monitoring in general are discussed.

Author Keywords :

machine vision, unsupervised mfg,FMS, autonomous mfg ,condition monitoring

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

INVESTIGATION OF THE EFFECTS OF HEAT GENERATION IN HSM ELECTROHEADSTOCKS

Zdzisław WINIARSKI¹, ZBIGNIEW KOWAL^1
1Wroclaw University of Technology Institute of Production Engineering and Automation ul. Lukasiewicza 5, 50-371 Wroclaw, POLAND, Zdzislaw.Winiarski@pwr.edu.pl

Abstract

The fundamentals of a computational model for determining the thermal behaviour of modern headstock designs with a built-in motor are explained. It is noted that experimental verification is needed in order improve the quality and reliability of computations. The results of computational analyses, illustrating the effects of heat generation in the high-speed headstock of a milling centre and in the headstock of a lathe centre are presented. Detailed analyses of power losses, running clearance and bearing lifetime for spindle bearing systems elastically tensioned by springs are provided. The influence of the rate of flow of different cooling fluids on the temperatures of the spindle and on the stability of its position is described

Author Keywords :

machine tools, motorized spindle, thermal analysis, computing

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

IDENTIFICATION SYSTEM OF MACHINING ERROR BASED ON ANALYSIS OF MACHINED SHAPE

Yusuke HOSOMI¹, Hideki AOYAMA^1
1Keio University, 3-14-1 Hiyoshi, Kohoku-Ku, Yokohama, Japan. hosomi@ina.sd.keio.ac.jp
²Keio University, 3-14-1 Hiyoshi, Kohoku-Ku, Yokohama, Japan. haoyama@sd.keio.ac.jp

Abstract

There are some studies to identify the machining errors by analyzing the driving behavior of the machine axes using the DBB(Double Ball Bar) method. The DBB method can analyze motion errors of a machine tool under the un-loaded condition. However, the method can not apply for the loaded conditions. Other researches on machining error analysis proposed so far can get precise results in estimation, but the use of them is limited to a certain condition. Machined shape information includes all of the effects caused by machining error factors under the loaded condition. If machining errors were identifiable from the analysis of machined shape, the identification method will be practical and useful. By adjusting and modifying the machine tools and the machining process based on the identified machining errors, it will be one approach to realize high quality machining. The objective of this study is to develop a system to analyze and identify the machining error factors by comparing the measurement data of a machined part with the CAD data. The usefulness of the proposed system was verified through tests.

Author Keywords :

CAM, CAT, machining error identification, machining error analysis

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

MODELLING HEADSTOCK MOTION INFLUENCE ON MACHINE TOOL THERMAL BEHAVIOUR

Miroslaw GROCHOWSKI¹, Jerzy JEDRZEJEWSKI^1
1Institute of Production Engineering and Automation, Wroclaw University of Technology

Abstrakt

This paper deals with modelling the motion of the milling machine's headstock relative to its column and with the assessment of the effect of this motion on the modelled machine's thermal properties. The main model assumptions and an algorithm for determining a machine tool's thermal state - the distribution of temperature and displacement - for different positions of an integrated hest source are presented. At this stage of the research, the thermal resistance of the quid's surface is not taken into account.

Author Keywords :

machine tool, thermal model, moving heat source

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

ANALYSIS OF SELF- EXCITED VIBRATIONS INVOLVING NON-LINEAR ELEMENTS BY SIMULATION OF TRANSIENT BEHAVIOUR

Jaromir ZELENY¹, Petr FOJTU^1
1Research Center of Manufacturing Technology, CVUT - Czech Technical University in Prague, Horska 2, 12800 Prague 2, Czech Republic

Abstract

Commonly applied theories of self-excited vibrations in machine tools are prevailingly based on frequency domain analysis of linear models and is devoted in most cases only to analysis of limit of stability. Certain important non-linear effects cannot be studied for difficulties connected with representation and analysis of complex non linear systems in the frequency domain. On the other hand, simulation and analysis of transient responses can contribute considerably to better understanding of complex, nonlinear dynamic systems and of their behaviour in various regimes and special situations. Interpretation of self-excited vibrations and processes as non-linear feedback systems makes it possible to apply highly developed Matlab/Simulink methods and study transient phenomena and interactions of cutting processes with other machine tool subsystems. The paper involves analysis and simulation of typical linear and non-linear cases in the area of self-excited vibrations of machine tools made in the RCMT Research Centre of Manufacturing Technology in Prague.

Author Keywords :

machine tools, cutting process, self excited vibrations

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

COMPACT SPHERICAL JOINT WITH INTEGRATED STRUT INCLINATION MEASUREMENT SYSTEM FOR PARALLEL KINEMATICS

Eckart UHLMANN¹, Christian NEUMANN², Norman TONN^2
1Institute for Machine Tools and Factory Management, Technical University Berlin, German Pascalstr. 8-9, 10587 Berlin.
²Machine Tools and Factory Management (IWF) of the TU Berlin since 2000

Abstract

Considering parallel kinematics it is common to ascertain the platform position via position measurement systems being integrated in actuator legs or linear tracks. With regard to the compliancy and thermal displacement of struts, base and joints, the distance between the manipulated platform and the measuring point evokes an additional inaccuracy of the kinematical structure. This paper introduces a new approach of detecting the platform position significantly closer to the working process by equipping the platform sided spherical joints with angle sensors. For this purpose a design concept for the mechanical components of the joints as well as the realization and implementation of an appropriate measurement system is proposed. Simulations show that the overall accuracy of parallel kinematic machines (PKM) can benefit from this concept. Furthermore, a proper bearing concept is introduced to ensure precision space motion of the spherical joint.

Author Keywords :

parallel kinematics, spherical joint, inclination sensor

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

PLACEMENT TRACKING OF OBJECTS USING 3D SCANNING TO SUPPORT INTERACTIVE DESIGN

Yu SONG¹, Joris S. M. VERGEEST¹, Bram de SMIT1^1
1Faculty of Industial Design Engineering, Delft University of Technology, Landbergstraat 15, 2628CE, Delft, The Nederlands. {y.song,j.s.m.vergesst, a.desmit}@tudelft.nl.

Abstract

In many industrial design applications, it is necessary to track the positions and orientations of a static object in 3D space. This paper presents a method to quickly and accurately locate the placements of an object based on 3D scanning techniques. By registering geometric data from different scans, the affine transformation from the base position to an arbitrary position within the scanner working envelope can be found. Depending on differen types of applications, the placements of the scanner, the object and a reference object are discussed. Based on a series of experiments, the robustness of the presented method is verified and the errors, both in translation and in rotation, are identified. The possible applications of the presented method in industrial design are investigated as well.

Author Keywords :

3D scan, register, placement, track, error

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

DIAGNOSTIC EXPERT SYSTEM FOR SPINDLES OF CNC MACHINING CENTERS

Petr CHVOJKA^1
1Czech Technical University in Prague

Abstrakt

The Diagnostic Expert System (DES) serves as a consultant software analyzing the vibration data gathered by a variety of measuring instruments. DES is based on the rule-based diagnostic expert shell FEL-Expert running under MS Windows. Now the DES is being developed from the didactic version (used for education at the Czech Technical University in Prague) to a power software that can be used by machine tool user at industrial plants for solving of real problems. The knowledge base of DES contains among others the following goal hypotheses: unbalance, misalignment, mechanical looseness, faults of the rolling element bearing, etc. The user is asked to fill the important data into the dialog box. DES contains also an education and explanation part, which can help the user to better orientate at problems in the vibration measuring. The current version has a simple connection to MS Excel via ODBC. The measuring data are imported to Excel from the measuring apparatus B&K Pulse.

Author Keywords :

machine tool spindle, vibration diagnostics, expert system, FEL-Expert

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

COMPLEX MODELLING OF SPINDLE ROLLING BEARINGS

Tomas HOLKUP¹, Stanislav HOLY^2
1Research Centre of Manufacturing Technology, Faculty of Mechnical Engineering, Czech Technical University in Prague; Horska 3; 128 00 Praha 2; tel. +420 605 205 936; e-mail: t.holkup@rcmt.cvut.cz
²Division of Strength of Materials, Faculty of Mechnical Engineering, Czech Technical University in Prague; Technická 4;166 07 Praha 6; e-mail: stanislav.holy@fs.cvut.cz

Abstrakt

In general, heat generation in rolling bearings is one of the major problems that occur in practical application of high-speed machining. Particularly, prediction of bearing failures caused by excessive thermally induced preload creates a need for optimization of spindle bearing system and of its surroundings, which could be enabled by a mathematical model. However such a model must consider all physical fields involved in the problem. The basis of presented model is a closed-loop analysis that enables updating of the bearing condition in time, considering instantaneous thermo-mechanical situation. A method of coupling between the finite element analysis (FEM) and a mathematical solution of bearing internal condition, described by system of nonlinear equations, has been proposed.

Author Keywords :

spindle, bearing preload, coupled-field simulation

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

REAL-TIME COMPENSATION OF WEIGHT AND THERMAL DEFORMATIONS OF HORIZONTALLY EXTENDABLE SPINDLE RAMS OF MILLING AND BORING MACHINES

Jaromir ZELENY¹, Petr SEDLACEK^1
1Research Center of Manufacturing Technology, CVUT - Czech Technical University in Prague, Horska 2, 12800 Prague 2, Czech Republic

Abstract

In medium and big size horizontal milling or boring machines, weight errors of horizontally extendable spindle rams may today, at full extension, reach hundreds of microns. Vertical displacements vary considerably with weight of tools or technologic heads fixed on the end of extendable rams. More over, such vertical "falling" of rams may introduce angular inclinations of tools and cause additional errors proportional to the length of applied tools. Vertical displacements and angular errors of tool position often combine with unpredictable thermal deformations of rams and guide ways which makes the commonly used compensation methods non-transparent and unreliable. Mechatronic solution of these problems, described in the paper is based on a continuous, real-time, temperature independent measurement of vertical drops and angular deviations of the end of ram. For highest precision, the measuring structure is temperature stabilized by through-flowing water. Continuous evaluating of errors produces control signals for servo systems which continuously eliminate both translatory and angular errors at any extension of the ram.

Author Keywords :

hybrid abrasive-ice-water jet, surface treatment, solid particles distributions, sublimation effect of CO₂ machine tool, accuracy, mechatronics, compensation

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

CONTROL OF MACHINE VIBRATION WITH ABSORBER

Jirí VONDRICH¹, Evzen THONDEL¹, Radek HAVLICEK^1
1Czech Technical University in Prague, Faculty of Mechanical Engineering, Research Centre for Manufacturing Technologies, Horska 3, 120 00 Praha 2, CZ, p.bach@rcmt.cvur.cz

Abstract

The present article will discuss a method of vibration control LQR for a structure by using the vibration absorber without damping. In the method, a variable stiffness vibration absorber is used for controlling the principle mode. The stiffness is controlled by the accelerometer a under the auto-tuning algorithm for creating an anti-resonance state. The optimal vibration absorber with damping with the air-operated spring is also utilized for controlling higher modes. The analyses and Matlab m-file for the auto-tuning control are developed.

Author Keywords :

absorber, Matlab, simulink, control

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

CHECK OF THE STRENGTH OF A HOLLOW NEEDLE BAR

Martin KONECNY^1
1TUL, Faculty of Mechanical Engineering,Textile Machine Design Department, Hálkova 6, 460 17, Liberec, CZ, martin.konecny@tul.cz

Abstract

There has been effected an optimisation of the balancing of needle and thread mechanisms of a household sewing machine. The purpose of the optimisation has been to minimise the resulting components of the reactions in the seating of the needle and thread mechanisms, which constitute the source of dominant vibrations of the sewing machine. Its part has been the lightening of the needle bar by means of a nearly through-going orifice in the sense of its longitudinal axis. Because of that, the resulting wall thickness has remained 1,15 mm only, with the overall diameter ? 6,3mm, and there has been carried out a check of the strength of such needle bar. The needle bar is stressed with a combined load, by the effect of the linkage rod of the needle mechanism and buckling from the punching of the material, together with the loading from the bending moment, produced by the side movement of the needle bar during the transfer from one extreme dead centre to the other one during the formation of zigzag stitches. The loading corresponds to the maximum r. p.m. of the machine. According to the results of the analyses, the needle bar can be employed in a sewing machine without the risk of damage.

Author Keywords :

frame of sewing-machine, needle mechanism, thread mechanism, dominant vibrations of the sewing machine

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

AUTOMATED DESIGN OF ROTARY DRAW BENDING TOOLS - AN APPROACH BASED ON GENERIC CAD-MODELS DRIVEN BY HEURISTIC AND ALGORITHMIC KNOWLEDGE

Joel JOHANSSON¹, Staffan SUNNERSJO^1
1Jonkoping University, School of Engineering, P.O. Box 1026, 551 11 Jonkoping, Sweden. E-mail: Joel.Johansson@ing.hj.se

Abstract

For parts suppliers in the manufacturing industry the process of preliminary production preparation and subsequent calculation of offers are critical business activities. A vital part of production preparation is the design of fixtures and tooling necessary for many processes of metal forming. For a company to give quick responses to customer enquiries, or changes in prior specifications, it would be highly beneficial with a degree of automation in this design process. This implies the development of a computer based system able to capture existing design procedures and associated knowledge for the classes of tooling required for the forming process.In this work we exemplify an automated design system for tooling by an implementation for rotary draw bending of aluminium tubing. The system is based on established design practice and heuristic knowledge developed over many years of practical experience. The system will evaluate whether a given specification is producible with existing materials and equipment, select suitable machine, determine process parameters and determine type and dimensions of components of form die, clamp die, follower or pressure die, wiper and mandrel. The system is built on readily available commercial software packages. When building a system of this kind it is essential that the knowledge documentation and structure is such that the functions of the system can be easily understood by the users of the system and by future developers. Aspects of user friendliness, transparency and scalability are addressed in the summary of this paper.

Author Keywords :

design automation, rotary draw bending, knowledge acquisition, CATIA V5

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

MOTION OF THE SINKER OF A DOUBLE-CYLINDER KNITTING MACHINE

Jirí MRAZEK¹, Martin BILEK^1
1Department of Textile Machine Design, Technical University of Liberec, Halkova 6, 46117 Liberec, Czech Republic. Tel. +420 48 5353174. Fax. +420 48 5353514. e-mail: jiri.mrazek @ tul.cz, martin.bilek@tul.cz

Abstract

The system cam - needle constitutes the basic element of every knitting machine. The article is concerned with dynamics of the tensile system. Every needle and bed in the needle cylinder have their own specifics, and from this point of view, the forces required for the movement of the needle differ considerably. An important effect upon the force is exerted by the rigidity of the butt, and as a matter of fact, by the whole design of the needle, eventually, of the sinker. The play of the needle in the needle bed, magnitude of the friction forces, pretension of the needle and some other phenomena, of technological nature, too, must be taken into account as well. The article intends to consider these phenomena, eventually, to substitute them and to describe them mathematically. As a result, a mathematical model of the system cam - needle is obtained, describing the behaviour of the said system with certain accuracy. An important advantage of the mathematical model is the possibility to change the respective parameters easily, and to study their influence upon the resulting motion of the needle. There has been effected an analysis of the forces and of the positions of their carriers, including the passive resistances, resulting in the courses of cinematic quantities in the needle, and in particular, in establishing the normal reaction between the needle butt and the cam. There have been studied also the passive resistances to the jamming of the needle in the groove, and their influence upon the eventual jamming of the needle in the groove. The character of the motion is determined by the course of the path of the needle, which exerts a jerky movement.

Author Keywords :

needle cam-needle system, circular knitting machine, dynamic model

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

MOMENT COURSE OPTIMIZATION FOR DRIVE OF THE DISTRIBUTION ROD OF ROTOR SPINNING MACHINE

Jaroslav BERAN¹, Michal HUBALEK^2
1Faculty of Mechanical Engineering, TU of Liberec
¹Textile Machine Department,Faculty of Mechanical Engineering, TU of Liberec

Abstract

The work contains proposal on the optimization of the moment course for drive of the thread guide rod of rotor spinning machine by means of springs placed before the dead center of the thread guide rod. Springs take up its inertial dynamical forces and accelerate it retrospectively. As follows the maximum of the moment and the total stress of the distribution mechanism are reduced in the dead centres. The stiffness and compression size were chosen as variables for optimization. Compression size corresponds to the placement in the dead center of the motion. The main goal of the optimization is to minimize moment peaks in the course during one rotation and consequently improve the course of the propulsive moment of driven electric drive. The result of the optimization is to find suitable combination of the stiffness and size of the spring stroke for parameters which were given. The springs placed in the dead centers markedly decrease in maximal value of the propulsive moment and herewith the requirements for drive motion have been reduced.

Author Keywords :

textile machine, traverse mechanism, driving moment

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

CASCADE FEEDBACK CONTROLLER WITH COMPENSATING TRANSFER BLOCK

Lukas NOVOTN1^1
1Czech Technical University in Prague, Faculty of Mechanical Engineering, Research Centre for Manufacturing Technologies, Horska 3, 120 00 Praha 2, CZ, p.bach@rcmt.cvur.cz

Abstract

One of the most important purposes in the modern machine tool design is not only a high dynamics of movements but mainly a working accuracy. Currently used standard cascade feed-back controller has its limits. In general, these limits are sequent on the mechanical construction of the feed axis (including a machine's structure) because of its dynamical behaviour. There are also some new types of controllers (e.g. state feed-back), but neither current CNC controls nor machine manufactures are ready to implement them. This paper describes a relatively simple method of how to improve a standard cascade feed-back controller to meet the needs of highly dynamic machine tools according to a precision position control. This text is oriented especially on the machine tools drives, but presented method is applicable in other domains too.The main aim here is not to explain all aspets of compensator design but to clarity the fundamental philosophy of this approach using simple model.

Author Keywords :

cascade regulation improvement, position accuracy increase,reduction of energy consumption, machine tools

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

CAUSES OF MACHINING INSTABILITY

Pavel BACH^1
1Czech Technical University in Prague, Faculty of Mechanical Engineering, Research Centre for Manufacturing Technologies, Horska 3, 120 00 Praha 2, CZ, p.bach@rcmt.cvur.cz

Abstract

Instability of machining is still a serious problem of all types of machine tool. The paper summarized some of the author's experimental experience. It is focused on milling machines, which have some sort of sliding block. The sliding block is moveable in one axis. It could be supported by a slide or a support. Generally, the instability or chatter could be caused by any flexible part of a machine tool, which is excited by the modulated cutting force. In reality, there are some parts of machine tool, which could change their flexibility even during machining process. Among them, spindle unit and sliding block are the most important parts, which could cause chatter when milling. Whether is it spindle or sliding block, it depends on technology used. The presented examples show typical machine tool configurations and discuss their dynamic properties.

Author Keywords :

machine tool, dynamic, instability

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

VARIATION OF THE RESULTANT CUTTING FORCES DURING THE COMPLEX SURFACE MILLING

Mohamed BOUJELBENE¹, Hassen LOUATI², Alphonse MOISAN³, Wassila BOUZID², Patrick ABELLARD¹, Serge TORBATY^1
1HANDIBIO Laboratory, Mechanical & HSM, University of the South-Toulon/Var, 83957 La Garde, France.
²Mechanical Production and Materials Laboratory, ENI Sfax, BPW. 3038, Sfax, Tunisia.
³LaBoMaP Laboratory, ENSAM, 71 250 Cluny, France

Abstract

In recent years, parametric or sculptured surfaces have been used in a wide variety of applications in the automotive, aerospace, dies and molds, shipbuilding and turbine industries. A parametric surface is generally machined with a ball-end cutter in a multi-axis NC machine tool. To reduce the machining cost of dies and molds, appropriate machining strategy and appropriate cutting conditions should be selected to improve the dimensional accuracy and the surface texture while fine milling the part. The machining strategy includes the tool path pattern, and the tool orientations. The cutting conditions include the cutting edge geometry, the feed rates, and the cutting speeds. In this paper, the performance of different machining strategies with different cutting conditions is experimentally assessed in terms of cutting forces. Multi-axis ball-nose end milling of a specific HB 300 pre-hardened mold steel Super Plast (SP 300), widely used for plastic injection mold making, is considered. This study shows the advantages offered by a C₁

Author Keywords :

multi-axis milling, cutting force, continuity of tangency, die and mold.

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

CONTRIBUTION OF QUALITATIVE PARAMETERS BY GRINDING

Zdenko LIPA¹, Alexander JANÁC¹, Katarína BRODZÁKOVA¹, Monika BÓNISOVA^1
1Department of Machining and Assembly, Faculty of Materials Science and Technology, Slovak Univer of Technology in Trnava, Slovak Republic, phone: +421 918 646031, fax: +421 33 5521019, e-mail: kom@stuba

Abstract

Quality of grinding surface is most important result of grinding. This contribution introduces quality parameters of abrasion surface at generally and concretely it deals one of these and that is surface roughness. It mention also generally relations acquired by several research scientists and introduce in the concrete terms among surface roughness abrasion surface and various factors of grinding, mainly for cover layers (hard metallic and ceramic). Some terms present in this contribution are in the technical literature introduced for a first time. The article suggests, that presented problem is needed to deal more oftentimes.

Author Keywords :

quality of surface, surface roughnes, abrasive grain, maximum depth of removal layer

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

EFFECT OF CUTTING SPEED ON THERMAL PHENOMENA IN HSC

Jirí SAFEK^1
1Research Centre of Manufacturing Technology Czech Technical University in Praque Faculty of Mechnical Eng. Horska 3,128 03 Praha 2, Czech Republic tel./fax: +420 221 990 922 email: J.Safek@remt.cvut.cz

Abstract

The paper describes some results of the research into cutting temperature and surface temperature of the workpiece in high speed milling of aluminium alloy 2024-T351. The effect of cutting speed on cutting temperature and surface temperature of workpiece has been studied. The experimental research was carried out by using sintered carbide inserts. The cutting temperature was measured by the tool-workpiece thermocouple and surface temperature of workpiece was measured by wire-workpiece thermocouple.

Author Keywords :

cutting temperature, surface temperature, tool-workpiece thermocouple

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

SIMULATION OF FIVE-AXES MILLING PROCESSES - APPROACHES AND APPLICATIONS

Andreas ZABEL^1
1Department of Machining Technology (ISF), University of Dortmund, Germany, www.isf.de, zabel@isf.de

Abstract

The paper describes some recent developments in modelling and simulation of five-axes milling processes. Two different modelling approaches are presented (CSG and multi-dexel). Special emphasize is taken on their computational complexity, determining the efficiency of the approaches. After the descriptions of the simulation approaches are given, some applications which are based on the described modelling techniques are discussed. Here the calculation of process forces is based on the CSG-modelling approach and it can be used for the prediction of chatter as well as for the modelling of the resulting workpiece surfaces. In the following a simulation based approach the prediction of tool wear and for the automatic generation of NC-paths for five axes milling are subsequently focused. Both are based on the multi-dexel model. The first approach is working on a semi-empiric wear model which was constructed with the help of the Design-of-Experiments (DoE) method from statistics while the second uses evolutionary algorithms to calculate and optimize NC-paths for five-axes milling.

Author Keywords :

milling simulation, workpiece and tool models, wear prediction, path optimization

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

MOS II MACHINING OPTIMIZATION SYSTEM SECOND VERSION

Nivaldo Lemos COPPINI¹, Raphael Furlan GRIVOL², Elesandro Antonio BAPTISTA^2
1Universidade Metodista de Piracicaba, Santa Bárbara d´Oeste, Sao Paulo, Brazil - ncoppini@unimep.br
²Universidade Metodista de Piracicaba, Santa Bárbara d´Oeste, Sao Paulo, Brazil

Abstract

Cutting process optimization could be considered in different levels and approaches. How to select tools and how to take care about evident loose time and costs can not be considered as a competitiveness market factor any more. Everyone responsible for cutting process planning must be up to date with these procedures and the tool makers are ready to help their costumers. Otherwise, after the best selected tool and cutting conditions are settled and the process is running in shop floor many things could be done to go more deep in the cutting process optimization. In the last five years, an expert system called "MOS" (http://www.elesandroab.eng.br) was developed to support an optimization methodology that could change cutting parameters to adequate them to reference cutting speeds. The purpose of this paper is to discuss, the addition of new features to this expert system, so it can become more flexible and user friendly.

Author Keywords :

cutting process, optimization, expert system

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

HF-CVD OF DIAMOND COATINGS ON CEMENTED TUNGSTEN CARBIDES: PROGRESS IN SUBSTRATE PREPARATION

Riccardo POLINI¹, Massimiliano BARLETTA¹,Stefano GUARINO¹, Nadia UCCIARDELLO^2
1Universita degli Studi di Roma "Tor Vergata", Dipartimento di Scienza e Tecnologie Chimiche, Via della Ricerca Scientifica, 1 - 00133 Roma.
¹Universita degli Studi di Roma "Tor Vergata", Dipartimento di Ingegneria Meccanica, Via del Politecnico, 1 - 00133 Roma.

Abstract

This study is aimed to comparatively evaluate the efficiency of mechanical and chemical surface treatments in CVD diamond coatings of tungsten carbide flat substrates and milling cutters. The efficiency of pre-treatments was first assessed on flat slabs. SEM and confocal microscopy was used to detect the evolution of the surface morphology of flat slabs submitted to both chemical and mechanical surface treatments. After being CVD diamond coated, the morphology of each resulting diamond film was characterized again. Standard hardness and tribological tests were led to establish the adhesion and wear endurance of the diamond coatings onto the WC-Co flat substrates. All the pre-treatments exhibited remarkable results, with the adhesion and wear endurance of diamond films noticeably improved. Second, first machining tests were carried out to estimate feed forces and diamond films resistance of chemically etched and mechanically treated diamond coated milling cutters. Chemically etched tools showed the best overall performances due to the uniform and low-scaling corrugation of the WC grains, which definitely improved the adhesion of diamond films. Mechanically pre-treated tools were very promising. They showed diamond films with the finest grains as result of the good seeding of the substrate during pre-treatment. This caused diamond films more suitable to reproduce the cutting edges shape of milling cutters, hence ensuring minimum friction during machining, maximum cutting precision, and the closest geometrical accuracy. Although smooth diamond films on mechanically-treated hard metal mills showed lower tool lives, with their failure occurring earlier than expected, the severe problems of chip evacuations exhibited by uncoated tools, made diamond coated tools largely preferable in dry machining of high strength aluminium alloys.

Author Keywords :

CVD; mechanical surface treatments, chemical surface treatments, surface overlay coatings

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

FLUIDIZED BED DEGREASING OF METAL COMPONENTS

M. BARLETTA¹, A. GISARIO¹, S. GUARINO¹, V. TAGLIAFERRI^1
1Universita degli Studi di Roma "Tor Vergata", Dipartimento di Ingegneria Meccanica, Via del Politecnico, 1 - 00133 (Italy). Corresponding author e-mail: barletta@mail.mec.uniroma2.it phone: +390672507193 fax: +3906202135

Abstract

Degreasing is one of most important stages of modern transformation processes in industries fabricating or assembling metal parts, such as in manufacturing of aircraft, appliance, automobiles, electronics, and railroad equipment. Chemical degreasing processes mostly employ chlorinated solvents in a liquid or vapour state in order to remove oils and oil-borne soils from previously processed parts, such as chips, metal fines and fluxes. Nevertheless, increased sensitivity to the environmental impact of cleaning agents is pushing scientists and technicians towards the development of alternative solutions. In this study, a relatively novel eco-efficient degreasing technique, namely Fluidized Bed Degreasing (FBD) based upon a fluidized bed of hard particles has been proposed. In this system, a bed of spherical shaped glass particles was taken in a fluidlike state in a confined fluidization chamber by using a low pressure air flux. The resulting impacts of the fluidized particles on the surface of targets to be degreased caused the removal of surface contaminants and the concurrent accurate cleaning of the exposed surfaces. In this context, a detailed experimental campaign was aimed at investigating the interrelationship among FBD operational parameters and degreasing effectiveness, with particular interest towards the analysis of target geometry and location inside the fluidized bed. Consistent trends of residual oil according to FBD process parameters were plotted and the influence of each individual operational variable understood. A related analytical model, basis for the development of more sophisticated control modulus, was developed and verified by the experimental findings. Finally, the reliability of FBD process even on complex shaped surface like pipes and blind holes was assessed.

Author Keywords :

fluidized bed degreasing, glass powder residual oil, complex shaped components

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

OPTIMIZATION OF TIME FOR MAINTENANCE IN A POWER PLANT

KORONEOS J. C.¹, TROMVOUKIS C.¹, ROVAS C. D.^1
1Laboratory of Heat Transfer and Environmental Engineering , Aristotle University of Thessaloniki P.O. Box 483, GR 54124, Thessaloniki, Greece, E-mail: Koroneos@aix.meng.auth.gr

Abstract

One of the outmost objectives of a power plant is the highest possible utilization of all units in use. Both, the operational time and the use of power are taken into consideration. This work investigates the optimal timetable to minimize the routine maintenance time of one production unit at Saint Dimitrios power plant in Greece. The tools used are the network analysis and the time planning Suretrak Software. The Saint Dimitrios power plant, property of the Greek Public Power Corporation S.A. (PPC S.A.), is located in Western Macedonia, 18 kilometres from the city of Kozani. The location selection was set to be the most optimal economic and environmental solution. The lignite mining, takes place near the power plant in a distance of 16 km. This work is based on the actual operation of the power plant and the results have led to major savings.

Author Keywords :

power plant optimization, maintenance time, suretrak software

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

SIMULATION OF SYSTEMS WITH MECHANICAL, HYDRAULIC AND THERMODYNAMIC ELEMENTS

Petr KOCARNIK¹, Slavomír JIRKU^1
1Czech Technical University in Praque, Faculty of Electrical Eng. Dept. of Mechanic and Materials Science Technicka 2, 166 27 Praque 6, Czech Republic

Abstract

This article shows modelling of a system with hydraulic, mechanic and pneumatic elements using the Matlab - Simulink program. To describe the hydrodynamics we use the equation for one-dimensional flow in a stream tube with respect to inertia and losses. The motion equations for mechanic parts are formularized using the d´ Alembert principle with respect to forces of gravity, pressure, body resistance etc. Thermodynamic elements are described by equations for thermodynamic changes, e.g. derived from the basic laws of thermodynamics, state gas equation etc. As an example is mentioned the dynamic solution of a water ram, which transfers water from the bottom tank to the top tank by means of changing the fluid motion energy into pressure. In article is shown the basic flow diagram for the simulation model. The model can be divided into four subsystems, which interact by means of changes in several parameters. The coefficient values for traction and local losses and for resistance forces were taken over from the literature data. The simulation results are presented by means of time dependencies. Some diagrams are divided into two parts; one for initial start-up and one for transition to periodically steady mode. The simulation model allows fast monitoring of parameter change effects on the system values being solved, and thus optimizing its characteristics.

Author Keywords :

mechanical systems, hydraulics, simulation, water ram

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

IDENTIFICATION AND MODEL BASED COMPENSATION OF CUTTING ERRORS

Jozef GAWLIK¹, Wojciech ZEBALA^1
1Instytut Technologii Maszyn i Automatyzacji Produkcji M6, Politechnika Krakowska Krakow, Al. Jana Pawła II 37

Abstract

The whole manufacturing system optimization permits the essential improve of the worpieces quality. For this purpose, the right optimization strategy is chosen, taking into consideration the measuring research setup for the position errors identification, changes of linear and angular travel speeds, edge wear prediction method and numerical method of simulation. Paper presents the identification method of cutting errors and some aspects of inaccuracy compensation, arising by the wear and vibrations reasons. The computer simulation technique, using the finite element method was applied.

Author Keywords :

measurements, errors, vibrations, wear

© Copyright by, Editorial Institution of the Wroclaw Board of Scientific Technical Societies Federation NOT, Wroclaw 2010, Poland

IMPLEMENTATION OF ACTIVITY BASED CONSTING (ABC) IN SMALL AND MEDIUM COMPANIENS USING PROPOSED PROCEDURE

Valentina GECEVSKA¹, Franc CUS², Zoran PANDILOV¹, Matjaz MILFELNER^2
1Faculty of Mechanical Engineering, University Ss. Cyril and Methodius, Skopje, Macedonia
²Faculty of Mechanical Engineering, University of Maribor, Maribor, Slovenia

Abstract

This paper describes a procedure that allows small and medium companies to smoothly switch from a traditional costing system to an Activity Based Costing (ABC), at low risk and with minimal investment. The paper focuses on any small and medium company for which the standard implementation of ABC is too expensive and complex. The implementation guide leads a company step-by-step through activity based cost system model. The complete implementation procedure consists of eight major steps. At first, decision-makers choose among three methods, educated guess, systematic appraisal, or actual data collection, for obtaining cost information. At this stage, the decision-makers determine the level of accuracy that is needed and the amount of money to be assigned to this project. Next, the overhead expenses such as administration, rent, utilities, and transportation are complied into product cost information using newly developed matrices. Using these matrices, cost related calculations are simplified and thus the overhead costs are easily traced to the cost objects in the final step. The easy-of-use of the proposed procedure is illustrated using actual data from a medium tool & die manufacturing.

Author Keywords :

cost estimating, activity-based costing, small and medium business