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

KEY TECHNOLOGIES FOR SUSTAINABLE MANUFACTURING

Eckart UHLMANN¹, Jens KOENIG^2
1Head of Department of Machine Tools and Manufacturing Technology at the IWF of the TU Berlin
²Research Team Cutting Technology of the Department of Machine Tools and Manufacturing Technology

Abstract

Innovative production techniques require an efficient utilization of human, material and energetic resources to ensure competitive manufacturing positions. The aim of modern industrial production processes is to provide products with a higher added value in a shorter time-to-market. On the other hand, shorter life cycles of products are contrary to the necessity of expanded service time of manufacturing systems. Moreover, the whole life cycle of products is accompanied by customer related service provisions. Flexible and adaptive as well as self-organising means of production are a considerable key to solve this conflict of objectives. Here, man with specific technological knowledge has to be integrated with it's permanently newly defined role in production. This paper presents production technology related new developments and strategies to fulfil the requirements of sustainable manufacturing.

Author Keywords :

sustainability, manufacturing, adaptive systems

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

ON-MACHINE MEASUREMENT SYSTEMS FOR HIGH-PRECISION WORKPIECES, PRODUCED ON FIVE-AXIS MILLING MACHINES

Jaromir ZELENY¹, Michal JANDA^1
1RCMT, Research Center of Manufacturing Technology, Czech Technical University in Prague, Horska 3, 12800 Prague 2, Czech Republic

Abstract

The paper describes control systems for measuring of complex workpieces machined on numerically controlled machine tools. The area is called "on-machine measurement" (OMM) and means measuring of workpieces still placed in the working space of the NC machine immediately after the NC machining operation. Measuring is performed by a touch probe inserted into the machine spindle and the movements of the probe are programmed to touch the workpiece in pre-selected points of machined surface. This makes it possible to compare the measured points with corresponding points of the CAD model and thus evaluate deviations in the normal direction between the ideal and real surfaces. In the RCMT - Research Center of Manufacturing Technology in Prague, the research of on-machine measurement methods has been performed with the aim to apply this technology for measuring of very precise and complex workpieces, produced on five-axis milling machines. Different types of control systems for three-axis, five-axis and "three and two" axis on-machine measurements have been analysed, verified and tested. The task has been solved as a part of the HARDPRECISION European project with the aim to verify possibilities in replacing application of conventional coordinate measuring machines (CMM) by on-machine measurements methods even for very complex parts with hardly accessible measured surfaces.

Author Keywords :

machining, accuracy, on-machine measuring

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

RECONFIGURABLE MACHINE TOOL: METHODOLOGY OF RMT DESIGN

Hasan ALADAD¹, Alain.D'ACUNTO¹, Patrick.MARTIN^1
1Laboratoire de Génie Industriel et de Production Mécanique (LGIPM)-ENSAM 4 rue Augustin Fresnel 57078 METZ-cedex 3- tél: (33) 03 87 37 54 65 mail : hasan.aladad@metz.ensam.fr

Abstract

Reconfigurable Machine Tool (RMT) is the active issue to realize both the flexibility and productivity of manufacturing systems and satisfy the mass-customization production. The purpose of this paper is to present a RMT design methodology. Specifically, the part analysis and the RMT architectural modelling. The method of RMT design is focused on a simultaneous machining process using multi-spindle in a single RMT. Based on the concept of machining features, the process data, retrieved as a starting point in identifying various functions necessary to carry out a given part family, are displayed. Moreover, geometrical and kinematical architectures of RMT are defined as a result of the specification of all manufacturing processes of features to be machined. Where, all architectural solutions and the criterions related to select the suited solution are presented. Our methodology presents all activities allowing to pass from machining features of part to be machined to the structure of RMT.

Author Keywords :

reconfigurable machine tool machine tool design machining features, process planning

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

TOOLPATHS PROGRAMMING IN AN INTELLIGENT STEP_NC MANUFACTURING CONTEXT

Raphael LAGUIONIE¹, Matthieu RAUCH¹, Jean-Yves HASCOET^1
1Institut de Recherche en Communication et Cybernétique de Nantes, France.

Abstract

The current language for CNC programming is G-code which dates from the beginning of the eighties with the norm ISO 6983. With the new technologies, G-code becomes obsolete. It presents drawbacks that create a rupture in the numerical chain at the manufacturing step. A new standard, Step_NC, aims to overtake these lacks. A Step_NC file includes all the information for manufacturing, as geometry description of the entities, workplan, machining strategies, tools, etc. For rough pocket milling, the ISO norms propose different kind of classical strategies as bidirectional, parallel or spiral contour, etc. This paper describes a new way of toolpath programming by the repetition of a pattern all along a guide curve. It presents several advantages as building fastness and easiness. The integration of pattern strategies in Step_NC standard is an other step for the development of these strategies but also for the enrichment of Step_NC possibilities. A complete Step_NC numerical chain was built, integrating these pattern strategies. The implementation of this approach of building pattern strategies was made by the development of tools for the complete manufacturing cycle, from the CAD file to the machined part. Several application cases were experimented on machine tool to validate this approach and the efficiency of the developed tools.

Author Keywords :

Step_NC, toolpath generation, pattern strategies

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

LIMITING PRECISION DISTORTIONS IN SPINDLE UNIT OF HSC MACHINING CENTRE

Jerzy JEDRZEJEWSKI¹, Wojciech KWASNY¹, Wojciech MODRZYCKI^1
1Wrocław University of Technology, Institute of Production Engineering and Automation, ul. Lukasiewicza 5, 50-371 Wroclaw, e-mail: jerzy.jedrzejewski@pwr.edu.pl, Poland

Abstract

The paper presents causes of excessive precision distortions, appearing in electrospindles of HSC machining centres. The influence of changing ambient temperature is shown, as well as the precision of its modelling. Phenomena, which appear in the electrospindle unit during large rotational speed changes, have been presented and the functioning of bearing loading sleeve has been shown, which has the task of compensating thermal expansions of a spindle. Conditions of proper functioning of the sleeve have been presented, which should assure minimal displacements of a spindle. Also, possibilities of increasing bearing life span have been pointed out.

Author Keywords :

HSC, machine tool, precision, distortions

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

PROCESSING WITH PARALLEL KINEMATICS - AN EXPERIMENTAL ANALYSIS

Reimund NEUGEBAUER^1,2, Markus WABNER¹, Steffen IHLENFELDT^1
1Fraunhofer Institute for Machine Tools and Forming Technology IWU, Chemnitz
²Institute of Machine Tools and Manufacturing Processes, Technical University of Chemnitz

Abstract

This article summarizes experimental analyses for the determination of process parameters that can be achieved in an industrial machine tool with parallel kinematics. Focus is on the examination of the machining results' dependency on position and direction. Therefore milling experiments are conducted, testing different positions and directions within the workspace. Surface quality, process forces, acceleration as well as vibration characteristics of the working platform are assessed. Based on measured frequency responses the stability limits are determined at different locations within the workspace. By these examinations it can be confirmed that the dependency of static and dynamic machine properties on position and direction has an influence on machining results. Best results are achieved in central positions of the machine used for most of respective operations. Furthermore it's represented that the machining results are comparable to conventional serial machines though parallel kinematics show a stronger dependency on direction.

Author Keywords :

machine tool, parallel kinematics, machining, milling

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

POTENTIAL OF MANIPULATING THE DAMPING PROPERTIES OF PARALLEL KINEMATIC MACHINE TOOLS

Markus WABNER¹, Sebastian GRZEJSZCZYK², Reimund NEUGEBAUER^1,2
1Fraunhofer Institute for Machine Tools and Forming Technology IWU, Chemnitz
²Institute of Machine Tools and Manufacturing Processes, Technical University of Chemnitz

Abstract

Parallel kinematics with a higher end-effector degree of freedom such as hexapods and pentapods consist of a large number of joints and slender struts. However, it is only possible to create comparably low levelsof bearing and strut bending stiffness atreasonable expense due to the limited construction space. That means that these structures are very susceptible to vibration. Even in the low-frequency range they have a large number of relevant eigenmodes that are only dampened slightly. Simultaneously, it is difficult to analyze vibrational properties due to coupled eigenmodes, which also makes it difficult to discover ways to remedy this situation. This article will take the example of a pentapod to analyze the dynamic properties of slightly dampened parallel kinematics by simulation to study potential means of manipulating it. This will include a description of the model formation of the mechanical system. The article will also address ways of reducing model size and using various simulation environments to boost analysis efficiency. Finally, both passive and active strategies will be studied and evaluated for boosting damping. Amongst others it could be shown that it is not necessary to damp every of the five kinematic chains to achieve effective improvement of the system damping behaviour.

Author Keywords :

machine tool, parallel kinematics, simulation, active damping

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

COMPUTER AIDED OPTIMAL DESIGN OF SERVO DRIVES FOR CNC MACHINE TOOLS

Zoran PANDILOV¹, Vladimir DUKOVSKI^1
1University "Sv. Kiril i Metodij"-Skopje, Faculty of Mechanical Engineering, Karpos II b.b., P.O.Box 464, MK-1000, Skopje, Republic of MACEDONIA, Tel.: 38923099259, Fax: 38023099298, E-mail: panzo@mf.edu.mk

Abstract

Generally servo drives for CNC machine tools have a very simple kinematic structure. But the optimal servo drives design is a problem which consists of an appropriate selection of AC or DC motors and mechanical transmission elements, which must satisfy some conditions as a system. Because of the extensive calculations and optimization algorithms, original computer programs are developed.

Author Keywords :

computer aided design, servo drives, CNC machine tools ,optimal

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

HYBRID MODELLING OF MACHINE TOOL WITH INTEGRATED COOLING SYSTEM

Adam BUKOWSKI¹, Miroslaw GROCHOWSKI¹, Jerzy JEDRZEJEWSKI^1
1Wrocław University of Technology, Institute of Production Engineering and Automation, ul. Łukasiewicza 5, 50-371 Wrocław, Poland

Abstract

In this paper, a method of hybrid modelling of machine's mechanic structure together with mechatronic cooling system of its body is presented. In this method, a FEM model, traditionally used for thermal analyses of machine's thermal behaviour, has been integrated with mechatronic model of cooling system, implemented in MATLAB. In such way, a hybrid model has been created, allowing to simulate the control of machine body cooling process. Applied simulation of cooling the region of body, adjacent to the guide, illustrates the possibility of controlling the temperature in chosen points of the machine tool, in transient state, which would ensure minimal body deformations, small enough not to require compensation, which is generally hard and of limited precision. Thermal model of machine tool has been built with the use of SATO system [1]. In this work, time-domain temperature changes with and without the use of regulation by means of PID regulator have been compared. Results of the simulation show the usefulness of presented hybrid modelling method for the improvement of machine tool thermal behaviour.

Author Keywords :

mechatronic model,machine tool,cooling system

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

CREATIVE DESIGNING OF MACHINE TOOLS - CONTEXTUALLY

Stanislav HOSNEDL¹, Jiri MAREK^2
1University of West Bohemia, Univerzitni 8, 306 14 Pilsen, Czech Republic
²TOSHULIN a.s., Wolkerova 845, 768 24 Hulin, Czech Republic

Abstract

This paper describes the matter how a developed product passes through the company. The important influence is underlined here, which the designing process has on the order passage through the company. The fact is underlined here that innovation cycles have been reduced in a considerable way. Especially in pre manufacturing stages, the innovation cycle can be reduced in a considerable way by means of theoretically supported system methods of creative designing. The paper describes key principles how to apply these principles which enable apparently contradictory system introduction to designers' work with simultaneous increasing of a space for their demanding creative work, with the target to increase the quality of their work and to increase the passage possibilities of this "narrow bottle neck" within development and order processes.

Author Keywords :

systematic designing, machine tool, engineering designer, running time, system approach,

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

DECISION ANALYSIS IN PROJECT MANAGEMENT PROCESS

Sergei KRAMARENKO¹, Eduard SHEVTSHENKO¹ ,Tatyana KARAULOVA¹, Yan WANG^2
1Tallinn Technical University, Ehitajate tee 5, 19086, Tallinn, Estonia, tatjana.karaulova@ttu.ee
²University of Central Florida, Orlando, FL 32816, USA wangyan@mail.ucf.edu

Abstract

Very often we complain about the decisions that were previously made. Yet the fact is that the decisions made were based on the knowledge we had before. By now we have gained more knowledge. Therefore the common problem of making decisions is that decisions are not made reliable enough because parameters in risk assessment and supply chain management are underestimated or not robust enough. In this paper we propose a framework that will try to predict future situations collectively and increase the reliability of decision making. Project management is the art of making right decision. Project managers are faced by huge array of choices. Decision analysis is used in strategic planning, operational management, and other areas of business. Decision analysis helps companies to determine optimal exploration and production strategies with uncertainties in cost, prices, and exploration prospects. This paper describes project management steps and the way they can be supported by Intelligent Decision Support system (IDSS). The main parameters assessed are total cost of the projects, time of the project total fulfilment, number of subcontractors, location factors, and etc. IDSS will enable to collect data, propose possible alternative decisions, and provide risk assessment.

Author Keywords :

intelligent decision support system, project management; decision analysis

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

THE PULLEY SYSTEM WITH THREE DEGREES OF FREEDOM

Petr KOCÁRNÍK¹, Slavomír JIRKU^1
1Czech Technical University in Prague, Faculty of Electrical Engineering, Dept. of Mechanic and Materials Science, Technická 2, 166 27 Prague 6, Czech Republic, e-mail kocarnik@fel.cvut.cz

Abstract

This paper discusses the dynamic system solution with three degree of freedom consist a weightless cable thrown over two fixed side pulleys and the third, free pulley moving along the rope. The cable is stretched with weights attached to its ends and the weight of the free pulley causes the cable dip. Passive resistance on the pulleys stops them from moving. The mathematical description uses a system of differential equations combined with complex kinematic relationships and a description of the passive resistances. The set of equations is converted to a format suitable for numerical solution and a simulation model is created in the Matlab -Simulink program. The results are presented in the form of various relations of kinematic and dynamic system variables.

Author Keywords :

mechanical systems, pulley system, simulation, Matlab

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

OPTIMIZATION OF MOUNTING OF A MACHINE AND ITS PARTS

Jiri VONDRICH¹, Radek HAVLICEK^1
1Czech Technical University in Prague, Faculty of Electrical Engineering, Dept. of Mechanic and Materials Science, Technická 2, 166 27 Prague 6, Czech Republic, e-mail vondrich@fel.cvut.cz

Abstract

Frequency dependence values of input or mutual mechanical impedances of vibrating machines and their parts can be measured using an impedance hammer and a two-channel frequence analyzer. The knowledge of the frequency response of mechanical impedance provides for the determination of properties of vibration energy transmission in the structure of the machine based on which it is possible to adjust the mounting arrangement of the machine and its parts in order to attenuate vibrations. The obtained data concerning the dynamicbehaviour of the machine then serve as a basic for a proper design and implementation of elastic mounting of the machine and its parts on damping elements which attenuate unwanted vibrations to the minimum. The design consists in assembling a model of the machine assuming that elastic mounting has been provided for, describing the model using equations of montion and elaborating their numerical solution. An efficient damping arrangement is achieved by mounting the vibrating parts of the machine using air springs. The air pressure in the air springs can be regulated according to deflections of the individual machine parts measured by accelerometers using a control element. The numeric solution provides for determination of values of stiffness coefficients k and damping coefficient c which would be optimal for the specified machine parameters in order to minimise the defections of the individual machine parts.

Author Keywords :

Matlab, Simulink, air spring, machine

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

APPROACHES TO THE PRODUCTION FLOW SCHEDULING AND CONTROL

Bozena SKOLUD^1
1Institute of Engineering Processes Automation and Integrated Manufacturing Systems, Silesian University of Technology

Abstract

In the paper different methods of production order scheduling and control that are elaborated by the author and the team are presented. The history starts from the dispatching rules and goes to the distributed control by the local dispatching rule allocation and application them in the software (KbRS, SWZ, etc). In the next stage of the paper the discussion goes to the integration of these approaches. Last stage of the paper the artificial intelligence (Immune Algorithm) application for optimization of the schedule under the condition that any permissible solution is attainable is proposed. This application is only the part of the integrated system and is utilized as a tool for the solution improvement.

Author Keywords :

production flow scheduling dispatching rule, constraints satisfaction immune algorithm

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

HYBRID SYSTEM FOR MODELING AND OPTIMIZATION OF PRODUCTION CHAIN IN METAL FORMING

Lukasz RAUCH¹, Lukasz MADEJ¹, Maciej PIETRZYK^1
1AGH University of Science and Technology, Krakow, Poland

Abstract

The paper presents design and implementation of the hybrid system, which is the part of investigation focused on application of multiscale modeling in simulation of real industrial processes. The hybrid system is dedicated to support production processes based on metal forming, by using artificial intelligence and optimization algorithms. The proposed system is based on the multilayer architecture and consists of several functional components responsible for management of production process, modeling and simulations and, finally, optimization. The latter module aims at searching for optimial parameters of selected production processes, which form production chain, i.e. rod rolling and cold forging. Optimization is performed using results obtained from multiscale modeling calculations. Then, the optimized approach is passed directly to the configuration and control centre of the real industrial process as a feedback to obtain better quality of products employing lower costs of manufacturing. Moreover, the hybrid system is designed to exchange information with other external systems implemented inside an enterprise e.g. ERP and its modules. The internal structure of presented system is described in the paper, as well as measurable advantages of hybrid system application to real environment.

Author Keywords :

optimization, modelling, production chain, metal forming

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

HYBRID OPTIMISATION OF ADDED VALUE WITH VALUE STREAM MAPPING AND METHODS-TIME MEASUREMENT

Peter KUHLANG¹, Juergen MINICHMAYR¹, Wilfried SIHN^1
1Vienna University of Technology and Fraunhofer Project Group for Production and Logistics Management, Theresianumgasse 27, A-1040 Vienna

Abstract

This paper is about a new methodical approach of the joint and simultaneous application of Value Stream Mapping and Methods-Time Measurement (MTM). The focus of Value Stream Mapping is the alignment and combination of individual processes to form a continuous, efficient value stream through the organisation (macro consideration). MTM provide an exact determination of times and focuses on executions of individual tasks and working places (micro consideration). A hybrid optimisation of added value originates from the reasonable and useful combination of Value Stream Mapping and Methods-Time Measurement for increasing productivity, reducing lead time and exact determination of times.

Author Keywords :

value stream mapping, MTM - methods-times measurement, productivity, added value optimisation

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

MODELLING OF PRODUCTION CHAINS AS A TOOL FOR INTELLIGENT MANUFACTURING IN METAL FORMING

Lukasz MADEJ¹, Stanislaw WEGLARCZYK¹, Lukasz RAUCH¹, Maciej PIETRZYK^1
1Akademia Górniczo-Hutnicza, Mickiewicza 30, 30-059 Kraków, Poland

Abstract

The objective of the paper is demonstration of the role of multi scale modelling in the system, which optimizes the whole production chain. Product exploitation and properties are the key parameters for formulation of the objective function in the optimization problem. Such parameters as fatigue resistance, wear resistance or thermal resistance are crucial for extending the life cycle of products, therefore, theoretical prediction of those parameters is inevitable for the optimization of the manufacturing system. Thus, the main focus in the paper is on description of the idea of multi scale modelling and on presentation of the multi scale model developed by the Authors. This model combines finite element (FE) solution of the macro scale problem with the cellular automata (CA) model of the micro scale phenomena. Simulation of the production chain is the second part of the paper. The chain under consideration is composed of stock heating, cold forging, machining and simulation of exploitation conditions. The correlation between the process parameters and the exploitation properties of the product is demonstrated. Finally, the optimization problem which would be the base of intelligent manufacturing, is formulated.

Author Keywords :

life cycle modelling, strain localization

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

CREATION OF BAS-RELIEF BASING ON PHOTOGRAPHY USING HIGH-PRESSURE ABRASIVE-WATER JET

Przemyslaw BORKOWSKI^1
1Przemysław BORKOWSKI, Koszalin University of Technology, Unconventional HydroJetting Technology Center

Abstract

Presented technology of spatial superficial material forming based on flat virtual image (picture) luminance is a new, original own application of high-pressure abrasive-water jet forming. Basis of spatial forming of ceramic and rock materials with high-pressure abrasive-water jet in conjunction with depth and jet velocity parameters are described in. It was built a control system and developed adequate algorithms allowing the 3D sculpturing operation of different complex objects to be mechanized.

Author Keywords :

high-pressure abrasive-water jet spatial superficial material forming

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

EFFECT OF PROCESS PARAMETERS ON THE CONDITION OF THE WIRE ELECTRODE IN WEDM OF TI6AL4V

Stanislaw ZABORSKI¹, Dariusz POROS^1
1Wroclaw University of Technology Institute of Production Engineering and Automation, ul. Lukasiewicza 5, 50-371 Wroclaw, POLAND

Abstract

Conventional machining of titanium alloy Ti6Al4V cause high temperature and rapid wear of tool which makes him hardly suitable for machining by machine cutting. The presented experimental study was carried out on a modern wire EDM Sodick AQ327L. Three types of the wire were used. Investigated were the effects of such input parameters as the pulse width and the time between two pulses on the output parameters such as area cutting efficiency, workpiece surface roughness and wear rate of the electrode. The resulting relationships were determined using the conventional regression analysis and neural networks. The results were checked for goodness of fit.

Author Keywords :

titanium alloys, wire electrode, artificial neural networks, WEDM

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

MODELLING OF COMPONENTS OF RESULTANT FORCE DURING FACE MILLING

Milenko SEKULIC¹, Pavel KOVAC^1
1University of Novi Sad, Faculty of Technical Sciences, Department for Production Engineering, Trg D. Obradovića 6, 21000 Novi Sad, Serbia, milenkos@uns.ns.ac.yu

Abstract

Cutting forces during face milling are investigated intensively analytically and experimentally. Some of previous approaches to cutting forces determination consider only main (tangential) cutting force component, and according to this define cutting power. The experimental investigations were performed during face milling with a goal to determine models of cutting force versus cutter revolution. Different models were determined according to the cutter approach to the workpiece during cutting angle of revolution.

Author Keywords :

face milling, cutting forces

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

EXPERIMENTAL ANALYSIS OF CUTTING FORCES IN DRY DRILLING OF UNS A92024 ALLOY

Rosario DOMINGO¹, Roberto ALVAREZ², Eva M. RUBIO¹, Miguel A. SEBASTIAN^1
1Department of Manufacturing Engineering, National Distance University of Spain (UNED). C/ Juan del Rosal 12, Madrid, E-28040 Spain, Tel. +34-91 398 6455, rdomingo@ind.uned.es ²Department of Engineering, Antonio de Nebrija University, C/ Pirineos 55, E-28040 Madrid, Spain

Abstract

Dry drilling is a process of interest in order to eliminate the lubrication fluids. Also the aeronautical industry has been expected to these advantages. This paper analyses the cutting forces obtained during the dry drilling of aluminium alloy plates, in particular UNS A92024-T3. Experiments were performed in CNC milling and several HSS Co drills were utilised with different diameters. Cutting forces were measured by means of a piezoelectric dynamometer Kistler. This analysis provides a statistical study, by means of multi-sample comparison, in particular, F-test in the analysis of variance. Results provide evidence that can provide information about hole drilling with a tool without wear, so forces are statistically similar.

Author Keywords :

dry drilling, aluminium alloys, cutting force

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

NUMERICAL MODEL OF MATERIAL - A CONCEPT OF FEM SIMULATION USING NEURON NETWORKS

Tomasz KROLIKOWSKI¹, Blazej BALASZ^2
1Koszalin University of Technology. Mechanical Department, Raclawicka 15, Koszalin, Poland
²Koszalin University of Technology. Mechanical Department, Raclawicka 15, Koszalin, Poland balasz@tu.koszalin.pl

Abstract

The paper presents new conceptions of numerical models of materials used for simulations of a process of grinding. Conceptions presented by authors are alternative for already existing computational solutions by finite elements method and are sources to determine new theoretical basis for their own solutions of computational systems connected with deformation of a material. The 'aiFEM' conception presented in the paper is based on elastic artificial neuron nets. Presented conceptions of numerical models material were used for simulations of a grinding process. One of conceptions presented in the article is based on a grain to the limit of a real material from which grain is made and a process of absorbing energy through a surface of a grain affecting on the material.

Author Keywords :

simulation, FEM, neuron networks

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

DIAGNOSING THE POROSITY AND LIQUID PERMEABILITY OF LARGE-PORE GRINDING WHEELS

Czeslaw NIZANKOWSKI^1
1Cracow University of Technology, Poland

Abstract

The paper presents a new method of diagnosing the porosity and liquid permeability of large-pore grinding wheels, consisting in the application of computer tomography, image analysis and finite elements method. This method was developed at the Faculty of Mechanical Engineering, Cracow University of Technology in 2006, and is covered by patent protection (P-382829). The method enables diagnosing the grinding wheel porosity not only as regards the percentage share of pores in entire grinding wheel capacity but also their number, shape, length and net of small ducts made by them. It also makes it possible to diagnose permeability of a large-pore grinding wheel without the need to run labour- and cost-consuming experiment tests.

Author Keywords :

porosity, permeability of liquids, large-pore grinding wheels

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

GRINDING PROCESS OPTIMIZATION WITH APPLICATION OF SIMULATION SYSTEM

Blazej BALASZ¹, Tomasz KRÓLIKOWSKI^1
1Koszalin University of Technology. Mechanical Department, Raclawicka 15, Koszalin, Poland. email: blazej.balasz@tu.koszalin.pl; tomasz.krolikowski@tu.koszalin.pl

Abstract

The author of this paper undertook a study on developing algorithms and programs for complex simulation of precision grinding process. The developed models of grinding processes reveals features which enables designing a new models of grinding tools with optimal grains shape and size, and its orientation on the grinding tool surface. The optimization process is feasible due to possibility of the models to carry out the simulation within a vast range of process parameters variability and exact gathering data concerning individual contact of grains. The innovation solution of presented models is based on isolation of individual grains during the simulation process and analyzing the phenomena in the grinding zone in relation to single grain. The most significant analyzes concern: the grain activity and its load, the average cut layers, flotation of single grain depth of cut along the grinding zone, and the influence of grains shape, size and arrangement on aforementioned phenomena.

Author Keywords :

grinding modelling, grinding simulation, optimization

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

MACHINABILITY ANALYSIS FROM ENERGY FOOTPRINT CONSIDERATIONS

M. F. RAJEMI¹, P. T. MATIVENGA^1
1Manufacturing and Laser Processing Research Group, Department of Mechanical, Aerospace and Civil Engineering The University of Manchester, Mohamadfarizal.Rajemi@postgrad.manchester.ac.uk

Abstract

Recent global developments have heightened the need to choose the best sustainable manufacturing methods in order to mitigate the effects of industrial processes on the environment. Energy consumption is seen as one of the key performance indices for assessment of the environmental credentials of an enterprise. It is through energy consumption that the carbon emission penalty (amount of carbon emitted in generating the energy) can be estimated. Machining remains one of the key discrete-parts manufacturing processes and its mechanics has received considerable attention in research and development. However, energy analysis for machining processes is a relatively new area. In this paper the environmental impacts of machine utilisation are assessed through energy consumption. The paper considers the energy requirements in machining of a number of alloys according to recommended cutting conditions. The energy is accessed through electrical power requirements of the machining process. The results illustrate the impact that high speed machining could have on energy consumption and hence a more sustainable machining industry.

Author Keywords :

machinability, energy footprint

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

ROBOTIC ASSEMBLY OF AERO-ENGINE COMPONENTS

Nirosh JAYAWEERA¹, Phil WEBB¹, Chen YE1Craig JOHNSON^1
1Mechanics, Materials & Structures Division and Manufacturing Division, Faculty of Engineering, University of Nottingham, University Park, Nottingham, NG7 2RD, UK

Abstract

The VITAL (EnVIronmenTALly Friendly Aero Engines) project funded by the European Commission under Framework 6 aims to provide significant reductions in aero-engine fuel burn, noise and emissions through the development of innovative design and manufacturing techniques. One method of reducing the amount of fuel burnt, and hence CO2 produced, is to reduce the weight of the engine. A significant proportion of an engine's weight is due to the large castings used to form the main non-rotating structures; the replacement of these with fabricated structures could provide a significant weight reduction. This paper describes the design and implementation of a robotic assembly cell for complex aero-engine components. A series of experiments were performed to prove the feasibility of the automated assembly process. The results presented indicate that automated robotic assembly is feasible and cost effective.

Author Keywords :

robotic assembly aero-engine components

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

CONTROL OF A WORKPIECE HOLDER WITH PIEZO-ELECTRIC-MECHANICAL ACTUATION

Otto Jan BAKKER¹, Atanas POPOV¹, Svetan RATCHEV^1
1Mechanics, Materials & Structures Division and Manufacturing Division, Faculty of Engineering, University of Nottingham, University Park, Nottingham, NG7 2RD, UK

Abstract

The main focus of research in part-fixture mechanics has been in the static deformation and part constraints. Little attention has been paid to the dynamic behaviour of these systems. However, the dynamics of the system largely determines the obtained precision during the machining process. The part is modelled as a lumped mass-spring model and the clampers and locators of the fixture are modelled as spring-dampers. The fixture frame is considered to be much stiffer than the locators, such that it provides zero displacement boundary conditions to the locators. In this study a piezoelectric actuator is utilized to provide adaptive clamping forces. The analysis has shown that position feedback can be used to minimize unnecessary displacement of the workpiece. Additionally, a lag filter can improve the steady state response.

Author Keywords :

fixturing technology, active fixture ,fixture control, dynamics modelling, piezoelectric actuation

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

PRECISE MODEL OF HSC MACHINING CENTRE FOR AEROSPACE PARTS MACHINING

Jerzy JEDRZEJEWSKI¹, Wojciech KWASNY¹, Zbigniew KOWAL¹, Wojciech MODRZYCKI^1
1Institute of Production Engineering and Automation, Wroclaw University of Technology, Wroclaw, Poland

Abstract

This article shows the aspects of precise modelling of precise High-speed Machining Centres for High-Speed Cutting (HSC) of parts used in the aerospace industry. The main focus was made on the thermal errors having a dominant influence on the precision of machining. Main assumptions for a hybrid thermal model of a centre thermal behaviour have been stated, taking into account the characteristics of heat sources. On the example of a 3-axis machining centre, measured runs of heating up and heat displacements have been shown, compared to these determined with the use of simulations of a behaviour in assumed working conditions. A special attention was drawn to the phenomena taking place in motorspindles, as well as to the displacements of a spindle face during high rotational speeds of spindles and step changes of rotational speeds. The significance and influence of the bearing preload and centrifugal forces on the spindle axial displacements was shown, which is decisive on the precision of part machining. Additionally, it was shown that the important component of a machining error is an error of spindle position identification by means of a linear encoder, resulting from the thermal deformation of a centre body, to which a quartz linear encoder is fixed.

Author Keywords :

machining centre, model, aerospace, precision

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

MODELLING THE BEHAVIOUR OF A CONTACT LAYER BETWEEN THE WORKPIECE AND A LOCATOR

Pawel MACIOLKA¹, Jerzy JEDRZEJEWSKI^1
1Wroclaw University of Technology, Institute of Production Engineering and Automation, Poland, 50-371 Wrocław, ul. Łukasiewicza 5, email: Pawel.Maciolka@pwr.edu.pl , Jerzy.Jedrzejewski@pwr.edu.pl

Abstract

The assurance of high precision alignment of workpieces with low stiffness requires thorough knowledge about the phenomena taking place in the contact area under the influence of forces exerted by actuators. It is indispensable to utilise the model of a contact and deformations taking place in it. In order to solve the problem of contact, the contact geometry was modelled by means of a flat and rough surface model based on stereometric measurements, as well as by means of the finite element method (FEM). In a FEM method, a spherical structure of the surface layer was assumed and only one zone was taken into consideration, i.e. 0.4.Rt (maximum surface roughness). Zone structure allows easy changing of mechanical properties of material during the introduction of data defined by a strengthening curve in the plastic region. The possibility of expanding the model by consecutive zones allows taking into consideration the physical properties in complex analyses of the surface layer. This paper presents the problem of contact related to the alignment and fixing process, a model of contact deformations between a flat and a rough surface, as well as the algorithm for determining the model of a surface profile according to the bearing ratio curve.

Author Keywords :

roughness, contact, model

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

COMPARISON OF TWO FEA-BASED APPROACHES IN PREDICTION OF WORKPIECE-FIXTURE STATIC BEHAVIOUR

Miroslaw GROCHOWSKI¹, Jerzy JEDRZEJEWSKI^1
1Wrocław University of Technology, Institute of Production Engineering and Automation, ul. Łukasiewicza 5, 50-371 Wrocław, Poland, e-mail: miroslaw.grochowski@pwr.edu.pl, jerzy.jedrzejewski@pwr.edu.pl

Abstract

Simulating of workpiece and fixture behaviour is commonly done with the use of Finite Element Analyses. In the most, if not all, cases researchers usually use traditional implicit integration scheme FEM codes (e.g. ANSYS, ABAQUS/Standard, NASTRAN, FEAP). In this paper a different approach is proposed. FEM code of ABAQUS/Explicit, based on explicit integration of equations of the motion is used to predict workpiece behaviour during alignment and fixing process in quasistatic state. Comparison of results obtained using both implicit and explicit techniques is also presented, results and differences are discussed.

Author Keywords :

workpiece, fixture, quasistatic analysis

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

MECHATRONIC APPROACH TO THE DEVELOPMENT OF AN INTELLIGENT FIXTURING DEVICE TEST-BED

Adam BUKOWSKI¹,Wojciech KWASNY¹, Jerzy JEDRZEJEWSKI^1
1 Wrocław University of Technology, Institute of Production Engineering and Automation, ul. Łukasiewicza 5,50-371, Wrocław, Poland, e-mail: adam.bukowski@pwr.edu.pl, jerzy.jedrzejewski@pwr.edu.pl,

Abstract

In order to improve the process of designing mechatronic devices, an approach, based on a mechatronic model, is proposed. The structure of such model is presented, consisting of partial models of single elements in a system. Methods of creating these models and integrating them into one mechatronic model are discussed. In order to illustrate the approach, a case study is shown, consisting of a mechatronic alignment and fixing device for high-precision machine tools. A test bed of such device is under construction, which will allow experimental verifying partial models of components, as well as the entire system's mechatronic model. An extended set of monitoring sensors will provide accurate system behaviour data useful for such process.

Author Keywords :

mechatronic approach, active fixturing system, intelligent controller

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

MEMETIC ALGORITHM FOR ASSEMBLY SEQUENCE PLANNING

Tomasz JANKOWSKI^1
1Wroclaw University of Technology, Institute of Production Engineering and Automation, ul. Lukasiewicza 5, 50-371 Wrocław, Poland, e-mail: tomasz.jankowski@pwr.edu.pl

Abstract

The paper presents the application of a memetic algorithm to searching for the optimal sequence of the assembly of parts. Such approach is based on the use of an algorithm connecting two methods of global and local search in order to increase the effectiveness of the conducted optimisation process. Based on a proper representation of assembly sequences and a set of geometrical, topological and technological constraints, connected with the attributes of a product, it is possible to create an evolutionary model. Through proper control of the evolution process in a model, based on the appropriate selection of parameters, it is possible to achieve good results in a short period of time. Although the evolutionary algorithm does not guarantee the obtaining of optimal solutions, it has been proven, based on sample simulations, that such solutions are obtained in a repeated manner. The application of the presented evolutionary approach enables creating fast assembly sequence planning tools, indispensable in tactical planning and operational control of manufacturing processes.

Author Keywords :

evolutionary computing, assembly, optimisation, process planning

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

PROCESS - MACHINE TOOL THERMAL INTERACTION

Jerzy JEDRZEJEWSK¹, Wit GRZESIK², Wojciech KWASNY¹, Wojciech MODRZYCKI^1
1Institute of Production Engineering and Automation, Wroclaw University of Technology, Wroclaw, Poland
²Department of Manufacturing Engineering & Production Automation, Opole University of Technology, Opole,Poland

Abstract

Hereby paper shows the structure of mutually connected thermal interactions in a machine tool, a tool and a workpiece, which finally leave their traces on a machined workpiece in form of machining errors. Thermal interactions of a machine tool and the environment on own and workpiece errors were discussed. Thermal interaction cases were considered, connected with the varying environment and the main drive operation, as well as total influence of the varying environment, main drive and two drives of controllable axes. The interactions of the cutting process itself were discussed, assuming three basic mechanisms: thermal, physically-mechanical and tribological. On the example of turning it was proven that the character of changes in total influences between the tool and workpiece has the shape of a temperature curve.

Author Keywords :

machine tool, cutting process device, part, interaction

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

INCREASING RECONFIGURABILITY BY ADAPTIVE MODULE FOR A LATHE

Uwe HEISEL¹, Norman TONN¹, Walther MAIER^2
1Head of the Institute for Machine Tools (IfW), University of Stuttgart, Germany
²Academic Staff in the team "Machine Design" of the Institute for Machine Tools

Abstract

To achieve a higher reconfigurability of machine tools, the Institute for Machine Tools at the University of Stuttgart developed a new spindle module in cooperation with the company INDEX-Werke GmbH & Co. KG (Esslingen, Germany) within the framework of a transfer project (TFB59), supported by the DFG. This spindle module enables the operator to exchange the spindle in clearly less time and hence represents an important device for the reconfigurability of machine tools. This paper describes important steps in the development and design of the new machine module.

Author Keywords :

reconfiguration, machine tool, design, spindle

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

MACHINING PERFORMANCE OPTIMIZATION OF PARALLEL KINEMATIC MACHINES TOOLS WITH REGARD TO THEIR ANISOTROPIC BEHAVIOUR

Sylvain PATELOUP¹,Thomas BONNEMAINS¹, Hélene CHANAL¹, Belhassen Chedli BOUZGARROU¹, Emmanuel DUC¹, Pascal RAY^1
1LaMI, IFMA/UBP, Campus des Cézeaux, BP 265, 63175 AUBIERE Cedex, FRANCE, E-mail:spateloup@ifma.fr

Abstract

Today, Parallel Kinematic Machines tools (PKMs) appear in automotive and aeronautic industries. These machines allow a benefit of productivity due to their higher kinematics performances than Serial Kinematic Machines tools (SKMs). However, their machining accuracy is lower. Moreover, the compensation of the defects which penalizes the machined parts quality is difficult due to their anisotropic behaviour. Thus, this article deals with the development of methods improving the machined parts quality and the productivity. In order to improve parts quality, the static behaviour of the machine structure is considered with a model taking into account joints and legs compliances. Then, it allows determining a static workspace. About the productivity, the improvement of kinematics performances is performed through an optimization work of the non productive tool path between cutting operations. The computed tool path must verify a minimum time constraint and avoid collisions between the tool and the machined part. All the methods are illustrated with the PKM Tripteor X7 developed by PCI.

Author Keywords :

parallel kinematic machine too, kinematic model, static model, tool path optimization

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

DEVELOPMENT OF A HIGH-SPEED AIR BEARING SPINDLE

Yang-HYUP HA¹, Deug-WOO LEE², Young-KUG HWANG³, Choon-MAN LEE^3
1 Pusan National University, Department of mechanical and precision engineering, e-mail address : hyh@pusan.ac.kr
²Pusan National University, College of nano science and technology, e-mail address : dwoolee@pusan.ac.kr
³ Changwon National University, Department of mechanical design and manufacturing engineering mccbreeze@empal.com, cmlee@changwon.ac.kr

Abstract

This paper investigates an air spindle with both radial and thrust air bearings of newly developing one-directional porous materials. At present, orifice type and porous type are adopted for thrust air bearings. Orifice type thrust air bearing is fabricated by machining several micro-holes on a bearing pad bearing, permeability significantly affected by particle size and machining conditions is an important factor of performance, but it is hard to c porosities is suggested. It has many micro-porosities through axial direction, so stable and plenty of air can be supplied to the thrust bearing pad. A radial air bearing also can be substituted by a radial direction porous bearing as the same reason. In case of driving parts, built-in motor type is widely applied. But it needs additional cooling parts to drop heat from a motor. So application of an air turbine drive with light-weight shaft is suggested and additionally it will reduce fabricating cost.

Author Keywords :

aerostatic bearing, metal foam, porous thrust bearing, porous radial bearing

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

FEED DRIVE SIMULATION FOR THE PREDICTION OF THE TOOL PATH FOLLOW UP IN HIGH SPEED MACHINING

David PREVOST¹, Sylvain LAVERNHE¹, Claire LARTIGUE^1
1 Laboratoire Universitaire de Recherche en Production Automatisée, ENS Cachan, Université Paris Sud 11, 61 avenue du Président Wilson, 94235 Cachan cedex, France, name@lurpa.ens-cachan.fr

Abstract

This paper deals with an advanced modeling of the feed drives of a five axis machine tool within the context of High Speed Machining. execution process. As a result, many errors are introduced during machining all process long affecting the surface quality. The paper aims at modeling the feed drive dynamics during trajectory follow-up including the current, the velocity and position loops as well as the feed forward terms, which characterize classical drives on actual HSM machines. It concerns translational axes as well as rotary axes. A procedure of identification of the virtual axis model are detailed for three and five axis trajectories presenting various types of geometrical discontinuities.

Author Keywords :

simulation; high speed machining, 5 axis machining; identification

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

EXPERIMENTAL TESTING OF ACTIVE FEED DRIVE

Jiri SVEDA¹, Michael VALASEK¹, Zbytek SIKA^1
1Departament of Mechanic, Biomechanice and Mechatronics, Faculty of Mechanical Eng., CTU in Praque, Karlovo nam. 13, 121 35 Praha 2, Contact e-mail: J.Sveda@remt.evut.cz

Abstract

The main disturbances of the machine tool frame are caused by operation of motion axes. Movement of high dynamic motion axes is connected with powerful force stroke that excite machine tool frame vibration and deteriorate machining surface quality and productivity. There are several possibilities how to suppress this vibration. This deals with the simulation and experimental testing of new advanced conception where the main motor is connected with the frame by an active element that is controlled by intelligent control technique.

Author Keywords :

machine tool, testing bed, linear motor, vibration suppresssion, control loop

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

SIMULATION INVESTIGATION OF BALL SCREWS FOR HIGH SPEED TRANSMITTING SYSTEMS

Jerzy Z. SOBOLEWSKI¹, Jarosław MAŁKIŃSKI², Przemysław PIENIECKI^3
1 Institute of Machine Design Fundamentals, Warsaw University of Technology, jso@simr.pw.edu.pl
² Institute of Machine Design Fundamentals, Warsaw University of Technology, jarmal@simr.pw.edu.pl
³Warsaw Institute of Aviation, p.pieniecki@gmail.com

Abstract

The ball screws are used in feed systems in CNC machines working with constantly higher cutting speed. When the speed of the balls reaches certain levels, the repetitive chock (impact forces) generated by the balls in the "transient" phase of the balls' motion and forces acting in the return channel cause damage to the recirculation ball system. A simulation of impact forces for variable length of transient phase in function of the rotational speed was made. The static axial rigidity is a very important factor to be considered in defining ball screws performance and exerts a major influence on positioning accuracy of NC machine tools. One of rigidity components is the balls/balltrack area rigidity, dependent on Hertz's deflections. However, due to machining inaccuracies, the ball screws properties (especially rigidity) are considerably lower than the theoretical ones. A coefficient known as the geometric correction factor makes it possible to predict the rigidity of the ball screw. A computer simulation of the influence of machining inaccuracies on contact deflections, rigidity and servo drive resonance was carried out. It was examined what rotational speeds set off the harmful phenomenon of the agreement of the frequency of the arrangement of the impact forces with the frequency of the servo drive system resonance. The presented method allows for the calculation of the impact forces, total rigidity and resonance of NC machine feed system, in the preliminary phase of technical project.

Author Keywords :

ball screws, CNC feed systems, rigidity, impact forces

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

ANALYSIS AND SIMULATION OF NONLINEAR SELF-EXCITED VIBRATIONS IN TURNING

Jaromir ZELENY¹, Tomas REPAK², Petr FOJTU^2
1Head of the research group: Machine tools of new concepts", RCMT - Research Center of Manufacturing Technology, Prague, Czech Republic
²Researchers, RCMT - Research Center of Manufacturing Technology, Prague, Czech Republic

Abstract

Commonly applied theories of self-excited vibrations in machine tools are prevailingly based on frequency domain analysis of linear models and are devoted in most cases only to evaluation of stability limits of strictly linear systems. In this way, the behaviour of more stable or more unstable systems cannot be studied and analyzed. Certain important nonlinear effects cannot be studied as well for limitations connected with classical representation of systems only in the frequency domain. Evaluation of stability by analysis of nonlinear systems in time domain has not been applied until now. The paper shows a new approach based on interpretation of the self-excited vibration systems as nonlinear servo-systems. With this approach, linear and nonlinear systems of any degree of stability can be studied by combination of frequency and time-domain methods. This can considerably contribute to better understanding of complex phenomena in various regimes and special situations.

Author Keywords :

machine tool, machining, machining process, self-excited vibrations

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

MACHINE VIBRATIONS WITH MORE DEGREES OF FREEDOM

Jirí VONDRICH¹, Evzen THONDEL^1
1Czech Technical University in Prague, Faculty of Electrical Engineering,, Department of Electric Drives and Traction, Technická 2, 166 27 Prague 6, Czech Republic, vondrich@fel.cvut.cz, thondee@fel.cvut.cz

Abstract

Rigid mounting of machines to a solid base is one of the requirements for high performance and quality of production. Machine vibrations occur as a result of unbalanced revolving masses, loading forces and moments, starting and coasting of driving motors and other effects. We try to eliminate these undesirable vibrations by suitable mounting of the machine and its parts as much as possible. Suitable mounting of the machine is possible using components such as torsion springs, pneumatic springs, rubber pads or other components. The article describes numerical calculation of optimal displacements the machine for the given his parameters.

Author Keywords :

Matlab, Simulink, vibration, machine

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

MACHINE VIBRATIONS WITH MORE DEGREES OF FREEDOM

Jirí VONDRICH¹, Evzen THONDEL^1
1Czech Technical University in Prague, Faculty of Electrical Engineering,, Department of Electric Drives and Traction, Technická 2, 166 27 Prague 6, Czech Republic, vondrich@fel.cvut.cz, thondee@fel.cvut.cz

Abstract

Rigid mounting of machines to a solid base is one of the requirements for high performance and quality of production. Machine vibrations occur as a result of unbalanced revolving masses, loading forces and moments, starting and coasting of driving motors and other effects. We try to eliminate these undesirable vibrations by suitable mounting of the machine and its parts as much as possible. Suitable mounting of the machine is possible using components such as torsion springs, pneumatic springs, rubber pads or other components. The article describes numerical calculation of optimal displacements the machine for the given his parameters.

Author Keywords :

Matlab, Simulink, vibration, machine

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

AN ANALYSIS ON THE THERMAL CHARACTERISTICS ACCORDING TO THE VISCOSITY OF BEARING LUBRICANT AND THE COOLING CONDITION FOR THE HIGH SPEED MOTOR SPINDLE

DaeBong CHOI¹, JaeJong Lee¹, SooTae KIM², HeeDon KWON², ChangYong KIM^3
1Machine Tools Group, Korea Institute of Machinery and Materials, Korea
²Dept. of Mechanical Engineering, Changwon National University, Korea
³HWACHEON Co., Ltd, Korea

Abstract

Thermal displacement of the high speed machine tools has a large influence on machining accuracy. The high speed motor spindle with many heat sources is widely used for the high speed machine tools recently. The important problem in this spindle is to reduce and minimize the thermal effects by motor and bearings. This paper presents the analysis on thermal characteristics for high speed motor spindle system with oil-air lubricated angular contact ceramic ball bearings and built-in motor. An analysis on the thermal characteristics of spindle is performed according to the cooling conditions and the viscosity of bearing lubricants by using finite element method. This results can be applied to the design and manufacturing for the high speed motor spindle.

Author Keywords :

+high speed motor spindle, thermal displacement cooling condition, lubricant viscosity

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

KNOWLEDGE REPRESENTATION AND THEIR APPLYING TO FIXTURE DESIGN

Grigori NEKRASSOV¹, Leonid PORTJANSKI^1
1Tallinn University of Technology, Department of Machinery, Ehitajate tee 5, 19086 Tallinn, Estonia, Grigori.Nekrassov@ttu.ee, Leonid.Portjanski@ttu.ee

Abstract

The aim is to develop an integrated design space for CAD of technological equipments. The model of the design environment is represented as a two-level hierarchical decision-making system. The proposed environment provides support for creating and manipulating 3D models of technological equipment and their components, calculating functional and structural properties and the evaluation criteria, and for determining the rules to control the design process for optimizing the portfolio of interdependent projects of technological equipments. As examples the design of workholder is considered. The computer aided workholder design system is created on Case Based Reasoning, in which the attributes of the workpiece and structure of workholder as case index code are designed for the retrieve of the similar cases, and the structure and hierarchical relation of case library are stored. The structure of case storage (database and knowledge base) for general workholders selected as an object for mining and sampling of the developed software are worked out. It is offered to apply a method of neural networks to realization procedure of forecasting of decisions. The considered algorithms of knowledge extraction are realized by development of invariant nucleus design space.

Author Keywords :

CAD, technological equipments, knowledge base, case based reasoning, neural networks

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

ADVANCED DETERMINATION OF SAFETY FACTOR OF FATIQUE STRENGTH OF COILED SPRINGS

Gennady ARYASSOV¹, Andres PETRITSHENKO^1
1Tallinn University of Technology, Department of Mechatronics, garjasov@staff.ttu.ee, petritsenko@hotmail.com

Abstract

Coiled compression springs are widely used in suspension systems of vehicles, light weight trailers, trains etc and their task is to minimize dynamic loading effect to vehicles body or frame in different road condition over many years. In these systems, springs are exposed to large number of cycles of loading and determination of their durability and reliability quantities is important. Consequently, to increase the reliability of these systems, a more accurate determination of the values of the endurance limits of springs is necessary. Usually, in many strength problems, the major components of stress are static, with less accurately alternating stresses superposed. Most failures of springs are originated with stress of alternating type. The solution of problem is accomplished due to acting shear and axial stresses in plane of cross-section of spring wire.By existing theory, when springs are loaded by non-steady loading, then to consider of unlimited number of combinations of amplitude and mean stresses, the line of failure of the material must be used. Since experimental data for the line of failure of material are usually not at hand, it is customary to make a conservative approximation, that it is a straight line. However, use this straight line may give considerable mistakes on determination of the limit range stresses. To avoid fore aft mentioned mistakes, the method of approximation of the failure curve line by the line with the properly chosen parameters for the coiled compression and tension springs is proposed in this paper. Theory to use proper parameters in approximation of failure curve and calculation example with results is given as well.

Author Keywords :

coiled springs, fatigue failure, safety factor, alternate stress, endurance limit stress

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

DECREASING OF THERMAL ERRORS IN A LATHE BY FORCED COOLING OF BALL SCREWS AND A HEADSTOCK

Zdzisław WINIARSKI¹, Zbigniew KOWAL¹, Andrzej BLAZEJEWSKI^1
1Wroclaw University of Technology, Institute of Production Engineering and Automation, ul. Lukasiewicza 5, 50-371 Wroclaw, Poland

Abstract

The goal of this paper is to present the effective methods of decreasing thermal deformations of a turning centre's structure in order to reduce the thermal error. The design of a machine tool as well as the scope of analyses are described, and calculation methods are specified. The paper also presents the results of computer simulations, concerning studies on the influence of type and parameters of a headstock-cooling liquid on the reduction of spindle displacements. Moreover, the results of feed mechanism's thermal studies are shown, describing the influence of heat generated during the operation of ball screws and their inner liquid cooling, on tool's thermal displacements.

Author Keywords :

lathe, feed mechanism, cooling, thermal error, calculation