Showing papers by "Konrad Wegener published in 2010"

Influence of the brazing parameters on microstructure, residual stresses and shear strength of diamond–metal joints

Abstract: The reliability and integrity of diamond cutting tools depend on the properties of diamond–metal joints as created by a brazing process. Block-shaped monocrystalline diamonds were brazed onto a steel substrate (X2CrNiMo 18-14-3), using silver–copper based Cusil-ABA™ (Ag–35wt%Cu–1.75wt%Ti) filler alloy. The experimental procedure includes a thorough microstructural investigation of the filler alloy, the determination of the induced residual stresses by Raman spectroscopy as well as the joint’s shear strength utilizing a special shear device. The brazing processes were carried out at 850, 880 and 910 °C for dwell durations of 10 and 30 min, respectively. At the steel interface two interlayers develop. The layers grow with extended dwell duration and higher brazing temperature. The residual stresses only slightly depend on the brazing parameters and exhibit a maximum value of −400 MPa. Unlike the residual stresses, the shear strength strongly depends on the brazing parameters and thus on the microstructure. Three failure modes could be identified; a ductile fracture in the filler alloy, a brittle fracture in the interlayers and a partly shattering of the diamond.

Evaluation of modelling approaches for machine tool design

Abstract: In order to evaluate the configuration of machine tools, the IWF Axis Construction Kit (ACK) has been developed. This paper describes the evaluation of this approach. The ACK supports rigid body simulations and simple elastic body simulations. The ACK is compared with commercial FEM software to investigate its usability and reliability. Required time was compared in modelling of a machine tool. The ACK needed 30% of the total required time for the FEM because of its modularity in machine modelling. Then, in order to investigate the reliability of the ACK, static and dynamic simulations of both approaches were compared with each other and with analytical calculations on basic beam models. The result showed that the ACK provided equivalent results to the FEM. Static and dynamic simulations were also compared with measurements on an actual machine tool. The ACK obtained almost equivalent results to the FEM. Almost all lower structural mode shapes and their natural frequencies could be reproduced with the ACK when crucial parts were modelled using elastic bodies.

Energy Consumption Measurement with a Multichannel Measurement System on a machine tool

Abstract: Considering the energy consumption of machine tools, in the future manufactures will face not only economic and environmental, but eventually statutory challenges as well, if machine tools are subjected to the European directive on Energy-using Products (EuP). From a life cycle engineering perspective, the knowledge of energy consumption during the use phase is crucial. Currently, there is no established method of measuring the energy consumption of machine tools, and due to the variety of products, it is not obvious to propose one. A comprehensive measurement system is seen as a basis for online energy monitoring, which can be used to control the consumption of energy and costs from a TCO-point of view and to provide overall less energy consuming production methods with higher reliability. The used measurement system was implemented on several machine tools to determine the main energy consumer and its behavior on different settings, such as machine dynamics, cooling, and electronics. The obtained results reveal considerable potentials in energy saving and process efficiency. This paper presents the developed measurement system architecture and related data acquisition as well as an analytical analysis approach. Moreover, an example of energy optimization measures will be described according to the applied analysis. Introduction and Objective “If you can not measure it, you can not improve it." Lord Kelvin Energy is an issue in science, politics and several industrial sectors; up to now, it carries less importance in manufacturing [1]. Due to climate change and environmental reasons, stricter industrial requirements, especially automotive sector [2], costs and resource reasons in the context of green production as well as statutory requirements [3], energy efficiency has become a large research field. The study of the BMWi [5] indicates that the industrial sector in Germany has a predominant share of 47% of the total energy consumption of all sectors. Going deeper into detail of the Life Cycle Assessment (LCA) of a machine tool, it can be seen that the use phase of a machine tool is the most relevant phase for energy consumption [6]. Awareness of energy consumption is seen as the basis for further analysis, and optimizations of the energy efficiency of a machine tool. It should also increase the awareness of consumption, provide 1 http://zapatopi.net/kelvin/quotes/ (5.05.2010). 2 ) cos(φ ⋅ ⋅ = eff eff eff I U P the grounds for energy efficiency improvements, and verify the improvements after implementation. This paper introduces a developed multichannel measurement system which is designed to measure the energy consumption of machine tools with its specific energy forms such as electricity and compressed air, to implement and verify improvements.

On-machine wire electrical discharge dressing (WEDD) of metal-bonded grinding wheels

Abstract: Metal-bonded diamond wheels, due to its strong grain retention and thermal conductivity properties, are generally used for grinding difficult-to-cut materials, such as high-performance ceramics. On the other hand, the poor dressability of this type of bond limits its application. This study aims to evaluate the use of a wire electrical discharge machining (EDM) principle for truing and dressing metal-bonded grinding wheels. Through the EDM process, the electrically conductive grinding bond is eroded, so that grain protrusion can be generated. For evaluating this dressing process, a wire electrical discharge dressing unit was designed, manufactured, and integrated into a universal cylindrical grinding machine. The dressing process is carried out using the grinding oil also as dielectric fluid. High material removal rates were achieved. Cylindrical plunge grinding tests on silicon nitride workpieces indicated that in comparison to conventionally dressed wheels, smaller cutting forces and wheel wear are achieved by using EDM-dressed grinding wheels.

Detection of surface defects on sheet metal parts by using one-shot deflectometry in the infrared range

Abstract: The early detection of surface defects on raw sheet metal parts is a critical problem in the automotive industry. Typical defects like dents, bumps and waviness are invisible at the early production stages because of the parts’ rough surfaces. The defects become visible and disturbing only after the later production steps, in which the parts get painted and varnished, meaning that they become specular reflecting. The later the defect gets detected, the more the correction will cost. Currently, the raw sheet metal parts are only randomly tested by special, trained experts, which means subjective and qualitative results. To overcome this problem, we propose a method that can be used on-line on each part directly at the production line. The system employs a one-shot deflectometry method in the infrared range. At sufficiently long wavelengths, the sheet metal’s surface becomes specular reflecting, thus enabling the use of the deflectometry method. For this method, a device capable of displaying a reference pattern at the infrared wavelengths was developed. This single infrared reference pattern is reflected from the surface of the raw sheet metal object and the reflected image is captured by a thermo-camera. The distortion of the reflected pattern due to the surface’s geometry and defects is analyzed by the Fourier-transform method. Due to the single exposure method, vibrations during the measurement are not disturbing and the alignment problem, that is characteristic for multi-exposure methods, is nonexistent in this case.

Evaluation of reflectivity of metal parts by a thermo-camera

Abstract: All objects, apart from black-bodies, reflect a part of the incident radiation. The reflected fraction of incident radiation is termed as „reflectivity‟. The reflectivity of surfaces is often a function of the wavelength, the material, the quality of the surface, and the incident angle of the radiation. In order to evaluate the specular reflectivity of a surface at small incident angles, a method, based on thermal radiation measurement by a thermo-camera, was developed. A quasi black-body, a so-called „Hohlraumstrahler‟, was realized and used as thermal radiation source. The temperature of the source was continuously monitored by temperature probes at 3 different locations inside the source, while the radiation flux of the source was measured by a thermo-camera. During a calibration process, the temperature data from the probes and the radiation flux measured by the thermo-camera were simultaneously recorded and evaluated. In a next step, the radiation from the source was reflected by the samples and measured by the thermo-camera along with the temperature data from the probes. Using the calibration data, the reflected radiation flux could be calculated. The surface profiles of the samples were also measured by a stylus instrument. The calculated reflectivities were evaluated together with the surface roughness of the samples. The results showed good coincidence with the theoretical model of Bennett and Porteus [1].

Comparison of rigid body mechanics and finite element method for machine tool evaluation

Abstract: Reconfigurable machine tools are proposed as manufacturing concepts coping with turbulent and quickly changing business environments. New tools for efficient modelling of different machine variants are required in order to facilitate and accelerate the reconfiguration of machine tools. This paper presents a software tool which allows the evaluation of the performance and conformance to requirements of machine structure variants at an early stage. In contrast to computer-aided manufacturing (CAM) tools which process numerical control (NC) code to predict the tool trajectory, this tool calculates the static and simulates the dynamic properties of the machine structure as a basis for machine evaluation. Models of different structure variants are assembled using a module library, which contains models of the available physical modules. Thus, different variants can be set up and analysed efficiently, significantly improving the data basis on which important and far-reaching decisions have to be made. An example illustrates how the tool can be used for obtaining information on the physical machine properties and how to interpret the results. The presented software tool is part of a methodology for the reconfiguration process of reconfigurable, modular machine tools.

Simulation zur Optimierung von Schleifwerkzeugen mit definierter Kornanordnung

Abstract: Schleifwerkzeuge mit definierter Kornanordnung sind eine Weiterentwicklung von einschichtig belegten Schleifwerkzeugen. Diese sind in der Industrie unter den Namen „Engineered Grinding Tools (EGT)“ bekannt. Es handelt sich heute um einschichtig belegte Werkzeuge, bei denen zur Optimierung von Spanraum und Kuhlschmiermittelzutritt die Korner entsprechend einem parametrisierbaren Belegungsmuster platziert und zumeist metallisch angebunden werden. Die Spanraumvergrosserung ist besonders bei Prozessen mit hohem Zeitspanvolumen erwunscht. Solche EGT haben galvanische oder gelotete metallische Bindungssysteme. Ein automatisiertes Verfahren zur Platzierung von Hartstoffkornern fur das gelotete Bindungssystem wurde von Burkhard und Rehsteiner [1-2] entwickelt. Die Positionsunsicherheit der Korner wurde von Pinto [3] untersucht. Diese wird mit Hilfe eines Kreises um die nominelle Kornposition beschrieben. Fur eine Kornung B251 betragt der Durchmesser mit 95%-Konfidenzintervall DKornlage=189μm. Zur Evaluation des Einflusses des Belegungsmusters auf den Schleifprozess wurden drei Werkzeuge mit unterschiedlichen Mustern hergestellt. Diese wurden mit einem konventionell einschichtig belegten Werkzeug verglichen [4]. Die hohere Korndichte von konventionell hergestellten Schleifscheiben resultiert in einem niedrigeren Wert fur den Mittenrauwert Ra, was durch die hohere Anzahl von aktiven Kornern hervorgerufen wird. Der Mittenrauwert wird durch den Anstieg des bezogenen Zeitspanvolumens Qw‘ reduziert. Dieser Effekt ist auf den Verschleiss bzw. den Bruch von Kornern zuruckzufuhren, wodurch die Anzahl der am Schleifprozess beteiligten Korner erhoht wird. Um den Einfluss des Belegungsmusters auf die Ergebnisse und deren Eignung fur eine Schleifapplikation untersuchen zu konnen, wird ein Prozessmodell fur die numerische Simulation prasentiert. Die Simulation basiert auf einem stochastischen kinematisch-geometrischen Schleifmodell und besteht aus einem Werkzeugmodell, einem kinematischen Prozessmodell, einem Materialabtragsmodell und einem Verschleissmodell. Dabei wird das Gesamtverhalten der Schleifscheibe aus den Elementarereignissen der Einzelkorneingriffe synthetisiert. Besonderes Interesse verdienen das Werkzeugund das Verschleissmodell. Das Werkzeugmodell beinhaltet eine detaillierte Beschreibung des Werkzeugs inklusive aller deterministischen und stochastischen Variablen des abrasiven Korns. Das Verschleissmodell berucksichtigt den Effekt der Belagsabnutzung ausgehend von der Belastung eines einzelnen abrasiven Korns. Sobald die Belastung einen Grenzwert uberschreitet und somit das Korn uberlastet wird, findet Verschleiss statt. Die Bestimmung des Grenzwerts basiert auf der aus dem Korneingriff resultierenden Schnittflache und wird fur cBN ABN800 charakterisiert. Die Validierung des Modells erfolgt durch den Vergleich zwischen Simulation und Experimenten, indem die Verschleisseigenschaften des Belags und die Werkstuckrauheit verglichen werden.

A key performance indicator system of process control as a basis for relocation planning

Abstract: Many companies build up manufacturing networks to cope with globalized competition. Among others, this requires a decision on a technical basis, which product should be manufactured at which location. In this paper a key performance indicator system is introduced to measure a location’s competence on a technical basis. This system consists of three key performance indicators: cycle time ratio, adjusted cycle time ratio, and stability of the cycle time. The most important performance indicator in this key performance indicator system is the stability of cycle time. It indicates how experienced and stable the serial production can be managed. This indicator is defined as the ratio of the mean absolute deviation of the cycle time and the achieved cycle time. Based on this, a company can take a more objective technical decision regarding relocation processes. The efficiency of this key performance indicator system will then be demonstrated in a case study.

AMOR - an agent for assisting monitoring, optimization and (re-)design in factory design

Abstract: Within the new paradigm “Factory as Product”, three essential activities are of major interest. This paper investigates and answers the question how Monitoring, Optimization and (Re-)Design can be linked and supported. Based on the feedback control theory, an agent for assisting the essential activities is proposed and its tasks are described.

Utilization of a bioinformatics algorithm for the comparison of process chains

Abstract: Large manufacturing companies usually work in manufacturing networks, where they add LCL (low cost locations) manufacturing sites into their network and fill these from different HCL (high cost locations) with their production lines. These different fillings give evidence to an inhomogeneous production structure at the LCL. To solve this problem, the method MAE-P3 (MAE-P3: Machines And Equipment; Processes; Products; Planning) is introduced, which visualizes complex production structures in a two-dimensional matrix. This method is integrated into a computer program, which displays the sequence of the production lines’ manufacturing processes together with the sequence of the products’ manufacturing processes. The comparison of production lines and products for relocation planning or production structure optimization is based on an algorithm for sequence alignment originally developed in the bioinformatics field. This paper introduces the application of this algorithm to a relocation problem and gives a practical example of this method.

Evaluation of reflectivity of metal parts by a thermo

Abstract: All objects, apart from black-bodies, reflect a part of the incident radiation. The reflected fraction of incident radiation is termed as „reflectivity‟. The reflectivity of surfaces is often a function of the wavelength, the material, the quality of the surface, and the incident angle of the radiation. In order to evaluate the specular reflectivity of a surface at small incident angles, a method, based on thermal radiation measurement by a thermo-camera, was developed. A quasi black-body, a so-called „Hohlraumstrahler‟, was realized and used as thermal radiation source. The temperature of the source was continuously monitored by temperature probes at 3 different locations inside the source, while the radiation flux of the source was measured by a thermo-camera. During a calibration process, the temperature data from the probes and the radiation flux measured by the thermo-camera were simultaneously recorded and evaluated. In a next step, the radiation from the source was reflected by the samples and measured by the thermo-camera along with the temperature data from the probes. Using the calibration data, the reflected radiation flux could be calculated. The surface profiles of the samples were also measured by a stylus instrument. The calculated reflectivities were evaluated together with the surface roughness of the samples. The results showed good coincidence with the theoretical model of Bennett and Porteus [1].