Andreas Otto

Does supply chain management really pay? Six perspectives to measure the performance of managing a supply chain

Does supply chain management really pay? This question addresses the critical problem of separating the outcome of all the different “managements”, which usually are at work concurrently in a living company. Besides supply chain management (SCM) you may find other areas, trying to improve the performance of a company at a single point in time. Isolating the impact of SCM on the bottom line will thus be difficult. The paper at hand explores suitable metrics to measure the effectiveness of SCM. The outcome of this piece of research will present six unique sets of metrics to measure performance of SCM. The different metrics refer to the main disciplines, which contributed to the field of SCM the most: System Dynamics, Operations Research/Information Technology, Logistics, Marketing, Organization and Strategy.

A 3D transient model of keyhole and melt pool dynamics in laser beam welding applied to the joining of zinc coated sheets

In order to get a deeper understanding of laser beam welding, a process model was developed at the Chair of Manufacturing Technology. It is based on the continuity equation, the equation of heat conduction and the Navier–Stokes equation. The model includes effects of Fresnel absorption, vapor pressure, surface tension, melting and evaporation enthalpy and energy loss due to evaporating material. This paper presents the results of a three-dimensional, transient finite volume simulation of a laser beam deep penetration welding process based on this model. The simulations show periodic keyhole oscillations and the complex fluid dynamics of the melt pool. A comparison of the evaporation rates calculated from the simulations and the experimentally observed process emissions shows good correlation. Furthermore, the simulations show pore formation at higher feed rates, the influence of a gap on the welding process and give an explanation for the welding behavior of zinc coated steel sheets.

General process-oriented management principles to manage supply chains: theoretical identification and discussion

Academic discussion in the field of supply chain management is influenced by descriptive, case‐oriented and consultancy‐driven research outcomes. The debate is often limited to the search for valid definitions and models of observable facts. The present research makes an alternative effort. This article deals with the question of whether there are any common suggestions that can be condensed to nine process‐based principles that contribute to the management of such chains. The applicability of these principles was evaluated using Thomas and Tymons notions of “necessary properties of relevant research”.

Der Beitrag des Supply Chain Management zum Management von Supply Chains — Überlegungen zu einer unpopulären Frage

SummarySupply Chain Management is a rather young, but fast growing discipline, which is concerned with the management of long, interwoven chains of industrial actors. So far, the overwhelming reception of this concept on current conferences, especially in logistics, mirrors the extent to which the field is involved not only in the implementation of the practices, but also in the conceptual advancement. Following all “managerial revolutions“ the question of the potential beneficiaries of supply chain management emerges. The paper addresses this question, which is relevant not only to the practitioner, but also to the academic. After a comprehensive review, criteria to evaluate the value of the supply chain management research are developed and applied in order to provide a systematic and transparent evaluation from the perspective of the practitioner.

Ziel erreicht? Sechs Perspektiven zur Ermittlung des Erfolgsbeitrags des Supply Chain Management

Welchen Beitrag zum Unternehmenserfolg leistet das Supply Chain Management? Eine eindeutige Antwort auf diese Frage zu geben, ist schwierig, da es keinen Konsens uber die spezifischen Aufgaben des Supply Chain Management gibt. Vielmehr sind unterschiedliche, durchaus voneinander abweichende, aber sowohl in der Theorie wie auch in der Praxis vertretene Perspektiven erkennbar — und von diesen hangt das Ergebnis der Leistungsmessung ab. Der vorliegende Beitrag beschaftigt sich mit den in der SCM-Literatur erkennbaren Perspektiven, identifiziert, portraitiert und grenzt dazu sechs Perspektiven voneinander ab und arbeitet deren Konsequenzen fur eine Leistungsbeurteilung heraus. Es ergeben sich jeweils unterschiedliche Indikatoren zur Leistungsbeurteilung.

Ultrafast microsphere near-field nanostructuring

Due to the steadily advancing miniaturization in all fields of technology nanostructuring becomes increasingly important. Whereas the classical lithographic nanostructuring suffers from both high costs and low flexibility, for many applications in biomedicine and technology laser based nanostructuring approaches, where near-field effects allow a sub-diffraction limited laser focusing, are on the rise. In combination with ultrashort pulsed laser sources, that allow the utilization of non-linear multi-photon absorption effects, a flexible, low-cost laser based nanostructuring with sub-wavelength resolution becomes possible. Among various near-field nanostructuring approaches the microsphere based techniques, which use small microbead particles of the size of the wavelength for a sub-diffraction limited focusing of pulsed laser radiation, are the most promising. Compared to the tip or aperture based techniques this approach is very robust and can be applied both for a large-scale production of periodic arrays of nanostructures and in combination with optical trapping also for a direct-write. Size and shape of the features produced by microsphere near-field nanostructuring strongly depend on the respective processing parameters. In this contribution a basic study of the influence of processing parameters on the microsphere near-field nanostructuring with nano-, pico- and femtosecond laser pulses will be presented. The experimental and numerical results with dielectric and metal nanoparticles on semiconductor and dielectric substrates show the influence of particle size and material, substrate material, pulse duration, laser fluence, number of contributing laser pulses and polarization on the structuring process.

Laser microwelding in electronics: limitations and solutions for a further miniaturization

Looking at todays production of microelectronics, the laser is a commonly used tool for many purposes. Especially laser micro welding of electronic contacts, the application discussed here, gains more and more importance in industrial production. The reasons are its high flexibility, the absence of a third joining partner like solder, the high temperature resistance and finally its high miniaturization potential.

Control of transient processes during CO2 laser beam welding

During welding of sheet metals with high performance CO2-lasers various unsteady processes occur which are disturbing the performance capabilities ofthe workpiece. Figure 1 gives a schematic overview on different kinds of these transient processes. They take place at the beginning (pos. 1) and the end of the process (pos. 4) as well as at critical workpiece contours (pos. 3). This kind of l;ransient processes can be predicted and therefore it is possible to take them into consideration while plaiiniiig the machining. But also during quasi steady periods (pos. 2) of the welding transient processes occur, that are caused e.g. by changes in the surface finish or by fluctuations of the laser output OWCF or only by the coupling of nonlinear effects. The latter kind of transient processes cannot be predicted. Therefore a highly precise local machining quality can only be achieved, if the transient process is well understood and controlled. Detector systems are required to get a deeper knowledge of the process. To influence the processing results a modular control system has been developed

Hochtemperatur-Umformung von zellularem Aluminium

Mit der Entwicklung von Aluminiumschaumen ist in den letzten Jahren eine neue Klasse von zellularen Werkstoffen entstanden, die aufgrund ihrer guten Eigenschaften bezuglich Dichte, Steifigkeit und Energieabsorptionsvermogen ein groses Einsatzpotential als Kernstruktur in Kernverbunden insbesondere fur Leichtbaukonstruktionen im Verkehrswesen besitzt. Kommerziell realisiert wurden bisher schmelzmetallurgisch und pulvermetallurgisch hergestellte Metallschaume, wobei die erst genannten wesentlich kostengunstiger produziert werden konnen. Aufgrund der geringen Umformeigenschaften der Kernverbunde sind zur Zeit jedoch die Einsatzmoglichkeiten stark eingeschrankt, denn bei Raumtemperatur fuhren die Umformkrafte zum Kollabieren der Zellstruktur an der Wirkflache zwischen Werkzeug und Werkstuck, da die Zellwande die auftretenden Spannungen nicht ertragen. Daraus entstand die Motivation zur Implementierung einer integrierten Prozeskette fur das Hochtemperatur-Umformen der zellularen Kernstruktur und das Fugen von Kernstruktur und Deckschichten zur endkonturnahen Herstellung komplexer 3D-Kernverbundbauteile. Dabei sollen die zellularen Kernstrukturen bei Temperaturen nahe der Solidustemperatur umgeformt werden, da in diesem Temperaturbereich die Fliesspannung extrem herabgesetzt ist und damit das Formanderungsvermogen deutlich erhoht wird. In diesem Beitrag werden Grundlagen fur die Hochtemperatur-Umformung von Aluminiumschaum dargelegt. Die Ausgangswerkstoffe werden charakterisiert, und es werden erste experimentelle Ergebnisse zum Materialverhalten und zum Umformen von zellularen Aluminiumwerkstoffen bei Temperaturen im Arbeitsbereich nahe der Solidustemperatur vorgestellt.

Dual beam Nd:YAG laser welding: influence of lubricants to lap joint welding of steel sheets

Laser welding is applied in large-volume production since the late eighties and has revolutionized the possibilities of designing and engineering products. Nevertheless, problems appear during application because the operational conditions in industrial environments fluctuate and can influence the welding process negatively. Contaminations, like lubricants and organic solids, are an example of changing conditions in laser beam welding. If a lap joint is welded, these materials have to be removed from the sheets, otherwise pores and surface failures may appear due to keyhole instabilities induced by uncontrolled outgassing. One possibility for solving this problem is the use of two separate laser beams. For producing these two beams several systems are available for all different kind of lasers. A bifocal optic is such a solution for an Nd:YAG laser. By using this system, the laser beam is divided after collimation with a prism. Afterwards the two beams are focussed with a lens to the surface of the sheet and two single spots are produced. If the distance between the two spots is low, one common, elliptical keyhole is created. With this system two different welding strategies are possible. The spots can be oriented parallel or normal to the feed direction. For stabilizing the laser welding of contaminated steel sheets the parallel arrangement is better, because the amount of contamination is nearly the same as in single spot welding but the total volume of the keyhole is greater and so pressure variations due to uncontrolled evaporation of contaminations are lower. In order to prove this theory and to determine the exact effects some investigations were made at the Chair of Manufacturing Technology of the University of Erlangen-Nuremberg. A 4 kW Nd:YAG laser with a beam parameter product of 25 mm*mrad and a focal distance of 200 mm was used to weld two 1 mm DC04 steel sheets together with a lap joint. Between the sheets a deep drawing lubricant, Castrol FST 6, was used to simulate the contaminations. The sheets were welded with mono- and bifocal optic, whereas with bifocal the power distribution between the two beams was varied. After welding, the seams were qualified by analyzing surface defects and mechanical properties. The results of the investigations show that the adoption of a bifocal optic can increase the stability of the welding process. The distribution between the two single spots has an essential influence on the welding result. In order to get a higher penetration and failure free seams, a 30 % to 70 % distribution between the two spots is better. Furthermore the blade angle has another slight impact on the welding result. For monofocus and bifocus a towing angle between the sheets and the beam produces better welding results. Considering these results it can be resumed that the application of a bifocal optic is a possibility to increase the quality and the stability of lap joint welding but the parameter settings for good results can only be varied in a tight tolerance zone.